Dissertations / Theses: 'Oxidation des lipides'

1

Garcia, Darras Carolina. "Conception et développement d'un microcalorimètre pour l'étude de l'oxydation d'une huile végétale." Thesis, Bordeaux 1, 2012. http://www.theses.fr/2012BOR14517/document.

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L’oxydation des lipides est un phénomène complexe qui génère de nombreux produits qu’il est nécessaire de caractériser de manière précise afin de prévenir leur apparition. Parmi les méthodes pour analyser les produits d’oxydation, l’analyse thermique différentielle, basée sur la mesure différentielle du flux de chaleur dissipé au cours des réactions d’oxydation, est intéressante car elle n’utilise pas de solvant organique. De plus, elle peut être corrélée à l’apparition de produits primaires ou secondaires d’oxydation. Dans ce contexte, nous avons conçu et développé un microcalorimètre basé sur le principe de l’analyse thermique différentielle mais plus adaptable dans la mesure où il permet l’analyse de plusieurs échantillons simultanément dans des coupelles d’analyse de dimensions variables (variation du rapport surface/volume en relation avec les phénomène de diffusion de l’oxygène). Pour le développement du microcalorimètre, les thermopiles sont utilisées dans la configuration adiabatique. Le système de mesure des flux est stable et possède une sensibilité élevée. La validation de la méthode est réalisée par effet Joule et par comparaison des points de fusion de paraffines en calorimétrie différentielle classique. La modélisation des réactions d’oxydation est réalisée afin de mettre en évidence l’influence de l’oxygène sur les cinétiques. Pour une huile riche en acides gras polyinsaturés (huile de cameline), l’enthalpie de la réaction d’oxydation (en début de cinétique) obtenue en condition isotherme (100°C) est corrélée avec la mesure des diènes conjugués (produits primaires d’oxydation). Dans l’ensemble, le microcalorimètre développé est suffisamment sensible et fiable pour mesurer les enthalpies de réactions d’oxydation des lipides des huiles alimentaires
Lipid oxidation results of many reactions generating numerous oxidation products that are worth characterizing in fats and oils. Among the analysis methods available, differential scanning calorimetry, based on the differential measurement of heat flux dissipated during the oxidation reactions, is convenient because it avoids the use of organic solvents. In this context, we have conceived and developed a microcalorimeter that allows the analysis of up to 5 samples simultaneously, in containers of variable sizes (allowing to vary the surface/volume ratio). For the conception of the microcalorimeter, the thermopiles are used in adiabatic configuration. The system is very stable and allowed flux measurement with a high sensitivity. The validation of the method is performed by Joule effect and by comparison of melting points of paraffins with classical differential scanning calorimetry. The modelization of the oxidation reaction is performed to point out the influence of oxygen on the kinetics. For a polyunsaturated oil (cameline oil), the enthalpy values obtained, at the beginning of the oxidation process, under isothermal condition (100°C) are correlated with the diene conjugated hydroperoxide amount. On the whole, the developed device provided an adaptable, sensitive, solvent-free and low cost method for the measurement of lipid oxidation, particularly suitable for the fast screening of a large set of samples

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Al-Sayed, Mahmoud Kassem. "Extraction, fractionnement et caractérisation des lipides polyinsaturés d'oeufs de la truite arc-en-ciel (Oncorhynchus mykiss)." Thesis, Vandoeuvre-les-Nancy, INPL, 2007. http://www.theses.fr/2007INPL087N/document.

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Parmi les œufs de poisson, qui sont une ressource aquatique nutritionnelle intéressante, ceux de la truite arc-en-ciel (Oncorhynchus mykiss) contiennent une quantité élevée de protéines et une huile riche en acides gras polyinsaturés (AGPI), avec une proportion très importante de phospholipides. Cependant, l’œuf de poisson présente une capacité élevée d’auto-protection contre les contraintes extérieures, qui limite la destructuration de son réseau protéique par attaque enzymatique. Ainsi, le degré d’hydrolyse des œufs de la truite l’Alcalase®, la Neutrase® et la Protamex® varie entre 3 et 7 %, ce qui est très faible (20 % dans la majorité des protéines animales). L’extraction des lipides après protéolyse partielle est incomplète, probablement en raison d’interactions fortes avec les protéines faiblement hydrolysées. Ils contiennent une teneur élevée en phospholipides (53 % des lipides totaux) et les acides gras polyinsaturés entrent pour 42 % des acides gras totaux. Les AGPI, notamment le DHA, sont situés préférentiellement en position sn-2 sur la molécule de glycérol ce qui est particulièrement intéressant du point de vue nutritionnel. La stabilité à l’oxydation de l’huile a été étudiée par diverses méthodes, dont la spectrométrie infrarouge à transformée de Fourier. Cette méthode s’est avérée extrêmement intéressante pour une analyse structurale de la dégradation de l’huile en cours d’oxydation. Il peut être conclu que les lipides tirés des œufs de la truite arc-en-ciel ou de poisson en général, ont un réel avenir en matière de complément alimentaire ou nutraceutique, à condition de lever l’obstacle de l’hydrolyse enzymatique des protéines du chorion et du vitellus
Fish eggs, especially those of the rainbow trout (Oncorhynchus mykiss) in the present study, are an interesting nutritional aquatic source. They contain proteins of high value, as well as an oil rich in polyunsaturated fatty acids (PUFA) with a large percentage of phospholipids. However, they exhibit a high auto-protection capacity against environmental constraints and thus, the degree of hydrolysis of rainbow trout eggs by Alcalase®, Neutrase® and Protamex® proteases varied solely within 3-7 %. This value was low compared with the 20 % obtained in most animal proteins. The phospholipid content was high (53 % of total lipids) and PUFA accounted for 42 % of total fatty acids. Among PUFA, DHA was found preferably at the sn-2 position of the glycerol backbone, which is of special interest about nutritional properties. The oil release by enzymatic hydrolysis was found limited compared with chemical methods, probably because of the strong interactions engaged with the incomplete destructured protein network. The oxidative stability of the oil was studied through several methods in which the infrared Fourier transform appeared as the best tool for structural analysis along the oxidation process. As a conclusion, lipids from fish eggs, especially from rainbow trout, could be a nutritional breakthrough, as far the enzymatic hydrolysis of the vitellus and of the chorion proteins is achieved

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Pernin, Aurélia. "Action antioxydante et antimicrobienne de composés phénoliques dans des milieux modèles et des émulsions riches en lipides insaturés." Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLA033/document.

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Les composés phénoliques pourraient être de bons candidats pour assurer la qualité et la sécurité des produits périssables tels que les aliments prêts-à-consommer. Très répandus dans les plantes et les co-produits agro-industriels, ils peuvent limiter l’oxydation de lipides insaturés d’intérêt nutritionnel (omega-3, dont DHA et EPA) et le développement de bactéries pathogènes alimentaires telles que Listeria monocytogenes.L'objectif de cette thèse est d'évaluer la double activité antioxydante et antimicrobienne de ces composés phénoliques dans des milieux alimentaires complexes et de mieux comprendre les mécanismes d'action associés.L’étude en milieux modèles a tout d’abord permis de mettre en évidence des relations structure-activités et de décrypter certains mécanismes d’action mettant en jeu des paramètres tels que le nombre et l’environnement chimique des groupements phénoliques, le logP, les formes dissociées / non dissociées des acides phénoliques. Les performances de trois composés sélectionnés (eugénol, acide férulique et α-tocophérol) ont ensuite été évaluées dans des milieux alimentaires complexes plus réalistes : des émulsions h/e composées d'huile de poisson, d’une phase aqueuse et de protéines de lactosérum ou Tween 80 en tant qu'émulsifiant. L’acide férulique ne présente aucune activité antioxydante mais peut inhiber le développement de L. monocytogenes. En revanche, l’eugénol et l’α-tocophérol sont de bons antioxydants dans les émulsions à base de protéines de lactosérum alors qu’ils n’y sont pas antimicrobiens. Quelques mécanismes d’action sont proposés pour expliquer ces comportements
Phenolic compounds appear to be good candidates for ensuring the quality and safety of several perishable products like ready-to-eat food. Widely found in plants and byproducts from agro-industries, they offer a potential solution to limit the oxidation of omega-3 polyunsaturated fatty acids (e.g. DHA and EPA) and the growth of foodborne pathogens such as Listeria monocytogenes.The aim of this PhD is to evaluate dual antioxidant and antimicrobial activity in complex food media and to better understand the associated mechanisms of action.First experiments carried out with a series of phenolic compounds in simple model media confirmed this dual efficiency.Interesting structure/activity relationships were highlighted and some mechanisms of action were decrypted, involving parameters like number and chemical environment of phenolic groups, logP, dissociated/undissociated forms of phenolic acids. The performances of three selected phenolic compounds, i.e. eugenol, ferulic acid and α-tocopherol (added alone or as a mixture), were evaluated in more realistic complex food media: o/w emulsions composed of fish oil, aqueous phase and whey proteins or Tween 80 as emulsifiers. Ferulic acid shows no antioxidant activity but can inhibit the development of L. monocytogenes. In contrast, eugenol and α-tocopherol are good antioxidants but not antimicrobials in emulsions formulated with whey proteins. Mechanisms of action are proposed to explain these behaviors

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Socrier, Larissa. "Influence de la localisation d’antioxydants sur la peroxydation des lipides membranaires : étude du mode d’action de dérivés PBN et de composés phénoliques." Thesis, Compiègne, 2017. http://www.theses.fr/2017COMP2382/document.

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Les espèces réactives de l’oxygène (EROs) sont essentielles à la survie des cellules car elles interviennent dans divers processus physiologiques comme la défense immunitaire ou encore la régulation de voies de signalisation cellulaires. Cependant, un excès d’EROs peut créer un déséquilibre de la balance EROs/antioxydants appelé « stress oxydant ». Le stress oxydant étant impliqué dans l’étiologie de plus de 200 pathologies, l’action des antioxydants est cruciale pour limiter les effets délétères des EROs. Les antioxydants utilisés par les cellules peuvent être de nature chimique. Parmi ceux-ci, l’α-phenyl-N-tert-butyl nitrone (PBN) est particulièrement efficace en milieu biologique pour piéger les radicaux. Cependant, comme cette molécule présente le désavantage majeur de mal cibler les membranes, des nitrones amphiphiles dérivées de la PBN ont été synthétisées. Le premier chapitre décrit l’étude des interactions de nitrones dérivées du cholestérol avec les lipides membranaires. Ces travaux ont souligné l’influence du groupement polaire sur la nature des interactions avec les lipides membranaires. Aussi, l’étude des propriétés antioxydantes a permis de mettre en évidence l’importance de la localisation membranaire et l’influence de l’orientation du groupement PBN sur l’activité protectrice des dérivés. Le second chapitre décrit les résultats des expériences menées avec une deuxième série de dérivés amphiphiles, présentant la particularité d’avoir une chaîne perfluorée comme groupement hydrophobe. Bien que la localisation membranaire de ces dérivés soit nécessaire pour obtenir un effet protecteur significatif, la nature de l’antioxydant semble être ici le paramètre le plus important. Enfin, la combinaison d’antioxydants de nature différente sur une même molécule semble être une stratégie prometteuse pour améliorer l’efficacité antioxydante et créer un effet de synergie. En outre, pour se défendre, les cellules utilisent aussi des antioxydants issus de l’alimentation, en particulier des fruits et légumes. Parmi ces derniers, les composés phénoliques sont reconnus pour leurs effets bénéfiques sur la santé. Les flavonoïdes, les acides phénoliques, les stilbènes et les lignanes constituent les 4 classes principales de composés phénoliques. Les lignanes sont particulièrement présents dans les graines de lin (Linum usitatissimum). Le lin est la plante qui contient le plus de secoisolaricirésinol diglucoside. Afin de mieux comprendre leur fonctionnement et leurs interactions avec les lipides membranaires, plusieurs molécules appartenant à cette classe de composés ainsi que des acides hydroxycinnamiques ont été purifiées à partir du lin. Le troisième chapitre décrit les résultats des expériences menées avec les composés phénoliques extraits du lin. De manière générale, les composés testés se sont avérés efficaces pour protéger les lipides membranaires de l’oxydation. L’étude de leurs interactions avec les lipides membranaires a permis de montrer que le mode d’action des lignanes, qui pénètrent les membranes, est plus efficace que celui des acides hydroxycinnamiques
Reactive oxygen species (ROS) are essential in living cells as they intervene in several physiological processes like the immune system and signaling pathways. However, an excess of the production of ROS can alter the equilibrium with antioxidants. This imbalance is called oxidative stress. As oxidative stress has been reported to be implicated in more than 200 diseases, the action of antioxidants to limit the deleterious effects of ROS is crucial. The antioxidants used by the cells can be chemical. Among them, α-phenyl-N-tert-butyl nitrone (PBN) is widely used in biological systems to neutralize ROS. Because this molecule possesses a poor ability to target membranes, our collaborators synthesized amphiphilic nitrones bearing a PBN moiety. The first chapter describes the interactions of cholesterol derived PBN derivatives with the membrane. Results underlined the influence of the polar moiety on the nature of their interactions with membrane lipids. In addition, the evaluation of the antioxidant properties revealed the importance of the membrane localization of the nitrone moiety on the protective activity of the derivatives. The second chapter deals with a second set of amphiphilic nitrones that have the particularity of bearing a perfluorinated chain that constitutes the hydrophobic moiety. We noticed the membrane localization is important for the antioxidant efficiency; however the nature of the antioxidant moiety remains the most important parameter in this case. Finally, the strategy of grafting two different antioxidants on the same carrier seems to be promising to enhance the protective effect and create a synergistic antioxidant effect. However, cells also use natural antioxidants to defend themselves. These antioxidants come from food, especially from vegetables and fruits. Among them, phenolic compounds are known for their beneficial effects on health. Flavonoïds, phenolic acids, stilbenes and lignans constitute the 4 main classes of phenolic compounds. Lignans are particularly present in flaxseed (Linum usitatissimum). Flaxseed is the plant that possesses the highest quantity of secoisolariciresinol diglucoside. In order to understand their mechanisms of action and their interactions with membranes, lignans as well as hydroxycinnamic acids were purified from flaxseed. The third chapter describes the results obtained on model membranes. Generally speaking, both classes of compounds are efficient against lipid oxidation. Studying their interactions with membrane lipids allowed us to show that the mechanism of lignans, that penetrate membranes, is more efficient than the mechanism of hydroxycinnamic acids

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Roman, Olesea. "Mesure et prédiction de la réactivité des lipides au cours du chauffage d'huiles végétales à haute température." Phd thesis, AgroParisTech, 2012. http://pastel.archives-ouvertes.fr/pastel-00806186.

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Si les lipides contribuent à la valeur nutritionnelle et sensorielle de nombreux aliments, ils sont particulièrement sensibles aux réactions d'oxydation. Les principaux mécanismes mis en jeu lors de l'oxydation des acides gras insaturés sont relativement bien connus. En revanche, il est aujourd'hui quasiment impossible de prédire l'avancement des réactions et souvent nécessaire de recommencer une nouvelle étude de stabilité oxydative pour tout nouveau couple produit alimentaire / procédé de transformation. L'objectif de la thèse est donc de construire un modèle mécanistique couplé à un modèle de transfert de l'oxygène dans le but de prédire l'avancement des réactions d'oxydation dans un milieu lipidique continu et dans des conditions expérimentales définies et contrôlées (température, oxygénation, composition en acides gras, composition en antioxydants). Pour cela, un schéma réactionnel visant à détailler l'ensemble des réactions impliquées dans le phénomène d'auto-oxydation des lipides a été proposé puis un modèle stoechio-cinétique a été construit à partir des valeurs des paramètres cinétiques issues de la littérature. La réactivité des acides gras insaturés présents dans trois huiles végétales d'usage courant (colza, tournesol, tournesol oléique), purifiées de leurs antioxydants naturels, a été étudiée entre 80 et 180°C, en suivant différents marqueurs d'oxydation (diènes conjugués, hydroperoxydes, aldéhydes, polymères). Comme attendu, les cinétiques d'oxydation se sont avérées dépendantes de la composition des huiles en acides gras, de la température et des conditions d'oxygénation. L'ajout d'antioxydant(s) a confirmé l'effet protecteur de l'α-tocophérol, qui n'a pas été amélioré par un enrichissement en acide chlorogénique, acide phénolique naturellement présent dans les graines de tournesol. Les résultats obtenus ont été utilisés pour valider le modèle développé, dont les prédictions permettent de reproduire les tendances expérimentales. Deux limitations ont été mises en évidence au cours de cette phase de validation dont la première concerne la description fiable et précise du mécanisme d'oxygénation du milieu, qu'il sera nécessaire de mesurer dans une huile à haute température pour valider le modèle d'oxydation. Par ailleurs, compte tenu du nombre important de réactions prises en compte, il sera indispensable de disposer d'un jeu de données expérimentales plus important, pouvant inclure des intermédiaires radicalaires. Pour cela, les potentialités de la résonance paramagnétique électronique ont été étudiées au cours de ce travail, à la fois pour suivre les radicaux lipidiques et pour accéder à des paramètres cinétiques pour des réactions radicalaires, peu disponibles dans la littérature.

