Artículos de revistas: "Quantification des radicaux"

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Schwarz-Selinger, T., V. Dose, W. Jacob y A. von Keudell. "Quantification of a radical beam source for methyl radicals". Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films 19, n.º 1 (enero de 2001): 101–7. http://dx.doi.org/10.1116/1.1326939.

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Blakley, Richard L., Dwight D. Henry, Walter T. Morgan, William L. Clapp, Carr J. Smith y David Barr. "Quantitative Electron Paramagnetic Resonance: The Importance of Matching the Q-Factor of Standards and Samples". Applied Spectroscopy 55, n.º 10 (octubre de 2001): 1375–81. http://dx.doi.org/10.1366/0003702011953504.

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Electron paramagnetic resonance (EPR) quantification of free radicals from different samples facilitates comparison of free radical concentrations. Stable free radicals, such as 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO), in a suitable solvent (e.g., benzene) can be used as a quantification standard. Free radicals found in samples can be shorter lived than radicals in prepared standards and require stabilizing spin-trapping agents such as N-tert-butyl-α-phenylnitrone (PBN) in an appropriate solvent (e.g., benzene). Analysis in our laboratory showed that free radicals from spin-trapped samples quantified against a standard of TEMPO in benzene displayed large differences among identical samples measured on either a Micro-Now 8300, Micro-Now 8400, or Bruker EMX EPR instrument. The Bruker instrument reported that the typical TEMPO in benzene standard had a Q-factor of ∼4400 while the Q-factor of our PBN-containing samples was ∼2500. (The Q-factor is inversely proportional to the amount of dissipated microwave energy in an EPR cavity.) By placing the TEMPO standard in a PBN/benzene solvent matrix we were able to match the Q-factor of our standards and samples, resulting in each of the three EPR instruments giving the same quantified free radical yields for the samples. This result points out the importance of matching the Q-factor between samples and standards for any quantitative EPR measurement.

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Morgan, Christopher G., Mark M. Gleason y Ronald Vane. "Quantification of Contaminant Removal by Evactron Cleaning Using Quartz Crystal Thickness Monitors". Microscopy Today 15, n.º 5 (septiembre de 2007): 22–25. http://dx.doi.org/10.1017/s1551929500061198.

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Hydrocarbon (HC) contamination is a persistent problem for users of electron microscopes (EMs), often leading to image distortion and interference with nanoprobing. The Evactron De-Contaminator (D-C) has been available for HC contamination removal in EMs since 1999. The Evactron D-C uses low power radio frequency (RF) generated plasma in order to produce oxygen radicals that clean the EM. The Oxygen Radical Source (ORS) is attached to the EM chamber, and a controlled leak of oxygen containing gas such as room air is passed through the plasma in order to produce oxygen radicals. The oxygen radicals chemically react with the HCs to form volatile oxidation products such as H2O, CO and CO2. These volatile compounds are pumped out of the EM chamber.

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Cho, Eun Chul, Ju A. La, Sora Lim y Ji Eun Song. "Gold/Silver-Polymer Hybrid Nanostructures as Thermoreversible Optical Sensors and Probes for the Quantification Radical Compounds". MRS Proceedings 1802 (2015): 41–44. http://dx.doi.org/10.1557/opl.2015.833.

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ABSTRACTWe present gold (Au) and silver (Ag) nanoparticles (NPs) could be used not only for stimuli-responsive optical sensors but also for the quantification of radical compounds when these nanoparticles are suitably combined with polymeric materials. When Au NPs are assembled 2-dimensionally on the surface of hydrogel NPs which respond to temperatures, the hybrid NPs displayed thermoreversible multiple color switching. Accordingly, optical bandwidths of the hybrid NPs are reversibly changed with temperatures: with hybrid NPs assembled with 51 nm Au NPs, prominent optical signals are recorded at 900 nm at 50 °C while most of extinction signals are shown below 600 nm at room temperatures. In addition, we demonstrate the modification of Ag NPs’ surfaces (nanocubes and nanospheres) with polyelectrolytes (either positive or negative) could extend the quantifiable detection ranges of radical compounds. Through the surface modification of Ag NPs, the polyelectrolytes protect the Ag NPs by probably either retarding (forming diffusion barriers) or preventing (blocking/entrapping/scavenging) the arrival of radicals to Ag NPs or both. The roles of the polyelectrolytes are demonstrated by using radical compounds produced from tetrahydrofuran and H2O2. From the results, we could obtain calibration curves for the wide-range quantification of radical compounds.

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Goyal, Parveen Kumar, Santosh Kumar Verma y Anil Kumar Sharma. "Quantification of Total Phenolic and Flavonoid Contents, and Evaluation of Free Radical Scavenging Potential of Vernonia cinerea". Asian Pacific Journal of Health Sciences 4, n.º 3 (30 de septiembre de 2017): 279–87. http://dx.doi.org/10.21276/apjhs.2017.4.3.42.

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Peralta, E., G. Roa, J. A. Hernandez-Servin, R. Romero, P. Balderas y R. Natividad. "Hydroxyl Radicals quantification by UV spectrophotometry". Electrochimica Acta 129 (mayo de 2014): 137–41. http://dx.doi.org/10.1016/j.electacta.2014.02.047.

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Koshiishi, Ichiro, Kazunori Tsuchida, Tokuko Takajo y Makiko Komatsu. "Quantification of lipid alkyl radicals trapped with nitroxyl radical via HPLC with postcolumn thermal decomposition". Journal of Lipid Research 46, n.º 11 (16 de agosto de 2005): 2506–13. http://dx.doi.org/10.1194/jlr.d500006-jlr200.

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Hughes, H. M., I. M. George, J. C. Evans, C. C. Rowlands, G. M. Powell y C. G. Curtis. "The role of the liver in the production of free radicals during halothane anaesthesia in the rat. Quantification of N-tert-butyl-alpha-(4-nitrophenyl)nitrone (PBN)-trapped adducts in bile from halothane as compared with carbon tetrachloride". Biochemical Journal 277, n.º 3 (1 de agosto de 1991): 795–800. http://dx.doi.org/10.1042/bj2770795.

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Halothane or CCl4 was co-administered with the spin trap N-tert-butyl-alpha-(4-nitrophenyl)nitrone (PBN) to rats fitted with bile duct cannuli or to isolated perfused liver preparations. Rats maintained under halothane anaesthesia generated significant amounts of free radicals, and 5-9 nmol was excreted in bile over 1 h. No adducts were detected in urine or plasma. The hepatic origin of these free radicals was confirmed by studies on isolated perfused livers where the addition of halothane to the perfusate resulted in the biliary elimination of the same PBN-trapped radical adducts. Similarly, following CCl4 administration, the same radical species were eliminated in bile in the whole animal and the perfused liver preparation. In the perfused liver, over 3 h the total biliary elimination of radicals derived from halothane or CCl4 (administered at equimolar concentrations) was approximately the same (5-7 nmol); however, the elimination of halothane-derived radicals was more rapid over the first 1 h.

