Repair of tryptophan radicals by antioxidants.
Oxidizing free radicals with redox potential greater than 1 V generate indole radicals, R-Ind+. and R-Ind., as in tryptophan. These resonance-stabilized free radicals can be repaired efficiently with electron donors (k = 5 X 10(6) - 1.3 X 10(9) dm3 mol-1 s-1) such as ascorbate, N,N,N',N'-tetramethyl-p-phenylenediamine dihydrochloride (TMPD), and phenolic antioxidants. Sulfhydryl compounds, which are good H-atom donors, were found to be relatively unreactive (k less than 10(6) dm3 mol-1 s-1). These indole radicals were also found to be unreactive with oxygen (k less than 10(6) dm3 mol-1 s-1).
D000975:Antioxidants / Q000494:pharmacology*; D004563:Electrochemistry; D004583:Electrons; D005609:Free Radicals; D066298:In Vitro Techniques; D010084:Oxidation-Reduction; D010100:Oxygen / Q000378:metabolism; D013329:Structure-Activity Relationship; D013438:Sulfhydryl Compounds / Q000494:pharmacology; D013772:Tetramethylphenylenediamine / Q000494:pharmacology; D014364:Tryptophan / Q000378:metabolism*
D000975:Antioxidants; D005609:Free Radicals; D013438:Sulfhydryl Compounds; D014364:Tryptophan; D013772:Tetramethylphenylenediamine; D010100:Oxygen