INHIBITION OF XANTHINE-OXIDASE BY PURPUROGALLIN AND SILYMARIN GROUP

Thirteen phenolic compounds were tested for their inhibitory effects o n xanthine oxidase. The enzyme xanthine oxidase catalyses the oxidatio n of hypoxanthine to xanthine and of xanthine to uric acid, which has lambda mar of 295nm, forming the basis for a spectrophotometric assay of the activity of xanthine oxidase. The results showed that purpuroga llin and silymarin group displayed the inhibitory effects on xanthine oxidase (IC50=2.96 +/- 0.12 and 27.58 +/- 3.48 mu M, respectively). Th eir apparent inhibition constants (Ki) were 1.16 and 5.85 mu M, and in duced uncompetitive and mired type (non-competitive-uncompetitive) inh ibitions respectively, with respect to the substrate xanthine.