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Gardner, Jonathan M. y Steven D. Aust. "Quantification of hydroxyl radical produced during phacoemulsification". Journal of Cataract & Refractive Surgery 35, n.º 12 (diciembre de 2009): 2149–53. http://dx.doi.org/10.1016/j.jcrs.2009.06.030.

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Tanev, Mihail, Georgi Tomov y Yordanka Karakirova. "EPR Spectroscopy Investigation of Oxygen Radical Production by Methylene Blue and Indocyanine Green in Aqueous Solutions under Laser Irradiation in the Context of Antibacterial Photodynamic Therapy". Folia Medica 63, n.º 3 (30 de junio de 2021): 372–76. http://dx.doi.org/10.3897/folmed.63.e52102.

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Introduction: Antibacterial photodynamic therapy is a promising treatment modality in the anti-infective therapy of numerous oral diseases. It involves photo activation of a reactive substance (dye), thus releasing reactive oxygen species (ROS-radicals) which are highly destructive to the bacterial cell. However, thorough investigation of radical production properties of different dyes is not common in literature.Aim: The aim of this study was to investigate and evaluate oxygen radical-producing potential of two commonly used photoactive dyes in the context of antibacterial photodynamic therapy.Materials and methods: The radical-producing properties of two commonly used dyes for photodynamic therapy in oral medicine, methylene blue and indocyanine green, irradiated under laser irradiation are investigated using electron paramagnetic resonance (EPR) spectroscopy. The detection of reactive oxygen species is performed with “spin-trapping” technique.Results: The selected photoactive dyes showed promising yields of reactive oxygen species (ROS) in aqueous solutions. The comparative analysis of the results deemed methylene blue as the more productive photoactive agent.Conclusions: By employing the spin-trapping technique, this study indicates EPR-spectroscopy as a promising method of relative quantification of reactive oxygen species released by the photodynamic reaction in aqueous solutions.

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Fuchs, Hendrik, Sascha Albrecht, Ismail–Hakki Acir, Birger Bohn, Martin Breitenlechner, Hans-Peter Dorn, Georgios I. Gkatzelis et al. "Investigation of the oxidation of methyl vinyl ketone (MVK) by OH radicals in the atmospheric simulation chamber SAPHIR". Atmospheric Chemistry and Physics 18, n.º 11 (7 de junio de 2018): 8001–16. http://dx.doi.org/10.5194/acp-18-8001-2018.

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Abstract. The photooxidation of methyl vinyl ketone (MVK) was investigated in the atmospheric simulation chamber SAPHIR for conditions at which organic peroxy radicals (RO2) mainly reacted with NO (“high NO” case) and for conditions at which other reaction channels could compete (“low NO” case). Measurements of trace gas concentrations were compared to calculated concentration time series applying the Master Chemical Mechanism (MCM version 3.3.1). Product yields of methylglyoxal and glycolaldehyde were determined from measurements. For the high NO case, the methylglyoxal yield was (19 ± 3) % and the glycolaldehyde yield was (65 ± 14) %, consistent with recent literature studies. For the low NO case, the methylglyoxal yield reduced to (5 ± 2) % because other RO2 reaction channels that do not form methylglyoxal became important. Consistent with literature data, the glycolaldehyde yield of (37 ± 9) % determined in the experiment was not reduced as much as implemented in the MCM, suggesting additional reaction channels producing glycolaldehyde. At the same time, direct quantification of OH radicals in the experiments shows the need for an enhanced OH radical production at low NO conditions similar to previous studies investigating the oxidation of the parent VOC isoprene and methacrolein, the second major oxidation product of isoprene. For MVK the model–measurement discrepancy was up to a factor of 2. Product yields and OH observations were consistent with assumptions of additional RO2 plus HO2 reaction channels as proposed in literature for the major RO2 species formed from the reaction of MVK with OH. However, this study shows that also HO2 radical concentrations are underestimated by the model, suggesting that additional OH is not directly produced from RO2 radical reactions, but indirectly via increased HO2. Quantum chemical calculations show that HO2 could be produced from a fast 1,4-H shift of the second most important MVK derived RO2 species (reaction rate constant 0.003 s−1). However, additional HO2 from this reaction was not sufficiently large to bring modelled HO2 radical concentrations into agreement with measurements due to the small yield of this RO2 species. An additional reaction channel of the major RO2 species with a reaction rate constant of (0.006 ± 0.004) s−1 would be required that produces concurrently HO2 radicals and glycolaldehyde to achieve model–measurement agreement. A unimolecular reaction similar to the 1,5-H shift reaction that was proposed in literature for RO2 radicals from MVK would not explain product yields for conditions of experiments in this study. A set of H-migration reactions for the main RO2 radicals were investigated by quantum chemical and theoretical kinetic methodologies, but did not reveal a contributing route to HO2 radicals or glycolaldehyde.

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Rutely C., Burgos Castillo, Fontmorin Jean-M., Tang Walter Z., Dominguez-Benetton Xochitl y Sillanpää Mika. "Towards reliable quantification of hydroxyl radicals in the Fenton reaction using chemical probes". RSC Advances 8, n.º 10 (2018): 5321–30. http://dx.doi.org/10.1039/c7ra13209c.

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Taha, Youssef M., Matthew T. Saowapon, Faisal V. Assad, Connie Z. Ye, Xining Chen, Natasha M. Garner y Hans D. Osthoff. "Quantification of peroxynitric acid and peroxyacyl nitrates using an ethane-based thermal dissociation peroxy radical chemical amplification cavity ring-down spectrometer". Atmospheric Measurement Techniques 11, n.º 7 (17 de julio de 2018): 4109–27. http://dx.doi.org/10.5194/amt-11-4109-2018.

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Abstract. Peroxy and peroxyacyl nitrates (PNs and PANs) are important trace gas constituents of the troposphere which are challenging to quantify by differential thermal dissociation with NO2 detection in polluted (i.e., high-NOx) environments. In this paper, a thermal dissociation peroxy radical chemical amplification cavity ring-down spectrometer (TD-PERCA-CRDS) for sensitive and selective quantification of total peroxynitrates (ΣPN = ΣRO2NO2) and of total peroxyacyl nitrates (ΣPAN = ΣRC(O)O2NO2) is described. The instrument features multiple detection channels to monitor the NO2 background and the ROx ( = HO2 + RO2 + ΣRO2) radicals generated by TD of ΣPN and/or ΣPAN. Chemical amplification is achieved through the addition of 0.6 ppm NO and 1.6 % C2H6 to the inlet. The instrument's performance was evaluated using peroxynitric acid (PNA) and peroxyacetic or peroxypropionic nitric anhydride (PAN or PPN) as representative examples of ΣPN and ΣPAN, respectively, whose abundances were verified by iodide chemical ionization mass spectrometry (CIMS). The amplification factor or chain length increases with temperature up to 69 ± 5 and decreases with analyte concentration and relative humidity (RH). At inlet temperatures above 120 and 250 °C, respectively, PNA and ΣPAN fully dissociated, though their TD profiles partially overlap. Furthermore, interference from ozone (O3) was observed at temperatures above 150 °C, rationalized by its partial dissociation to O atoms which react with C2H6 to form C2H5 and OH radicals. Quantification of PNA and ΣPAN in laboratory-generated mixtures containing O3 was achieved by simultaneously monitoring the TD-PERCA responses in multiple parallel CRDS channels set to different temperatures in the 60 to 130 °C range. The (1 s, 2σ) limit of detection (LOD) of TD-PERCA-CRDS is 6.8 pptv for PNA and 2.6 pptv for ΣPAN and significantly lower than TD-CRDS without chemical amplification. The feasibility of TD-PERCA-CRDS for ambient air measurements is discussed.