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Du, Zhen-Yu. "Consequences of fat feeding on growth and body lipids in a herbivorous fish (Grass carp, Ctenopharyngodon idella) : mechanisms related to fatty acid oxidation." Dijon, 2005. http://www.theses.fr/2005DIJOS019.

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L'objectif de cette thèse est d'évaluer si des régimes riches en graisse peuvent être donnés en élevage aux poissons herbivores. La carpe d'herbe prise comme modèle présente des capacités limitées à utiliser les lipides, avec, sur le long terme, de l'anorexie, une croissance diminuée et une accumulation de lipides dans plusieurs organes. Les capacités du foie à oxyder les acides gras, via les mitochondries et peroxysomes, sont faibles et associées à une accumulation d'acides gras polyinsaturés (PUFA) dans les liquides corporels. L'ingestion en excès d'huile de poisson aboutit à une peroxydation marquée des acides gras s'accompagnant d'effets délétères. L'activité peroxysomale réduite freine la dégradation des PUFA qui s'accumulent dans les lipides. Le fénofibrate, ligand de PPARα , augmente faiblement l'oxydation peroxysomale et atténue quelques effets négatifs des régimes à forte proportion de PUFA. L'augmentation de l'activité mitochondriale pendant le jeûne ne permet pas d'utiliser davantage les PUFA. Globalement la carpe apparaît être un poisson peu exigeant énergétiquement avec des capacités réduites à utiliser les régimes riches en graisses.

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Ayoub, Pierre. "Molecular dynamics study of pyrene excimer formation and oxidation in lipid bilayer models." Thesis, Strasbourg, 2015. http://www.theses.fr/2015STRAE038/document.

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Nous proposons une nouvelle approche pour déterminer le coefficient de diffusion dans des membranes lipidiques se basant sur la formation d'excimères. Alors que les autres modèles statistiques considèrent le système comme un ensemble de points sur un réseau, nous utilisons un modèle à gros grain afin d'étudier des bicouches lipidiques simulées à l'aide du champs de force Martini. Nous déterminons le taux de réaction dépendant du temps à partir des probabilités de survie obtenues a posteriori à l'aide des trajectoires numeriques des bicouches symétriques de DOPC (1,2-Dioleoyl-sn-glycero-3-phosphocholine) et POPC (1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine) simulées à 283 K et 293 K respectivement. Les dynamiques de collision sont obtenues en distinguant virtuellement les molécules simulées. Les sondes fluorescentes sont supposées semblables aux lipides, et par conséquent, ne modifient pas la dynamique. Nous obtenons une expression générale pour la probabilité de survie en combinant approximation des paires indépendantes et propriétés d'échelle, mais aucune hypothèse n'est faite pour le taux de formation d'excimère. En superposant les intensités d'émission de fluorescence normalisées, déterminées numériquement, aux courbes de titrations expérimentales, nous obtenons deux ensembles de résultats pour le coefficient de diffusion latéral, selon que l'association entre feuillets est autorisée ou pas. Nous utilisons un rayon de capture de 0.5 nm, la distance à partir de laquelle les deux sondes réagissent pour former un excimère. En comparant la dynamique Martini aux expériences de fluorescence, il est possible d'estimer le facteur d'accélération
We propose a novel approach to extract the lateral diffusion coefficient in lipid bilayers using excimer formation. In contrast to previous statistical models that modeled the system as points undergoing jumps from site to site on a lattice, we use coarse-grained molecular dynamics to study lipid bilayers simulated using the Martini force field. We derive time dependent reaction rates from survival probabilities obtained a posteriori from numerically generated trajectories of symmetric DOPC (1,2-Dioleoyl-sn-glycero-3-phosphocholine) and POPC (1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine) bilayers at 283K and 293K respectively. Collision dynamics are determined by virtually relabeling the simulated molecules. The fluorescent probes are assumed to behave like ordinary membrane lipids and therefore the dynamics remain unaffected. We derive a generalized expression for the survival probability combining independent pairs and size scaling assumptions, but no assumption is made regarding the kinetic rate of the excimer formation process. By fitting the numerically determined normalized fluorescence emission intensities to experimental titration curves, we obtain two sets of results for the lateral diffusion coefficients depending whether interleaflet excimer association is allowed or not. We use a capture radius of 0.5 nm, the distance at which the probes react to form excimers. By relating Martini dynamics to real fluorescence experiments, we estimate the numerical Martini acceleration factor. We also study mixtures of oxidized-non oxidized DOPC and POPC bilayers using a hydroperoxidized model of these lipids for different concentrations of the oxidized component (3.1%, 25% and 50%). Using pair correlation functions, we extract structural information on the systems and determine whether the two components are prone to mixing or not. Finally, we calculate the thermodynamic mixing parameters within the framework of the virial expansion

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Garcia, Mendoza Maria del Pilar. "Enrichissement d’huiles végétales par des antioxydants de type phenolique en vue d’applications alimentaires." Thesis, Bordeaux, 2020. http://www.theses.fr/2020BORD0196.

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Les huiles végétales comme les huiles de cameline et tournesol sont des sources d’acides gras polyinsaturés bon pour la santé mais également très sensibles à la dégradation oxydative. Ce travail vise à améliorer la stabilité oxydative d’huiles alimentaires (principalement l’huile de cameline) via l’incorporation de composés phénoliques antioxydants soit comme composé pur (quercétine) soit comme un mélange plus complexe extrait à partir d’un coproduit de la noix. La faible solubilité de la quercétine dans l’huile a été contournée avec succès par le développement d’une voie d’enrichissement sans solvant en présence de phospholipides. Ainsi, la formulation à base de quercétine-phospholipides a permis d’augmenter significativement à la fois la solubilité de la quercétine and la stabilité oxydative de l’huile. Cette stabilité oxydative, mesurée par vieillissement accéléré à chaud, s’est révélée variable selon les concentrations en quercétine et phospholipides. L’hypothèse du rôle central des associations colloïdales dans ces observations a été formulée. Des données sur la solubilité de la quercétine dans différents solvants d’intérêt industriel ont également été générées. Pour les extraits phénoliques à base de tourteau de noix, en plus de l’amélioration de la stabilité oxydative, les paramètres influençant l’extraction ont été identifiés et une modélisation des procédés batch et semi-continu proposée. L’effet protecteur contre l’oxydation de l’huile d’un extrait de noix présentant une haute activité antiradicalaire s’est révélé dose-dépendant et a permis un accroissement significatif de la durée de conservation des huiles enrichies
Vegetable oils like camelina and sunflower oils are sources of healthy polyunsaturated fatty acids that are however highly susceptible to oxidative degradation. This work aimed at enhancing the oxidative stability of edible oils, mostly camelina oil by incorporating phenolics antioxidants, either as a pure component, quercetin, or as a more complex mixture extracted from a walnut by-product. The low solubility of quercetin in oils was successfully circumvented by developing a solvent-free route of enrichment in presence of phospholipids, so that quercetin-phospholipids formulation allowed to significantly increase both quercetin solubility and the oxidative stability of the oils. The enhanced oxidative stability, monitored under accelerated conditions of heating, was found to vary according to quercetin-phospholipid concentrations and ratios, and it was assumed that colloidal associations played a key role in the enhancement. Data of quercetin solubility in various solvents of industrial interest were also provided. For phenolic extract recovered from a walnut press-cake in addition to oxidative stability enhancement, modelling of batch and semi-continuous extractions was performed and influent parameters were identified. The protective effect against lipid oxidation of a walnut extract exhibiting high antiradical activity was dose-dependent and significantly extended the shelf life of enriched oils

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Masoud, Rawand. "Modulating the activity of NADPH oxidase by oxidative stress participants ; lipids and nanoparticles A cell-free system study." Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLS028/document.

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La NADPH oxydase de phagocyte est un complexe enzymatique impliqué dans la défense immunitaire contre les pathogènes. Elle est constituée du flavocytochrome b558 membranaire (Cyt b558), composé de deux sous-unités (gp91phox et p22phox) et de quatre sous-unités cytosolubles, p47phox, p67phox, p40phox, et Rac. Sa fonction est de produire au niveau de la paroi des pathogènes des ions superoxyde (O2•−) qui sont transformés en d'autres espèces réactives de l'oxygène (ROS) qui attaquent les lipides, les protéines et l’ADN environnants. Après activation du phagocyte, les sous-unités cytosoliques subissent des modifications post-traductionnelles et migrent vers la membrane pour constituer le complexe NADPH oxydase activé. Le rôle délétère des ROS dans les maladies est connu depuis longtemps. Le but de ma thèse a été d’étudier l’influence de molécules exogènes qui induisent une augmentation du stress oxydatif, sur l’activité de la NADPH oxydase.Dans ce travail, nous avons étudié le fonctionnement de la NADPH oxydase dans un système in vitro dans lequel l’enzyme était activée par la présence d'acide arachidonique (AA). J’ai étudié l'influence de deux types de molécules: une classe de lipides et des nanoparticules (NPs). Pour simplifier le système, nous avons remplacé l’ensemble des sous-unités cytosoliques par une protéine unique appelé trimère qui correspond à une fusion des trois protéines cytosoliques p47phox, p67phox et Rac. Nous avons montré que le trimère est fonctionnellement comparable aux sous-unités cytosoliques séparées. La vitesse de production de O2•−, sa dépendances en fonction de la concentration en AA et de la température, et sa sensibilité aux radicaux libres étaient comparables lorsque le trimère ou les sous-unités séparées étaient utilisés.J’ai étudié les conséquences de la présence de cholestérol et de ses formes oxydées sur la production de O2•− par la NADPH oxydase. Nos résultats montrent clairement que le cholestérol et l’oxystérols ne sont pas des activateurs efficaces de la NADPH oxydase. L’addition d’une quantité physiologique de cholestérol déclenche une faible production d’ions superoxyde. L’addition de cholestérol à des concentrations du même ordre de grandeur pendant le processus d'assemblage (en présence de AA), a un rôle inhibiteur sur la production d’O2•−. Le cholestérol ajouté agit sur les composantes, cytosoliques et membranaires, conduisant à un assemblage imparfait. En conclusion, le cholestérol déjà présent dans la membrane des neutrophiles est optimale pour le fonctionnement de la NADPH oxydase.Il était intéressant de vérifier l'influence des nanoparticules de dioxyde de titane (TiO2) et de platine (Pt) sur le comportement de la NADPH oxydase sachant que l'internalisation cellulaire de ces NPs a pour effet d’activer les neutrophiles et les macrophages et contribue à une sur-production de ROS. En l’absence d'activateur mais en présence de NPs de TiO2 ou Pt, aucune production de O2•− n’était détectée indiquant que les NPs de TiO2 et Pt sont incapables d'activer le complexe par eux-mêmes aussi bien dans le système acellulaire que dans les neutrophiles. Cependant, une fois la NADPH oxydase activée (par AA), la vitesse de production des O2•− est augmentée jusqu’à 40% de sa valeur en l’absence de NPs de TiO2, cet effet étant fonction de leur concentration. Par contre, les NPs de Pt n’ont aucun effet sur l’activité de la NADPH oxydase aussi bien in vitro que dans les neutrophiles. En conclusion, l'hyperactivation de la NADPH oxydase et l'augmentation subséquente de la production de ROS induites par les NPs de TiO2 pourraient participer au développement du stress oxydatif tandis que l'absence d'effet Pt-NPs suggère qu'ils ne provoquent pas de sur-inflammation
NADPH oxidase from phagocytes is a multi-subunit enzyme complex involved in the innate defense of organisms against pathogens. It is composed of the membrane-bound flavocytochrome b558 (Cyt b558), comprising two subunits (gp91phox, and p22phox) and four cytosolic components, p47phox, p67phox, p40phox, and Rac. Its function is to produce in the vicinity of the pathogen, superoxide ions that are transformed subsequently into other reactive oxygen species (ROS) and will damage lipids, proteins and DNA. Upon phagocyte activation, the cytosolic subunits undergo posttranslational modifications and migrate to the membrane bound Cyt b558 to constitute the activated NADPH oxidase complex. The damaging role of ROS in cardiovascular diseases has been known for some decades. The aim of my thesis was to study the influence on NADPH oxidase activity, of molecules coming from food and industrial products and known to be involved in increase of oxidative stress.In this work, we studied the NADPH oxidase functioning in an in vitro system in which the components of the enzyme are mixed and activated by the introduction of an amphiphile the arachidonic acid (AA). During my PhD, I have studied the influence of two types of oxidative stress participants: lipids and nanoparticles (NPs). For simplicity, we have replaced the cytosolic subunits by a single protein called trimera, which is a fused construction of three cytosolic proteins p47phox, p67phox and Rac. We have shown that trimera is functionally comparable with the separated cytosolic subunits. The rates of production of O2•−, the dependences of the activity in function of AA concentration and temperature, the presence of two states in the activation process and the sensitivity of NADPH oxidase to free radicals were comparable when either trimera or separated subunits were used.I investigated the consequences of the addition of cholesterol on NADPH oxidase, on the production of ROS. Our results clearly show that cholesterol and oxysterols are not efficient activators of NADPH oxidase. Concentrations of cholesterol similar to what found in neutrophiles trigger a low superoxide production. Addition of cholesterol during the assembly process (in presence of AA) at similar or higher concentrations, has an inhibitory effect on the production of O2•−. Added cholesterol acts on both cytosolic and membrane components, leading to imperfect assembly and decreasing the affinity of cytosolic subunits to the membrane ones. In conclusion, we showed that the cholesterol already present in the phagocyte membrane is optimal for the function NADPH oxidase.It was of interest to check the influence of titanium dioxide (TiO2) and platinum (Pt) NPs on NADPH oxidase especially that cellular internalization of NPs was shown to activate neutrophils and contribute to O2•− overproduction via NADPH oxidase. In the absence of activators and presence of TiO2 or Pt NPs, no production of O2•− could be detected in in vitro system as well as in neutrophils indicating that TiO2 and Pt NPs were unable to activate by themselves the complex. However once the NADPH oxidase was activated by AA, TiO2 NPs increased the rate of O2•− production by up to 40%, this effect being dependent on their concentration. Differently, Pt NPs had no effect both on in vitro system as well as on neutrophils. In conclusion, the hyper-activation of NADPH oxidase and the subsequent increase in ROS production by TiO2 NPs could participate to oxidative stress development while the absence of Pt-NPs effect suggest that they do not induce inflammation status via this complex

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Kaleem, Muhammad. "Effets des produits d'oxydation de l'acide linoléique sur sa biohydrogénation ruminale." Thesis, Toulouse, INPT, 2013. http://www.theses.fr/2013INPT0042/document.

