A method for inhibiting xanthine oxidase and for reducing uric acid levels using a beta-carboline alkaloid compound of formula (I), wherein R1 is selected from the group consisting of a carboxyl group, a carboxylate group, a carboxamide group and hydrogen, and R2 is selected from the group consisting of —CH2COOCH3, a methoxy group, hydrogen and a methyl group. Also disclosed is a method for monitoring xanthine oxidase inhibiting activity level.