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Xu, Jing, Xinguo Wu, Wei Yan, Ruxiu Cai y Zhixin Lin. "A new kinetic method for quantification phenoxyl free radicals". Talanta 70, n.º 2 (15 de septiembre de 2006): 323–29. http://dx.doi.org/10.1016/j.talanta.2006.02.055.

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Fogarasi, Erzsébet, Mircea Dumitru Croitoru, Ibolya Fülöp, Enikő Nemes-Nagy, Robert Gabriel Tripon, Zsuzsanna Simon-Szabo y Daniela-Lucia Muntean. "Malondialdehyde levels can be measured in serum and saliva by using a fast HPLC method with visible detection / Determinarea printr-o metodă HPLC-VIS rapidă a concentraţiilor serice şi salivare ale malondialdehidei". Revista Romana de Medicina de Laborator 24, n.º 3 (1 de septiembre de 2016): 319–26. http://dx.doi.org/10.1515/rrlm-2016-0029.

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Abstract Oxidative stress appears when the amount of free radicals that are formed in a living organism exceed its spin-trapping ability. One of the most dangerous free radicals that are formed in the human body is the hydroxyl radical. It can alter several biomolecules, including the unsaturated fatty acids; this process is known as lipid peroxidation and can lead to cell necrosis and generation of several harmful byproducts including malondialdehyde, which serves also as a biomarker of oxidative stress. A new HPLC method with visible detection was developed for the detection of malondialdehyde in human serum and saliva samples. The method was verified in terms of specificity, linearity, limits of detection (0.35 ng/ml), limit of quantification (1.19 ng/ml), recovery (90.13±10.25 – 107.29±14.33) and precision (3.84±1.49% – 6.66±1.76%). An analysis time of only 1 minute was obtained and no interferences from the matrices were observed. Statistical analysis (Pearson correlation test) showed a moderate correlation (R = 0.5061, p = 0.0099) between serum and saliva concentrations (N = 25). The possibility of measuring salivary concentrations of malondialdehyde extents the applications of oxidative stress/lipid peroxidation estimations to categories of population unreachable before (pregnant women, small children, etc); repeated sample studies are also easier to make.

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Chatgilialoglu, Chryssostomos, Carla Ferreri, Nicholas E. Geacintov, Marios G. Krokidis, Yuan Liu, Annalisa Masi, Vladimir Shafirovich, Michael A. Terzidis y Pawlos S. Tsegay. "5′,8-Cyclopurine Lesions in DNA Damage: Chemical, Analytical, Biological, and Diagnostic Significance". Cells 8, n.º 6 (28 de mayo de 2019): 513. http://dx.doi.org/10.3390/cells8060513.

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Purine 5′,8-cyclo-2′-deoxynucleosides (cPu) are tandem-type lesions observed among the DNA purine modifications and identified in mammalian cellular DNA in vivo. These lesions can be present in two diasteroisomeric forms, 5′R and 5′S, for each 2′-deoxyadenosine and 2′-deoxyguanosine moiety. They are generated exclusively by hydroxyl radical attack to 2′-deoxyribose units generating C5′ radicals, followed by cyclization with the C8 position of the purine base. This review describes the main recent achievements in the preparation of the cPu molecular library for analytical and DNA synthesis applications for the studies of the enzymatic recognition and repair mechanisms, their impact on transcription and genetic instability, quantitative determination of the levels of lesions in various types of cells and animal model systems, and relationships between the levels of lesions and human health, disease, and aging, as well as the defining of the detection limits and quantification protocols.

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Chiorcea-Paquim, Ana-Maria. "Electrochemical Sensing of Curcumin: A Review". Antioxidants 12, n.º 12 (22 de noviembre de 2023): 2029. http://dx.doi.org/10.3390/antiox12122029.

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Curcumin is a natural polyphenol derived from turmeric (Curcuma longa) root that has been used for centuries as a spice, coloring agent, and medicine. Curcumin presents anti-inflammatory, antioxidant, anticarcinogenic, antimicrobial, antiviral, antimalarial, hepatoprotective, thrombosuppressive, cardiovascular, hypoglycemic, antiarthritic, and anti-neurodegenerative properties. It scavenges different forms of free radicals and acts on transcription factors, growth factors and their receptors, cytokines, enzymes, and genes, regulating cell proliferation and apoptosis. Curcumin is electroactive, and a relationship between its electron transfer properties and radical-scavenging activity has been highlighted. The objective of this review is to provide a comprehensive overview of the curcumin electron transfer reactions, with emphasis on the controversial aspects related to its oxidation mechanism. The final sections will focus on the electroanalysis of curcumin in natural products, highlighting the most important sensing strategies, based on functional electrodes and nanostructured materials, essential for the development of more efficient in vitro methods of detection and quantification of curcumin in food samples, supplements, and nutripharmaceuticals.

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Botelho, Ricardo Vieira, Matheus Fernandes de Oliveira y Jose Marcus Rotta. "Quantification of Vertebral Involvement in Metastatic Spinal Disease". Open Orthopaedics Journal 7, n.º 1 (19 de agosto de 2013): 286–91. http://dx.doi.org/10.2174/1874325001307010286.

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Introduction: For patients with a solitary and well-delimitated spinal metastasis that resides inside the vertebral body, without vertebral canal invasion, and who are in good general health with a long life expectancy, en bloc spondylectomy/total vertebrectomy combined with the use of primary stabilizing instrumentation has been advocated. However, clinical experience suggests that these qualifying conditions occur very rarely. Objective: The purpose of this paper is to quantify the distribution of vertebral involvement in spinal metastases and determine the frequency with which patients can be considered candidates for radical surgery (en bloc spondylectomy). Methods: Consecutive patients were classified accordingly to Enneking’s and Tomita’s schemes for grading vertebral involvement of metastases. Results: Fifty-one (51) consecutive patients were evaluated. Eighty-three percent of patients presented with the involvement of multiple vertebral levels and/or spinal canal invasion. Conclusion: Because of diffuse vertebral involvement of metastases, no patients in this sample were considered to be candidates for radical spondylectomy of vertebral metastasis.

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ICHIKAWA, Kazuhiro, Sang-Kuk HAN y Hideo UTSUMI. "Quantification of hydroxyl radical during ozonation in batch system." Journal of Japan Society on Water Environment 22, n.º 11 (1999): 921–25. http://dx.doi.org/10.2965/jswe.22.921.

