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Venkatachalapathi, A., Abdul Kaffoor H e S. Paulsamy. "In vitro antioxidant activity and polyphenol estimation of methanolic fruit extract of Carissa spinarum L." Journal of Ayurvedic and Herbal Medicine 3, n.º 3 (30 de setembro de 2017): 122–26. http://dx.doi.org/10.31254/jahm.2017.3304.
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Antioxidant property of methanolic fruit extract of the medicinal tree species, Carissa spinarum was evaluated by studying the contents of total phenolics, tannins and flavonoids, free radical scavenging activity using 1,1-diphenyl-2- picryl hydrozyl (DPPH), hydroxyl radical scavenging activity, reducing power activity, ABTS•+ assay and metal chelating activity. The results of the study revealed that both the parts studied were found to have potent antioxidant activity against DPPH, hydroxyl and ABTS•+ radicals with the IC50 value of 88.98 for methanolic fruit extract for DPPH radicals and 849.70 for hydroxyl radicals. Therefore methanolic fruit extract of C. spinarum can be considered as a new potential source of natural antioxidants for pharmaceutical industries.
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Utsumi, Hideo, Sang-Kuk Han e Kazuhiro Ichikawa. "Enhancement of hydroxyl radical generation by phenols and their reaction intermediates during ozonation". Water Science and Technology 38, n.º 6 (1 de setembro de 1998): 147–54. http://dx.doi.org/10.2166/wst.1998.0247.
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Generation of hydroxyl radicals, one of the major active species in ozonation of water was directly observed with a spin-trapping/electron spin resonance (ESR) technique using 5,5-dimethyl-1-pyrrolineN-oxide (DMPO) as a spin-trapping reagent. Hydroxyl radical were trapped with DMPO as a stable radical, DMPO-OH. Eighty μM of ozone produced 1.08 X 10-6M of DMPO-OH, indicating that 1.4% of •OH is trapped with DMPO. Generation rate of DMPO-OH was determined by ESR/stopped-flow measurement. Phenol derivatives increased the amount and generation rate of DMPO-OH, indicating that phenol derivatives enhance •OH generation during ozonation of water. Ozonation of 2,3-, 2,5-, 2,6-dichlorophenol gave an ESR spectra of triplet lines whose peak height ratio were 1:2:1. ESR parameters of the triplet lines agreed with those of the corresponding dichloro-psemiquinone radical. Ozonation of 2,4,5- and 2,4,6-trichlorophenol gave the same spectra as those of 2,5- and 2,6-dichlorophenol, respectively, indicating that a chlorine group in p-position is substituted with a hydroxy group during ozonation. Amounts of the radical increased in an ozone-concentration dependent manner and were inhibited by addition of hydroxyl radical scavengers. These results suggest that p-semiquinone radicals are generated from the chlorophenols by hydroxyl radicals during ozonation. The p-semiquinone radicals were at least partly responsible for enhancements of DMPO-OH generation.
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Rao, Ashwathanarayana. "STUDY ON ANTIOXIDANT AND CYTOTOXIC PROPERTIES OF OLEA DIOICA ROXB. CRUDE EXTRACT AND ITS PURE COMPOUND COLLECTED FROM WESTERN GHATS, KARNATAKA, INDIA." Asian Journal of Pharmaceutical and Clinical Research 10, n.º 2 (1 de fevereiro de 2017): 356. http://dx.doi.org/10.22159/ajpcr.2017.v10i2.15727.
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Introduction: Olea dioica Roxb. an important medicinal tree plants used by local siddha tribes, belongs to the family Oleaceae. The parts such asleaves, bark, root, and fruits used in the traditional medicine to cure skin diseases, rheumatism, fever, and cancer.Objectives: The anti-oxidant experiment by metal chelating activity, superoxide radicals, hydroxyl radical, 2,2-diphenyl-2-picrylhydrazyl radicals,2,2-azino-bis(3-ethylbenzothiazoline)-6-sulfonic acid radical scavenging assays with in vitro cytotoxicity was tested using trypan blue dye exclusiontechnique and 3-(4, 5 dimethylthiazole-2yl)-2, 5-diphenyltetrazolium bromide assay was conducted.Results: Anti-oxidant experiments revealed that the bark ethanolic extract of the O. dioica plant parts has excellent radical scavenging activity and itsextracted pure compound, Benzene ethanol, 4-hydroxy-alcohol, showed excellent radical scavenging activity higher than the standards used. In vitrocytotoxicity experiments revealed that bark ethanolic extract has excellent cytotoxicity activity and its pure compound benzene-ethanol, 4-hydroxyalcoholalso showed excellentactivitywhichis comparablewith the standardcurcumin.Conclusion: O. dioica bark could be exploited as a valuable source of antioxidant and cytotoxic agent for pharmaceutical industry.Keywords: Olea dioica Roxb, Metal chelating, Superoxide radicals, Hydroxyl radical, 2,2-diphenyl-2-picrylhydrazyl radicals, 2,2-azinobis(3-ethylbenzothiazoline)-6-sulfonic acid radical scavenging,Trypan blue, 3-(4,5dimethylthiazole-2yl)-2,5-diphenyltetrazolium bromide assay, Benzeneethanol, 4-hydroxy-alcohol.
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Zheng, Cheng-Dong, Gang Li, Hu-Qiang Li, Xiao-Jing Xu, Jin-Ming Gao e An-Ling Zhang. "DPPH-Scavenging Activities and Structure-Activity Relationships of Phenolic Compounds". Natural Product Communications 5, n.º 11 (novembro de 2010): 1934578X1000501. http://dx.doi.org/10.1177/1934578x1000501112.
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Thirty-eight phenolic compounds (including 31 flavonoids) were examined for their DPPH radical-scavenging activities, and structure-activity relationships were evaluated. Specifically, the presence of an Ortho-dihydroxyl structure in phenolics is largely responsible for their excellent antiradical activity. 3-Hydroxyl was also essential to generate a high radical-scavenging activity. An increasing number of hydroxyls on flavones with a 3′,4′-dihydroxyl basic structure, the presence of a third hydroxyl group at C-5′, a phloroglucinol structure, glycosylation and methylation of the hydroxyls, and some other hydroxyls, for example 5-, and 7-hydroxyl in ring A, decreased the radical-scavenging activities of flavonoids and other phenolics.
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Duwe, A. K., J. Werkmeister, J. C. Roder, R. Lauzon e U. Payne. "Natural killer cell-mediated lysis involves an hydroxyl radical-dependent step." Journal of Immunology 134, n.º 4 (1 de abril de 1985): 2637–44. http://dx.doi.org/10.4049/jimmunol.134.4.2637.
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Abstract The role of oxygen radicals in lysis of K562 target cells by human natural killer (NK) cells was determined by addition of scavengers of these free radicals. Lysis was greatly reduced under hypoxic conditions. Superoxide dismutase and cytochrome c, scavengers of superoxide anions, and catalase and scavengers of hypochlorite had no effect on lysis. Of 15 hydroxyl radical scavengers tested, 13 inhibited lysis. These were not toxic, because cell morphology and spontaneous chromium release were not affected and preculture with scavengers was not inhibitory. These scavengers differed widely in structure, but degree of inhibition of lysis correlated with their rate constants (k) for reaction with hydroxyl radical (k vs log inhibitor concentration required to decrease lysis by 50%: r = -0.9202, p less than 0.001), showing that inhibition was due to inactivation of the hydroxyl radical. Target cell binding was not reduced at concentrations that inhibited lysis. Inhibitors of the lipoxygenase pathway also decreased lysis, suggesting this pathway to be the source of hydroxyl radicals. In view of the reported requirements for hydroxyl radical-mediated lipid peroxidation for optimal secretory activity in a number of cell types, it appears that the generation of hydroxyl radicals by NK cells is required for delivery of cytotoxic factors.
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Flitter, W. D., e R. P. Mason. "The spin trapping of pyrimidine nucleotide free radicals in a Fenton system". Biochemical Journal 261, n.º 3 (1 de agosto de 1989): 831–39. http://dx.doi.org/10.1042/bj2610831.
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The reaction of the hydroxyl radical, generated by a Fenton system, with pyrimidine deoxyribonucleotides was investigated by using the e.s.r. technique of spin trapping. The spin trap t-nitrosobutane was employed to trap secondary radicals formed by the reaction of the hydroxyl radical with these nucleotides. The results presented here show that hydroxyl-radical attack on thymidine, 2-deoxycytidine 5-monophosphate and 2-deoxyuridine 5-monophosphate produced nucleotide-derived free radicals. The results indicate that .OH radical attack occurs predominantly at the carbon-carbon double bond of the pyrimidine base. The e.s.r. studies showed a good correlation with previous results obtained by authors who used x- or gamma-ray irradiation to generate the hydroxyl radical. A thiobarbituric acid assay was also used to monitor the damage produced to the nucleotides by the Fenton system. These results showed qualitative agreement with the spin-trapping studies.
