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

The kinetics of several processes involving the potential antioxidant role of urate in physiological systems have been investigated by pulse radiolysi s. While the monoanionic urate radical, (UH-)-U-., can be produced directly by oxidation with Br-.(2)- or (OH)-O-., it can also be generated by oxidat ion with the neutral tryptophan radical, (.)Trp, with a rate constant of 2 x 10(7) M(-1)s(-1). This radical, (UH-)-U-., reacts with O-.(2)- with a rat e constant of 8 x 10(8) M(-1)s(-1). Also, (UH-)-U-. is reduced by flavonoid s, quercetin and rutin in CTAB micelles at rate constants of 6 x 10(6) M(-1 )s(-1) and 1 x 10(6) M(-1)s(-1), respectively. These results can be of valu e by providing reference data useful in further investigation of the antiox idant character of urate in more complex biological systems.