title: Free radical studies of ellagic acid, a natural phenolic antioxidant.
abstract: Ellagic acid, a plant-derived polyphenol, inhibits gamma-radiation (hydroxyl radical) induced lipid peroxidation in rat liver microsomes in a dose- and concentration-dependent manner. Its antioxidant capacity has been estimated using the 1,1-diphenyl-2-picrylhydrazyl radical assay. To understand the actual mechanisms involved in antioxidant activity and the free radical scavenging ability,a nanosecond pulse radiolysis technique has been employed. The rate constants for the reactions of several reactive oxygen species and reactive nitrogen species such as hydroxyl, peroxyl, and nitrogen dioxide radicals have been found to be in the range of 10(6)-10(9) M(-1) s(-1). The ellagic acid radicals have been characterized by the absorption spectra and decay kinetics. Studies on the reactions of ellagic acid with the 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonate) radical and the radicals of ellagic acid with ascorbate have been used to estimate its one-electron reduction potential. Ellagic acid has also been found to be a good scavenger of peroxynitrite. Using stopped-flow reaction analyzer with absorption detection, the rate constant for this reaction has been determined to be 3.7 x 10(3) M(-1) s (-1). The electron spin resonance spectra of the oxidized ellagic acid radicals have been recorded by horseradish peroxidase and hydrogen peroxide method.
authors.affiliation: Radiation Chemistry and Chemical Dynamics Division and Cell Biology Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085, India. kindira@apsara.barc.ernet.in
authors.forename: K Indira
authors.initials: KI
authors.lastname: Priyadarsini
authors.forename: Sujata M
authors.initials: SM
authors.lastname: Khopde
authors.forename: S Santosh
authors.initials: SS
authors.lastname: Kumar
authors.forename: Hari
authors.initials: H
authors.lastname: Mohan
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000494:pharmacology*; D015764:Bepridil / Q000031:analogs & derivatives* / Q000737:chemistry; D001713:Biphenyl Compounds; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D004578:Electron Spin Resonance Spectroscopy; D004610:Ellagic Acid / Q000737:chemistry / Q000494:pharmacology*; D016166:Free Radical Scavengers; D005609:Free Radicals; D005720:Gamma Rays; D017665:Hydroxyl Radical / Q000378:metabolism / Q000494:pharmacology; D015227:Lipid Peroxidation / Q000187:drug effects / Q000528:radiation effects; D008297:Male; D008862:Microsomes, Liver / Q000378:metabolism; D010545:Peroxides; D030421:Peroxynitrous Acid / Q000737:chemistry; D010636:Phenols / Q000737:chemistry; D010851:Picrates; D011675:Pulse Radiolysis; D051381:Rats; D017208:Rats, Wistar; D017382:Reactive Oxygen Species; D013053:Spectrophotometry; D017392:Thiobarbituric Acid Reactive Substances / Q000032:analysis
chemical_list: D000975:Antioxidants; D001713:Biphenyl Compounds; D016166:Free Radical Scavengers; D005609:Free Radicals; D010545:Peroxides; D010636:Phenols; D010851:Picrates; D017382:Reactive Oxygen Species; D017392:Thiobarbituric Acid Reactive Substances; D030421:Peroxynitrous Acid; D004610:Ellagic Acid; C049375:perhydroxyl radical; C042329:phenoxy radical; D017665:Hydroxyl Radical; D015764:Bepridil; C004931:1,1-diphenyl-2-picrylhydrazyl