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Gebicka, L., e J. L. Gebicki. "Scavenging of oxygen radicals by heme peroxidases." Acta Biochimica Polonica 43, n.º 4 (31 de dezembro de 1996): 673–78. http://dx.doi.org/10.18388/abp.1996_4463.
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The reactions of two heme peroxidases, horseradish peroxidase and lactoperoxidase and their compounds II (oxoferryl heme intermediates, Fe(IV) = O or ferric protein radical Fe(III)R.) and compounds III (resonance hybrids [Fe(III)-O2-. Fe(II)-O2] with superoxide radical anion generated enzymatically or radiolytically, and with hydroxyl radicals generated radiolytically, were investigated. It is suggested that only the protein radical form of compound II of lactoperoxidase reacts with superoxide, whereas compound II of horseradish peroxidase, which exists only in oxoferryl form, is unreactive towards superoxide. Compound III of the investigated peroxidases does not react with superoxide. The lactoperoxidase activity loss induced by hydroxyl radicals is closely related to the loss of the ability to form compound I (oxoferryl porphyrin pi-cation radical, Fe(IV) = O(Por+.) or oxoferryl protein radical Fe(IV) = O(R.)). On the other hand, the modification of horseradish peroxidase induced by hydroxyl radicals has been reported to cause also restrictions in substrate binding (Gebicka, L. & Gebicki, J.L., 1996, Biochimie 78, 62-65). Nevertheless, it has been found that only a small fraction of hydroxyl radicals generated homogeneously does inactivate the enzymes.
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Bi, Yong Guang, e Chun Chun Liu. "Study on Scavenging Free Radical Activity with Polysaccharides Materials in Chuanxiong Based on Composite Properties of Biomaterials". Advanced Materials Research 583 (outubro de 2012): 244–47. http://dx.doi.org/10.4028/www.scientific.net/amr.583.244.
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By using spectrophotometric detection of the Chuanxiong polysaccharides on the free radical scavenging. The results show that the Chuanxiong polysaccharides on DPPH radical, hydroxyl radical (HO•) and superoxide anion radical (•) clearance. Scavenging ability with the the Chuanxiong polysaccharide concentration increased, and showed the dose-effect relationship. Concentration of 2.0mg/mL when DPPH radicals clear the rate of 35.61%, while the rate of hydroxyl radicals and superoxide anion radical scavenging, clear the rate of 57.78% and 57.14%. Chuanxiong polysaccharide is an ideal natural antioxidants and good prospects for the development of biomedical composites.
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Wasselin-Trupin, V., G. Baldacchino e B. Hickel. "Détection des radicaux OH et O2 issus de la radiolyse de l'eau par chimiluminescence résolue en temps". Canadian Journal of Physiology and Pharmacology 79, n.º 2 (1 de fevereiro de 2001): 171–75. http://dx.doi.org/10.1139/y00-090.
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A new method for the detection of low concentrations of hydroxyl and superoxide radicals, formed by water radiolysis, is described in this article. The method used is the time resolved chemiluminescence. It has been performed with an electron beam delivered by a Febetron 707 accelerator. This method allows to measure hydroxyl and superoxide radical concentrations in a large range of concentrations, between 105 and 108 M.Key words: chemiluminescence, pulse radiolysis, hydroxyl radical, superoxyde radical.[Traduit par la Rédaction]
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Elliot, A. John, Shahsultan Padamshi e Jana Pika. "Free-radical redox reactions of uranium ions in sulphuric acid solutions". Canadian Journal of Chemistry 64, n.º 2 (1 de fevereiro de 1986): 314–20. http://dx.doi.org/10.1139/v86-053.
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The radiolytic reduction of uranyl ions in degassed sulphuric acid solutions containing various organic solutes was studied. It was shown that while ĊOOH, CO2−, and α-hydroxy-alkyl radicals reduced uranyl ions, the β-hydroxy-alkyl radicals and those derived from gluconic acid could not affect the reduction. The oxidation of uranium(IV) by hydrogen peroxide at pH 0.7 involves hydroxyl radicals in a chain mechanism but at pH 2.0 the oxidation proceeds by a non-radical reaction pathway. From the enhancement of the rate of oxidation of uranium(IV) by oxygen in the presence of 2-propanol, a mechanism involving the perhydroxyl radical, which reconciles earlier published data on kinetics and oxygen tracer studies, is proposed for the oxygen-uranium(IV) reactions.
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Kiruthiga, N. "MOLECULAR MODELLING AND EVALUATION ON SYNTHESISED 2-PHENYL-2,3-DIHYDRO-4 H-CHROMAN-4-ONE CORE AGAINST OXIDATIVE STRESS". Journal of Medical pharmaceutical and allied sciences 10, n.º 6 (15 de novembro de 2021): 4060–65. http://dx.doi.org/10.22270/jmpas.v10i6.2557.
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The aim of the study was to synthesis and characterization of 2,3-dihydro-4h-chroman-4-one core screened for antioxidant activity. The oxidative stress was related to the generation of Reactive oxygen species (ROS), which is responsible for the enhancement of several degenerative diseases, such as osteoarthritis, cancer, diabetes, cardiovascular diseases, etc. Due to this fact, the study was targeted for the development of myeloperoxidase inhibitor for overcoming the oxidative stress. The molecular docking analysis were afforded that the titled compounds possess noteworthy potency against myeloperoxidase (PDB ID: 1DNU). The docking simulation of seven hybrid of flavanone showed the better binding score ranging between -6.66 to -8.56 kcal/mol. Based on the result, the synthesised compounds were screened for the evaluation of various in-vitro antioxidant studies by hydroxy radical and nitric oxide radical scavenging assay. In which, the hydroxyl substituted flavanones (HFA3-HFA7) were afforded significant IC50 values compared with their respective standards due to their electron donating property which foraging the radicals responsible for oxidative stress were noted. Among the synthesised compounds, HFA5 and HFA6 produced excellent free radical scavenging on hydroxyl radical and nitric oxide radical methods were observed. From which the study initiated that synthesised flavanone core with hydroxyl and electron donating groups over the moiety should helpful in the management of major chronic diseases were initiated.
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Cho, Min, Hyenmi Chung, Wonyong Choi e Jeyong Yoon. "Different Inactivation Behaviors of MS-2 Phage and Escherichia coli in TiO2 Photocatalytic Disinfection". Applied and Environmental Microbiology 71, n.º 1 (janeiro de 2005): 270–75. http://dx.doi.org/10.1128/aem.71.1.270-275.2005.
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ABSTRACT Despite a wealth of experimental evidence concerning the efficacy of the biocidal action associated with the TiO2 photocatalytic reaction, our understanding of the photochemical mechanism of this particular biocidal action remains largely unclear. It is generally accepted that the hydroxyl radical (�OH), which is generated on the surface of UV-illuminated TiO2, plays the main role. However, our understanding of the exact mode of action of the hydroxyl radical in killing microorganisms is far from complete, and some studies report that other reactive oxygen species (ROS) (H2O2 and O2�−, etc.) also play significant roles. In particular, whether hydroxyl radicals remain bound to the surface or diffuse into the solution bulk is under active debate. In order to examine the exact mode of action of ROS in inactivating the microorganism, we tested and compared the levels of photocatalytic inactivation of MS-2 phage and Escherichia coli as representative species of viruses and bacteria, respectively. To compare photocatalytic microbial inactivation with the photocatalytic chemical degradation reaction, para-chlorobenzoic acid, which rapidly reacts with a hydroxyl radical with a diffusion-limited rate, was used as a probe compound. Two different hydroxyl radical scavengers, tert-butanol and methanol, and an activator of the bulk phase hydroxyl radical generation, Fe2+, were used to investigate their effects on the photocatalytic mode of action of the hydroxyl radical in inactivating the microorganism. The results show that the biocidal modes of action of ROS are very different depending on the specific microorganism involved, although the reason for this is not clear. It seems that MS-2 phage is inactivated mainly by the free hydroxyl radical in the solution bulk but that E. coli is inactivated by both the free and the surface-bound hydroxyl radicals. E. coli might also be inactivated by other ROS, such as O2�− and H2O2, according to the present results.
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Taiwo, F. A., H. J. Powers, E. Nakano, H. R. Griffiths e D. F. Nugent. "Free radical reactions in atherosclerosis; An EPR spectrometry study". Spectroscopy 20, n.º 2 (2006): 67–80. http://dx.doi.org/10.1155/2006/474183.