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La biohydrogénation (BH) ruminale des acides gras polyinsaturés (AGPI) est à l’origine de la production d’AG trans pouvant se retrouver dans les productions de ruminants, dont le lait. Parmi ceux-ci, les isomères t11 auraient des effets bénéfiques pour la santé des consommateurs alors que les isomères t10 sont potentiellement défavorables. En élevage, l’apport de graines oléagineuses dans la ration des vaches permet d’augmenter la teneur du lait en ces acides gras. Or ces graines sont souvent distribuées chauffées pour améliorer leur valeur nutritionnelle. Expérimentalement, les effets des graines chauffées sur les teneurs en isomères t11 dans le rumen ou le lait sont variables, mais généralement elles permettent une augmentation des isomères t11 et une protection des AGPI. Au contraire, des huiles très oxydées par chauffage diminuent fortement les isomères t11 et augmentent parfois les isomères t10. Les produits d’oxydation des lipides générés pendant le chauffage des graines ou des huiles pourraient être incriminés. Les objectifs de la présente étude étaient d’explorer les éventuels effets des produits d’oxydation du c9,c12-C18:2 sur sa BH ruminale. In vitro, la protection des AGPI dans des graines de soja chauffées a été liée aux aldéhydes et en particulier à l’hexanal. L’augmentation des isomères t11 a été observée avec un aldéhyde long et insaturé, le t2,t4-décadiénal, suite à une inhibition de la dernière étape de la BH. Cet effet était concomitant à une modification marquée de la communauté bactérienne du rumen induite par cet aldéhyde. Les hydroperoxydes issus du c9,c12-C18:2 sont le 13HPOD et le 9HPOD. L’augmentation des isomères t10 a systématiquement été reliée au 13HPOD dans nos différentes expérimentations. Aucun mécanisme d’action n’a pu être formellement démontré mais l’effet du 13HPOD s’exercerait plutôt sur le microbiote, car il ne module pas l’activité de la Δ9-isomérase. Quant à la diminution des isomères t11 observée avec les huiles chauffées, elle n’a pas pu être expliquée. Elle pourrait également être liée, au moins partiellement, aux 13HPOD et 9HPOD, capables d’inhiber la Δ12-isomérase. Des modifications des fermentations ruminales, sans altération mesurable de l’abondance, de la diversité ou de la structure de la communauté bactérienne, suggèrent aussi un effet des AGPI chauffés sur l’activité des bactéries
Ruminal biohydrogenation (BH) of polyunsaturated fatty acids (PUFA) produces some trans FA which can be found in ruminant products. Among them, t11 isomers would be beneficial for human health while t10 isomers are potentially deleterious. In farms, addition of oilseeds to the diet of dairy cows increases these fatty acids in milk. Oilseeds are often heated before incorporation to cow’s diets, to enhance their nutritional value. Experiments investigating effects on t11 isomers content in rumen and milk of cows receiving heated oilseeds provided variable results, but they usually increased t11 isomers and protected PUFA from BH. On the contrary, highly oxidized oil decrease t11 isomers and sometimes increase t10 isomers. Lipid oxidation products generated during heating of oilseeds and oils could be incriminated. The objectives of the present study were to investigate the effects of c9,c12-C18:2 oxidation products on its BH. Protection of PUFA in heated soybeans was linked to aldehydes, mainly hexanal. An increase of t11 isomers was observed with a long and unsaturated aldehyde, the t2,t4-decadienal, due to an inhibition of the last BH step. This effect was concomitant with a modification of bacterial community by t2,t4-decadienal. Hydroperoxides formed during c9,c12-C18:2 heating are 13HPOD and 9HPOD. The increase of t10 isomers in all of our experimentations was systematically linked with 13HPOD. No definitive explanation about the mechanism of action could be proposed, but 13HPOD would most probably act on microbiote since it had no effect on Δ9-isomerase. Our experiments did not explain the decrease of t11 isomers observed with heated oils, which could, at least in part, be due to 13HPOD and 9HPOD, which were able to inhibit Δ12-isomerase Some modifications of ruminal fermentation without measurable alteration of bacterial community abundance, diversity or structure also suggest an action of heated PUFA on bacterial activity

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MEBARKI, SLIMANE. "Contribution a l'etude de l'utilisation metabolique de divers acides gras par l'adipocyte de rat : effets de l'age et des lipides alimentaires." Paris 7, 1987. http://www.theses.fr/1987PA077225.

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Guzun-Cojocaru, Tatiana. "Peroxydation des lipides émulsionnés et transfert d'ions fer à l'interface huile / eau stabilisée par des protéines de lait : influence des résidus phosphates et de la stabilité du chélate de fer." Thesis, Dijon, 2010. http://www.theses.fr/2010DIJOS012/document.

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Le fer ajouté dans des systèmes complexes tels que les aliments induit divers problèmes comme l'oxydation des lipides ou la précipitation d’autres composés présents dans la matrice. Il s’en suit une diminution de sa biodisponibilité et des défauts de goût. L'utilisation de chélates de fer, comme le bisglycinate de fer ou l’EDTA de fer, constitue une voie intéressante : le fer ainsi protégé n’interagirait pas avec la matrice alimentaire. La stabilité des chélates de fer (bisglycinate de fer et NaFe EDTA), supposés peu réactif pour l’initiation de peroxydation, a été attestée sur des modèles d’émulsions huile dans eau stabilisées par du caséinate de sodium ou de la β lactoglobuline. Dans un second temps, le travail a consisté à vérifier la faible influence de ces complexes sur la nature de l’interface huile/eau (étude de la tension et de la rhéologie interfaciales). La stabilité du bisglycinate de fer en solution aqueuse et en présence de β lactoglobuline a également été évaluée en fonction du pH (pH 2, 3,5 et 6,5) par rayons X. Il a ainsi été montré que la nature des protéines formant l’interface huile/eau et le type de sels de fer jouent un rôle crucial sur la stabilité oxydative des émulsions enrichies en fer. L'affinité des protéines de lait pour les ions fer libres est le premier facteur qui contrôle la peroxydation des matières grasses par l’absence de transfert à l'interface huile/eau. La capacité du complexe bisglycinate à retenir les ions fer et donc à limiter la présence d’ions fer libres (ferriques ou ferreux) apparaît comme le second facteur principal à contrôler. La compétition pour les ions fer entre les groupes fonctionnels des protéines et les contre ions de chélates (glycinate ou EDTA) gouverne ainsi l'état d'oxydation du système dans des conditions acide/base proche de la neutralité. En milieu acide, l'oxydation est principalement gouvernée par l’instabilité du complexe bisglycinate de fer et par conséquent la lente libération fer ionique dans la phase aqueuse. Pour résumer, si le complexe de fer n’est pas déstabilisé et que la protéine à l’interface huile/eau ne présente pas de groupe fonctionnel ayant une forte affinité pour le fer, alors la peroxydation des lipides en émulsion est faible. Dans notre démonstration, si une protéine n’est pas phosphorylée et pour des pH proches de 7, alors l’émulsion ne sera pas peroxydée car le fer ne migre pas à l’interface huile/eau
Iron incorporated into food systems induces oxidation and precipitation. The consequences are a reduced bioavailability and a modification of other food flavor. The iron chelates such as Fe-bisglycinate and Fe-EDTA represent a possibility to avoid side effects, since the iron is protected. The inertety of Fe bisglycinate and NaFe EDTA for lipid peroxidation has been verified in oil-in-water emulsion models stabilized by sodium caseinate or by β lactoglobulin through the following studies: i/ increase of primary and secondary products of oxidation, ii/ change of the properties of the oil/water interface (tension and interfacial rheology), iii/ the stability of the chelate iron (Fe-bisglycinate) in the aqueous phase with β lactoglobulin at different pH (pH 2, 3.5 and 6.5). The oil/water interface stabilized by proteins with phosphate groups has induced peroxidation, which was not observed with proteins containing no phosphate residue. These results demonstrate also that the type of iron salts plays a crucial role in the oxidative stability of emulsions. The ability of the complex to retain iron ion and to avoid “free” ferrous ion is the first important factor to be controlled. The affinity of milk proteins to bind these free iron ions is the second factor that controls the transfer to oil/water interface. To sum up, the competition for iron ions between functional groups of protein and salt counter ions (glycinate, sulfate or EDTA) governs the oxidation state of the system in neutral conditions. In acidic medium, the oxidation is mainly governed by the stability of the complex and the possibility to free iron in bulk

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Musigamart, Natedao. "Study of the role of lipids from maturated coagula from Hevea brasiliensis latex on natural rubber behavior in oxidative conditions." Thesis, Montpellier, SupAgro, 2015. http://www.theses.fr/2015NSAM0004/document.

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Le caoutchouc naturel (CN), un produit dérivé du latex d'Hevea brasiliensis, est connu pour ses propriétés mécaniques supérieures pour certaines à celles de ses concurrents synthétiques. Néanmoins, le haut degré d'insaturation du poly(cis-1,4-isoprene) le rend susceptible à la thermo-oxydation. Heureusement, le CN est doté de composés non-isoprènes dont certains ont des propriétés antioxydantes. Les lipides sont les plus importants non-isoprènes retenus dans le caoutchouc et contiennent des molécules à activité antioxydante en particulier les tocotriènols. Il est connu que durant la maturation de coagula de latex, la composition chimique et les propriétés du caoutchouc obtenu sont altérées, mais les mécanismes complexes de cette altération ne sont pas encore complètement élucidés. Dans cette étude, l'évolution de certaines molécules antioxydantes natives pendant la maturation a été suivie en relation avec certaines propriétés physiques du caoutchouc. Deux expérimentations de maturation ont été mises en œuvre. La première mettait en jeu des conditions non contrôlées de maturation suivies d'un procédé de confection du caoutchouc basé sur celui des feuilles fumées (RSS) ou non (USS). La seconde a été conduite dans un dispositif expérimental dédié permettant le contrôle des facteurs de l'environnement tels que l'humidité relative, la température et la concentration en oxygène. Le procédé de confection du caoutchouc était dans ce cas basé sur celui des caoutchoucs spécifiés techniquement (TSR). L'évolution des échantillons pendant la maturation a été étudiée à différentes échelles : propriétés en masse (P0, P30 et PRI), mésostructure (% gel, Mw and Mn) et composition biochimique (lipides). En parallèle, l'activité antioxydante in vitro des extraits lipidiques correspondants a été mesurée en utilisant une méthode DPPH optimisée. La quantité et la qualité des lipides extraits évoluent pendant la maturation, en particulier en aérobiose. La quantité totale de lipides décroit, avec, en début de maturation, une libération d'acides gras dont la quantité diminue ensuite, avec une disparation des espèces insaturées en premier. La quantité de γ-tocotrienol libres extraits change peu au cours de la maturation alors que sa forme estérifiée montre un enrichissement en acides gras saturés. L'activité antioxydante de l'extrait lipidique mesurée in vitro est corrélée avec la concentration de γ-tocotrienol libre mais pas avec les valeurs de P30 et PRI qui estiment la résistance du caoutchouc à la thermo-oxydation. Cette absence de corrélation pourrait être due à la différence des conditions de mesure in-vitro de celles existantes au sein du matériau caoutchouc. La localisation des antioxydants dans le caoutchouc et en particulier leur possibilité physique d'interagir avec les doubles liaisons du poly(cis-1,4-isoprene) ou avec des espèces oxydantes reste à étudier afin de comprendre ce qui régit la chute de P30 au cours de la maturation. Des lipides non extractibles ou des molécules non-isoprènes plus polaires (protéines, polyphénols, …) pourraient également influencer la résistance du caoutchouc à la thermo-oxydation
Natural rubber (NR), a derived product from H. brasiliensis latex, is known for its high mechanical properties that are, for some, superior to those of its synthetic counterparts. However, the high degree of unsaturation of poly(cis-1,4-isoprene) makes it susceptible to thermo-oxidation. Fortunately, NR is endowed with non-isoprene components of which some have antioxidant properties. Especially, lipids, the main non-isoprene component retained in NR, have been reported to contain antioxidant substances, especially tocotrienols. It is well known that during the maturation of latex coagula, both NR physical properties and chemical composition are altered, but the complex mechanisms of this alteration are still to be elucidated. In the present work, the evolution of some native antioxidant molecules during maturation was followed in relation with some physical properties. Two experimental conditions of maturation were chosen. The first experiment involved uncontrolled conditions based on traditional unsmoked (USS) or ribbed smoked sheet (RSS) processing, while the second was performed in a dedicated maturation device with full control of environmental factors (relative humidity, temperature and oxygen content) followed by a processing based on that of Technically Specified Rubber (TSR). The evolution of samples during maturation was studied at different scales: bulk properties (P0, P30 and PRI), mesostructure (% gel content, Mw and Mn) and biochemical composition (lipids components). In parallel, in vitro antioxidant activity of NR lipid extracts was also investigated using an optimized DPPH method. Lipid quantity and quality evolved during maturation, especially under aerobic conditions. The total amount of lipid extract decreased, with a release of free fatty acids at early stage of maturation followed by a later decrease, unsaturated fatty acids being the first to disappear. The amount of extractable free γ-tocotrienol did not change much during maturation, while its esterified form was enriched in saturated fatty acids. The antioxidant activity measured in vitro correlated well with free γ-tocotrienol concentration but not with the resistance of rubber to thermo-oxidation assessed by P30 or PRI. Indeed, the in vitro conditions of measurement were far from those occurring inside rubber material. The localization of antioxidants in rubber and especially their physical possibility to interact with the double bonds of poly(cis-1,4-isoprene) or with oxidant species should be further investigated to understand what drives the drop of P30 along maturation time. Non extractable lipids or more polar non-isoprene molecular species (proteins, polyphenols, etc…) could also influence the resistance to thermo-oxidation

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Škrabalová, Lada. "Hemoglobin-mediated oxidation of marine liposomes." Master's thesis, Vysoké učení technické v Brně. Fakulta chemická, 2012. http://www.nusl.cz/ntk/nusl-216833.

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Cílem této práce bylo studium mechanismu oxidace lipidů katalyzované hovězím methemoglobinem a zhodnocení účinků různých experimentálních podmínek a antioxidantů (EDTA, askorbová kyselina, kávová kyselina, a-tokoferol, d-tokoferol, astaxanthin a L-askorbyl-6-palmitát) na methemoglobinem zprostředkovanou oxidaci lipidů v modelovém systému liposomů připravených z fosfolipidů. K monitorování oxidace lipidů při pH 5,5 a teplotě 30 °C bylo použito spotřeby kyslíku. Pro zhodnocení antioxidační aktivity v modelovém systému liposomů se ukázaly být důležitými faktory typ prooxidantu a koncentrace prooxidantu a antioxidantu. Dalšími důležitými faktory jsou struktura molekuly antioxidantu, jeho hydrofilita/lipofilita a umístění v systému. Všechny testované antioxidanty ve všech koncentracích (kromě koncentrace 0.1 % astaxanthinu and 0.1 % askorbyl palmitátu) inhibovaly oxidaci vyvolanou methemoglobinem. Účinnost antioxidantu stoupala s jeho zvyšující se koncentrací. Koncentrace 0.1 % astaxanthinu neměla žádný vliv na oxidaci liposomů. Koncentrace 0.1 % askorbyl palmitátu měla prooxidační efekt, který lze vysvětlit prooxidačním působením radikálu askorbylu, který může urychlit štěpení hydroperoxidů. Volné železo uvolněné z methemoglobinu se podílelo jen velmi málo na oxidaci liposomů, zatímco část prooxidační aktivity methemoglobinu byla přisouzena tvorbě singletového kyslíku (methemoglobin jako fotosenzitizátor). Antioxidační aktivita astaxanthinu, askorbyl palmitátu a tokoferolu byla z části přisouzena schopnosti zhášet singletový kyslík. Ovšem hlavním prooxidačním mechanismem methemoglobinu se ukázal být rozklad lipidových hydroperoxidů, tvorba volných radikálů a hypervalentních forem hemoglobinu. EDTA utlumila oxidaci liposomů díky chelataci přechodných kovů obsažených v liposomech a chelataci volného železa přítomného v methemoglobinovém roztoku. Velmi důležitým antioxidačním mechanismem (který vykazují askorbyl palmitát, askorbová a kávová kyselina) se ukázala být redukce hypervalentních forem hemoglobinu. Askorbová kyselina, kávová kyselina, tokoferoly a astaxanthin inhibovaly methemoglobinem zprostředkovanou oxidaci lipidů odstraňováním volných radikálů. Při použití peroxidu vodíku nebyl pozorován žádný vliv na oxidaci liposomů vyvolanou methemoglobinem. Působení vysoké teploty (tepelná denaturace) mírně utlumilo oxidaci. Významná inhibice oxidace byla pozorována u liposomů obsahujících TPP (triphenylphosphin), což značí, že je methemoglobinem vyvolaná oxidace liposomů závislá na přítomnosti již vzniklých lipidových peroxidů. Výsledky této práce přispívají k hlubšímu pochopení prooxidačních a antioxidačních mechanismů a faktorů, které ovlivňují oxidaci liposomálních roztoků, buněčných membrán a emulzí typu olej ve vodě stabilizovaných fosfolipidy.

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Janani, Tahereh. "Herbs as antioxidants in oxidation of marine lipids." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for biologi, 2013. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-23597.

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Marine lipids have beneficial health effects due to the high content of long chain polyunsaturated omega-3-fatty acids (LC-PUFA), especially EPA (eicosapentanoic acid) and DHA (docosahexanoic acid) and they aretherefore of interest to use in products for human consumption.Marine phospholipids are very susceptible to lipid oxidation, due to the high amount of n-3 PUFAs, which cause loss of sensory and nutritional value in foods.In order to prevent the oxidation reactions, it is important to find out more on how different factors and compounds, such as pro- and antioxidants in the food, affect these reactions.The prooxidant activity of 𝐹𝑒3+, 𝐹𝑒2+ and Hemoglobin was tested and 𝐹𝑒3+ was selected as a prooxidant in the studied lipid system, which is the most abundant prooxidant in the emulsified system.The aim of this study was to evaluate the antioxidant activity in 12 selected herbs using three different antioxidant capacity assays: Folin-Ciocalteu (FC), 2,2-diphenyl-1-1-picrylhydrazyl (DPPH), 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS). Based on the results of these assays, antioxidant capacity of the most prominent antioxidants from the assays was determined in a liposome model system with marine phospholipids, where the rate of oxygen uptake was used to measure rate of lipid oxidation. Propyl gallate, a representative of a synthetic food antioxidant, was used as a reference due to its known high antioxidant capacity. This study also showed inhibitory effects of propyl gallate on iron catalyzed oxidation of marine phospholipids in liposomes.Antioxidant activity of the 5 selected herbs was measured by means of inhibition percentage of oxygen uptake in the liposome (phospholipid dispersion in buffer). With respect to the obtained results, Sage, Rosemary and Dill exhibited antioxidative effects, while Lemon balm and basil were found to be prooxidants at the tested concentrations.The comparison of the results obtained by the assays and by the study of the antioxidant effects in the liposome model system with catalyzed oxidation indicates that the AOC of the compounds could be dependent on the oxidation system and the applied prooxidants.

