Inhibition Of Xanthine Oxidase By Flavonoids

Abstract

The influence of nineteen flavonoids on cow's milk xanthine oxidase (xanthine: oxygen oxidoreductase, EC 1.2.3.2) was investigated. The enzyme activity was estimated by measuring the increase in absorbance at 290 nm due to uricate formation as well as by a colorimetric method assaying hydrogen peroxide generated from uricate by uricase. Among the flavonoids tested, myricetin, kaempferol, quercetin, fisetin, quercitrin, and morin inhibited the enzyme strongly at 50 ¼M; the concentrations which gave 50% inhibition (ID50) were 2, 2, 3, 7, 15, and 19¼M, respectively. The inhibition mode of the former three compounds was of mixed type and the kinetic parameters were determined. Chrysin and naringenin were moderately inhibitory, while other flavonoids showed weak to no inhibition. © 1985, Japan Society for Bioscience, Biotechnology, and Agrochemistry. All rights reserved.