Redox reactions of the urate radical/urate couple with the superoxide radical anion, the tryptophan neutral radical and selected flavonoids in neutral aqueous solutions

• Published in: Free radical research 2001-01, Vol.35 (2), p.129-136
• Main Authors: Santus, René, Patterson, Larry K., Filipe, Paulo, Morlière, Patrice, Hug, Gordon L., Fernandes, Afonso, Mazière, Jean-Claude
• Format: Article
• Language: English
• Subjects: Animals; Antioxidants; Catechin - metabolism; Cattle; electron transfer; flavonids; Flavonoids - metabolism; Kinetics; Micelles; Oxidation-Reduction; Pulse Radiolysis; Quercetin - metabolism; Rutin - metabolism; Solutions - metabolism; Spectrophotometry, Ultraviolet; Superoxides - chemistry; Superoxides - metabolism; tryptophan; Tryptophan - chemistry; Tryptophan - metabolism; Uric Acid - chemistry; Uric Acid - metabolism; Water - metabolism
• ISSN: 1071-5762; 1029-2470
• DOI: 10.1080/10715760100300671

The kinetics of several processes involving the potential antioxidant role of urate in physiological systems have been investigated by pulse radiolysis. While the monoanionic urate radical, ·UH-, can be produced directly by oxidation with ·Br-2 or ·OH, it can also be generated by oxidation with the neutral tryptophan radical, ·Trp, with a rate constant of 2 × 107 M-1s-1. This radical, ·UH-, reacts with ·O-2 with a rate constant of 8 × 108 M-1s-1. Also, ·UH- is reduced by flavonoids, quercetin and rutin in CTAB micelles at rate constants of 6 × 106 M-1s-1 and 1 × 106 M-1s-1, respectively. These results can be of value by providing reference data useful in further investigation of the antioxidant character of urate in more complex biological systems.