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Sparks, Darrell Lynn. "Oxidation of lipids in a supercritical-fluid medium." Diss., Mississippi State : Mississippi State University, 2008. http://library.msstate.edu/etd/show.asp?etd=etd-03252008-162949.

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Reid, Vanessa Claire. "Macrophage toxicity of lipid oxidation." Thesis, University of Cambridge, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.308384.

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Nogueira, Marina Sayuri. "Avaliação do consumo de lipídios oxidados na indução do estresse oxidativo associado à aterosclerose em modelo animal." Universidade de São Paulo, 2015. http://www.teses.usp.br/teses/disponiveis/9/9132/tde-22122015-091244/.

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Estudos envolvendo cultura de células, animais e humanos tem sido extensivamente aplicados no monitoramento da aterosclerose, visando seu controle ou mesmo reversão. Entre os modelos animais atualmente utilizados, tem-se observado uma resposta adequada à indução de dislipidemia e inflamação, porém elevada resistência à indução de estresse oxidativo. Uma alternativa para superar essa limitação seria a ingestão de dietas contendo ácidos graxos oxidados. Entretanto, os estudos que investigaram o efeito do consumo de peróxidos e produtos secundários da oxidação lipídica na progressão da aterosclerose têm mostrado resultados inconclusivos. Portanto, o objetivo deste estudo foi de alterar um modelo animal de referência para desenvolvimento de aterosclerose, visando elevar a variação de biomarcadores de estresse oxidativo, através do consumo crônico de ácidos graxos poli-insaturados parcialmente oxidados, em concentrações naturalmente presentes na dieta humana. Camundongos \"knockout\" para receptores LDL (C57BL/6), foram divididos em 4 grupos experimentais. Todos os grupos receberam uma dieta hiperlipídica modificada composta por 30% de lipídios durante 90 dias. Três níveis de oxidação foram induzidos no óleo de linhaça, representando neste estudo um nível baixo, moderado e elevado, caracterizados por uma concentração de hidroperóxidos de 2,47 ± 0,02 (LOW), 3,87 ± 0,04 (MED) e 4,69 ± 0,04 meq LOOH/Kg (HIGH), respectivamente. O grupo que recebeu a ração LOW pode ser considerado o grupo controle negativo, pois o óleo utilizado na formulação de sua ração não sofreu o processo de oxidação. O quarto grupo recebeu a dieta LOW, além da indução de diabetes mellitus do tipo 1 através de estreptozotocina no inicio do estudo sendo esse o grupo controle positivo (CONT+). O óleo de linhaça pré-oxidado utilizado no preparo das rações foi mantido a 4ºC. A peletização das rações alterou a concentração dos marcadores primários e secundários, porém de forma proporcional, mantendo assim a diferença entre os três níveis. O grupo CONT+ apresentou menor ganho de peso que os demais. Nenhuma diferença foi observada entre os grupos em relação ao perfil lipoproteico. Os grupos CONT+ e HIGH apresentaram menor concentração de ácidos graxos no fígado, em especial de ácidos graxos poli-insaturados. Igualmente, ambos os grupos CONT+ e HIGH apresentaram maior concentração de MDA hepático que os grupos MED e LOW, sugerindo um aumento do estresse oxidativo decorrente da ingestão de ácidos graxos poli-insaturados parcialmente oxidados. O grupo HIGH também apresentou um aumento da espessura da parede vascular e do tamanho do lúmen da aorta. Este perfil de resultados sugere que a ingestão crônica de ácidos graxos poli-insaturados parcialmente oxidados contribui para o aumento do estresse oxidativo em camundongos LDLr (-/-), promovendo um aumento na concentração de MDA hepático similar àquele obtido com modelos que utilizam formas mais agressivas de indução. Considerando-se a tendência de aumento no consumo de ácidos graxos poli-insaturados Omega 3, os resultados deste estudo realizados com o óleo de linhaça apontam para a necessidade controle da estabilidade oxidativa desses óleos durante seu processamento e armazenamento, visto que níveis moderados de oxidação já poderiam apresentar potencial aterogênico.
Studies involving cell culture, animals and humans have been extensively applied in the monitoring of atherosclerosis, aiming its control or even this reversal. Among the animal models, it has been observed an appropriate response to the induction of dyslipidemia and inflammation, but a high resistance to oxidative stress induction. An alternative to overcome this limitation would be by the intake of diets containing oxidized fatty acids. However, studies that investigated the effect of consumption of peroxides and secondary products of lipid oxidation in the progression of atherosclerosis have shown controversial results. Therefore, the aim of this study was to alter an animal model for the development of atherosclerosis, aiming to raise the variation in biomarkers of oxidative stress through chronic consumption of polyunsaturated fatty acids partially oxidized under concentrations naturally present in the human diet. LDL receptor \"knockout\" mice (C57BL / 6) were divided into 4 experimental groups. All groups received a modified fat diet containing 30% fat for 90 days. Three levels of oxidation were induced in flaxseed oil, representing low, moderate and high levels, characterized by a hydroperoxide concentration of 2.47 ± 0.02 (LOW), 3.87 ± 0.04 (MED) and 4.69 ± 0.04 LOOHs meq / kg (HIGH), respectively. The fourth group received the LOW diet, beyond diabetes mellitus type 1 through induction by streptozotocin at baseline (CONT +). The pre-oxidized flaxseed oil used to prepare the diets was maintained at 4 °C. The pelletization changed the concentration of primary and secondary products, but proportionally, maintaining the difference between the three levels. CONT + group showed less weight gain than the others. No differences were observed between groups in relation to the lipoprotein profile. The CONT + and HIGH groups showed lower concentration of fatty acids in the liver, especially polyunsaturated fatty acids. In addition both CONT+ and HIGH groups showed higher concentrations MDA in the liver than MED and LOW groups, suggesting increased oxidative stress resulting from the intake of polyunsaturated fatty acids partially oxidized. The HIGH group also showed an increase in the thickness of the vascular wall and the size of the aorta lumen. This profile suggests that the chronic ingestion of partially oxidized polyunsaturated fatty acids contributes to increase oxidative stress in mice LDLr (-/-) , similar to that obtained with models using more aggressive forms of induction. Considering the trend of increased consumption of polyunsaturated fatty acids Omega 3, the results of this study conducted with flaxseed oil highlight to the need of controlling the oxidative stability of these oils during processing and storage, since moderate oxidation levels already present atherogenic potential.

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Ma, Yanshan. "Factors Influencing the Oxidation of Lipoproteins and Plasma Lipids." Digital Commons @ East Tennessee State University, 1994. https://dc.etsu.edu/etd/2724.

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The hypothesis that antioxidant vitamins (ascorbate and tocopherols) along with urate protect blood plasma lipids from oxidation was tested. Dietary fat is also an important factor influencing plasma lipid peroxidation. The purpose of this study was to investigate the role of plasma antioxidants and dietary fat on low density lipoprotein (LDL) and plasma lipid oxidation. In the first part of this study, we compared the ability of urate and ascorbate to protect human LDL from in vitro oxidation. LDL oxidation was initiated by 15 mM of a water soluble azo-initiator in the presence or absence of ascorbate or urate. The rate of lipid hydroperoxide (LOOH) formation was increased after the LDL tocopherols were totally consumed, i.e., after the lag phase. Urate (50 $\mu$M) was more effective than ascorbate (50 $\mu$M) in extending the lag phase. Moreover, urate was consumed more slowly than ascorbate under identical oxidation conditions. The combination af 25 $\mu$M ascorbate and 25 $\mu$M urate was more effective in extending the lag phase than ascorbate alone but less effective than urate alone. An empirical mathematical model was developed to describe the oxidation kinetics of LDL tocopherols. In the second part of this study, we studied the role of dietary fat and dietary $\alpha$-tocopherol ($\alpha$-toc) levels on rat plasma oxidation. The fatty acid composition of plasma was found to be modulated by the type of dietary fat. Neither dietary fat nor $\alpha$-toc influenced the plasma levels of water soluble antioxidants (ascorbate, urate and sulfhydryl content). Rat plasma was oxidized either by a water soluble azo-initiator (25 mM) or a lipid soluble azo-initiator (10 mM). In both cases, the rate of LOOH formation in plasma from rats fed butter oil diets was markedly suppressed compared to the plasma from rats fed corn oil diets. When oxidation was initiated by a lipid soluble azo-initiator, plasma from rats fed $\alpha$-toc supplemented diets showed higher LOOH levels than plasma from rats fed $\alpha$-toc deficient diets. Surprisingly, when oxidation was initiated by water soluble azo-initiator, tocopherol appeared to act as a pro-oxidant. The results suggest that urate may be more significant than ascorbate in delaying the consumption of tocopherols in human LDL and that low dietary PUFAs levels are more important in preventing the in vitro oxidation of plasma lipids than high dietary levels of $\alpha$-tocopherol.

20

Anderson, Richard Anthony. "Lipids, oxidative stress and endothelial function." Thesis, King's College London (University of London), 2004. https://kclpure.kcl.ac.uk/portal/en/theses/lipids-oxidative-stress-and-endothelial-function(ca261d48-d716-4156-9a38-dbb72775b36a).html.

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21

Fogaça, Fabíola Helena dos Santos [UNESP]. "Efeito do tocoferol no desempenho e na estabilidade lipidica da tilápia nilotica (Oreochromis niloticus)." Universidade Estadual Paulista (UNESP), 2006. http://hdl.handle.net/11449/86711.

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Made available in DSpace on 2014-06-11T19:22:23Z (GMT). No. of bitstreams: 0 Previous issue date: 2006-01-27Bitstream added on 2014-06-13T19:48:40Z : No. of bitstreams: 1 fogaca_fhs_me_jabo.pdf: 596326 bytes, checksum: 558f30e4e45f55982f56059d2fab70b4 (MD5)
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
Universidade Estadual Paulista (UNESP)
A vitamina E é usada nas dietas com a finalidade de melhorar o crescimento, a resistência ao estresse e a doenças, assim como a sobrevivência de peixes. Também pode ser eficiente na conservação do pescado durante o processamento e estocagem, inibindo a degradação dos lipídios pela oxidação. O presente trabalho avaliou os efeitos antioxidantes da vitamina E in vivo e in vitro na qualidade final dos hambúrgueres produzidos com filés de tilápias congelados durante 0, 30, 60 e 90 dias. Foi utilizado um delineamento inteiramente casualizado, com seis tratamentos, em esquema fatorial 3x2, caracterizado pela suplementação de dois níveis de vitamina E nas dietas (100 e 200 mg / kg de ração) e o grupo controle (zero mg/kg de ração) e adição ou não de 100 ppm de vitamina E aos hambúrgueres, com quatro repetições. Os peixes, com peso médio inicial de 184,23 + 1,68g foram alimentados com as dietas experimentais durante 63 dias. Após esse período, foram abatidos e os filés processados em hambúrgueres. Foram avaliados os parâmetros de desempenho, composição centesimal e a oxidação lipídica, determinada pelas substâncias reativas ao ácido tiobarbitúrico (SRATB). Os resultados mostraram que não houve diferença significativa para as variáveis de ganho de peso, conversão alimentar e crescimento específico entre os tratamentos. A composição química variou dentro dos valores encontrados para pescados. O aumento do nível de vitamina E promoveu redução nos valores de SRATB das amostras em todos os intervalos de tempo, e que a adição in vivo da vitamina E protegeu os hambúrgueres da oxidação lipídica de forma mais eficiente do que a adição in vitro, sendo que a interação entre ambas resultou em maior redução nas taxas de oxidação.
Vitamin E is used in diets with the aim of enhancing growth, resistance to stress and pathology, and also fish survival. It can be efficient in fish conservation during processing and frozen storage, inhibiting lipid degradation from oxidation. The present work evaluated the antioxidant effects of vitamin E utilization in vivo and in vitro in the final quality of hamburgers made from tilapia filets during frozen storage over 3 months. A randomized design, in a 3x2 factorial scheme was utilized, which correspond to the two levels of diet vitamin E (100 and 200 mg / kg diet) and the control group (zero mg/kg diet) and addition or not of 100 ppm of vitamin E to the hamburgers, with four repetitions. The fishes, with initial weight 184.23 + 1.68 g, were fed the experimental diets for 63 days, after which they were killed and processed into hamburgers. The performance parameters analyzed were centesimal composition and lipid oxidation, determined by the thiobarbituric acid reactive substances (TBARS). The results showed no significant difference between treatments for weight gain, food conversion or specific growth. The chemical composition varied within the values found for fish. Increased vitamin E levels promoted reduction of TBARS values over all time intervals. This means values suggested that the addition in vivo of tocopherol protected the hamburgers from lipid oxidation more efficiently when compared to in vitro addition, but the interaction between both resulted in higher reduction in rate of oxidation.

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Ng, Su Chuen. "Effects of accelerated aging on lipid oxidation in quinoa (Chenopodium quinoa)." Online version, 2003. http://www.uwstout.edu/lib/thesis/2003/2003ngs.pdf.

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Telles, Scott Gerard. "Change in zinc permeability of lipid bilayers as a function of fluidity and oxidation." Virtual Press, 1997. http://liblink.bsu.edu/uhtbin/catkey/1061869.

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The main goal in my project was find out if the rate of zinc crossing the bilayer was either due to the fluidity of vesicles or the level of oxidation of the vesicles.To measure the oxidation a simple procedure called the TBA Test was used to measure each PC tested. The fluidity measurement was a calculation using the temperature the vesicles went from gel to liquid crystalline phase and the experimental temperature.Measuring the rate at which zinc crossed the bilayer was done using spectral changes that occur as zinc binds with APIII, a metal chelator entrapped inside the vesicles. To measure these rates we used k', the rate constant at which zinc is crossing the bilayer at a certain concentration and k, the second order diffusion rate constant which is the slope of k' vs. [Zn].The rates at which zinc was crossing the bilayer for each PC was then compared to the fluidity and oxidation levels for each PC. There was no direct correlation between the rates and fluidity but there was a good linear correlation between the rates and oxidation.So it seemed as if oxidation was the main reason zinc was crossing the bilayer so we wanted to see if our measurements could be obtained by biological cells. The comparison showed that rates obtained by biological cells can only be matched by the vesicle models when there oxidation levels are found to be high.In conclusion we believe that the reason zinc is crossing the bilayer is due to oxidation that occurs to the vesicle and as oxidation increases so do the rates at which zinc crosses the bilayer.
Department of Chemistry

24

Chido, Chakanya. "Fatty acid composition, colour stability and lipid oxidation of mince produced from fresh and frozen/thawed fallow deer meat." Thesis, University of Fort Hare, 2016. http://hdl.handle.net/10353/2479.

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The aim of the study was to determine the fatty acid composition, colour stability and lipid oxidation of fresh mince produced from fallow deer and to evaluate the effect of frozen storage duration on the retail display shelf life of the mince. A total of 31 fallow deer carcasses were used in the study. After cooling for 24hrs, the carcasses were deboned, external fat from the fore and hindquarter muscles removed and individually vacuum packed. For the first trial, seven fallow deer carcasses were used. Meat from the hind and fore-quarters of each carcass was divided into two equal batches per animal. One batch was minced (through a 5 mm die) and packed into oxygen permeable overwraps and refrigerated at 4°C for a period of eight days under retail display conditions. The second batch was vacuum packed and frozen at -20°C for 2 months at the end of which mince was also produced and monitored over an eight-day period under the same conditions that were used for the fresh mince. Colour, pH, lipid and myoglobin stability was determined. Proximate and fatty acid composition was also determined. No differences (P>0.05) were noted between proximate composition of fresh and frozen/thawed minced meat. The lipid content of fallow deer was 2.4 percent (±0.04). Total n3 fatty acids differed (P<0.05) between treatments and decreased with increased storage and display day. There were significant (P<0.05) treatment and time interactions on all measured colour parameters, TBARS and myoglobin forms. Fresh mince was lighter and had higher redness (a*) and yellowness (b*) values than mince from two months frozen stored meat. Hue angle for fresh mince remained stable throughout display whereas it increased for frozen/thawed mince. Fresh mince had lower TBARS values than frozen/thawed mince. Minced meat produced from frozen/thawed deer meat had higher surface met-myoglobin and total met-myoglobin percentages. Surface and total oxy-myoglobin percentage was higher in fresh mince. The first trial clearly showed colour and lipid stability differences between fresh mince and mince from frozen/thawed meat. It also showed that fresh mince has a longer retail display life than mince produced from frozen/thawed meat (six days and four days, respectively). In the second trial, the effects of frozen storage duration on colour and lipid stability were investigated. Twenty-four fallow deer were used. Twelve were harvested in June (6male 6female) and the other twelve in August (6 male 6female) of the same year.Twenty four hours after harvesting, the fore and hindquarter muscles of the carcasses were deboned, vacuum packed and kept at -20°C until October (i.e. 2months and 4months frozen storage period). Upon thawing, the meat was processed into mince following the same procedure used for the first trialand displayed for a fiveday period under retail display conditions. Frozen duration and gender had no effect (P>0.05) on the proximate composition of fallow deer meat. The total amount of saturated fatty acids (SFA) increased and total amount of poly unsaturated fatty acids (PUFA) decreased as frozen duration and display day increased (P<0.05). Frozen duration affected (P<0.01) lipid oxidation and percentage oxy-myoglobin. Mince pH and all colour parameters (L*, a*, b*,hue and chroma) differed (P<0.05) between treatments on day zero and three. Display day was a significant factor (P<0.05) on all measured parameters. By day three all parameters except pH showed signs of extended oxidation and discolouration as evidenced by reduced redness, decreased colour intensity and high TBARS values. This study showed that prolonged frozen storage negatively affects the colour and lipid stability of meat and increases oxidation of PUFAs during frozen storage. However, the study also suggests that although frozen/thawed meat has a shorter retail display shelf life; the proximate composition of the meat remains unchanged.