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20

Hu, Na y Sarah A. Green. "Acetyl radical generation in cigarette smoke: Quantification and simulations". Atmospheric Environment 95 (octubre de 2014): 142–50. http://dx.doi.org/10.1016/j.atmosenv.2014.06.027.

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Mitra, Indrani, Achintya Saha y Kunal Roy. "Quantification of contributions of different molecular fragments for antioxidant activity of coumarin derivatives based on QSAR analyses". Canadian Journal of Chemistry 91, n.º 6 (junio de 2013): 428–41. http://dx.doi.org/10.1139/cjc-2012-0527.

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Attempts have been made in the present work using in silico techniques for identification of essential structural features imparting antioxidant potential to naturally available coumarin molecules and their synthetic derivatives. Four different types of modeling tools have been employed for the qualitative and quantitative assessment of the molecular fragments constituting the biological pharmacophore. The descriptor-based quantitative structure–activity relationship (QSAR) and group-based QSAR (G-QSAR) models provide a quantitative estimation of the substituent requirements and the chemical nature of the parent moiety. Subsequently, 3D pharmacophore and hologram QSAR (HQSAR) models enable identification of the key molecular components necessary for the antioxidant potency to the molecules. All of the different models infer the importance of the hydrogen bond acceptor ketonic fragment for interaction of the antioxidant molecules with the neighbouring toxic radicals. Additionally, the phenyl substituent attached to the side chain and the benzene nucleus of the benzopyran moiety also constitute the response pharmacophore for the molecules under study. The models thus developed may serve as an essential query tool for screening of databases for selection of molecules bearing the essential fragments and subsequent prediction of their free radical scavenging potency.

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Wang, Wenjie, Jipeng Qi, Jun Zhou, Bin Yuan, Yuwen Peng, Sihang Wang, Suxia Yang, Jonathan Williams, Vinayak Sinha y Min Shao. "The improved comparative reactivity method (ICRM): measurements of OH reactivity under high-NO<sub><i>x</i></sub> conditions in ambient air". Atmospheric Measurement Techniques 14, n.º 3 (24 de marzo de 2021): 2285–98. http://dx.doi.org/10.5194/amt-14-2285-2021.

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Abstract. The comparative reactivity method (CRM) was developed more than a decade to measure OH reactivity (i.e., OH loss frequency) in both laboratory and field studies. However, accurate OH reactivity quantification remains challenging under real ambient conditions, especially for OH reactivity measurements in high-NOx (e.g., > 10 ppbv) environments, as ambient NO enhances the regeneration of OH radicals in the CRM reactor. To solve this problem, we design a new and improved CRM reactor (ICRM) and add NO into the system continuously so that the HO2 radical concentration is suppressed. We confirmed the appropriate level of NO by determining the maximum decrease in the pyrrole level caused by regenerated OH radicals from NO + HO2. RO2 radicals induced by volatile organic compounds (VOCs) in the ICRM reactor were also found to react with NO, which led to the regeneration of OH radicals and thus the underestimation of OH reactivity. This effect was quantified by the calibration of representative VOC species at different NO levels, and the correction coefficients obtained were used to correct the measured OH reactivity. All these efforts resulted in reducing the uncertainty of the NO-artifact correction by at least an order of magnitude compared to the original CRM system. Additionally, these technological improvements also considerably reduced the systematic errors from pyrrole photolysis in the original system. A new operation mode was proposed for the ICRM, which is able to avoid the interference resulting from OH radicals produced by photolysis of residual humidity and save time for ambient measurement. The ICRM system was employed in a field campaign to measure OH reactivity and performed well with ambient NO levels ranging from 0 to 50 ppbv, which are typically observed in the urban and suburban atmosphere.

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Krewenka, Christopher, Sandra Rizzi, Chi Huu Nguyen, Marcin Delijewski, Lars Gille, Katrin Staniek, Johanna Catharina Duvigneau et al. "Radical Scavenging Is Not Involved in Thymoquinone-Induced Cell Protection in Neural Oxidative Stress Models". Antioxidants 12, n.º 4 (1 de abril de 2023): 858. http://dx.doi.org/10.3390/antiox12040858.

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Thymoquinone (TQ), an active compound from Nigella sativa seeds, is often described as a pharmacologically relevant compound with antioxidative properties, while the synthesis of TQ in the plant via oxidations makes it inapplicable for scavenging radicals. Therefore, the present study was designed to reassess the radical scavenging properties of TQ and explore a potential mode of action. The effects of TQ were studied in models with mitochondrial impairment and oxidative stress induced by rotenone in N18TG2 neuroblastoma cells and rotenone/MPP+ in primary mesencephalic cells. Tyrosine hydroxylase staining revealed that TQ significantly protected dopaminergic neurons and preserved their morphology under oxidative stress conditions. Quantification of the formation of superoxide radicals via electron paramagnetic resonance showed an initial increase in the level of superoxide radicals in the cell by TQ. Measurements in both cell culture systems revealed that the mitochondrial membrane potential was tendentially lowered, while ATP production was mostly unaffected. Additionally, the total ROS levels were unaltered. In mesencephalic cell culture under oxidative stress conditions, caspase-3 activity was decreased when TQ was administered. On the contrary, TQ itself tremendously increased the caspase-3 activity in the neuroblastoma cell line. Evaluation of the glutathione level revealed an increased level of total glutathione in both cell culture systems. Therefore, the enhanced resistance against oxidative stress in primary cell culture might be a consequence of a lowered caspase-3 activity combined with an increased pool of reduced glutathione. The described anti-cancer ability of TQ might be a result of the pro-apoptotic condition in neuroblastoma cells. Our study provides evidence that TQ has no direct scavenging effect on superoxide radicals.

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Cassin, Savannah R., Sean Flynn, Pierre Chambon y Steve P. Rannard. "Quantification of branching within high molecular weight polymers with polyester backbones formed by transfer-dominated branching radical telomerisation (TBRT)". RSC Advances 11, n.º 39 (2021): 24374–80. http://dx.doi.org/10.1039/d1ra03886a.

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The characterisation and quantification of branching is key to understanding new complex macromolecules. Here we establish approaches to evaluate the unique and novel architectures formed by Transfer-dominated Branching Radical Telomerisation (TBRT).

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Xie, Jiangzhou, Changyong Zhang y T. David Waite. "Hydroxyl radicals in anodic oxidation systems: generation, identification and quantification". Water Research 217 (junio de 2022): 118425. http://dx.doi.org/10.1016/j.watres.2022.118425.

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Campbell, Steven J., Svetlana Stevanovic, Branka Miljevic, Steven E. Bottle, Zoran Ristovski y Markus Kalberer. "Quantification of Particle-Bound Organic Radicals in Secondary Organic Aerosol". Environmental Science & Technology 53, n.º 12 (10 de mayo de 2019): 6729–37. http://dx.doi.org/10.1021/acs.est.9b00825.

