Literatura científica selecionada sobre o tema "Radical hydroxyl"

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.

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.

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.

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.