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The copper catalysed oxidation of homocysteine has been studied by electron paramagnetic resonance (EPR) spectroscopy and spin trapping techniques to determine the nature of free radical species formed under varying experimental conditions. Three radicals; thiyl, alkyl and hydroxyl were detected with hydroxyl being predominant. A reaction mechanism is proposed involving Fenton chemistry. Inclusion of catalase to test for intermediate generation of hydrogen peroxide showed a marked reduction in amount of hydroxyl radical generated. In contrast, the addition of superoxide dismutase showed no significant effect on the level of hydroxyl radical formed. Enhanced radical formation was observed at higher levels of oxygen, an effect which has consequences for differential oxygen levels in arterial and venous systems. Implications are drawn for a higher incidence of atherosclerotic plaque formation in arteries versus veins.
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Carlsson, Magnus, David Stenman, Gábor Merényi e Torbjörn Reitberger. "A comparative study on the degradation of cotton linters induced by carbonate and hydroxyl radicals generated from peroxynitrite". Holzforschung 59, n.º 2 (1 de fevereiro de 2005): 132–42. http://dx.doi.org/10.1515/hf.2005.020.
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Abstract Carbonate (CO3 •−) and hydroxyl (HO•) radicals were chemically produced in cotton linter suspensions using peroxynitrite as a radical precursor. Both radicals could degrade cotton linters, as shown by viscosity and GPC-SEC measurements. As evidenced by the viscosity measurements, the presence of oxygen during the cotton linter treatments slightly increased cellulose degradation by both radicals. For the carbonate radical, more than 90% of the viscosity losses could be recovered by reductive NaBH4 treatment before measuring the viscosity, whereas only approximately 40% of the viscosity was recovered after hydroxyl radical degradation and subsequent NaBH4 treatment. This indicates that carbonate radicals mainly abstract H-atoms adjacent to hydroxyl groups, i.e., at C2, C3 and C6. This intramolecular selectivity may reflect a polar effect, whereby hydrogen atom abstractions from these positions are favoured. In addition, abstraction at C6 would be sterically and statistically favoured.
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Haire, D. Larry, Yashige Kotake e Edward G. Janzen. "An EPR/ENDOR study of aminoxyls (nitroxides) capable of intramolecular bonding: hydroxyalkyl radical spin adducts of nitrones". Canadian Journal of Chemistry 66, n.º 8 (1 de agosto de 1988): 1901–11. http://dx.doi.org/10.1139/v88-307.
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A comparison of the effect of solvent and 13C labeling (of the radical addend) on the EPR (electron paramagnetic resonance) spectra of hydroxyalkyl vs. alkyl radical adducts of α-phenyl-N-tert-butyl nitrone (PBN) and 5,5-dimethyl-1-pyrroline-1-oxide (DMPO) has been investigated. The solution ENDOR spectra in toluene and in ethanol are the first examples studied of aminoxyls with hydroxyl substituents in close proximity to the free radical centre. Diastereomeric mixtures of hydroxyalkyl radical adducts are clearly resolved by ENDOR spectroscopy. Conformations of these radicals have been assigned based on the 1H and 13C hyperfine splittings (HFS's) and by differential optimum ENDOR temperatures. Definitive assignments of carbon-centered radical adducts of DMPO and PBN are shown to be feasible by monitoring the β-13C HFS's of the radical addend. Long-range γ-H HFS's from the added radical group can be observed when the deuterated spin trap PBN-d14 is used. The production of 13C labeled hydroxyalkyl adducts of nitrones (e.g., DMPO–13CH2OH, from the reaction of hydroxyl radicals with added 13CH3OH) is shown to be useful as an improved EPR spectroscopic method for the verification of the presence of hydroxyl radicals.
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Gonzalez, Teresa, Franck Peiretti, Catherine Defoort, Patrick Borel e Roland Govers. "2′,7′-dichlorofluorescin-based analysis of Fenton chemistry reveals auto-amplification of probe fluorescence and albumin as catalyst for the detection of hydrogen peroxide". Biochemical Journal 477, n.º 24 (18 de dezembro de 2020): 4689–710. http://dx.doi.org/10.1042/bcj20200602.
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Fluorophore 2′,7′-dichlorofluorescin (DCF) is the most frequently used probe for measuring oxidative stress in cells, but many aspects of DCF remain to be revealed. Here, DCF was used to study the Fenton reaction in detail, which confirmed that in a cell-free system, the hydroxyl radical was easily measured by DCF, accompanied by the consumption of H2O2 and the conversion of ferrous iron into ferric iron. DCF fluorescence was more specific for hydroxyl radicals than the measurement of thiobarbituric acid (TBA)-reactive 2-deoxy-D-ribose degradation products, which also detected H2O2. As expected, hydroxyl radical-induced DCF fluorescence was inhibited by iron chelation, anti-oxidants, and hydroxyl radical scavengers and enhanced by low concentrations of ascorbate. Remarkably, due to DCF fluorescence auto-amplification, Fenton reaction-induced DCF fluorescence steadily increased in time even when all ferrous iron was oxidized. Surprisingly, the addition of bovine serum albumin rendered DCF sensitive to H2O2 as well. Within cells, DCF appeared not to react directly with H2O2 but indirect via the formation of hydroxyl radicals, since H2O2-induced cellular DCF fluorescence was fully abolished by iron chelation and hydroxyl radical scavenging. Iron chelation in H2O2-stimulated cells in which DCF fluorescence was already increasing did not abrogate further increases in fluorescence, suggesting DCF fluorescence auto-amplification in cells. Collectively, these data demonstrate that DCF is a very useful probe to detect hydroxyl radicals and hydrogen peroxide and to study Fenton chemistry, both in test tubes as well as in intact cells, and that fluorescence auto-amplification is an intrinsic property of DCF.
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Siriwardhana, Nalin, K. W. Lee, Y. J. Jeon, S. H. Kim e J. W. Haw. "Antioxidant Activity of Hizikia fusiformis on Reactive Oxygen Species Scavenging and Lipid Peroxidation Inhibition". Food Science and Technology International 9, n.º 5 (outubro de 2003): 339–46. http://dx.doi.org/10.1177/1082013203039014.
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Water and organic extracts (diethyl ether, chloroform, ethyl acetate, acetone, ethanol and methanol) obtained from Hizikia fusiformis were screened on reactive oxygen species (ROS) scavenging assays (1,1-diphenyl-2-picrylhydrazyl (DPPH), superoxide anion, hydrogen peroxide and hydroxyl radical) and lipid peroxidation (inhibition of linoleic acid oxidation) inhibitory assays. Water, methanol and ethanol extracts showed significant ROS radical scavenging activities. Water extracts showed high scavenging activities on hydrogen peroxide (around 76%) and DPPH radicals (around 75%) while it presented a moderate scavenging activity on hydroxyl radicals (around 54%). Comparatively higher ROS scavenging activities were recorded in hydroxyl radical and DPPH scavenging assays. DPPH radical scavenging activities were well correlated with the polyphenolic content. ROS scavenging and lipid peroxidation inhibition activities indicated that H. fusiformis might be a valuable natural antioxidative source containing both water and fatsoluble antioxidative components.
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Li, Mengqi, Fuminori Yoneyama, Nayu Toshimitsu, Takeshi Zendo, Jiro Nakayama e Kenji Sonomoto. "Lethal Hydroxyl Radical Accumulation by a Lactococcal Bacteriocin, Lacticin Q". Antimicrobial Agents and Chemotherapy 57, n.º 8 (3 de junho de 2013): 3897–902. http://dx.doi.org/10.1128/aac.00638-13.
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ABSTRACTThe antimicrobial mechanism of a lactococcal bacteriocin, lacticin Q, can be described by the toroidal pore model without any receptor. However, lacticin Q showed different degrees of activity (selective antimicrobial activity) against Gram-positive bacteria even among related species. The ability of lacticin Q to induce pore formation in liposomes composed of lipids from different indicator strains indicated that its selective antimicrobial activity could not be attributed only to membrane lipid composition. We investigated the accumulation of deleterious hydroxyl radicals after exposure to lacticin Q as a contributing factor to cell death in the indicator strains. When lacticin Q of the same concentration as the MIC or minimum bactericidal concentration was added to the indicator cultures, high levels of hydroxyl radical accumulation were detected. Treatment with hydroxyl radical scavengers, thiourea and 2,2′-bipyridyl, decreased the levels of hydroxyl radical accumulation and recovered cell viability. These results suggest that, with or without pore formation, the final antimicrobial mechanism of lacticin Q is the accumulation of hydroxyl radicals, which varies by strain, resulting in the selective antimicrobial activity of lacticin Q.
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Li, Cheng Shuai, Ai Ling Du e Ai Qin Du. "Influence of pH on Hydroxyl Radical Scavenging Ratio by Gingerol". Advanced Materials Research 781-784 (setembro de 2013): 1265–69. http://dx.doi.org/10.4028/www.scientific.net/amr.781-784.1265.
