Sulfur-centered radical formation from the antioxidant dihydrolipoic acid.
Lipoic acid and its reduced form, dihydrolipoic acid, are thought to be strong antioxidants. There are also reports of dihydrolipoic acid acting as a pro-oxidant under certain circumstances. This article reports the direct observation by ESR spectrometry of the disulfide radical anion and the spin trapping of the primary thiyl radical formed from the oxidation of dihydrolipoic acid through thiol pumping with phenol and horseradish peroxidase. The disulfide radical anion reacts rapidly with oxygen to form the reactive radical superoxide, which is also trapped. The radical species formed show a potential for pro-oxidant activity of this compound. Although antioxidants, in general, have been shown to have pro-oxidant potential, the pro-oxidant chemistry of dihydrolipoic acid has not been well characterized.
Mottley
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Department of Chemistry, Luther College, Decorah, Iowa 52101, USA.
Mason
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RP
D000975:Antioxidants / Q000737:chemistry*; D004578:Electron Spin Resonance Spectroscopy; D005609:Free Radicals; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008956:Models, Chemical; D010100:Oxygen / Q000737:chemistry / Q000378:metabolism; D019800:Phenol / Q000737:chemistry; D013053:Spectrophotometry; D013438:Sulfhydryl Compounds / Q000737:chemistry; D013455:Sulfur / Q000737:chemistry*; D013482:Superoxide Dismutase / Q000737:chemistry; D008063:Thioctic Acid / Q000031:analogs & derivatives* / Q000737:chemistry*
D000975:Antioxidants; D005609:Free Radicals; D013438:Sulfhydryl Compounds; D019800:Phenol; D013455:Sulfur; D008063:Thioctic Acid; C015144:dihydrolipoic acid; D013482:Superoxide Dismutase; D010100:Oxygen