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Mahachi, Leo Nyikadzino. "Physiochemical, fatty acids, lipid oxidation, sensory characteristics and consumer acceptance of warthog cabanossi produced with pork backfat and fat-tailed sheep backfat." Thesis, University of Fort Hare, 2017. http://hdl.handle.net/10353/6259.

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The objective of this study was to determine the effect of different fat inclusion levels and fat types on the physical and chemical attributes, lipid oxidation, fatty acid composition and sensory characteristics of warthog cabanossi. To achieve this, three types of cabanossi with different pork backfat levels (10 percent, 20 percent and 30 percent) were produced for the first experiment. The results from the study showed that different inclusion levels of pork backfat had an influence (P ≤ 0.05) on the physicochemical and fatty acid composition of warthog cabanossi but did not influence lipid oxidation (P > 0.05). The highest (P ≤0.05) pH, weight and moisture decline was observed in the 10 percent pork backfat cabanossi compared to the 20 percent and 30 percent treatments. However, no differences (P > 0.05) in the water activity of the product were observed. As expected total fat was lower in the 10 percent fat treatment and increased concomitantly. Similarly, protein, ash and salt were higher in the 10 percent fat cabanossi and decreased concomitantly. Differences in the fatty acid composition were observed between treatments. Furthermore, backfat level affected the sensory attributes and consumer acceptance of the cabanossi. Ten percent backfat cabanossi was scored higher (P ≤0.05) for most sensory attributes. Consequently, it was observed that the consumer panel preferred and scored the 10 percent fat cabanossi higher with regards to appearance and taste. In the second experiment, two cabanossi treatments of different fat types (pork backfat and fat-tailed sheep backfat) were produced. The weight loss, moisture content, pH, water activity and salt content did not differ (P > 0.05) between the two cabanossi products. However, there were differences (P ≤0.05) in the protein, fat and ash contents; where protein and ash were higher in the pork backfat cabanossi whilst fat was higher in the sheep backfat cabanossi. Thiobarbituric reactive substances (TBARS) were similar (P > 0.05) between the two fat types cabanossi which could be explained by similar fatty acid profiles being reported for the two cabanossi although the n-6:n-3 ratio was higher (P ≤0.05) in sheep backfat cabanossi. Results from the descriptive sensory analysis showed two distinct products (P ≤0.01) where pork backfat cabanossi scored higher for most attributes. However, the lower scores for sheep backfat cabanossi were within an acceptable range. Sheep backfat cabanossi were also scored for unique attributes that were not detected in the pork backfat cabanossi. This study concluded that fat-tailed sheep backfat can be used to produce an unique cabanossi product of acceptable quality.

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Prado-Barragan, Lilia Arely. "Lipid oxidation in a meat fibre system." Thesis, University of Nottingham, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.294811.

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Walters, Louise. "Lipid oxidation in salt-dried pelagic fish." Thesis, University of Lincoln, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.262195.

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McMoneagle, Andrew. "Antioxidant behaviour in photo-oxidation studies of model lipid compounds." Thesis, University of the West of Scotland, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.311777.

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Pradhan, Arati S. "Diffusion of zinc through oxidized lipid bilayers." Virtual Press, 2000. http://liblink.bsu.edu/uhtbin/catkey/1166400.

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Egg phosphatidylcholine was oxidized by atmospheric oxygen under UV light for 16 hours, and the oxidized products formed were fractionated with high-pressure liquid chromatography in reverse phase. Three fractions that appeared at retention times of 19 minutes, 21 minutes and 24 minutes respectively (fraction 19, fraction 21 and fraction 24) were isolated and stabilized by reduction with triphenylphosphine. Zinc diffusion across 1-palmitoyl-2 oleoyl-sn-glycero-3-phosphocholine (POPC) liposome bilayers mixed with the isolated oxidized fractions was measured. The rate constant for zinc diffusion through the POPC liposome was highest in fraction 19 followed by fraction 21 and fraction 24.NMR data suggests that all oxidized fractions were derived from the major egg polyunsaturated PC, 1-palmitoyl-2-linoleoyl-sn-glycero-3-phosphocholine. The primary oxidized product, fraction 24 contains a mixture of isomers in which the linoleoyl group has formed the 9-hydroxy-10,12-trans-cis diene and trans-trans diene or the 13-hydroxy12,10-trans-cis diene and trans-trans diene. The primary oxidized products on further oxidation, result in secondary oxidized products, contained in fraction 21 and fraction 19.Experimental data indicates that the major components of fraction 21 are the 9-hydroxy12,13-epoxy-l0-trans-monoene (and 13-hydroxy-9,10-epoxy-11-trans-monoene) and the major components of fraction 19 are the 9,12,13-trihydroxy-l0-trans-monoene (and 9,10,13-trihydroxy-1 l-trans-monoene).
Department of Chemistry

30

Noble, Ronald. "Sensory methods used in meat lipid oxidation studies." Kansas State University, 2018. http://hdl.handle.net/2097/38563.

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Master of Science
Food Science Institute
Kadri Koppel
Oxidation of meat decreases consumer acceptance and reduces market value making it an important problem for the meat industry. Odor and flavor of meat are significantly affected by lipid oxidation and researchers continue to explore new ways to control meat oxidation. Natural antioxidants, irradiation and oxygen treatments are major areas of research in meat lipid oxidation. In recent studies researchers have been exploring ways to extend shelf life of meat and in many case rely on sensory results. This report deals with sensory methods used to measure changes associated with treatments and outlines how researchers are using these methods.

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Hoyland, David Vernon. "Chemical methods for assessing lipid oxidation in food." Thesis, University of Nottingham, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.254588.

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32

Smith, G. "Lipid oxidation in S.E. Asian salted-dried fish." Thesis, University of Lincoln, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.380661.

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33

Jenkins, Benjamin John. "The role of alpha oxidation in lipid metabolism." Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/278025.

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Recent findings have shown an inverse association between the circulating levels of pentadecanoic acid (C15:0) and heptadecanoic acid (C17:0) with the risk of pathological development in type 2 diabetes, cardio vascular disease and neurological disorders. From previously published research, it has been said that both these odd chain fatty acids are biomarkers of their dietary intake and are significantly correlated to dietary ruminant fat intake. However, there are profound studies that show the contrary where they do not display this biomarker correlation. Additionally, several astute studies have suggested or shown odd chain fatty acid endogenous biosynthesis, most often suggested via alpha oxidation; the cleavage of a single carbon unit from a fatty acid chain within the peroxisomes. To better understand the correlations and interactions between these two fatty acids with pathological development, the origin of these odd chain fatty acids needed to be determined, along with confirming their association with the disease aetiology. To minimise animal & human experimentation we made use of existing sample sets made available through institutional collaborations, which produced both animal and human interventional study samples suitable for odd chain fatty acid investigations. These sample collaborations allowed us to comprehensively investigate all plausible contributory sources of these odd chain fatty acids; including from the intestinal microbiota, from dietary contributions, and derived from novel endogenous biosynthesis. The investigations included two intestinal germ-free studies, two ruminant fat diet studies, two dietary fat studies and an ethanol intake study. Endogenous biosynthesis was assessed through: a stearic acid infusion, phytol supplementation, and an Hacl1 knockout mouse model. A human dietary intervention study was used to translate the results. Finally, a study comparing circulating baseline C15:0 and C17:0 levels with the development of glucose intolerance. We found that the circulating C15:0 and C17:0 levels were not significantly influenced by the presence or absence of intestinal microbiota. The circulating C15:0 levels were significantly and linearly increased when the C15:0 dietary composition increased; however, there was no significant correlation in the circulating C17:0 levels with intake. Circulating levels of C15:0 were affected by the dietary composition and factors affecting the dietary intake, e.g. total fat intake and ethanol, whereas circulating C17:0 levels were found to be independent of these variables. In our studies, the circulating C15:0 levels were not significantly affected by any expected variations in alpha oxidation caused by pathway substrate inhibition or gene knockout. However, C17:0 was significantly related, demonstrating it is substantially endogenously biosynthesised. Furthermore, we found that the circulating C15:0 levels, when independent of any dietary variations, did not correlate with the progression of glucose intolerance when induced, but the circulating C17:0 levels did significantly relate and linearly correlated with the development of glucose intolerance. To summarise, the circulating C15:0 and C17:0 levels were independently derived; the C15:0 levels substantially correlated with its dietary intake, whilst the C17:0 levels proved to be separately derived from its endogenous biosynthesis via alpha oxidation of stearic acid. C15:0 was found to be minimally endogenously biosynthesised via a single cycle of beta oxidation of C17:0 in the peroxisomes, however, this did not significantly contribute to the circulating levels of C15:0. Additionally, only the baseline levels of C17:0 significantly correlated with the development of glucose intolerance. These findings highlight the considerable differences between both of these odd chain fatty acids that were once thought to be homogeneous and similarly derived. On the contrary, they display profound dietary, metabolic, and pathological differences.

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Vereb, Heather A. "Biomarkers of Lipid Oxidation in the Oral Cavity." Thesis, Virginia Tech, 2011. http://hdl.handle.net/10919/76887.

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Measuring lipid oxidation is useful as a means of monitoring oxidative stress, such as that induced by clinical conditions or environmental exposure. Characteristic volatile compounds, often with low threshold odors, are secondary products of lipid oxidation reactions. Metallic flavor in food and beverages has been linked with oxidation of lipids in the oral cavity. Breath, an emerging medium for analysis of internal condition, is one means of measuring the metal-induced lipid oxidation responsible for this flavor. This project analyzes the breath of human subjects, as well as lipid oxidation of in vitro samples to identify compounds responsible for producing metallic flavor, which result from the oxidation of lipids in the oral cavity. Because these analytes are found at extremely low (picomolar to nanomolar) concentrations, preconcentration of samples prior to gas chromatography-mass spectrometry analysis is crucial. This study utilizes both solid phase microextraction (SPME) and micromachined silicon micropreconcentrators to concentrate compounds in breath to optimize analysis.
Master of Science

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Saeed, Suhur. "Lipid oxidation mechanisms and lipid-protein interactions in frozen mackerel (Scomber scombrus)." Thesis, University of Surrey, 1998. http://epubs.surrey.ac.uk/843251/.

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Atlantic mackerel (Scomber scombrus) is a pelagic fish widely distributed along the Northern coast of Great Britain. The lipid content of mackerel was found to be about 13% of the total body weight and 50% of total fatty acids were eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) (fatty acids which are reported to reduce the concentration of plasma triglycerides, LDL (low density lipoproteins) and cholesterol in humans and animals). The proximate analysis also showed that mackerel is a good source of protein (20% w/w). The poly unsaturated fatty acids (PUFA) are prone to oxidation during frozen storage leading to rancidity and protein damage. Thus the objective of this project was to prolong the shelf-life of mackerel by controlling and understanding lipid oxidation mechanisms. HPLC, GCMS and 13C NMR spectroscopy were used for the first time to monitor the production of hydroperoxides and their secondary products in fish matched pairs of mackerel fillets were stored at either -20°C or -30°C. In addition fillets were also stored with or without different antioxidants at -20°C. The development of lipid oxidation products were recorded for up to 24 months. The oxidation products identified were mixtures of alcohol derivatives of hydroperoxides, namely: 13-hydroxy-9-trans, 11-cis-octadecadienoic, 13-hydroxy-9-trans, 11-trans-octadecadienoic, 9-hydroxy-10-cis, 12-transoctadecadienoic and 9-hydroxy-10-trans, 12-transoctadecadienoic acids. The amount of hydroxides produced were higher in fillets stored at -20°C compared with fillets stored at -30°C. Similarly, the hydroperoxides produced were considerably higher in samples stored without antioxidant than in fillets stored with vitamin E. In this study the transfer of radicals from lipid oxidation to proteins and subsequent formation of protein-cross-links has been reported for the first time. The interaction between lipids and proteins were examined by both ESR and fluoroscence spectroscopy. A central esr free radical (g )signal was observed in both simple systems (methyl linoleate and pure amino acids) and complex systems (fish lipid and pure proteins (lysozyme, ovalbumin) or fish protein (myosin)). The esr signal reached a maximum within a week and then started to decline and with a concomitant increase in a pinkish yellow chromogen. This chromogen which was soluble in organic solvent and fluoresced at an excitation wavelength 360 nm and emission wavelength 420 nm and indicated the formation of protein cross-links. Synthetic (BHT, BHA) and natural (vitamins E, C) antioxidants were capable of preventing both the radical transfer and protein cross-linking. In this study lipoxygenase was isolated from mackerel flesh and its involvement in lipid oxidation mechanism was established. The molecular weight of partially purified lipoxygenase was 119,000 Daltons. This enzyme was capable of oxidising arachidonic acid to 12-hydroeicosatetraenoic acid (12-HETE), which was identified by HPLC. This 12-HETE was absent in pure arachidonic acid and in samples to which boiled enzyme was added. Conventional inhibitors, synthetic and natural antioxidants also inhibited the formation of 12-HETE, indicating the importance of lipoxygenase in fish lipid oxidation. During frozen storage, protein solubility decreased and the texture deteriorated in Atlantic mackerel stored for 3, 6, 12 and 24 months at -20°C and -30°C. There was an increase in peroxide value and TBARS; decrease in myosin ATPase activity a decrease in myofibrillar protein solubility in high salt concentration as well as formation of high molecular weight aggregates which showed low thermal stability and high G' and G" modulus values. There were significant differences (P < 0.01) between samples stored at -20°C and -30°C, with greater deterioration evident in samples stored at -20°C. Similarly, there were significant differences (P < 0.01) between samples stored with and without antioxidants; the samples stored without antioxidants deteriorated faster than samples stored with antioxidants. This suggests the involvement of lipid oxidation products in protein deterioration during frozen storage.

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de, Miguel Pastor Cristina. "Lípidos de la dieta y cáncer de mama experimental: efectos sobre el estrés oxidativo." Doctoral thesis, Universitat Autònoma de Barcelona, 2016. http://hdl.handle.net/10803/399983.