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Gál, Dezső, András Németh y Tamás Kriska. "Quantification of the formation of free radicals in macrophage systems". Reaction Kinetics and Catalysis Letters 68, n.º 1 (septiembre de 1999): 105–13. http://dx.doi.org/10.1007/bf02475492.

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RHEMREV, JOHANN P. T., FLORIS W. P. C. VAN OVERVELD, GUIDO R. M. M. HAENEN, TOM TEERLINK, AALT BAST y JAN P. W. VERMEIDEN. "Quantification of the Nonenzymatic Fast and Slow TRAP in a Postaddition Assay in Human Seminal Plasma and the Antioxidant Contributions of Various Seminal Compounds". Journal of Andrology 21, n.º 6 (12 de noviembre de 2000): 913–20. http://dx.doi.org/10.1002/j.1939-4640.2000.tb03422.x.

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ABSTRACT: Total radical‐trapping antioxidant potential (TRAP) measurements of human seminal plasma (N = 25) were performed by using a post‐addition assay based on trapping 2,2′ Azino‐bis(3‐ethylbenzthiazoline‐6‐sulfonic acid) (ABTS) radicals. This method enables the antioxidant capacity of human seminal plasma and its constituents to be quantified. The standard procedure consisted of determination of the Trolox equivalent antioxidant capacity (TEAC) after incubating the test sample in the ABTS radical solution for 10 seconds (fast TRAP) and 300 s (total TRAP). Interestingly, seminal plasma showed a fast TRAP and a high slow TRAP (Total TRAP ‐ Fast TRAP). The final total TRAP of seminal plasma is about 10 times higher than that of blood plasma. Various components of seminal plasma contribute to its fast TRAP; 37% can be attributed to vitamin C, uric acid, and tyrosine; proteins and polyphenolic compounds contribute a further 57%. In contrast, the slow TRAP was attributed to vitamin C (1%), uric acid (2%), and tyrosine (15%) and to proteins and polyphenolic compounds (33%). It was not possible to account for the remaining 49%. Neither known putative antioxidants, such as spermine, pyruvate, and taurine, nor other seminal compounds, such as carnitine, sialic acid, fructose, spermidine, glycerophosphorylcholine, and hyaluronic acid, contributed to any significant radical‐trapping activity at a standard concentration of 1 mM. Of the amino acids, only tyrosine possessed a slow TRAP, and it is present at a high concentration in seminal plasma. Glutathione and hypotaurine show high fast and slow TRAPs, respectively. However, because of their low concentration in seminal plasma, their contribution to the TRAP is negligible. In conclusion, seminal plasma possesses a high antioxidant buffer capacity that protects spermatozoa from oxidative stress. Moreover, these findings suggest that the fast and slow TRAPs may have an important role as infertility markers and treatment targets in future antioxidant therapies.

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Zaytsev, Alexander, Martin Breitenlechner, Anna Novelli, Hendrik Fuchs, Daniel A. Knopf, Jesse H. Kroll y Frank N. Keutsch. "Application of chemical derivatization techniques combined with chemical ionization mass spectrometry to detect stabilized Criegee intermediates and peroxy radicals in the gas phase". Atmospheric Measurement Techniques 14, n.º 3 (31 de marzo de 2021): 2501–13. http://dx.doi.org/10.5194/amt-14-2501-2021.

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Abstract. Short-lived highly reactive atmospheric species, such as organic peroxy radicals (RO2) and stabilized Criegee intermediates (SCIs), play an important role in controlling the oxidative removal and transformation of many natural and anthropogenic trace gases in the atmosphere. Direct speciated measurements of these components are extremely helpful for understanding their atmospheric fate and impact. We describe the development of an online method for measurements of SCIs and RO2 in laboratory experiments using chemical derivatization and spin trapping techniques combined with H3O+ and NH4+ chemical ionization mass spectrometry (CIMS). Using chemical derivatization agents with low proton affinity, such as electron-poor carbonyls, we scavenge all SCIs produced from a wide range of alkenes without depleting CIMS reagent ions. Comparison between our measurements and results from numeric modeling, using a modified version of the Master Chemical Mechanism, shows that the method can be used for the quantification of SCIs in laboratory experiments with a detection limit of 1.4×107 molecule cm−3 for an integration time of 30 s with the instrumentation used in this study. We show that spin traps are highly reactive towards atmospheric radicals and form stable adducts with them by studying the gas-phase kinetics of the reaction of spin traps with the hydroxyl radical (OH). We also demonstrate that spin trap adducts with SCIs and RO2 can be simultaneously probed and quantified under laboratory conditions with a detection limit of 1.6×108 molecule cm−3 for an integration time of 30 s for RO2 species with the instrumentation used in this study. Spin trapping prevents radical secondary reactions and cycling, ensuring that measurements are not biased by chemical interferences, and it can be implemented for detecting RO2 species in laboratory studies and potentially in the ambient atmosphere.

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DYKENS, JAMES A., J. MALCOLM SHICK, CRAIG BENOIT, GARRY R. BUETTNER y GARY W. WINSTON. "Oxygen Radical Production in the Sea Anemone Anthopleura Elegantissima and its Endosymbiotic Algae". Journal of Experimental Biology 168, n.º 1 (1 de julio de 1992): 219–41. http://dx.doi.org/10.1242/jeb.168.1.219.

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Host animals in algal-invertebrate endosymbiotic associations are exposed to photosynthetically generated hyperoxia while in sunlight, conditions conducive to photodynamic excitations and production of cytotoxic oxygen-derived radicals such as the superoxide anion (O2−) and the hydroxyl radical (OH). All previous vidence of oxyradical production in symbiotic associations has been circumstantial. We here present direct evidence, from electron paramagnetic resonance studies on tissue homogenates of the photosymbiont-containing sea anemone Anthopleura elegantissima (Brandt), of substantial light-dependent OH and O2 production that is abolished by dichlorophenyldimethylurea (DCMU), an inhibitor of photosynthesis. Shade-adapted A. elegantissima lacking endosymbiotic algae likewise show OH production upon illumination. The latter flux is not dependent on photosynthesis, and DCMU has no effect. Rather, OH production in apozooxanthellate anemones is via direct photoexcitations. The selective reaction of dimethyl sulfoxide (DMSO) with OH to form methane sulfinic acid allows quantification of OH produced in vivo. Such in vivo measurements confirm the production of OH in both host and algae in illuminated zooxanthellate anemones, where the amount of OH in the zooxanthellae is disproportionately large relative to their fractional contribution to the biomass of the symbiosis. In vivo studies using DMSO also suggest a photochemical production of OH in apozooxanthellate anemones exposed to simulated sunlight enriched in ultraviolet (UV) wavelengths, and the enhancement by UV light of OH production in zooxanthellate individuals. Such chronic radical exposure necessitates defenses

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31

Regoli, Francesco y Gary W. Winston. "Quantification of Total Oxidant Scavenging Capacity of Antioxidants for Peroxynitrite, Peroxyl Radicals, and Hydroxyl Radicals". Toxicology and Applied Pharmacology 156, n.º 2 (abril de 1999): 96–105. http://dx.doi.org/10.1006/taap.1999.8637.