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In this paper, the work was mainly studying influence of pH on Fenton reaction and gingerol scavenging hydroxyl radical. The antioxidant activity of gingerol was characterized by the scavenging hydroxyl ratio and scavenging hydroxyl ratio was analyzed by the spectrophotometry. Hydroxyl radical was produced by Fenton reaction. In the experiment pH and buffer solution have influence on the scavenging hydroxyl radical and Fenton reaction. Gingerol exhibits a strong scavenging radical activity for hydroxyl radical (OH.). The scavenging hydroxyl radical of different extractions of ginger oleoresin is different.
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Diaz-Uribe, Carlos, William Vallejo e Cesar Quiñones. "Physical-Chemical Study of Anthracene Selective Oxidation by a Fe(III)-Phenylporhyrin Derivative". International Journal of Molecular Sciences 21, n.º 1 (5 de janeiro de 2020): 353. http://dx.doi.org/10.3390/ijms21010353.
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In this work, we studied the anthracene oxidation by hydroxyl radicals. Hydroxyl radical was generated by reaction of 5,10,15,20-tetrakis(4-carboxyphenyl)porphyrin Fe (III) (TPPFe) with hydrogen peroxide under visible radiation at a nitrogen atmosphere. The TPPFe was synthesized by Adler Method followed by metal complexation with Fe (III) chloride hexahydrate. Hydroxyl radical was detected by fluorescence emission spectroscopy and we studied kinetic of anthracene selective oxidation by hydroxyl radicals through the differential method. The TPPFe was characterized by UV-Vis spectrophotometry, Dynamic Light Scattering (DLS) and Scanning Electron Microscopy (SEM) measurements. The results indicated that TPPFE was compound by micro-particles with a size distribution of around 2500 nm. Kinetic results showed that the apparent rate constant for the oxidation of anthracene increased exponentially on as temperature increases, furthermore, the activation energy for the Anthracene oxidation by hydroxyl radicals under visible irradiation was 51.3 kJ/mol. Finally, anthraquinone was the main byproduct generated after oxidation of anthracene by TPP-Fe under visible irradiation.
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Carey, M., e S. T. Smale. "Hydroxyl-Radical Footprinting". Cold Spring Harbor Protocols 2007, n.º 24 (1 de dezembro de 2007): pdb.prot4810. http://dx.doi.org/10.1101/pdb.prot4810.
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Puntarulo, S., e A. I. Cederbaum. "Effect of oxygen concentration on microsomal oxidation of ethanol and generation of oxygen radicals". Biochemical Journal 251, n.º 3 (1 de maio de 1988): 787–94. http://dx.doi.org/10.1042/bj2510787.
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The iron-catalysed production of hydroxyl radicals, by rat liver microsomes (microsomal fractions), assessed by the oxidation of substrate scavengers and ethanol, displayed a biphasic response to the concentration of O2 (varied from 3 to 70%), reaching a maximal value with 20% O2. The decreased rates of hydroxyl-radical generation at lower O2 concentrations correlates with lower rates of production of H2O2, the precursor of hydroxyl radical, whereas the decreased rates at elevated O2 concentrations correlate with lower rates (relative to 20% O2) of activity of NADPH-cytochrome P-450 reductase, which reduces iron and is responsible for redox cycling of iron by the microsomes. The oxidation of aniline or aminopyrine and the cytochrome P-450/oxygen-radical-independent oxidation of ethanol also displayed a biphasic response to the concentration of O2, reaching a maximum at 20% O2, which correlates with the dithionite-reducible CO-binding spectra of cytochrome P-450. Microsomal lipid peroxidation increased as the concentration of O2 was raised from 3 to 7 to 20% O2, and then began to level off. This different pattern of malondialdehyde generation compared with hydroxyl-radical production probably reflects the lack of a role for hydroxyl radical in microsomal lipid peroxidation. These results point to the complex role for O2 in microsomal generation of oxygen radicals, which is due in part to the critical necessity for maintaining the redox state of autoxidizable components of the reaction system.
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Derwent, Richard G. "Representing Organic Compound Oxidation in Chemical Mechanisms for Policy-Relevant Air Quality Models under Background Troposphere Conditions". Atmosphere 11, n.º 2 (7 de fevereiro de 2020): 171. http://dx.doi.org/10.3390/atmos11020171.
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This intercomparison has taken thirteen chemical mechanisms and compared how they treat VOC oxidation and degradation and its relationship to the photochemical formation of ozone and hydroxyl radicals. Here, we have looked in some detail at the incremental responses of hydroxyl radicals to incremental additions of a range of organic compounds under conditions appropriate to the background atmosphere. Most of the time, with most organic compounds and most chemical mechanisms, incremental additions of an organic compound led to depletion of hydroxyl radical concentrations. The chemical mechanisms studied demonstrated increasingly negative incremental hydroxyl radical reactivities with increasing carbon numbers for the alkanes ethane, propane and n-butane. Hydroxyl radical incremental reactivities for the simple alkenes, ethylene and propylene, were reasonably consistent across the chemical mechanisms studied. However, this consistent representation did not extend to trans but-2-ene, where reactivity estimates spanned a range of a factor of five. Incremental reactivities were reasonably well-defined for isoprene which was encouraging in view of its importance to background tropospheric chemistry. The most serious discrepancies emerging from this study were found with the aromatics toluene and o-xylene, and with the Master Chemical Mechanism and these are discussed in some detail.
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Chen, Yuan, Yingqi Mi, Jingjing Zhang, Fang Dong, Qing Li, Naiyun Ji e Zhanyong Guo. "Radical Scavenging Activities of Novel Cationic Inulin Derivatives". Polymers 10, n.º 12 (22 de novembro de 2018): 1295. http://dx.doi.org/10.3390/polym10121295.
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Many saccharides are attractive targets for biomaterial applications, due to their abundance, biocompatibility, and biodegradability. In this article, a synthesis process of 6-N-substituted cationic inulin derivatives, including 6-pyridyl-6-deoxyinulin bromide (PIL), 6-(2-amino-pyridyl)-6-deoxyinulin bromide (2APIL), 6-(3-amino-pyridyl)-6-deoxyinulin bromide (3APIL), 6-(4-amino-pyridyl)-6-deoxyinulin bromide (4APIL), 6-(2,3-diamino-pyridyl)-6-deoxyinulin bromide (2,3DAPIL), 6-(3,4-diamino-pyridyl)-6-deoxyinulin bromide (3,4DAPIL), and 6-(2,6-diamino-pyridyl)-6-deoxyinulin bromide (2,6DAPIL) was described. The C6-OH of inulin was first activated by PPh3/N-bromosuccinimide (NBS) bromination. Then, pyridine and different kinds of amino-pyridine groups (different position and different numbers of amino) were grafted onto inulin, respectively, via nucleophilic substitution. Then, we confirmed their structure by Fourier transform infrared spectroscopy (FT-IR) and nuclear magnetic resonance (NMR) spectroscopy. After this, their radical scavenging activities against hydroxyl radical and diphenylpicryl phenylhydrazine (DPPH) radical were tested in vitro. Each derivative showed a distinct improvement in radical scavenging activity when compared to inulin. The hydroxyl-radical scavenging effect decreased in the following order: 3APIL > PIL > 3,4DAPIL > 4APIL > 2,3DAPIL > 2,6DAPIL > 2APIL. Amongst them, 3APIL revealed the most powerful scavenging effect on hydroxyl radicals, as well as DPPH radicals. At 1.6 mg/mL, it could completely eliminate hydroxyl radicals and could clear 65% of DPPH radicals. The results also showed that the steric hindrance effect and the substitute position of the amino group had an effect on the radical scavenging activity. Moreover, the application prospects of inulin derivatives as natural antioxidant biomaterials are scientifically proven in this paper.
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Moore, Peter W., Jordan P. Hooker, Athanasios Zavras, George N. Khairallah, Elizabeth H. Krenske, Paul V. Bernhardt, Gina Quach, Evan G. Moore, Richard A. J. O'Hair e Craig M. Williams. "Hydroxyl Radicals via Collision-Induced Dissociation of Trimethylammonium Benzyl Alcohols". Australian Journal of Chemistry 70, n.º 4 (2017): 397. http://dx.doi.org/10.1071/ch16602.
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The hydroxyl radical is a well known reactive oxygen species important for interstellar, atmospheric, and combustion chemistry in addition to multiple biochemical processes. Although there are many methods to generate the hydroxyl radical, most of these are inorganic based, with only a few originating from organic precursor molecules. Reported herein is the observation that trimethylammonium benzyl alcohols and their corresponding deuterated isotopologues act as a good source of hydroxyl and deuteroxyl radicals in the gas-phase under collision-induced dissociation (CID) conditions. Attempts to replicate this chemistry in the condensed phase are described.
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Leser, Micheal, Jessica R. Chapman, Michelle Khine, Jonathan Pegan, Matt Law, Mohammed El Makkaoui, Beatrix M. Ueberheide e Michael Brenowitz. "Chemical Generation of Hydroxyl Radical for Oxidative ‘Footprinting’". Protein & Peptide Letters 26, n.º 1 (13 de fevereiro de 2019): 61–69. http://dx.doi.org/10.2174/0929866526666181212164812.
