title: One-electron oxidation of "photo-Fenton" reagents and inhibition of lipid peroxidation.
abstract: The "photo-Fenton" reagent, 2-mercaptopyridine N-oxide (MPO), which releases a hydroxyl radical on ultraviolet irradiation, has been found to act as an antioxidant. In the peroxidation of linoleate initiated by a water-soluble azo-initiator, MPO has about one-third the activity of the water-soluble vitamin E analogue Trolox C. In contrast, the oxygen-containing analogue, 2-hydroxypyridine N-oxide (HPO), does not have measurable antioxidant activity in this system. Both reagents react with hydroxyl radical with second order rate constants very close to the diffusion-controlled limit. With the less oxidising dithiocyanate radical anion, MPO reacts approximately 50 times more rapidly than HPO at pH>7. The more reducing properties of MPO result in its activity as an antioxidant and make it less suitable than HPO as a source of hydroxyl radicals for investigation of oxidative stress in biological systems.
authors.affiliation: BioSciences Research Institute, Peel Building, University of Salford, The Crescent, M5 4WT, Salford, UK.
authors.forename: Darren
authors.initials: D
authors.lastname: Tobin
authors.forename: Morfakis
authors.initials: M
authors.lastname: Arvanitidis
authors.forename: Roger H
authors.initials: RH
authors.lastname: Bisby
mesh_terms: D000975:Antioxidants / Q000494:pharmacology; D001667:Binding, Competitive; D004305:Dose-Response Relationship, Drug; D004583:Electrons; D006861:Hydrogen Peroxide / Q000737:chemistry* / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D017665:Hydroxyl Radical; D007501:Iron / Q000737:chemistry* / Q000378:metabolism; D007700:Kinetics; D015227:Lipid Peroxidation; D008956:Models, Chemical; D018384:Oxidative Stress; D010100:Oxygen / Q000378:metabolism*; D011725:Pyridines / Q000494:pharmacology*; D013871:Thiones; D013997:Time Factors
chemical_list: D000975:Antioxidants; C045076:Fenton's reagent; D011725:Pyridines; D013871:Thiones; D017665:Hydroxyl Radical; C008704:pyrithione; D006861:Hydrogen Peroxide; D007501:Iron; D010100:Oxygen