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Gielis, Jan F., Gaëlle A. Boulet, Jacob J. Briedé, Tessa Horemans, Tom Debergh, Max Kussé, Paul Cos y Paul E. Y. Van Schil. "Longitudinal quantification of radical bursts during pulmonary ischaemia and reperfusion". European Journal of Cardio-Thoracic Surgery 48, n.º 4 (5 de enero de 2015): 622–29. http://dx.doi.org/10.1093/ejcts/ezu518.

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33

Tannous, Joy H. y Arno de Klerk. "Quantification of the Free Radical Content of Oilsands Bitumen Fractions". Energy & Fuels 33, n.º 8 (12 de julio de 2019): 7083–93. http://dx.doi.org/10.1021/acs.energyfuels.9b01115.

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34

Zhang, Xianhui, Renwu Zhou, Kateryna Bazaka, Yan Liu, Rusen Zhou, Guangliang Chen, Zhong Chen, Qinghuo Liu, Size Yang y Kostya Ken Ostrikov. "Quantification of plasma produced OH radical density for water sterilization". Plasma Processes and Polymers 15, n.º 6 (30 de abril de 2018): 1700241. http://dx.doi.org/10.1002/ppap.201700241.

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Arangio, Andrea M., Haijie Tong, Joanna Socorro, Ulrich Pöschl y Manabu Shiraiwa. "Quantification of environmentally persistent free radicals and reactive oxygen species in atmospheric aerosol particles". Atmospheric Chemistry and Physics 16, n.º 20 (26 de octubre de 2016): 13105–19. http://dx.doi.org/10.5194/acp-16-13105-2016.

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Abstract. Fine particulate matter plays a central role in the adverse health effects of air pollution. Inhalation and deposition of aerosol particles in the respiratory tract can lead to the release of reactive oxygen species (ROS), which may cause oxidative stress. In this study, we have detected and quantified a wide range of particle-associated radicals using electron paramagnetic resonance (EPR) spectroscopy. Ambient particle samples were collected using a cascade impactor at a semi-urban site in central Europe, Mainz, Germany, in May–June 2015. Concentrations of environmentally persistent free radicals (EPFR), most likely semiquinone radicals, were found to be in the range of (1–7) × 1011 spins µg−1 for particles in the accumulation mode, whereas coarse particles with a diameter larger than 1 µm did not contain substantial amounts of EPFR. Using a spin trapping technique followed by deconvolution of EPR spectra, we have also characterized and quantified ROS, including OH, superoxide (O2−) and carbon- and oxygen-centered organic radicals, which were formed upon extraction of the particle samples in water. Total ROS amounts of (0.1–3) × 1011 spins µg−1 were released by submicron particle samples and the relative contributions of OH, O2−, C-centered and O-centered organic radicals were ∼ 11–31, ∼ 2–8, ∼ 41–72 and ∼ 0–25 %, respectively, depending on particle sizes. OH was the dominant species for coarse particles. Based on comparisons of the EPR spectra of ambient particulate matter with those of mixtures of organic hydroperoxides, quinones and iron ions followed by chemical analysis using liquid chromatography mass spectrometry (LC-MS), we suggest that the particle-associated ROS were formed by decomposition of organic hydroperoxides interacting with transition metal ions and quinones contained in atmospheric humic-like substances (HULIS).

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36

Borges, J. C., M. R. Silva, A. C. Tedesco, D. S. Costa, C. R. Esper y P. H. Franceschini. "12 QUANTIFICATION OF REACTIVE OXYGEN SPECIES IN BOVINE SEMEN WITH DIFFERENT SEMINAL QUALITY AND WITH EXTENDER CONTAINING ANTIOXIDANT EVALUATED BY ARTIFICIAL INSEMINATION". Reproduction, Fertility and Development 22, n.º 1 (2010): 164. http://dx.doi.org/10.1071/rdv22n1ab12.

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The aim this study was to evaluate the effects on artificial insemination (AI) of minimizing oxidative stress by adding an antioxidant into the sperm microenvironment. For that purpose, semen of bulls with different seminal quality was evaluated in nature and after addition of extender with and without antioxidant, followed by freezing and thawing, with respect to thiobarbituric acid reactive substances (TBARS) concentration, total antioxidant capacity (TAC), and AI success. TBARS is an indicator of lipid peroxidation and TAC measures free radicals. Twelve ejaculates from 5 bulls were treated with Tris egg yolk extender (CE) and in half of each ejaculate the extender was supplemented with 200 μL of Trolox (AE). Three of these 5 bulls had high-quality semen (mean 11.9 ± 5.9 total defect, 7.7 ± 3.1 major defect, and 4.2 ± 3.9 minor defect) and 2 animals had poor-quality sperm (mean 31.9 ± 9.7 total defect, 26.3 ± 8.5 major defect, and 5.6 ± 5.0 minor defect) (P < 0.05). For AI, 300 Nelore heifers were divided in 10 groups and the females in each group were inseminated with semen of the same bull and extender treatment. To evaluate oxidative damage, TBARS concentration was measured to indirectly determine malondialdehyde (lipid-peroxidation metabolite) concentration, whereas TAC was measured using myoglobin, as a source of radicals, which interact with a chromogen 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonate) (ABTS), whose cation radical is spectroscopically detectable. The latency phase (lag) in the accumulation of ABTS cation is proportional to the antioxidant concentration. The pregnancy rates 60 days after AI were analyzed by chi-square test, and data of free radical production were evaluated by ANOVA, followed by the Tukey test with significance level of 5%. Reactive oxygen species (ROS) production in nature semen (0.351 nmol of TBARS in 50 × 108 spermatozoa) was lower (P < 0.05) when compared to diluted semen (0.367 nmol of TBARS in 50 × 108 spermatozoa). No difference (P > 0.05) between extenders was observed after thawing. The bulls with poor-quality semen presented total ROS production (0.967) superior (P < 0.05) to that of bulls with good-quality semen (0.753). Although the use of antioxidant in the extender did not decrease ROS and TAC production (P > 0.05), pregnancy rates after AI in bulls with poor quality semen with AE (60.0%) was superior (P < 0.06) to that in bulls with high-quality sperm with AE (56.6%). In conclusion, bulls with poor-quality semen present higher ROS and TAC production, and the use of antioxidant in the extender for cryopreservation with poor-quality bovine semen, in spite of not decreasing ROS and TAC production, improves pregnancy rates. Financial support: FAPESP.

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Wang, Yun, Xuefei Lv, Yu Li, Guang Peng, Javed Iqbal y Yulin Deng. "Preparation of trypsin aptamer modified silica particles by surface initiated atom transfer radical polymerization for proteome identification". Analytical Methods 8, n.º 21 (2016): 4277–84. http://dx.doi.org/10.1039/c5ay02080h.

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Craciun, Veronica Isabela, Felicia Gabriela Gligor, Anca Maria Juncan, Luca Liviu Rus y Claudiu Morgovan. "Ubidecarenone Quantification in Food Supplements A new HPLC method". Revista de Chimie 70, n.º 10 (15 de noviembre de 2019): 3575–78. http://dx.doi.org/10.37358/rc.19.10.7599.