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Background: For almost four decades, hydroxyl radical chemically generated by Fenton chemistry has been a mainstay for the oxidative ‘footprinting’ of macromolecules. Objective: In this article, we start by reviewing the application of chemical generation of hydroxyl radical to the development of oxidative footprinting of DNA and RNA and the subsequent application of the method to oxidative footprinting of proteins. We next discuss a novel strategy for generating hydroxyl radicals by Fenton chemistry that immobilizes catalytic iron on a solid surface (Pyrite Shrink Wrap laminate) for the application of nucleic acid and protein footprinting. Method: Pyrite Shrink-Wrap Laminate is fabricated by depositing pyrite (Fe-S2, aka ‘fool’s gold’) nanocrystals onto thermolabile plastic (Shrinky Dink). The laminate can be thermoformed into a microtiter plate format into which samples are deposited for oxidation. Results: We demonstrate the utility of the Pyrite Shrink-Wrap Laminate for the chemical generation of hydroxyl radicals by mapping the surface of the T-cell co-stimulatory protein Programmed Death – 1 (PD-1) and the interface of the complex with its ligand PD-L1. Conclusion: We have developed and validated an affordable and reliable benchtop method of hydroxyl radical generation that will broaden the application of protein oxidative footprinting. Due to the minimal equipment required to implement this method, it should be easily adaptable by many laboratories with access to mass spectrometry.
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Ragnar, M., T. Eriksson e T. Reitberger. "Detection of Radicals Generated by Strong Oxidants in Acidic Media". Holzforschung 53, n.º 3 (10 de maio de 1999): 285–91. http://dx.doi.org/10.1515/hf.1999.048.
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Summary A new method to study superoxide and hydroxyl radicals in aqueous solution in the pH range 1 to 6 is described and critically evaluated. The method primarily detects superoxide, which reacts with tetranitromethane (TNM) by reductive cleavage. The strongly coloured nitroform anion (ε350nm = 15000M−1 cm−1) formed, is easily measured in a spectrophotometer or in a stopped-flow equipment. Hydroxyl radicals are measured indirectly. In a first step the hydroxyl radical reacts with iso-propyl alcohol to give acetone and superoxide. The superoxide formed is then in a second step detected with TNM. The TNM-method was primarily designed to monitor the radical formation under ozone bleaching conditions, but it is also applicable in acidic hydrogen peroxide.
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Tumbas, Vesna, Gordana Cetkovic, Sonja Djilas, Jasna Canadanovic-Brunet, Jelena Vulic, Zeljko Knez e Mojca Skerget. "Antioxidant activity of mandarin (Citrus reticulata) peel". Acta Periodica Technologica, n.º 41 (2010): 195–203. http://dx.doi.org/10.2298/apt1041195t.
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Mandarin peel, a waste product coming from juice production, was extracted by conventional extraction with 70% acetone. Content of flavonoids in mandarin peel extract (MPE) was determined by HPLC. Hesperidin was the most dominant flavonoid. Free radical scavenging activity of MPE on stable DPPH radicals and reactive hydroxyl radicals was also evaluated. EC50 value determined in spectrophotometrical DPPH radical assay was 0.179 mg/ml, while this value in ESR spin trapping hydroxyl radical assay was 0.415 mg/ml. Also, MPE showed protective effects in stabilising sunflower oil during accelerated storage. The results indicated that mandarin peel can be a valuable source of natural antioxidants.
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Xu, Li Ping, e Xin Wang. "Evaluation the Effect of Anti-Oxidation of Chondroitin Sulfate". Advanced Materials Research 989-994 (julho de 2014): 793–96. http://dx.doi.org/10.4028/www.scientific.net/amr.989-994.793.
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Study of the antioxidant activity of chondroitin sulfate extracted from chicken cartilage. The total antioxidant capacity, inhibition the capacity of anti-superoxide anion, hydroxyl radical, anti-liposome and Alkyl radical was determined, respectively; the effect of the anti-oxidation of chondroitin sulfate was observed. The result indicated that chondroitin sulfate had the strong elimination ability to the five free radicals. The ability of total antioxidant the values of scavenging activities of the maximum inhibition rate to anti-superoxide anion, hydroxyl radical, anti-liposome and alkyl radical was 30.56 U/mL, 97.74%, 80.69% ,48.05% and 78.57%, respectively.
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Kozlov, Andrey V., Sabzali Javadov e Natascha Sommer. "Cellular ROS and Antioxidants: Physiological and Pathological Role". Antioxidants 13, n.º 5 (14 de maio de 2024): 602. http://dx.doi.org/10.3390/antiox13050602.
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Reactive oxygen species (ROS) are highly reactive oxygen derivatives that include free radicals such as superoxide anion radical (O2•−) and hydroxyl radical (HO•), as well as non-radical molecules hydrogen peroxide (H2O2), peroxynitrite (ONOO−), and hypochlorous acid (HOCl) [...]
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Wang, Ying, Anni B. Hougaard, Wilhelm Paulander, Leif H. Skibsted, Hanne Ingmer e Mogens L. Andersen. "Catalase Expression Is Modulated by Vancomycin and Ciprofloxacin and Influences the Formation of Free Radicals in Staphylococcus aureus Cultures". Applied and Environmental Microbiology 81, n.º 18 (6 de julho de 2015): 6393–98. http://dx.doi.org/10.1128/aem.01199-15.
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ABSTRACTDetection of free radicals in biological systems is challenging due to their short half-lives. We have applied electron spin resonance (ESR) spectroscopy combined with spin traps using the probes PBN (N-tert-butyl-α-phenylnitrone) and DMPO (5,5-dimethyl-1-pyrrolineN-oxide) to assess free radical formation in the human pathogenStaphylococcus aureustreated with a bactericidal antibiotic, vancomycin or ciprofloxacin. While we were unable to detect ESR signals in bacterial cells, hydroxyl radicals were observed in the supernatant of bacterial cell cultures. Surprisingly, the strongest signal was detected in broth medium without bacterial cells present and it was mitigated by iron chelation or by addition of catalase, which catalyzes the decomposition of hydrogen peroxide to water and oxygen. This suggests that the signal originates from hydroxyl radicals formed by the Fenton reaction, in which iron is oxidized by hydrogen peroxide. Previously, hydroxyl radicals have been proposed to be generated within bacterial cells in response to bactericidal antibiotics. We found that whenS. aureuswas exposed to vancomycin or ciprofloxacin, hydroxyl radical formation in the broth was indeed increased compared to the level seen with untreated bacterial cells. However,S. aureuscells express catalase, and the antibiotic-mediated increase in hydroxyl radical formation was correlated with reducedkatAexpression and catalase activity in the presence of either antibiotic. Therefore, our results show that inS. aureus, bactericidal antibiotics modulate catalase expression, which in turn influences the formation of free radicals in the surrounding broth medium. If similar regulation is found in other bacterial species, it might explain why bactericidal antibiotics are perceived as inducing formation of free radicals.
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McArdle, A., J. van der Meulen, G. L. Close, D. Pattwell, H. Van Remmen, T. T. Huang, A. G. Richardson, C. J. Epstein, J. A. Faulkner e M. J. Jackson. "Role of mitochondrial superoxide dismutase in contraction-induced generation of reactive oxygen species in skeletal muscle extracellular space". American Journal of Physiology-Cell Physiology 286, n.º 5 (maio de 2004): C1152—C1158. http://dx.doi.org/10.1152/ajpcell.00322.2003.
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Contractions of skeletal muscles produce increases in concentrations of superoxide anions and activity of hydroxyl radicals in the extracellular space. The sources of these reactive oxygen species are not clear. We tested the hypothesis that, after a demanding isometric contraction protocol, the major source of superoxide and hydroxyl radical activity in the extracellular space of muscles is mitochondrial generation of superoxide anions and that, with a reduction in MnSOD activity, concentration of superoxide anions in the extracellular space is unchanged but concentration of hydroxyl radicals is decreased. For gastrocnemius muscles from adult (6–8 mo old) wild-type ( Sod2+/+) mice and knockout mice heterozygous for the MnSOD gene ( Sod2+/-), concentrations of superoxide anions and hydroxyl radical activity were measured in the extracellular space by microdialysis. A 15-min protocol of 180 isometric contractions induced a rapid, equivalent increase in reduction of cytochrome c as an index of superoxide anion concentrations in the extracellular space of Sod2+/+ and Sod2+/- mice, whereas hydroxyl radical activity measured by formation of 2,3-dihydroxybenzoate from salicylate increased only in the extracellular space of muscles of Sod2+/+ mice. The lack of a difference in increase in superoxide anion concentration in the extracellular space of Sod2+/+ and Sod2+/- mice after the contraction protocol supported the hypothesis that superoxide anions were not directly derived from mitochondria. In contrast, the data obtained suggest that the increase in hydroxyl radical concentration in the extracellular space of muscles from wild-type mice after the contraction protocol most likely results from degradation of hydrogen peroxide generated by MnSOD activity.
