title: Carotenoids as scavengers of free radicals in a Fenton reaction: antioxidants or pro-oxidants?
abstract: The spin trapping EPR technique was used to study the influence of carotenoids (beta-carotene, 8'-apo-beta-caroten-8'-al, canthaxanthin, and ethyl 8'-apo-beta-caroten-8'-oate) on the yield of free radicals in the Fenton reaction (Fe(2+) + H(2)O(2) --> Fe(3+) + .OH + -OH) in the organic solvents, DMSO, and methanol. DMPO and PBN were used as spin trapping agents. It was demonstrated that carotenoids could increase or decrease the total yield of free radicals depending on the oxidation potential of the carotenoids and the nature of the radicals. A reaction mechanism is suggested which includes the reduction of Fe(3+) to Fe(2+) by carotenoids. The effectiveness of this carotenoid-driven Fenton reaction increases with a decrease of the scavenging rates for free radicals and with decreasing oxidation potentials of carotenoids.
authors.affiliation: Institute of Chemical Kinetics and Combustion, Novosibirsk, Russia.
authors.forename: N E
authors.initials: NE
authors.lastname: Polyakov
authors.forename: T V
authors.initials: TV
authors.lastname: Leshina
authors.forename: T A
authors.initials: TA
authors.lastname: Konovalova
authors.forename: L D
authors.initials: LD
authors.lastname: Kispert
mesh_terms: D000975:Antioxidants / Q000737:chemistry*; D016644:Canthaxanthin / Q000737:chemistry; D002338:Carotenoids / Q000737:chemistry*; D004121:Dimethyl Sulfoxide; D004578:Electron Spin Resonance Spectroscopy / Q000379:methods; D016166:Free Radical Scavengers / Q000737:chemistry*; D005609:Free Radicals / Q000032:analysis; D006861:Hydrogen Peroxide / Q000737:chemistry*; D017665:Hydroxyl Radical / Q000032:analysis; D007501:Iron / Q000737:chemistry*; D007700:Kinetics; D000432:Methanol; D015394:Molecular Structure; D016877:Oxidants / Q000737:chemistry*; D012997:Solvents; D013053:Spectrophotometry; D019207:beta Carotene / Q000031:analogs & derivatives / Q000737:chemistry
chemical_list: D000975:Antioxidants; C045076:Fenton's reagent; D016166:Free Radical Scavengers; D005609:Free Radicals; D016877:Oxidants; D012997:Solvents; D019207:beta Carotene; D017665:Hydroxyl Radical; D002338:Carotenoids; D016644:Canthaxanthin; D006861:Hydrogen Peroxide; D007501:Iron; D000432:Methanol; D004121:Dimethyl Sulfoxide