Inhibition of xanthine oxidase by anthraquinones.

Abstract
Inhibitory activities of nine anthraquinone derivatives against xanthine oxidase (EC 1.2.3.2) were assayed in vitro. Anthragallol (1,2,3-trihydroxyanthraquinone, 8) was the most active inhibitor among them. The concentration of 8 in the assay mixture required to give 50% inhibition (IC50) was 1.2 .times. 10-5 M. The type of inhibition by 8 with respect to xanthine as a substrate was uncompetitive.