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Huang, Chenkun, Qiuyue Chen, Shengqiang Li e Jian Wang. "The Detection Methods of Hydroxyl Radical: A Review". E3S Web of Conferences 375 (2023): 03009. http://dx.doi.org/10.1051/e3sconf/202337503009.
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Hydroxyl radical (·OH) can rapidly react with biological macromolecules, organic and inorganic substances on account of its strong oxidizing property, so it is widely used in sewage treatment, chemiluminescence analysis, biological macromolecule modification and other fields. The strengthening effect of Hydrodynamic cavitation on chemical reactions depends on the number of free radicals initiated by cavitation. These free radicals are highly reactive and react rapidly with pollutants and other species in wastewater. Therefore, the systematic summary of detection methods of hydroxyl radical and the description of its advantages and disadvantages can provide technical support for scientific researchers, and guides the research in the future.
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Rudziński, Krzysztof J., e Rafał Szmigielski. "Aqueous Reactions of Sulfate Radical-Anions with Nitrophenols in Atmospheric Context". Atmosphere 10, n.º 12 (9 de dezembro de 2019): 795. http://dx.doi.org/10.3390/atmos10120795.
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Nitrophenols, hazardous environmental pollutants, react promptly with atmospheric oxidants such as hydroxyl or nitrate radicals. This work aimed to estimate how fast nitrophenols are removed from the atmosphere by the aqueous-phase reactions with sulfate radical-anions. The reversed-rates method was applied to determine the relative rate constants for reactions of 2-nitrophenol, 3-nitrophenol, 4-nitrophenol, 2,4-dinitrophenol, and 2,4,6-trinitrophenol with sulfate radical-anions generated by the autoxidation of sodium sulfite catalyzed by iron(III) cations at ~298 K. The constants determined were: 9.08 × 108, 1.72 × 109, 6.60 × 108, 2.86 × 108, and 7.10 × 107 M−1 s−1, respectively. These values correlated linearly with the sums of Brown substituent coefficients and with the relative strength of the O–H bond of the respective nitrophenols. Rough estimation showed that the gas-phase reactions of 2-nitrophenol with hydroxyl or nitrate radicals dominated over the aqueous-phase reaction with sulfate radical-anions in deliquescent aerosol and haze water. In clouds, rains, and haze water, the aqueous-phase reaction of 2-nitrophenol with sulfate radical-anions dominated, provided the concentration of the radical-anions was not smaller than that of the hydroxyl or nitrate radicals. The results presented may be also interesting for designers of advanced oxidation processes for the removal of nitrophenol.
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Jiang, Feng, Jiansha Gao e Di Lang. "Photocatalytic Selective Degradation of Catechol and Resorcinol on the TiO2 with Exposed {001} Facets: Roles of Two Types of Hydroxyl Radicals". Catalysts 12, n.º 4 (29 de março de 2022): 378. http://dx.doi.org/10.3390/catal12040378.
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Photocatalytic studies on contaminant degradation in water suspension generally suggest that the degradation reaction mainly takes place on the surface of the photocatalysts rather than in the water phase. The mechanism of selective degradation is often difficult to distinguish concerning the contribution of adsorption and radical selectivity. This study is thus designed to investigate the roles of two types of hydroxyl radicals, adsorbed hydroxyl radical (·OHa) and free hydroxyl radical (·OHf), on the selective degradation of catechol (CT) and resorcinol (RE). CT and RE are significantly different in adsorption on a TiO2 photocatalyst with a highly exposed {001} facet. CT can be selectively degraded by TiO2 and was highly correlated with adsorption. Free radical quenching experiment results showed that the degradation of CT can be identified as the combined effect of both ·OHa and ·OHf, while the degradation of RE was mainly due to the ·OHf. Electron paramagnetic resonance coupled with spin trapping agents was used to detect the relative concentration of hydroxyl radicals in all the photocatalytic degradation processes. After a series analysis, we proposed that the mechanism of selective degradation mainly depends on the concentration of ·OHf for the pollutant molecules with weak adsorption on the catalyst surface.
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Raja, Boobalan, e Kodukkur Pugalendi. "Evaluation of antioxidant activity of Melothria maderaspatana in vitro". Open Life Sciences 5, n.º 2 (1 de abril de 2010): 224–30. http://dx.doi.org/10.2478/s11535-010-0005-5.
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AbstractIn this study, an aqueous extract of leaves from Melothria maderaspatana was tested for in vitro antioxidant activity. Free radical scavenging assays, such as hydroxyl radical, hydrogen peroxide, superoxide anion radical and 2,2-diphenyl-1-picryl hydrazyl (DPPH), 2,2’-azinobis-(3-ethyl-enzothiazoline-6-sulfonic acid) (ABTS) radical scavenging, and reducing power assay, were studied. The extract effectively scavenged hydroxyl radical, hydrogen peroxide and superoxide anion radicals. It also scavenged DPPH and ABTS radicals. Furthermore, it was found to have reducing power. All concentrations of leaf extract exhibited free radical scavenging and antioxidant power, and the preventive effects were in a dose-dependent manner. The antioxidant activities of the above were compared to standard antioxidants such as butylated hydroxytoluene (BHT), ascorbic acid, and α-tocopherol. The results obtained in the present study indicate that the M. maderaspatana extract could be considered a potential source of natural antioxidant.
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Shirato, Midori, Hiroyo Ikai, Keisuke Nakamura, Eisei Hayashi, Taro Kanno, Keiichi Sasaki, Masahiro Kohno e Yoshimi Niwano. "Synergistic Effect of Thermal Energy on Bactericidal Action of Photolysis of H2O2in Relation to Acceleration of Hydroxyl Radical Generation". Antimicrobial Agents and Chemotherapy 56, n.º 1 (24 de outubro de 2011): 295–301. http://dx.doi.org/10.1128/aac.05158-11.
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ABSTRACTThe purpose of the present study is to evaluate the effect of thermal energy on the yield of and the bactericidal action of hydroxyl radical generated by photolysis of H2O2. Different concentrations of H2O2(250, 500, 750, and 1,000 mM) were irradiated with light-emitting diodes (LEDs) at a wavelength of 400 ± 20 nm at 25°C to generate hydroxyl radical. The 500 mM H2O2was irradiated with the LEDs at different temperatures (25, 35, 45, and 55°C). Electron spin resonance spin trapping analysis showed that the yield of hydroxyl radicals increased with the temperature, as well as the concentration of H2O2.Streptococcus mutansandEnterococcus faecaliswere used in the bactericidal assay. The LED-light irradiation of the bacterial suspensions in 500 mM H2O2at 25°C could hardly kill the bacteria within 3 min, while the bactericidal effect was markedly enhanced with the temperature rise. For instance, a temperature increase to 55°C resulted in >99.999% reduction of viable counts of both bacterial species only within 1 min. The photolysis of 500 mM H2O2at 55°C could reduce the viable counts of bacteria more efficiently than did the photolysis of 1,000 mM H2O2at 25°C, although the yields of hydroxyl radical were almost the same under the both conditions. These findings suggest that the thermal energy accelerates the generation of hydroxyl radical by photolysis of H2O2, which in turn results in a synergistic bactericidal effect of hydroxyl radical and thermal energy.
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Hadjimitova, Vera, Trayko Traykov, Milka Mileva e Stefan Ribarov. "Effect of Some Psychotropic Drugs on Luminol - Dependent Chemiluminescence Induced by O2–, •OH, HOCl". Zeitschrift für Naturforschung C 57, n.º 11-12 (1 de dezembro de 2002): 1066–71. http://dx.doi.org/10.1515/znc-2002-11-1220.
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We studied antioxidant activity of six neuroleptics (chlorpromazine, levomepromazine, promethazine, trifluoperazine and thioridazine) and two antidepressants (imipramine and amitriptyline) in the range of concentration of 10−7−10−4 м. We applied luminol-dependent chemiluminescence to test the ability of these drugs to scavenge the biologically relevant oxygen-derived species: hydroxyl radical, superoxide radical, hypochlorous acid in vitro. We found that the phenothiazines were powerful scavengers of hydroxyl and superoxide radicals. Chlorprothixene, amitriptyline and imipramine had no scavenge activity to the superoxide radical. All drugs showed a moderate scavenger effect on hypochloric anion.
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Mojovic, Milos, Ivan Spasojevic, Mirjana Vuletic, Zeljko Vucinic e Goran Bacic. "An EPR spin-probe and spin-trap study of the free radicals produced by plant plasma membranes". Journal of the Serbian Chemical Society 70, n.º 2 (2005): 177–86. http://dx.doi.org/10.2298/jsc0502177m.