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Coenzyme Q10 has a powerful antioxidant effect because it protects cells against free radicals and plays an important role in metabolism. Although controversial some preliminary evidence suggests that Coenzyme Q10 can help prevent or treat treatment of diseases of the cardiovascular and musculoskeletal systems and liver problems. Age increase and medical conditions are associated with lower Coenzyme Q10. There are evidences that diet supplementation with supplements containing Coenzyme Q10 may be beneficial. This paper aims to develop an HPLC method for identifying and dosing Ubidecarenone in food supplements. Using this technique, several supplements containing varying Ubidecarenone, ranging from 76 to 103% of the stated amount per dosage form were tested.

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39

Allabaksh, Shaik y R. Senthilraj. "A QUANTITATIVE HPLC ANALYSIS OF PHYTOCONSTITUENTS AND ASSESSMENT OF ANTIOXIDANT PROPERTIES OF THE RHIZOME OF Curcuma angustifolia ROXB". Rasayan J. Chem 17, n.º 02 (2024): 588–97. http://dx.doi.org/10.31788/rjc.2024.1728798.

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The study undertaken aimed to rigorously standardize the primary phytochemical categories within the rhizome of Curcuma angustifolia, commonly referred to as Indian Arrowroot, by employing reverse-phase High-Performance Liquid Chromatography (HPLC). This research also ventured into assessing the antioxidant potential of rhizomederived extracts from Curcuma angustifolia. In this context, the ethanol extract of the Curcuma angustifolia Roxb. rhizome was meticulously analyzed for its content of vital phytochemicals such as flavonoids (0.013±0.78mg/ml), alkaloids (0.11±0.45mg/ml), and phenolics (4.08±0.08 mg/ml). The precision and accuracy of HPLC facilitated the identification and quantification of these significant compounds. Further, results from this study indicated that the extracts, with a particular emphasis on the ethanol extract, demonstrated notable antioxidant activities with IC50 values of 235.53±0.25µg/ml (DPPH Assay), 61.90±0.34µg/ml (Hydroxy Radical Assay), and 420.53±0.33µg/ml (Nitric Oxide Assay). This is primarily attributed to their capacity to scavenge free radicals effectively, highlighting the considerable potential of Curcuma angustifolia Roxb. for ethnomedicinal use and its prospective pharmacological applications. The findings lay the groundwork for further exploration into the traditional medicinal applications of Curcuma angustifolia Roxb. and its potential integration into pharmaceutical developments.

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40

Agatonovic-Kustrin, Snezana y David W. Morton. "Quantification of polyphenolic antioxidants and free radical scavengers in marine algae". Journal of Applied Phycology 30, n.º 1 (26 de abril de 2017): 113–20. http://dx.doi.org/10.1007/s10811-017-1139-x.

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Kozuleva, Marina, Irina Klenina, Ivan Mysin, Igor Kirilyuk, Vera Opanasenko, Ivan Proskuryakov y Boris Ivanov. "Quantification of superoxide radical production in thylakoid membrane using cyclic hydroxylamines". Free Radical Biology and Medicine 89 (diciembre de 2015): 1014–23. http://dx.doi.org/10.1016/j.freeradbiomed.2015.08.016.

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42

La, Ju A. y Eun Chul Cho. "Manipulation of Silver Nanocubes Detection Sensitivity to Radical Compounds by Modifying Their Surfaces with Anionic/Cationic Polyelectrolytes for Wide-Range Quantification of Radicals". Analytical Chemistry 86, n.º 13 (19 de junio de 2014): 6675–82. http://dx.doi.org/10.1021/ac501430t.

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43

Sholola, M. T., E. M. Adongbede, L. L. Williams y A. A. Adekunle. "Antioxidant and Antibacterial Activities of Secondary Metabolites from Microporus xanthopus (Fr.) Kuntze (Polypore) Collected from the Wild in Lagos, Nigeria". Journal of Applied Sciences and Environmental Management 26, n.º 5 (31 de mayo de 2022): 877–83. http://dx.doi.org/10.4314/jasem.v26i5.15.

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The secondary metabolites in medicinal mushrooms are responsible for their activity against infectious diseases, cancer, diabetes, and diseases caused by presence of free radicals in the body. Microporus xanthopus a polypore medicinal mushroom was collected from the wild in Lagos Nigeria and identified using standard manuals and oligosaccharides, polysaccharide and polyphenols extracted from its tissues were investigated for antibacterial and antioxidant activities. M. xanthopus oligosaccharides were extracted with neutral and acid detergents and hydrolysis with concentrated H2SO4. Polysaccharides and polyphenols extracted with hot water and acidified methanol, respectively. Concentrations of oligosaccharides, polysaccharides and polyphenols were determined with the total carbohydrate and total phenolic quantification assay kits, respectively. The antioxidant activities of the extractsnvestigated using the DPPH Radical Scavenging Assay and Trolox Antioxidant Equivalent Capacity (TEAC) Assay in In-Vitro experiments in 96-well microtiter plates. The antibacterial effect of the extracts was determined with broth microdilution assay using human pathogenic bacteria (Escherichia coli (0157:H7) and Staphylococcus aureus ATCC®700698 (MRSA). Oligosaccharides showed the highest DPPH radical scavenging activity (86%) with half maximal effective (EC50) of 16.46µg/mL. The highest TEAC value (1.18µM TE/g) was recorded in the oligosaccharide extract and the least TEAC value (0.39µM TE/g) was in the polyphenol extract. The most potent antimicrobial agent was the oligosaccharide extract with IC50 of 44.64 µg/mL and 40.08 µg/mL for E. coli and S. aureus, respectively. Oligosaccharide extracts were more active than the polyphenol and polysaccharide extracts. M. xanthopus oligosaccharides can be developed as potential new dietary supplements with antioxidant and antibacterial activities.

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44

Pugalenthi, M., M. Pradheeba, S. Vishnu Kumar, G. Vasukipriyadharshini, S. Swathi y G. Divya Bharathi. "UNVEILING THE PHYTOCHEMICAL PROFILE, SECONDARY METABOLITE QUANTIFICATION AND ANTIOXIDANT ACTIVITY OF CLEMATIS WIGHTIANA WALL. EX WIGHT and ARN." Journal of Advanced Scientific Research 13, n.º 03 (30 de abril de 2022): 70–77. http://dx.doi.org/10.55218/jasr.202213312.

