title: A novel method of measuring hydroxyl radical-scavenging activity of antioxidants using gamma-irradiation.
abstract: A new method using ESR spin trapping was proposed for measuring the scavenging activity of antioxidants for the hydroxyl (OH) radical. (-)-Epigallocatechin gallate (EGCg) and 5,5-dimethyl-1-pyrroline N-oxide (DMPO) were used as the antioxidant and spin trapping agent, respectively. The conventional method using a Fenton reaction had problems associated with the estimation of activity, because the antioxidant disturbs the system for generating OH radical by coordinating on Fe2+ and by consuming H2O2, besides scavenging the spin adduct (DMPO-OH). Intense gamma-irradiation was therefore used to generate OH radicals, and the intensity decrease in DMPO-OH after irradiation was followed to obtain the rate constant for the scavenging of DMPO-OH by EGCg. The intensities were extrapolated to zero time to estimate the quantity of DMPO-OH formed during gamma-irradiation. By using these values, the reaction rate constant between OH radical and EGCg was calculated as a ratio to that of DMPO. It was shown that this method is useful for comparing the OH radical-scavenging activity of various antioxidants.
authors.affiliation: Radiochemistry Research Laboratory, Faculty of Science, Shizuoka University, 836 Ohya, Shizuoka-shi 422-8529, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Yoshioka
authors.forename: Y
authors.initials: Y
authors.lastname: Ohashi
authors.forename: M
authors.initials: M
authors.lastname: Akaboshi
authors.forename: Y
authors.initials: Y
authors.lastname: Senba
authors.forename: H
authors.initials: H
authors.lastname: Yoshioka
mesh_terms: D000975:Antioxidants / Q000737:chemistry / Q000528:radiation effects*; D002392:Catechin / Q000031:analogs & derivatives* / Q000737:chemistry / Q000528:radiation effects*; D003497:Cyclic N-Oxides / Q000737:chemistry; D004578:Electron Spin Resonance Spectroscopy / Q000379:methods; D016166:Free Radical Scavengers / Q000032:analysis*; D005609:Free Radicals; D005720:Gamma Rays; D017665:Hydroxyl Radical / Q000032:analysis*; D013113:Spin Labels; D019097:Spin Trapping
chemical_list: D000975:Antioxidants; D003497:Cyclic N-Oxides; D016166:Free Radical Scavengers; D005609:Free Radicals; D013113:Spin Labels; D017665:Hydroxyl Radical; C069977:2,2-dimethyl-5-hydroxy-1-pyrrolidinyloxy; C017245:5,5-dimethyl-1-pyrroline-1-oxide; D002392:Catechin; C045651:epigallocatechin gallate