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Plant plasma membranes are known to produce superoxide radicals, while the production of hydroxyl radical is thought to occur only in the cell wall. In this work it was demonstrated using combined spin-trap and spin-probe EPR spectroscopic techniques, that plant plasma membranes do produce superoxide and hydroxyl radicals but by kinetically different mechanisms. The results show that superoxide and hydroxyl radicals can be detected by DMPO spin-trap and that the mechanisms and location of their production can be differentiated using the reduction of spin-probes Tempone and 7-DS. It was shown that the mechanism of production of oxygen reactive species is NADH dependent and diphenylene iodonium inhibited. The kinetics of the reduction of Tempone, combined with scavengers or the absence of NADH indicates that hydroxyl radicals are produced by a mechanism independent of that of superoxide production. It was shown that a combination of the spin-probe and spin-trap technique can be used in free radical studies of biological systems, with a number of advantages inherent to them.
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Aditya, Manashi, e Soumen Bhattacharjee. "Foliar anti-diabetic and antioxidant potential of a promising accession of Amaranthus hypochondriacus L.: GC-MS based evidences". Journal of Phytopharmacology 7, n.º 2 (10 de abril de 2018): 121–26. http://dx.doi.org/10.31254/phyto.2018.7204.
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The present study makes an effort to investigate the foliar neutraceutical potential of a promising green accession of a seed amaranth (Amaranthus hypochondriacus, accession no. IC94661) based on anti-lipid peroxidation property, reducing power, metal chelating activity, hydroxyl radical scavenging property, antidiabetic factor and GC-MS based identification of hydroxyl containing phytochemicals. Methanol and aqueous fractions possessed exhibited better anti-lipid peroxidation, reducing, hydroxyl radical scavenging, and metal chelating properties in the experimental accession. Estimation of anti-diabetic factors from the young leaf extract also revealed significantly high α-glucosidase and α- amylase inhibition properties. When GC-MS study was carried out, it exhibited presence of several hydroxyls containing phytochemicals in the accession, some of which are having antioxidant properties. Taken as a whole, the data not only provide evidence of rich sources of marker antioxidant properties but also the availability of several phytochemicals with hydroxyls, in support of its rich pharmaceutical potential
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Lankin, V. Z., O. I. Shadyro, K. B. Shumaev, K. B. Shumaev, A. K. Tikhaze e A. A. Sladkova. "Non-Enzymatic Methylglyoxal Formation From glucose Metabolites and Generation of Superoxide Anion Radical During Methylglyoxal-Dependent Cross-Links Reaction". Journal of Antioxidant Activity 1, n.º 4 (25 de setembro de 2019): 33–45. http://dx.doi.org/10.14302/issn.2471-2140.jaa-19-2997.
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The paper explores the formation of a-oxoaldehydes during the interaction of glucose metabolites with hydroxyl or alkoxyl radicals. Hydroxyl radicals were generated under radiolysis of aqueous solutions, and alkoxyl radicals (t-BuO) were obtained in the model system tert-butyl hydroperoxide/Fe2+. High-performance liquid chromatography revealed that methylglyoxal was one of the organic products resulting from t-BuO-induced transformations of fructose-1,6-bisphosphate under hypoxic conditions. The interaction of lysine and methylglyoxal one of the main targets of a-oxoaldehydes in proteins was also studied. As chemiluminescence and EPR spectroscopy demonstrated, this reaction generates a methylglyoxal anion radical, a cation-radical of methylglyoxal dialkylamine and a superoxide anion radical. EPR signal of methylglyoxal-derived free radicals was observed in hypoxia, whereas only the trace amounts of these free radicals were recorded in the aerated reaction medium.
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Francés, Daniel E., María T. Ronco, Juan A. Monti, Paola I. Ingaramo, Gerardo B. Pisani, Juan P. Parody, José M. Pellegrino, Paloma Martín Sanz, María C. Carrillo e Cristina E. Carnovale. "Hyperglycemia induces apoptosis in rat liver through the increase of hydroxyl radical: new insights into the insulin effect". Journal of Endocrinology 205, n.º 2 (17 de fevereiro de 2010): 187–200. http://dx.doi.org/10.1677/joe-09-0462.
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AbstractIn this study, we analyzed the contribution of hydroxyl radical in the liver apoptosis mediated by hyperglycemia through the Bax–caspase pathway and the effects of insulin protection against the apoptosis induced by hyperglycemia. Male adult Wistar rats were randomized in three groups: control (C) (sodium citrate buffer, i.p.), streptozotocin (STZ)-induced diabetic (SID) (STZ 60 mg/kg body weight, i.p.), and insulin-treated SID (SID+I; 15 days post STZ injection, SID received insulin s.c., twice a day, 15 days). Rats were autopsied on day 30. In liver tissue, diabetes promoted a significant increase in hydroxyl radical production which correlated with lipid peroxidation (LPO) levels. Besides, hyperglycemia significantly increased mitochondrial BAX protein expression, cytosolic cytochrome c levels, and caspase-3 activity leading to an increase in apoptotic index. Interestingly, the treatment of diabetic rats with desferoxamine or tempol (antioxidants/hydroxyl radical scavengers) significantly attenuated the increase in both hydroxyl radical production and in LPO produced by hyperglycemia, preventing apoptosis by reduction of mitochondrial BAX and cytosolic cytochrome c levels. Insulin treatment showed similar results. The finding that co-administration of antioxidants/hydroxyl radical scavengers together with insulin did not provide any additional benefit compared with those obtained using either inhibitors or insulin alone shows that it is likely that insulin prevents oxidative stress by reducing the effects of hydroxyl radicals. Importantly, insulin significantly increased apoptosis inhibitor protein expression by induction of its mRNA. Taken together, our studies support that, at least in part, the hydroxyl radical acts as a reactive intermediate, which leads to liver apoptosis in a model of STZ-mediated hyperglycemia. A new anti-apoptosis signal for insulin is shown, given by an increase of apoptosis inhibitor protein.
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Xiao, Helan, Guoping Cai e Mingyao Liu. "Hydroxyl radical induced structural changes of collagen". Spectroscopy 21, n.º 2 (2007): 91–103. http://dx.doi.org/10.1155/2007/496174.
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Extracellular matrix (ECM) plays an important role in cell differentiation, growth, migration and apoptosis. Collagen is the most abundant protein familyin vivo, but its function has still not been clearly defined yet. Reactive oxygen species (ROS) have a central role in oxidative cell stress. Electron spin resonance (ESR) spectroscopy indicates that type I collagen could uniquely scavenge hydroxyl radicals in dose- and time-dependent manner; whereas BSA and gelatin (a denatured collagen) have no such an effect. However, the mechanism by which type I collagen scavenges hydroxyl radicals is different from that of GSH, a well-known free radical scavenger. Using a new method, two-dimensional FTIR correlation analysis, for the first time, we show that the order of functional group changes of type I collagen in this process is amide I earlier than amide II than amide III than –CH– thanν(C=O). The results indicates that the structure of the main chain of collagen changed first, followed by more residue groupν(C=O) exposed to hydroxyl radicals. The reaction with the carbonyl group in collagen causes the hydroxyl free radicals to be scavenged. Therefore, ECM can effectively scavenge ROS under normal physiological conditions. When the proteins of ECM were denatured in the same way as gelatin, they lost their function as a free radical scavenger. All of these results provide new insight into therapy or prevention of oxidative stress, apoptosis and ageing.
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Chang, Chen-Yu, Yung-Hsu Hsieh, Kai-Yuan Cheng, Ling-Ling Hsieh, Ta-Chih Cheng e Kuo-Shan Yao. "Effect of pH on Fenton process using estimation of hydroxyl radical with salicylic acid as trapping reagent". Water Science and Technology 58, n.º 4 (1 de setembro de 2008): 873–79. http://dx.doi.org/10.2166/wst.2008.429.
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This study estimates the yield of hydroxyl radical using salicylic acid as the trapping reagent and investigates the relationship between hydroxyl radical and pH value. The formation and variation of hydroxyl radical under different pH values were evaluated using reaction products, 2,3-DHBA, 2,5-DHBA, and catechol. The formation rate of hydroxyl radical was dependent on the ratio of ferrous ion to hydrogen peroxide and pH values. The difference between various pH values was explored. The kinetics and mechanisms of hydroxyl radical reactions were established in the Fenton process. Experimental results showed that the best reaction conditions were 8.5 mM H2O2, 1.25 mM Fe2 + , Fe2 + /H2O2=0.147 at pH 3 and the formation rate constant of hydroxyl radical was 1.12 × 1011 M−1 s−1.
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Orthen, Birgit, Marianne Popp e Nicholas Smirnoff. "Hydroxyl radical scavenging properties of cyclitols". Proceedings of the Royal Society of Edinburgh. Section B. Biological Sciences 102 (1994): 269–72. http://dx.doi.org/10.1017/s0269727000014226.