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El cáncer de mama es el más frecuente en mujeres de todo el mundo. Además de los factores genéticos, epigenéticos y hormonales, existen evidencias epidemiológicas y experimentales de que los factores nutricionales y ambientales tienen un papel en la etiología y el desarrollo de esta enfermedad. Los lípidos de la dieta se han relacionado directamente con el cáncer, fundamentalmente, el de mama. Resultados previos demostraron que las dietas hiperlipídicas de aceite de maíz, rico en ácidos grasos poliinsaturados (PUFA) n-6, y el aceite de oliva virgen extra, rico en ácidos grasos monoinsaturados (MUFA) n-9 y diversos compuestos bioactivos, ejercen un efecto estimulador y potencialmente protector, respectivamente, en el cáncer de mama experimental. Estos efectos se realizan durante la etapa de la promoción de la carcinogénesis, pero existen indicios de una influencia sobre la iniciación. El objetivo de este trabajo fue investigar si estos lípidos podían ejercer sus efectos moduladores mediante cambios en el estado de estrés oxidativo en el organismo a diferentes niveles: en el animal sano, en la etapa de la iniciación de la carcinogénesis y en el animal adulto afectado de cáncer de mama. Así, se desarrolló una serie experimental basada en el modelo de cáncer de mama inducido en la rata Sprague Dawley con el hidrocarburo aromático policíclico 7,12-dimetilbenz(a)antraceno (DMBA). Se estudiaron la defensa antioxidante enzimática, mediante la expresión de las enzimas CAT, SOD1, SOD2, GPX1, GPX4 y GR en hígado y glándula mamaria y su actividad en hígado, y la no-enzimática, mediante los parámetros del glutatión en plasma GSHtotal, GSH, GSSG, GSH/GSHtotal y GSH/GSSG. Además, se estudió el daño oxidativo en lípidos y proteínas en plasma, y en el ADN de la glándula mamaria, mediante los niveles de 8-OHdG y la expresión de las enzimas de reparación OGG y PARP. Los resultados mostraron que, en general, las dietas hiperlipídicas aumentaron el nivel de estrés oxidativo en comparación a la dieta control. Este efecto fue mayor para la dieta de aceite de maíz, tanto en los animales sanos como, sobre todo, en la etapa de la iniciación de la carcinogénesis. Ello se correspondió con una aparición más temprana de la enfermedad y mayores incidencia y contenido tumorales. En cambio, la dieta rica en aceite de oliva tuvo un efecto débilmente estimulador de la carcinogénesis y se asoció a unos niveles de estrés oxidativo en hígado y plasma intermedios entre los inducidos por la dieta de aceite de maíz y la control, tanto en los animales sanos como durante la iniciación. En la glándula mamaria iniciada los lípidos de la dieta ejercieron sus efectos sobre los parámetros de estrés mediante mecanismos específicos. Finalmente, los lípidos de la dieta ejercieron una influencia mucho menor sobre el estrés oxidativo una vez el cáncer está establecido.
Breast cancer is the most common malignancy among women all over the world. Besides the genetic, epigenetic and hormonal factors, there are epidemiologic and experimental evidences that nutritional and environment factors have a role in the etiology and the development of this cancer. The dietary lipids are directly related with cancer, mainly breast cancer. Previous results have demonstrated that high corn oil, rich in polyunsaturated fatty acids (PUFA) n-6, and the high extra virgin olive oil diets, rich in monounsaturated fatty acids (MUFA) n-9 and several bioactive compounds, in the experimental breast cancer, resulting in a stimulating and a potentially protective effect, respectively. These diets mostly acted on the carcinogenesis promotion stage, but there are evidences of their action on the initiation stage. The aim of this study was to investigate whether these lipids could exert their modulatory effects through changes on the oxidative stress state in the organism at different levels: in the healthy animal, in the carcinogenesis initiation stage and in the tumor-bearing adult animal. Results proceed from and experimental series, developed in the breast cancer model induced in the Sprague-Dawley rat with the polycyclic aromatic hydrocarbon 7,12-dimethylbenz(a)anthracene (DMBA). The antioxidant enzymatic defense was studied through CAT, SOD1, SOD2, GPX1, GPX4 and GR expression on the liver and mammary gland, and the non-enzymatic defense through total GSH, GSH, GSSG, GSH/GSHtotal and GSH/GSSG glutathione parameters in plasma. Furthermore, plasmatic oxidative damage in lipids and proteins, and DNA damage in the mammary gland though 8-OHdG levels and reparation OGG and PARP reparation damage enzymes were determined. Results showed that, high fat diets increased oxidative levels comparing with the control diet. The high corn oil diet showed a higher effect, both in healthy and especially in the carcinogenesis initiation stage. This was in accordance with an earlier tumor appearance and higher tumor content due to the high corn oil diet. On the other hand, the high extra virgin olive oil diet showed a weak stimulatory c effect which was associated with intermediate oxidative stress levels in serum and liver between the high corn oil and control diets, both in healthy and initiated animals. In the initiated mammary gland, dietary lipids exerted their effects on the oxidative stress parameters through specific mechanisms. Finally, once cancer disease was established, dietary lipids exerted a much lower effect.

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Ingram, Katherine Heimburger. "Skeletal Muscle Lipid Peroxidation and its Relationships with Intramyocellular Lipids and Insulin Sensitivity in Obese Subjects." Digital Archive @ GSU, 2009. http://digitalarchive.gsu.edu/kin_health_diss/6.

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Intramyocellular lipid (IMCL), an ectopic fat depot found within skeletal muscle fibers, is highly associated with obesity and strongly correlated with insulin resistance. IMCL accumulation in sedentary individuals may contribute to insulin resistance by interfering with insulin signaling in skeletal muscle, leading to inadequate glucose uptake by the cell. Lipid peroxidation is also associated with both obesity and insulin resistance, and with IMCL, but a relationship has yet to be established among all of these variables. The purpose of this project is to study for the first time the relationships among lipid peroxidation, IMCL content, and glucose uptake in skeletal muscle. Nine insulin-sensitive adults (IS), 13 insulin-resistant adults (IR), 10 diabetic (DB) and 8 subjects pre- and post- 12-week intervention with insulin-sensitizing thiazolinedione (TZD) were assessed for soleus IMCL with nuclear magnetic resonance, insulin sensitivity by both hyperinsulinemic-euglycemic clamp (GDR) and homeostasis model assessment index (HOMA1), and anthropometrics, including body mass index (BMI), percent fat by DEXA scan, and waist circumference. Vastus lateralis biopsies of all subjects were homogenized and analyzed by immunoblotting for post-translational protein modifications occurring from lipid-peroxidation (HNE). GDR and HOMA were significantly different among IS, IR, and DB groups, as expected, as were waist circumference and BMI. IMCL was significantly higher in DB than in IS and IR. HNE was also higher in DB than in IS, although it did not differ from IR. HNE was significantly correlated to GDR, HOMA1, and BMI, but not to IMCL, WAIST, or percent fat measures. IMCL showed a strong, negative correlation with GDR and was the primary, independent predictor of GDR in stepwise multiple regression. HNE was the primary, independent predictor of HOMA in stepwise multiple regression. Paired t-tests revealed improvements in insulin sensitivity measures after 12 weeks of TZD intervention, but no significant differences were observed in IMCL or HNE after intervention. These data show that skeletal muscle HNE and IMCL are both determinants of insulin resistance in obese, sedentary adults. HNE and IMCL are not related and therefore impact insulin resistance independently. These results reveal, for the first time, a negative relationship between skeletal muscle HNE and insulin sensitivity in sedentary individuals and underscore the importance of lipid peroxidation in insulin resistance.

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Bôas, Eloísa Aparecida Vilas. "Tratamento crônico com ácido palmítico aumenta o conteúdo de superóxido e a apoptose de células BRIN-BD11com participação da NADPH oxidase, sem envolvimento do GPR40." Universidade de São Paulo, 2013. http://www.teses.usp.br/teses/disponiveis/42/42137/tde-18062014-132020/.

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A exposição crônica a ácidos graxos (AG) saturados leva à disfunção da célula beta pancreática com redução da secreção de insulina e apoptose, fenômeno conhecido como lipotoxicidade, que está relacionado a: estresse de retículo endoplasmático (RE), estimulação crônica do receptor de AG GPR40 e aumento de espécies reativas de oxigênio (ERO) provenientes, entre outras fontes, da enzima NADPH oxidase. Pretendeu-se explorar como mecanismos de lipotoxicidade: o estresse de RE, a estimulação crônica do GPR40 e a geração de ERO pela NADPH oxidase, bem como relações entre NADPH oxidase e estresse de RE. Verificamos que cronicamente o ácido palmítico (AP) provocou aumento do conteúdo de superóxido, proveniente em parte da NADPH oxidase. A inibição da NADPH oxidase com VAS2870 reverteu a apoptose provocada pela exposição crônica ao AP e apresentou relação com menor expressão proteica de um marcador do estresse de RE (PERK). O GW9508 (agonista do GPR40) não provocou os mesmos efeitos crônicos do AP, sugerindo que a ativação da via do GPR40 não está envolvida nos processos.
Chronic exposure to saturated fatty acids can lead to pancreatic beta cell dysfunction, reduction of insulin secretion and apoptosis, condition known as lipotoxicity, that has been related to: endoplasmic reticulum stress, chronic stimulation of GPR40 and increased production of reactive oxygen species (ROS) from, among other sources, the enzime NADPH oxidase. We intended to explore as mechanisms of lipotoxicity: reticulum stress, chronic stimulation of GPR40 and NADPH oxidase generation of ROS, as well as relations between NADPH oxidase and reticulum stress. Our results show that chronically palmitic acid induced an increase in the superoxide, in part from NADPH oxidase. NADPH oxidase inhibition by VAS2870 reverted the apoptosis induced by chronic exposure to palmitic acid, and was related to a lower expression of a reticulum stress marker (PERK). GW9508, GPR40 agonist, did not produced the same effects observed after chronic treatment with palmitic acid, suggesting that activation of GPR40 pathway is not involved in these processes.

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Oliveira, Patrícia Martinez. "Avaliação dos efeitos hipolipêmico e antioxidante in vivo dos extratos hidroalcoólicos da folha e raíz do yacon (smallanthus sonchifolius)." Universidade Federal do Pampa, 2015. http://dspace.unipampa.edu.br:8080/xmlui/handle/riu/261.

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As doenças cardiovasculares (DCV) lideram as causas de morte em todo o mundo, sendo a dislipidemia o principal fator de risco. A alimentação é reconhecida como a intervenção mais importante na prevenção de patologias e as plantas são consideradas a melhor fonte de antioxidantes naturais. Entre elas, um alimento funcional que tem se destacado é o Yacon, uma raiz tuberosa, originária da região Andina que possui frutooligossacarídeos (FOS) como principal carboidrato de reserva, diferenciando-se da maioria das espécies tuberosas que estocam energia na forma de amido. Além desses compostos, o Yacon apresenta polifenóis em quantidade significativa tanto nas raízes como nas folhas. Estudos demonstram que o Yacon possui atividade hipoglicêmica, entretanto pouco se sabe sobre outras propriedades. Assim, o objetivo deste estudo foi investigar os efeitos hipolipêmico e antioxidante in vivo dos extratos hidroalcoólicos da folha e raiz do Yacon (Smallanthus sonchifolius). Foram utilizados ratos Wistar, machos, divididos em: G1 (controle dieta normal), G2 (controle dieta hipercalórica) (NaCl 0,9%), G3: suspensão oral de sinvastatina 10 mg/Kg (SIM), G4: extrato folha Yacon 20 mg/kg (EFY20), G5: extrato folha Yacon 40 mg/kg (EFY40), G6: extrato folha Yacon 20 mg/kg + sinvastatina (EFY20+SIM), G7: extrato folha Yacon 40 mg/kg + sinvastatina (EFY40+SIM), G8: extrato raiz Yacon 20 mg/kg (ERY20), G9: extrato raiz Yacon 40 mg/kg (ERY40), G10: extrato raiz Yacon 20 mg/kg + sinvastatina (ERY20+SIM) e G11: extrato raiz Yacon 40 mg/kg + sinvastatina (ERY40+SIM). As formulações foram administradas uma vez ao dia por gavage durante 14 dias consecutivos. Os parâmetros hematológicos, bioquímicos e de estresse oxidativo foram determinados através de metodologias clássicas. Os grupos que receberam o extrato de Yacon apresentaram melhora do perfil glicêmico e lipídico. A dieta hipercolesterolêmica aumentou os níveis séricos da creatina-quinase, CK-MB, homocisteína e LDH porém a administração do extrato diminuiu significativamente os níveis destes marcadores quando comparado ao grupo não tratado. Além disso, o extrato, reduziu a peroxidação lipídica, a carbonilação proteica, e frequência de micronúcleos induzida por hipercolesterolemia e aumentou as defesas antioxidantes (CAT, SOD, GPx, GSH, vitamina C e polifenóis) no sangue. Verificou-se ainda que, a suplementação do Yacon não mostrou efeito hepatotóxico ou nefrotóxico. A dieta hipercolesterolêmica aumentou o processo inflamatório, avaliado através de seus marcadores, e a administração do extrato melhorou esse parâmetro. Além disso, a suplementação com a raiz do Yacon controlou o ganho de peso dos animais. Assim, os resultados sugerem que o extrato liofilizado do Yacon apresentou uma atividade hipoglicêmica, hipolipêmica e antioxidante, possivelmente devido ao seu alto conteúdo de compostos fenólicos.
Cardiovascular diseases (CVD) are the leading cause of death worldwide, and dyslipidemia a major risk factor. Feeding is recognized as the most important intervention in the prevention of diseases and plants are considered the best source of natural antioxidants. Among them, a functional food that has been highlighted is the Yacon, a tuberous root, originate in the Andean region with fructooligosaccharides (FOS) as the main reserve carbohydrate, differing from most tuberous species which store energy in the form of starch. In addition to these compounds, Yacon presents significant amount of polyphenols in both roots and leaves. Studies show that Yacon has hypoglycemic activity, however little is known about other properties. The objective of this study was to investigate the hypolipemic and antioxidant effects in vivo of hydroalcoholic extracts of leaf and root of Yacon (Smallanthus sonchifolius). Male Wistar rats were used, divided into: G1 (normal control diet), G2 (control calorie diet) (NaCl 0.9%), group 3: oral suspension of simvastatin 10 mg/kg (SIM), group 4: Yacon leaf extract 20 mg/kg (YLE20), group 5: Yacon leaf extract 40 mg/kg (YLE50), group 6: Yacon leaf extract 20 mg/kg and simvastatin 10 mg/kg (YLE20+SIM), group 7: Yacon leaf extract 40 mg/kg and simvastatin 10 mg/kg (YLE40+SIM), group 8: Yacon root extract 20 mg/kg (YRE20), G9: Yacon root extract 40 mg/kg (YRE40), G10: Yacon root extract 20 mg/kg and simvastatin 10 mg/kg (YRE20+SIM), G11: Yacon root extract 40 mg/kg and simvastatin 10 mg/kg (YRE40+SIM), The formulations were administered once daily by gavage for 14 consecutive days. Hematological, biochemical and oxidative stress parameters were determined by classical methods. The groups that received the Yacon extract showed improvement of glycemic and lipid profile. The hypercholesterolemic diet increased serum levels of creatine kinase, CK-MB, homocysteine and LDH, but the extract administration decreased the levels of these markers significantly when compared to the untreated group. Moreover, the extract, reduced lipid peroxidation, protein carbonylation and frequency of micronucleus induced by hypercholesterolemia and increase antioxidant defenses (CAT, SOD, GPx, GSH, vitamin C, polyphenols) in the blood. Moreover, supplementation of Yacon showed no hepatotoxic or nephrotoxic effect. The hypercholesterolemic diet increased the inflammatory process, evaluated through your markers, and extract administration has improved this parameter. Furthermore, supplementation with the root of Yacon controlled weight gain of animals. Thus, the results suggest that the lyophilized Yacon extract showed a hypoglycemic, hypolipemic and antioxidant activity, possibly due to its high content of phenolic compounds.

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Kristinova, Vera. "Oxidation of marine lipids in liposomes and emulsions mediated by iron and methemoglobin." Doctoral thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for bioteknologi, 2014. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-25022.

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Long chain omega-3 polyunsaturated fatty acids (LC omega-3 PUFA) are vital for physiological functions and have therapeutic and health benefits. The consumption of LC PUFA in the Western world has been below recommended intake levels the past decades, despite promotion of seafood and omega-3 supplements. Incorporation of the LC PUFA into processed food consumed on a daily basis might therefore bridge the gap between the recommended and actual consumption of LC omega-3 PUFA. Unfortunately, the development of omega-3 enriched food is hampered by a very high susceptibility of LC PUFA to oxidative deterioration. Furthermore, oxidised lipids are believed to create health risks. It has also been suggested that gastric juice may deteriorate the healthy LC PUFA after they are ingested. Important lipid oxidation promoters in food are low molecular weight (LMW) iron (Fe) and methemoglobin (metHb). To incorporate the LC omega-3 PUFA safely into food with respect to oxidation, it is necessary to understand both Fe- and metHb-mediated oxidation of PUFA and how the oxidation is influenced by conditions and dietary antioxidants. The main objective of this thesis is therefore to study Fe- and metHb-mediated lipid oxidation in food-related lipid model systems – emulsions stabilised with phospholipids and liposomes made of phospholipids – containing LC omega-3 PUFA from fish. The focus was on clarifying the reaction mechanisms and the impact of different factors, including dietary antioxidants and gastric juice, on the prooxidant activity of Fe and metHb. Measurement of the consumption rate of the essential substrate for lipid oxidation – oxygen – by the LC PUFA was used for assessment of lipid oxidation. The continuous measurement of the dissolved oxygen concentration has been shown to be a robust method for direct and instantaneous monitoring of peroxidation in both the liposomes and emulsions. The method was especially useful for measurement of the oxygen consumption kinetics in the lipid systems. The determination of oxygen uptake rates (OUR) enabled screening and evaluation of the impact of the different factors and antioxidants on the prooxidant activity of Fe and metHb. Pre-formed lipid hydroperoxides (LOOH) were shown to be essential for the prooxidant activity of both Fe and metHb, and the prooxidant activity of metHb was not affected by the lack of light. The oxygen uptake kinetics revealed that iron behaved as a catalyst in lipid oxidation while the prooxidant activity of metHb weakened over time, presumably due to degradation of meHb molecule during lipid oxidation. MetHb was shown to be a stronger prooxidant than Fe, but the strong prooxidative activity was facilitated by a complete structure of the metHb molecule. The prooxidant mechanism of both Fe and metHb was not limited by the level of dissolved oxygen, as long as oxygen was present, or the level of pre-formed LOOH and double bonds in fatty acids, as long as they were present in higher concentrations than the prooxidant. The extent of the prooxidative activity of Fe was shown to vary in dependence on: The total surface area: Smaller liposomal vesicles with lower lipid content were more prone to oxidation than larger emulsion droplets with a higher lipid content, presumably due to more frequent interactions of Fe with pre-formed LOOH in the interphase. The amount of phospholipid emulsifier: Higher levels of phospholipids resulted in the formation of smaller droplets. The highest OUR were measured for emulsifier concentrations ranging from 5 – 10% (w/w lipid base). pH of the aqueous phase: Fe-mediated oxidation was highest at pH interval 4.5 – 5.5. Dissolved compounds: Sodium chloride (NaCl) and 0.2% of xanthan gum dissolved in the aqueous phase inhibited Fe-mediated oxidation in a concentration dependent manner. Electrostatic retention of Fe by phosphate groups within phospholipid heads has been suggested to facilitate the contact between pre-formed LOOH and Fe, and to create competitive reactions for iron precipitation at pH > 5 and iron complexation by chelating compounds. The activity of dietary antioxidants has been shown to be affected by the type of prooxidant in the lipid system. Ascorbic acid, caffeic acid, propyl gallate, astaxanthin, ascorbyl palmitate, α-tocopherol, and δ-tocopherol inhibited metHb-mediated oxidation in concentration dependent manners. EDTA had a minor effect on metHb-mediated oxidation. In Fe-mediated oxidation, caffeic acid, ascorbic acid and α-tocopherol were prooxidants. They directly interacted with Fe, reducing Fe3+ to the more catalytically active Fe2+. The magnitude of the pro-oxidative behaviour was dependent on the Fe-to-antioxidant ratio, antioxidant concentration and pH. Ascorbic acid was depleted by interactions with Fe, and decreased the pro-oxidative activity of α-tocopherol. EDTA and citric acid inhibited Fe-mediated oxidation completely at twice the ratio to Fe and pH > 3.5. Propyl gallate efficiently inhibited Fe-mediated oxidation, while astaxanthin and β-carotene had only minor effects. In addition, chemical structure and physical location of the antioxidants determined their effects. The work in this thesis shows that for correct interpretation of the effects of antioxidants it is important to assess what types of prooxidants are present in the system. Both gastric juice and hydrochloric acid solution (HCl) did not prevent oxidation of marine lipids in emulsions and liposomes (pH 4.0). Furthermore, gastric juice did not inhibit metHb-mediated oxidation, but it was capable of reducing the prooxidant activity of dietary LMW iron, compared to HCl solution. Berry juice, green tea, red wine, and caffeic acid reduced the OUR in the acidic environments while coffee, ascorbic acid and orange juice increased the OUR. Therefore, beverages accompanying foods rich in marine lipids will affect the course of post-prandial lipid oxidation.

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Filho, Adriano de Britto Chaves. "Eventos redox na biologia dos lipídios: modificação de tióis e alterações do lipidoma em ALS." Universidade de São Paulo, 2018. http://www.teses.usp.br/teses/disponiveis/46/46131/tde-20072018-085559/.

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Os lipídeos abrangem uma ampla gama de moléculas hidrofóbicas presentes nas células. As características moleculares dos lipídios determinam sua localização celular e função biológica. Em geral, os lipídios são considerados componentes essenciais de membranas, reservatórios de energia e moduladores de vias de sinalização ligadas ao metabolismo celular, sobrevivência, entre outros. Em mamíferos, grande parte dos lipídios é esterificada em ácidos graxos poli-insaturados (PUFAs), especialmente os ácidos docosahexaenóico (DHA) e araquidônico (ARA), essenciais para vários processos fisiológicos, incluindo o desenvolvimento normal do cérebro. No entanto, os PUFAs são muito suscetíveis à oxidação por espécies reativas de oxigênio (ROS) geradas endogenamente. Uma vez oxidados, lipídios são capazes de modificar grupos tióis de peptídeos e proteínas, levando à modulação das vias de sinalização e alterando o balanço redox celular. No capítulo 1, foram investigados os mecanismos envolvidos na modificação de grupos tióis de peptídeos e proteínas por produtos de auto-oxidação de PUFAs. Com as análises realizadas foi possível identificar vários adutos de glutationa (GSH) covalentemente modificados por endoperóxidos cíclicos derivados de DHA e ARA. Uma análise detalhada dos espectros de MS/MS dos adutos de GSH revelou que GSH e endoperóxidos cíclicos são provavelmente ligados através de uma ligação química de enxofre-oxigênio, em uma reação que envolve um ataque nucleofílico do ânion tiolato. Além disso, sugerimos que a eficiência da modificação do tiol por endoperóxidos cíclicos também é dependente da reatividade do tiol, como demonstrado pela modificação covalente do resíduo de cisteína mais reativo (Cys111) da enzima antioxidante superóxido dismutase 1(SOD1). Modificações químicas de tióis por endoperóxidos cíclicos podem modular a agregação proteica e o status redox celular, produzindo adutos de GSH capazes de modular a inflamação, como relatado para os conjugados de GSH gerados enzimaticamente. No capítulo 2, nós investigamos o papel dos lipídios na esclerose lateral amiotrófica (ALS), uma vez que a inflamação e o estresse oxidativo nos neurônios motores contribuem para o desenvolvimento desta doença neurodegenerativa. Usando uma abordagem lipidômica não direcionada baseada em espectrometria de massa acoplada à cromatografia líquida (UHPLC-MS/MS), nós investigamos o metabolismo lipídico no córtex motor e na medula espinhal de um modelo de ratos com ALS. A análise do córtex motor mostrou que as principais alterações lipídicas foram dependentes da idade e ligadas ao metabolismo dos esfingolipídios. Em contraste, as principais alterações lipídicas na medula espinhal foram encontradas no grupo sintomático da ALS, sendo o metabolismo de ceramidas, ésteres de colesterol e cardiolipinas os mais afetados. De acordo com os resultados obtidos e dados relatados na literatura, propusemos um mecanismo baseado em neuroproteção que envolve o acúmulo de ésteres de colesterol esterificados em PUFAs em astrócitos. Coletivamente, nossos achados sugerem que os lipídios desempenham um papel crucial na modulação de processos celulares ligado à oxidação de tióis e à neurodegeneração.
Lipids encompass a wide range of hydrophobic molecules present in cells. The molecular characteristics of lipids determine their cellular localization and biological function. In general, lipids are regarded as essential components of membranes, as energy reservoir and modulators of signaling pathways linked to cellular metabolism and survival, among others. In mammals, a large part of the lipids are esterified to polyunsaturated fatty acids (PUFAs), especially docosahexaenoic (DHA) and arachidonic (ARA) acids, essential for several physiological processes, including normal brain development. However, PUFAs are very susceptible to oxidation by reactive oxygen species (ROS) generated endogenously. Once oxidized, lipids are able to modify thiol groups of peptides and proteins leading to modulation of signaling pathways and cellular redox balance. In the chapter 1, we investigated the mechanisms involved in modification of thiol groups of peptides and protein by autoxidation products derived from PUFAs. Here, we identified several glutathione (GSH) adducts covalently modified by hydroxy-endoperoxides derived from both DHA and ARA. Detailed inspection of MS/MS spectra of GSH-adducts revealed that GSH and hydroxy-endoperoxides are likely bonded through a sulfur-oxygen chemical bond in a reaction which involves a nucleophilic attack by the thiolate anion. Also, we suggest that the efficiency of modification of thiol by hydroxy-endoperoxides are also dependent of the thiol reactivity, as demonstrated by covalent modification of the most reactive cysteine residue (Cys111) of the antioxidant enzyme Cu,Zn-superoxide dismutase (SOD1). Chemical modifications of thiol groups by hydroxy-endoperoxides may modulate protein aggregation and cellular redox status, yieldingGSH adducts capable to modulate inflammation, as reported for the enzymatically generated counterparts. In the chapter 2, we investigated the role of lipids in amyotrophic lateral sclerosis (ALS), since inflammation and oxidative stress in motor neurons are hallmarks of this neurodegenerative disease. Using an untargeted lipidomics approach based on mass spectrometry coupled to liquid chromatography (UHPLC-MS/MS), we investigated the lipid metabolism in motor cortex and spinal cord tissues of a rodent model of ALS. Analysis of the motor cortex showed that the main lipid alterations were age-dependent and linked to metabolism of sphingolipids. In contrast, the major lipid alterations in the spinal cord were found in ALS symptomatic group, being the metabolism of ceramides, cholesteryl esters and cardiolipin the most affected. According to our findings and data reported in the literature, we proposed a mechanism based on neuroprotection that involves accumulation of cholesteryl esters esterified to PUFAs in astrocytes. Collectively, our findings suggest that lipids play a crucial role in modulation of cellular process linked to thiol metabolism and neurodegeneration.

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Bothma, Karien. "The involvement of lipid and protein oxidation in hypertension : the SABPA study / Karien Bothma." Thesis, North-West University, 2012. http://hdl.handle.net/10394/8652.

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Oxidative stress, caused by increased levels of reactive oxygen species (ROS)and reactive nitrogen species (RNS) and/or a decrease in antioxidant capacity, can result in the oxidation of various bio-molecules, such as proteins, lipids and deoxyribonucleic acid (DNA). These oxidized bio-molecules may contribute to pathologies such as cardiovascular diseases, neurodegenerative disorders and cancer. The Sympathetic Activity and Ambulatory Blood Pressure in Africans (SABPA) study was initiated in 2008 to investigate the coping styles and catecholamine metabolic markers of Africans, contributing to their higher sympathetic output and poorer psychosocial wellbeing. This study forms part of the SABPA study, but with a specific aim to investigated lipid and protein oxidation markers in hypertensive Africans versus their normotensive counterparts. Analytical methods for the quantification of specific lipid and protein oxidation markers were optimized and validated. Urine samples from 172 urbanized black South Africans were collected and 3-nitrotyrosine (3NT) and thiobarbituric acid reactive substances (TBARS) were quantified in these samples, using the optimized spectrophotometric and LC-MS/MS methods. Statistical analyses showed that in both males and females, TBARS and 3NTcorrelated with each other. In males, 3NT also correlated with physical activity level (PAL) and C-reactive protein (CRP), while TBARS also correlated with body mass index (BMI). In females 3NT correlated with BMI, while TBARS correlates with PAL. These correlations meant that they could influence the calculations of the true effect of 3NT and TBARS levels between normotensive and hypertensive subjects. After analyses of covariance (ANCOVA) analyses it was determined that the hypertensive male subjects had higher TBARS values than the normotensive male subjects did (p-value = 0.03) and the normotensive female subjects had higher 3NT levels compared to the hypertensive female subjects (p-value = 0.04). These results partially supported the hypothesis that that elevated concentrations of specific urinary lipid and protein oxidation markers will be observed in the hypertensive test subjects compared to their normotensive counterparts. The results also indicated that there were indeed a difference in lipid and protein oxidation between hypertensive and normotensive subject.
Thesis (MSc (Biochemistry))--North-West University, Potchefstroom Campus, 2013

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Turner, Rufus. "Lipid oxidation by denatured haemproteins in heat-processed vegetables." Thesis, University of Reading, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.365990.

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44

Arnold, Andrew Richard. "Lipid oxidation in a model system and in meat." Thesis, University of St Andrews, 1989. http://hdl.handle.net/10023/14168.

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Lipid oxidation is the main factor which limits the shelf-life of meat when held under frozen storage. Research undertaken used pork phospholipid liposomes as a model for studying lipid oxidation in meat. Oxidation was followed by monitoring the decrease in the phospholipid unsaturated fatty acyl chains. It was found that the greater the level of unsaturation of the phospholipid fatty acyl chain the greater was their susceptibility to peroxidation. However, the results were not consistent and several reasons for the variation in rate are provided. At ambient temperatures copper (II) was found to be pro-oxidant in the peroxidation of liposomes. At temperatures below 0°C the prooxidant activity of copper (II) was significantly reduced. However copper again became highly pro-oxidant if sodium chloride was present. It is suggested that salt controls the copper ion concentration at sub-zero temperatures as the pro-oxidant activity of copper (II) is reduced on increasing the copper (II) concentration from 0.9 to 90 ppm. Other experiments found sodium nitrite and pholyphosphate to act as antioxidant and that liposome structure was an important factor in the rate of peroxidation. Four storage trials on pork burgers were undertaken to determine whether salt was also pro-oxidant in the stability of pork when held under frozen storage. The oxidative deterioration of the meat was followed by the following methods of analysis:- 1. The decrease in the unsaturated acyl chains of both total lipid and phospholipid. 2. The change in the colour parameters of the meat using reflectance spectroscopy. 3. The analysis of neutral lipid oxidation products by HPLC. 4. The organoleptic qualities of the pork using a trained panel of food assessors. The results from these storage trails showed that the deterioration of pork was minimised by storing the burgers at lower temperatures within the range 0 to -30°C. Salt was found to accelerate the oxidative deterioration of both uncooked and cooked pork when stored at -20°C. Nitrite was found to exhibit some antioxidant behaviour and reduce the pro-oxidant effect of salt.

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Sickler, Marsha Lynn. "Inhibition of Lipid Oxidation with Phosphates in Muscle Foods." Thesis, Virginia Tech, 2000. http://hdl.handle.net/10919/9866.

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Lipid oxidation degrades the quality and decreases the shelf-stability of muscle foods. The depletion of phosphates prior to cooking may be a major factor in this undesirable reaction. Thus, the effects on lipid oxidation with the use of an encapsulate to protect the phosphates during raw storage was investigated. Unencapsulated and encapsulated sodium tripolyphosphate (STP) and sodium acid pyrophosphate (SAPP), at a level of 0.5%, were compared to control samples in cooked, ground beef patties at 0 and 6 days. The unencapsulated and encapsulated treated samples were different (P<0.05) from the controls with an 81.1% to 89.7% improvement in the reduction of lipid oxidation. However, encapsulated phosphates did not decrease the level of oxidation beyond the unencapsulated treatment. This observation was attributable to the lack of a storage time prior to evaluating rancidity. Therefore, with an increase of precooked storage time, the 0.10% active encapsulated STP was essentially as effective as 0.20% unencapsulated STP for both 3 and 11 days. Unencapsulated STP (0.3% or 0.5%), encapsulated STP (0.3% or 0.5% active), a blend of unencapsulated (0.3%) and encapsulated (0.2% active) STP, and a control treatment was incorporated in ground turkey breast and stored at 3Â°C for 0, 5, and 10 days. The treated samples were cooked to two different endpoint temperatures (74°C and 79°C) and stored at 3°C (4 and 24 hr) before cooking. An improvement of 77% and 80% was found in the reduction of Thiobarbituric Acid Reactive Substances (TBARS) with the 0.3% and 0.5% encapsulated STP, respectively, in comparison to the unencapsulated STP. The best results were seen with a shorter storage time (4 hr) prior to cooking and a higher endpoint temperature (79°C). The unencapsulated and encapsulated STP were compared to commercial antioxidant blends, Lemo-fos and Freez-Gard FP 15, at a level of 0.5%, to determine differences in their capabilities of lipid oxidation reduction. The encapsulated phosphate was lower (P<0.05) in TBARS (3.5 mg/kg) in comparison to the treatments which ranged from 15.6 to 20.4 mg/kg. However, the CIE a* values were higher in the encapsulated samples due to the decrease in lipid oxidation. The effect of liquid nitrogen on TBARS values was investigated to identify a means of analyzing a large quantity of samples. The use of cryogenic freezing was not significantly different in TBARS in comparison with a fresh, unfrozen control. Raw and cooked ground turkey samples were submerged into liquid nitrogen and stored intact or immediately reduced in particle size to compare particle reduction effects on TBARS. The different particle reduction methods were not significantly different, although, the immediately reduced sample was more efficient in TBARS determination. The samples stored in an ultralow freezer (-80°C) for 14 and 33 days were not different (P>0.05). Overall, when encapsulated STP is used with sufficient pre-cook storage time, lipid oxidation can be more effectively reduced than with the use of unencapsulated phosphates. The use of cryogenic freezing and ultralow temperature storage can also aid in the determination of lipid oxidation in large sample quantities due to the stability of TBARS values.
Master of Science

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Romain, Cindy. "Effets et recherche de mécanismes d'action d'un extrait de sarments de vigne et de vins rouges riches en resvératrol et ses oligomères : Quel rôle dans la prévention des maladies cardio-vasculaires ?" Thesis, Montpellier 2, 2013. http://www.theses.fr/2013MON20199/document.

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Les maladies cardiovasculaires (MCV) sont en augmentation au niveau mondial et sont désormais un problème de santé publique coûteux. La suralimentation et le manque d'activité physique sont des facteurs clé dans le développement pathologique. Ces dernières années, les études sur la pathogenèse des MCV ont mis en évidence de nombreux facteurs contribuant au développement de ces pathologies complexes, notamment le surpoids, l'obésité centrale, le stress oxydant, l'inflammation vasculaire et systémique, la résistance à l'insuline ou encore la dysfonction endothéliale. La prévention de ces désordres est donc la cible des stratégies pharmaceutiques et diététiques et les polyphénols ont d'ores et déjà démontré des effets bénéfiques et préventifs. Parmi les 8000 composés phénoliques décrits à ce jour, le resvératrol a émergé en tant que candidat robuste dans la prévention des pathologies liées à la nutrition. L'objectif de ce travail a été d'étudier les potentialités d'action d'un extrait de sarment de vigne (Vineatrol®) et de vins rouges riches en resvératrol et ses oligomères, sur un modèle animal d'athérosclérose nutritionnellement induite. La première partie de cette étude a consisté à mettre au point un régime alimentaire déclenchant au mieux l'athérosclérose précoce chez le hamster Syrien doré. A partir de ce modèle, un effet préventif du Vineatrol® a été mis en évidence : le Vineatrol® induit une diminution des dépôts lipidiques aortiques mais améliore également le statut oxydatif et inflammatoire des animaux. Dans une troisième partie, des vins rouges enrichis en Vineatrol® ont démontré des effets préventifs sur certains facteurs de risque de la pathologie athéromateuse et sur les désordres liés à la consommation d'un régime gras. Des mécanismes d'action possibles, expliquant les effets bénéfiques de ces vins, ont été envisagés et recherchés. Ces mécanismes pourraient impliquer une modulation de la voie du NF-κB et/ou de SIRT1. Le degré d'importance de ces différentes voies devra être confirmé
Cardiovascular diseases (CVD) are increasing globally and are now an expensive public health problem. Overnutrition and lack of physical activity are key factors in the disease development. In recent years, studies on the pathogenesis of CVD showed many factors contributing to the development of these complex diseases including overweight, centralobesity, oxidative stress, vascular and systemic inflammation, insulin ressitance or endothelial dysfunction. Prevention of these disorders is the focus of pharmaceutical and dietarystrategies and polyphenols have already demonstrated beneficial and preventive effects. Among the 8000 phenolic compounds described to date, resveratrol has emerged as a strong candidate for the prevention of nutrition-related diseases.The objective of this work was to study the potential action of vine shoot extract (Vineatrol®) and red wines rich in resveratrol and its oligomers, in an animal model of nutritionallyinduced atherosclerosis.The first part of this study was to develop a diet triggering the best early atherosclerosis in theSyrian golden hamster. From this model, a preventive effect of Vineatrol® was highlighted: Vineatrol® induces adecrease in aortic lipid deposition but also improves the oxidative and inflammatory status of the animals. In the third part , Vineatrol®-enriched red wines showed preventive effects on risk factors foratherosclerotic disease and disorders related to the consumption of a high-fat diet. Possible mechanisms of action, explaining the beneficial effects of these wines have been consideredand sough. These mechanisms could involve modulation of the NF-κB and/or SIRT1pathways. The degree of importance of these different pathways will have to be confirmed

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Zopyrus, Nadia. "On the Origin of Secosterols Upon Oxidation of Cholesterol." Thesis, Université d'Ottawa / University of Ottawa, 2017. http://hdl.handle.net/10393/35885.

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Cholesterol is one of the most abundant lipids in the body, and like all unsaturated lipids, it can be oxidized by a variety of reactive oxygen species (ROS). Lipid peroxidation is one of the main pathways by which ROS induce oxidative damage, and has been linked to neurodegenerative and cardiovascular diseases. In 2003, Wentworth et al. detected both 3β-hydroxy-5-oxo-5,6-secocholestan-6-al (secosterol-A) and its intramolecular aldolization product 3β-hydroxy-5β-hydroxy-B-norcholestane-6β-carboxaldehyde (secosterol-B) in human atherosclerotic plaques – compounds which, at the time, were only known to be formed by cholesterol ozonolysis. However, our group has shown that cholesterol 5α-hydroperoxide, which is the product of the reaction of cholesterol with singlet oxygen, can undergo acid-catalyzed Hock fragmentation to generate secosterol-A and -B as well. Nevertheless, cholesterol 5α-hydroperoxide readily rearranges to a more thermodynamically stable cholesterol 7-hydroperoxide. Herein we show that cholesterol 7-hydroperoxide, the main product of cholesterol autoxidation, can also undergo acid-catalyzed Hock fragmentation that gives rise to electrophilic species with similar chromatographic characteristics to those that were allegedly identified as secosterol-A and -B. We also proposed to prepare authentic products of the Hock fragmentation of cholesterol 7-hydroperoxide by subjecting Δ⁶’⁷-cholesterol to ozonolysis. Herein, we explore the limitations and complications of Δ⁶’⁷-cholesterol ozonolysis as well as cholesterol 7-OOH Hock fragmentation which both resulted in unexpected (unprecedented) products.

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Irankunda, Rachel. "Nickel Chelating Peptides & Chromatography : From Peptides Separation Simulation up to their Antioxidant Activities - related Applications." Electronic Thesis or Diss., Université de Lorraine, 2023. http://www.theses.fr/2023LORR0213.

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Les peptides chélateurs de métaux (PCMs), issus d'hydrolysats de protéines, présentent diverses applications dans les domaines de la nutrition, de la pharmacie, des cosmétiques, etc. Cependant, l'approche empirique généralement utilisée pour découvrir des peptides bioactifs à partir d'hydrolysats est longue et coûteuse en raison de nombreuses étapes de fractionnement, de séparation et d'évaluation des activités biologiques. Cette thèse a donc pour but de développer une nouvelle approche pour la prédiction de la séparation des PCMs en utilisant la modélisation et la simulation chromatographiques basées sur l'analogie entre la chromatographie d'affinité sur ions métalliques immobilisés (IMAC) et la résonance plasmonique de surface (SPR). Pour la première fois, l'analogie SPR-IMAC a été étudiée expérimentalement sur 22 peptides et 70% d'entre eux ont validé cette analogie, puisque les peptides bien retenus en IMAC étaient également dotés d'une bonne affinité pour Ni2+ en SPR. Dans un deuxième temps, des peptides ayant une forte affinité pour Ni2+ (c'est-à-dire une faible constante de dissociation KD en SPR et un temps de rétention élevé en IMAC) ont été utilisés pour étudier la simulation des profils de concentration de peptides à la sortie de la colonne en IMAC. La connaissance des isothermes d'adsorption étant nécessaire pour effectuer la simulation, il a fallu développer une méthodologie pour prédire les paramètres de l'isotherme de Langmuir en IMAC à partir des données SPR. La simulation a été évaluée en comparant les temps de rétention expérimentaux et simulés qui devraient être proches pour une prédiction fiable. Par conséquent, plusieurs approches ont été étudiées pour déterminer les paramètres de sorption de Langmuir. L‘approche la plus intéressante a introduit un facteur correctif sur la capacité d'adsorption maximale qmax seulement. En effet, l'affinité des peptides pour le Ni2+ immobilisé étant supposée constante quelle que soit technologie utilisée (SPR vs. IMAC), la constante d'affinité KA n'a pas été modifiée. Parallèlement, les applications industrielles des PCMs et des hydrolysats peptidiques ont été étudiées. Tout d'abord, des hydrolysats de protéines de pois ont été produits par protéolyse enzymatique soit avec l'Alcalase® suivi de la Flavourzyme® (Alc+Flav≤1kDa), soit par la Protamex® suivi de la Flavourzyme® (Prot+Flav≤1kDa). La technologie SwitchSENSE® a mis en évidence la présence de peptides chélateurs de Ni2+ et les tests antioxydants ont montré que l'hydrolysat Prot+Flav≤1kDa avait une activité antiradicalaire et un pouvoir réducteur plus élevés, liés à son degré d'hydrolyse plus élevé et à la quantité de peptides de petite taille. Les hydrolysats de protéines de pois et les PCMs ont ensuite été étudiés pour leur capacité à inhiber l'oxydation des lipides dans les émulsions. Ils ont ralenti l'oxydation des lipides par chélation des métaux pro-oxydants (tels que Fe2+) en réduisant les produits d'oxydation primaires et secondaires, responsables de la détérioration des produits contenant des lipides. Ainsi, les hydrolysats de pois et les PCMs pourraient être utilisés comme antioxydants dans les produits alimentaires et cosmétiques, comme alternatives aux produits chimiques tels que l'EDTA, le BHT et le TBHQ
Metal-Chelating Peptides (MCPs), from protein hydrolysates, present various applications in nutrition, pharmacy, cosmetic etc. Yet, the empirical approach generally used to discover bioactive peptides from hydrolysates is time consuming and expensive due to many steps of fractionation, separation and biological activities evaluation. Thus, this PhD aimed to develop a novel approach for MCPs separation prediction using chromatography modelling and simulation based on the analogy between Immobilized Metal ion Affinity Chromatography (IMAC) and Surface Plasmon Resonance (SPR). For the first time, the SPR-IMAC analogy was experimentally investigated on 22 peptides and 70% of them validated this analogy, since peptides well retained in IMAC were also endowed with a good affinity for Ni2+ in SPR. In the second time, peptides with high affinity for Ni2+ (i.e low dissociation constant KD in SPR and a high retention time in IMAC) were used to study the modelling and simulation of peptide concentration profiles at the column outlet in IMAC. Since knowledge of adsorption isotherms was required to perform simulation, it was necessary to develop a methodology for predicting Langmuir isotherm parameters in IMAC from SPR data. The validity of simulation was evaluated by comparing experimental and simulated retention times that should be close for reliable prediction. Therefore, several approaches were evaluated to determine Langmuir sorption parameters, the most interesting one introduces a correction factor on the maximum adsorption capacity qmax alone, assuming that the affinity of peptides for immobilized Ni2+ did not change depending on the technology used (SPR vs. IMAC), thus affinity constant KA was not modified. Meanwhile, industrial application of MCPs and hydrolysates were studied. First, pea protein hydrolysates were produced by either Alcalase® followed by Flavourzyme® (Alc+Flav≤1kDa) or Protamex® followed by Flavourzyme® (Prot+Flav≤1kDa). SwitchSENSE® technology evidences the presence of Ni2+ chelating peptides and antioxidants tests showed that Prot+Flav≤1kDa has higher radical scavenging and reducing power, related to its higher degree of hydrolysis and small-size peptides quantity. Secondly, pea hydrolysates and MCPs were investigated for their ability to inhibit the lipid oxidation in emulsions. They slowed down lipid oxidation through chelation of prooxidant (metals such as Fe2+) reducing primary and secondary oxidation products responsible of deterioration of lipid containing products. Thus, pea hydrolysates and MCPs could be used as antioxidants in food and cosmetic products, as alternative to chemicals such as EDTA, BHT and TBHQ

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Shehadeh, Sandra C. "The Effects of Soy Protein and Isoflavones on Lipid Oxidation and Blood Lipid Profile on Humans Participating in Moderate Physical Activity." Thesis, Virginia Tech, 1999. http://hdl.handle.net/10919/36112.

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The purpose of our study was to compare the effects of dietary soy protein and animal protein (casein) on plasma lipoprotein concentrations, and exercise induced oxidation in human subjects. Sixteen normocholesterolemic young men participated in 30 min of cycling at 70% VO2pk to induce plasma oxidation. Each subject then followed a 4wk dietary treatment replacing 33g animal protein in a self-selected solid food diet with either soy protein or casein. The exercise was then repeated and plasma lipoproteins and oxidation were compared. Soy protein and casein dietary treatments did not affect plasma concentrations. Our study therefore, suggests that in healthy normocholesterolemic individuals, 33g of soy protein does not effectively reduce plasma lipoprotein concentrations or exercise induced oxidation.
Master of Science

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Afonso, Milessa da Silva. "Avaliação do efeito do extrato aquoso e da fração fenólica livre do Alecrim (Rosmarinus officinalis L.) sobre o estado antioxidante e o perfil lipídico em ratos com hipercolesterolemia induzida pela dieta." Universidade de São Paulo, 2010. http://www.teses.usp.br/teses/disponiveis/9/9132/tde-17012011-163651/.

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Abstract:

A hipercolesterolemia é considerada um importante fator de risco para as doenças cardiovasculares, já que a hiperlipidemia associada ao estresse oxidativo é um dos fatores para estabelecimento destas doenças. Neste contexto, antioxidantes presentes em alimentos como vitaminas, compostos fenólicos, entre outros têm recebido crescente atenção devido sua função quimiopreventiva contra danos oxidativos. O alecrim (Rosmarinus officinalis L.) é um membro da família Labiatae, cujas propriedades antioxidantes têm sido atribuídas a uma variedade de compostos fenólicos capazes de finalizar as reações de radicais livres e varrer as espécies reativas de oxigênio. O objetivo deste trabalho foi avaliar a capacidade antioxidante in vitro dos extratos e frações de ácidos fenólicos obtidos das folhas de alecrim e seu efeito sobre ratos com hipercolesterolemia induzida pela dieta suplementada com 0,50% de colesterol e 0,25% de ácido cólico. Os resultados mostraram que tanto os extratos quanto as frações apresentaram altos teores de compostos fenólicos totais e expressiva atividade antioxidante in vitro nos métodos de cooxidação de substratos β-caroteno/ácido linoleico e na varredura do radical DPPH. No ensaio in vivo, observou-se aumento significativo (p≤0,05) de colesterol total e de LDL colesterol nos animais que consumiram a dieta hipercolesterolêmica. Os compostos fenólicos presentes tanto no extrato aquoso quanto na fração não esterificada do alecrim foram capazes de atuar sobre a atividade das enzimas antioxidantes endógenas CAT, GPx e SOD, confirmando a ação dos compostos antioxidantes presentes nesta especiaria sobre parâmetros do estresse oxidativo. O extrato aquoso na concentração 70 mg/Kg reduziu os valores de colesterol total (39,8%) e LDL-c (45,6%) e melhorou o estado antioxidante dos animais, uma vez que aumentou a atividade da GPx no tecido cardíaco (43,2%) e reduziu a formação de SRATB (32,3%) no soro dos animais. Não foi observado efeito dose resposta no lipidograma destes animais, sugerindo um limiar de atuação do extrato aquoso. Em um contexto geral, o extrato aquoso e a fração não esterificada do alecrim apresentaram capacidade antioxidante in vitro significativa e, nas condições do estudo, exerceram um papel importante sobre o estresse oxidativo presente na hipercolesterolemia experimental, uma vez que os resultados obtidos para o extrato aquoso administrado na concentração de 70 mg/Kg sugerem um papel importante dos compostos fenólicos presentes neste extrato sobre o metabolismo de colesterol.
Hypercholesterolemia is considered an important risk factor for cardiovascular diseases, since hyperlipidemia associated to oxidative stress is one of the risk factors for these diseases. In this context, antioxidants derived from foods such as vitamins, phenolic compounds and others have been receiving increased attention due to their chemopreventive function against oxidative damages. Rosemary (Rosmarinus officinalis L.) belongs to the Labiatae family, whose antioxidant properties have been attributed to a variety of phenolic compounds capable of reacting with free radicals and quenching reactive oxygen species. The aim of this work was to evaluate the in vitro antioxidant capacity of extracts and phenolic acids fractions obtained from rosemary leaves and their effect on rats fed with 0.50% cholesterol and 0.25% cholic acid enriched diet. The results showed that extracts and fractions had high levels of total phenolic compounds and expressive antioxidant activity in vitro in both methods β-caroteno/ linoleic acid cooxidation and in the DPPH radical scavenge. Analysis in vivo showed a significant increase (p≤0.05) in total cholesterol and LDL cholesterol in hypercholesterolemic animals. Phenolic compounds present in rosemary aqueous extract and non-esterified fraction were capable to act on the activity of CAT, GPx and SOD, confirming the action of antioxidant compounds present in this spice on parameters of oxidative stress. Aqueous extract in concentration of 70 mg/Kg had reduced total cholesterol (39.8%) and LDL-c (45.6%) values and improved the animals\' antioxidant status, once it increased heart GPx activity (43.2%) and decreased SRATB production (32.3%) in the serum of this group. There was no dose response effect on serum lipids of these animals, suggesting a threshold of the aqueous extract activity. In a general context, the aqueous extract and non-esterified fraction of rosemary presented significant antioxidant capacity in vitro and in the conditions of the study, played an important role on the oxidative stress in experimental hypercholesterolemia, and the results obtained for the aqueous extract administered in the concentration of 70 mg/kg suggests an important role of phenolic compounds present in this extract on cholesterol metabolism.

Dissertations / Theses on the topic 'Oxidation des lipides'

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