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Traditionally, the leaves of Clematis wightiana have been used in the treatment of rheumatism, indigestion, headaches, varicose veins, bone problems, nasal congestion and sinus. The present study was conducted to evaluate the phytochemical profile, quantification of secondary metabolites and free radical scavenging capacity of C. wightiana leaf. The total phenolic, tannin and flavanoid content of C. wightiana leaves were quantified and were found to be higher in the ethyl acetate extract. Subsequently, the extracts were subjected to appraise their antioxidant capacity by availing various in vitro antioxidant assays namely DPPH radical scavenging assay, ABTS assay, Phosphomolybedenum assay, Ferric Reducing assay, Superoxide Radical Scavenging assay and Reducing power assay. The results of the antioxidant assays revealed that the ethyl acetate extract of C. wightiana leaves possess better free radical scavenging activity than other solvent extracts. Thus, the finding of the study elucidates the perception on phytochemical and bioactivity of C. wightiana which could be used in development of phytotherapeutics to enchance human health. Keywords: Clematis wightiana, Antioxidant, Superoxide radical scavenging, In vitro antioxidant assay, DPPH, Ethnomedicine.

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45

Sahni, Mayank y Bruce R. Locke. "Quantification of Hydroxyl Radicals Produced in Aqueous Phase Pulsed Electrical Discharge Reactors". Industrial & Engineering Chemistry Research 45, n.º 17 (agosto de 2006): 5819–25. http://dx.doi.org/10.1021/ie0601504.

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46

Jackson, Malcolm J. "An overview of methods for assessment of free radical activity in biology". Proceedings of the Nutrition Society 58, n.º 4 (noviembre de 1999): 1001–6. http://dx.doi.org/10.1017/s0029665199001317.

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Assays which purport to assess free radical activity in biological systems are multiple. However, despite numerous published descriptions of new methods and modifications of methods to assess free radical activity in biological materials, there is still a lack of reliable techniques for quantification of activity in vivo. Analysis of a number of related indicators and use of a variety of approaches appears the only reliable way to evaluate these processes in vivo. In studies of free radical generation by contracting skeletal muscle we have attempted to use a variety of indicators, including measurement of endogenous antioxidant levels, measurement of indirect indicators of free radical activity (e.g. products of lipid peroxidation, DNA oxidation or protein oxidation) and, where possible, measurement of direct indicators of free radical activity by electron spin resonance techniques. In view of the relative lack of specificity of many available techniques, caution should be exerted in evaluating the numerous examples of isolated single measures of free radical activity which are present in the scientific literature.

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47

Wilson, David H., David W. Hanlon, Gail K. Provuncher, Lei Chang, Linan Song, Purvish P. Patel, Evan P. Ferrell et al. "Fifth-Generation Digital Immunoassay for Prostate-Specific Antigen by Single Molecule Array Technology". Clinical Chemistry 57, n.º 12 (1 de diciembre de 2011): 1712–21. http://dx.doi.org/10.1373/clinchem.2011.169540.

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BACKGROUND Measurement of prostate-specific antigen (PSA) in prostate cancer patients following radical prostatectomy (RP) has been hindered by the limit of quantification of available assays. Because radical prostatectomy removes the tissue responsible for PSA production, postsurgical PSA is typically undetectable with current assay methods. Evidence suggests, however, that more sensitive determination of PSA status following RP could improve assessment of patient prognosis and response to treatment and better target secondary therapy for those who may benefit most. We developed an investigational digital immunoassay with a limit of quantification 2 logs lower than current ultrasensitive third-generation PSA assays. METHODS We developed reagents for a bead-based ELISA for use with high-density arrays of femtoliter-volume wells. Anti-PSA capture beads with immunocomplexes and associated enzyme labels were singulated within the wells of the arrays and interrogated for the presence of enzymatic product. We characterized analytical performance, compared its accuracy with a commercially available test, and analyzed longitudinal serum samples from a pilot study of 33 RP patients. RESULTS The assay exhibited a functional sensitivity (20% interassay CV) <0.05 pg/mL, total imprecision <10% from 1 to 50 pg/mL, and excellent agreement with the comparator method. All RP samples were well within the assay measurement capability. PSA concentrations following surgery were found to be predictive of prostate cancer recurrence risk over 5 years. CONCLUSIONS The robust 2-log improvement in limit of quantification relative to current ultrasensitive assays and the validated analytical performance of the assay allow for accurate assessment of PSA status after RP.

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48

Sushila Saini. "In vitro antioxidant activity and total phenolic content of Digera muricata leaves". World Journal of Biology Pharmacy and Health Sciences 14, n.º 3 (30 de junio de 2023): 105–12. http://dx.doi.org/10.30574/wjbphs.2023.14.3.0255.

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In the present study quantification of total phenolic content and evaluation of in vitro antioxidant capability of five different extracts of Digera muricata was carried out by different assays. DPPH radical, superoxide radical, hydroxyl radical scavenging activity and metal chelating activity were calculated and compared with standard antioxidants. Reducing power of the extract was also determined. All extracts showed good free radical scavenging ability which gets enhanced with increasing concentration. Methanolic extract possessed highest scavenging ability and it has maximum phenolic content (41.87 mg/g GAE). Significant correlation was observed between antioxidant assays and total phenolic content indicating that phenolics may be contributing towards antioxidant activity. The results conclude that D. muricata extracts are a potential source of natural antioxidants and could show promise as therapeutic agent in preventing the progression of oxidative stress related degenerative disorders.

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49

Passos, Marcele F., Nayara M. S. Carvalho, Ana Amélia Rodrigues, Vanessa P. Bavaresco, André L. Jardini, Maria Regina W. Maciel y Rubens Maciel Filho. "PHEMA Hydrogels Obtained by Infrared Radiation for Cartilage Tissue Engineering". International Journal of Chemical Engineering 2019 (31 de enero de 2019): 1–9. http://dx.doi.org/10.1155/2019/4249581.

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Although the exposure of polymeric materials to radiation is a well-established process, little is known about the relationship between structure and property and the biological behavior of biomaterials obtained by thermal phenomena at 1070 nm wavelength. This study includes results concerning the use of a novel infrared radiation source (ytterbium laser fiber) for the synthesis of poly(2-hydroxyethyl methacrylate) (PHEMA) hydrogel in order to produce medical devices. The materials were obtained by means of free radical polymerization mechanism and evaluated regarding its cross-linking degree, polymer chain mobility, thermal, and mechanical properties. Their potential use as a biomaterial toward cartilage tissue was investigated through incubation with chondrocytes cells culture by dimethylmethylene blue (DMMB) dye and DNA quantification. Differential scanning calorimetry (DSC) results showed that glass transition temperature (Tg) was in the range 103°C–119°C, the maximum degree of swelling was 70.8%, and indentation fluency test presented a strain of 56%–85%. A significant increase of glycosaminoglycans (GAGs) concentration and DNA content in cells cultured with 40 wt% 2-hydroxyethyl methacrylate was observed. Our results showed the suitability of infrared laser fiber in the free radicals formation and in the rapid polymer chain growth, and further cross-linking. The porous material obtained showed improvements concerning cartilage tissue regeneration.

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50

Rostro, Lizbeth, Aditya G. Baradwaj y Bryan W. Boudouris. "Controlled Radical Polymerization and Quantification of Solid State Electrical Conductivities of Macromolecules Bearing Pendant Stable Radical Groups". ACS Applied Materials & Interfaces 5, n.º 20 (3 de octubre de 2013): 9896–901. http://dx.doi.org/10.1021/am403223s.

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