title: Oxygen dependency of one-electron reactions generating ascorbate radicals and hydrogen peroxide from ascorbic acid.
abstract: The effect of oxygen on the two separate one-electron reactions involved in the oxidation of ascorbic acid was investigated. The rate of ascorbate radical (Asc(-)) formation (and stability) was strongly dependent on the presence of oxygen. A product of ascorbic acid oxidation was measurable levels of hydrogen peroxide, as high as 32.5 μM from 100 μM ascorbic acid. Evidence for a feedback mechanism where hydrogen peroxide generated during the oxidation of ascorbic acid accelerates further oxidation of ascorbic acid is also presented. The second one-electron oxidation reaction of ascorbic acid leading to the disappearance of Asc(-) was also strongly inhibited in samples flushed with argon. In the range of 0.05-1.2 mM ascorbic acid, maximum levels of measurable hydrogen peroxide were achieved with an initial concentration of 0.2 mM ascorbic acid. Hydrogen peroxide generation was greatly diminished at ascorbic acid levels of 0.8 mM or above.
authors.affiliation: Department of Animal and Food Sciences, University of Kentucky, 412 W.P. Garrigus Building, Lexington, KY 40546-0215, United States. Electronic address: wlboat1@uky.edu.
authors.forename: William L
authors.initials: WL
authors.lastname: Boatright
mesh_terms: D001205:Ascorbic Acid / Q000494:pharmacology*; D003683:Dehydroascorbic Acid; D004583:Electrons; D005609:Free Radicals; D006861:Hydrogen Peroxide / Q000494:pharmacology*; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry*
chemical_list: D005609:Free Radicals; D006861:Hydrogen Peroxide; D001205:Ascorbic Acid; D010100:Oxygen; D003683:Dehydroascorbic Acid
keywords: Ascorbate radical; Ascorbic acid; Ascorbyl radical; Dehydroascorbate; Hydrogen peroxide