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Cyclitols are low molecular weight substances which accumulate in plant cells in response to various environmental stress situations, for example drought (Ford 1984), salinity (Gorham et al. 1984), low temperature (Richter et al. 1990).Apart from their more general role in osmotic adjustment, only in the case of salt stress is their mode of function well understood. Cyclitols (e.g. pinitol) accumulate when plants are exposed to increasing salt concentration (Paul & Cockburn 1989) and act as compatible solutes (Sommer et al. 1990) as defined by Brown & Simpson (1972).The significance of cyclitol accumulation in stress adaptation of plants to drought and cold still remains uncertain. However, it is generally accepted that drought and cold as well as several other stress situations lead to an enhanced generation of oxygen free radicals (Elstner 1990; Smirnoff & Colombe 1988), including the hydroxyl radical as the most harmful one. The report by Smirnoff & Cumbes (1989) that myo-inositol is an effective hydroxyl radical scavenger prompted us to test other naturally-occuring cyclitols like pinitol, quebrachitol, 1-D-1-O-methyl-muco-inositol, ononitol and quercitol for their ability to scavenge hydroxyl radicals.
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Novelli, Anna, Luc Vereecken, Birger Bohn, Hans-Peter Dorn, Georgios I. Gkatzelis, Andreas Hofzumahaus, Frank Holland et al. "Importance of isomerization reactions for OH radical regeneration from the photo-oxidation of isoprene investigated in the atmospheric simulation chamber SAPHIR". Atmospheric Chemistry and Physics 20, n.º 6 (20 de março de 2020): 3333–55. http://dx.doi.org/10.5194/acp-20-3333-2020.
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Abstract. Theoretical, laboratory, and chamber studies have shown fast regeneration of the hydroxyl radical (OH) in the photochemistry of isoprene, largely due to unimolecular reactions which were previously thought not to be important under atmospheric conditions. Based on early field measurements, nearly complete regeneration was hypothesized for a wide range of tropospheric conditions, including areas such as the rainforest where slow regeneration of OH radicals is expected due to low concentrations of nitric oxide (NO). In this work the OH regeneration in isoprene oxidation is directly quantified for the first time through experiments covering a wide range of atmospherically relevant NO levels (between 0.15 and 2 ppbv – parts per billion by volume) in the atmospheric simulation chamber SAPHIR. These conditions cover remote areas partially influenced by anthropogenic NO emissions, giving a regeneration efficiency of OH close to 1, and areas like the Amazonian rainforest with very low NO, resulting in a surprisingly high regeneration efficiency of 0.5, i.e. a factor of 2 to 3 higher than explainable in the absence of unimolecular reactions. The measured radical concentrations were compared to model calculations, and the best agreement was observed when at least 50 % of the total loss of isoprene peroxy radicals conformers (weighted by their abundance) occurs via isomerization reactions for NO lower than 0.2 ppbv. For these levels of NO, up to 50 % of the OH radicals are regenerated from the products of the 1,6 α-hydroxy-hydrogen shift (1,6-H shift) of Z-δ-RO2 radicals through the photolysis of an unsaturated hydroperoxy aldehyde (HPALD) and/or through the fast aldehydic hydrogen shift (rate constant ∼10 s−1 at 300 K) in di-hydroperoxy carbonyl peroxy radicals (di-HPCARP-RO2), depending on their relative yield. The agreement between all measured and modelled trace gases (hydroxyl, hydroperoxy, and organic peroxy radicals, carbon monoxide, and the sum of methyl vinyl ketone, methacrolein, and hydroxyl hydroperoxides) is nearly independent of the adopted yield of HPALD and di-HPCARP-RO2 as both degrade relatively fast (<1 h), forming the OH radical and CO among other products. Taking into consideration this and earlier isoprene studies, considerable uncertainties remain on the distribution of oxygenated products, which affect radical levels and organic aerosol downwind of unpolluted isoprene-dominated regions.
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Ekanayake, P., Y. D. Lee e J. Lee. "Antioxidant Activity of Flesh and Skin of Eptatretus Burgeri (Hag Fish) and Enedrias Nebulosus (White Spotted Eel)". Food Science and Technology International 10, n.º 3 (junho de 2004): 171–77. http://dx.doi.org/10.1177/1082013204044822.
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Ethyl acetate and diethyl ether extracts, previously extracted with methanol, were obtained from flesh and skin of Eptatretus burgeri (hag fish) and Enedrias nebulosus (white spotted eel). Eight different extracts (4 mg/mL) were tested for DPPH free radical scavenging activity and the values were compared with commercial antioxidants (α-tocopherol and BHT). All extracts of E. burgeri exhibited significantly positive results (> 65%) in scavenging DPPH radicals compared to E. nebulosus. Thus, only E. burgeri extracts were tested for dose effect, hydrogen peroxide, hydroxyl radical, superoxide scavenging assays and heat stability at 25, 50, 75 and 100 °C for 30 min. All extracts of E. burgeri showed higher DPPH radical scavenging activities by increasing concentration. Significantly higher results were observed for hydroxyl radical scavenging activity when compared with commercial antioxidants. Relatively moderate activity and very low activity were exhibited for superoxide scavenging and hydrogen peroxide activities, respectively. Diethyl ether extracts of E. burgeri were stable with increased temperature, while ethyl acetate extracts were stable up to 75 °C. Thus, there is a high potential for E. burgeri being rich with heat-stable antioxidants that can scavenge hydroxyl radicals.
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Shao, Youxiang, Hua Hou e Baoshan Wang. "Theoretical study of the mechanisms and kinetics of the reactions of hydroperoxy (HO2) radicals with hydroxymethylperoxy (HOCH2O2) and methoxymethylperoxy (CH3OCH2O2) radicals". Phys. Chem. Chem. Phys. 16, n.º 41 (2014): 22805–14. http://dx.doi.org/10.1039/c4cp02747g.
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Bandala, Erick R., e Oscar M. Rodriguez-Narvaez. "On the Nature of Hydrodynamic Cavitation Process and Its Application for the Removal of Water Pollutants". Air, Soil and Water Research 12 (janeiro de 2019): 117862211988048. http://dx.doi.org/10.1177/1178622119880488.
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Cavitation is considered a high energy demanding process for water treatment. For this study, we used a simple experimental setup to generate cavitation at a low pressure (low energy) and test it for hydroxyl radical production using a well-known chemical probe as a hydroxyl radical scavenger. The conditions for generating the cavitation process (eg, pressure, flow velocity, temperature, and other significant variables) were used to degrade model contaminants, an azo dye and an antibiotic. The amount of hydroxyl radicals generated by the system was estimated using N,N-dimethyl-p-nitrosoaniline (pNDA) as hydroxyl radical scavenger. The capability of hydrodynamic cavitation (HC) to degrade contaminants was assessed using Congo red (CR) and sulfamethoxazole (SMX) as model contaminants. Different chemical models were analyzed using UV-visible spectrophotometry (for pNDA and CR) and high-performance liquid chromatography (HPLC) (for SMX) after HC treatment under different process conditions (ie, pressure of 13.7 and 10.3 kPa, and flow rates of 0.14 to 3.6 × 10−4 m3/s). No pNDA bleaching was observed for any of the reaction conditions tested after 60 minutes of treatment, which suggests that there was no hydroxyl radical generation during the process. However, 50% degradation of CR and 25% degradation of SMX were observed under the same process conditions, comparable with previously reported results. These results suggest that the process is most likely thermally based rather than radically based, and therefore, it can degrade organic pollutants even if no hydroxyl radicals are produced. Hydrodynamic cavitation, either alone or coupled with other advanced water technologies, has been identified as a promising technology for removing organic contaminants entering the water cycle; however, more research is still needed to determine the specific mechanisms involved in the process and the optimal operation conditions for the system.
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Han, Zhen Xing, Bing Wu, Ian Brown, Mark Beck e Srini Raghavan. "Detection of HO2•/O2•- Radicals Formed in Aqueous Solutions Irradiated with Megasonic Waves Using a Cavitation Threshold (CT) Cell Set-Up". Solid State Phenomena 219 (setembro de 2014): 170–73. http://dx.doi.org/10.4028/www.scientific.net/ssp.219.170.
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Acoustic cavitation, especially transient cavitation, in solutions is accompanied by a number of physical and chemical effects. Due to high temperature and pressure conditions inside bubbles at their collapse, excitation of various species as well as formation of radicals occurs in solution [1-4]. Water molecules excited by megasonic irradiation typically dissociate to hydrogen and hydroxyl radicals (H• and OH•) [5]. The hydroxyl radical is a strong oxidant while the hydrogen radical has reducing properties. In presence of O2 in the solution, H• reacts with O2 to form hydroperoxyl (HO2•) radicals, which act as a reducing as well as a (weak) oxidizing agent [6]. Dissociation of hydroperoxyl radicals result in the formation of superoxide anion radicals (O2•-) as follows [6]: