Xanthine oxidase inhibitory activity of selected Australian native plants

Twenty-eight extracts from 17 species of Australian native plants traditionally used as general anti-inflammatory medicines by Australian Aboriginal people were examined for inhibition of the enzyme xanthine oxidase (XO). The extracts from nine species were found to have more than 25% inhibition at a concentration of 100 microg/ml in the assay mixture. Extracts from three species Clerodendrum floribundum R. Br. (Verbenaceae), Eremophila maculata (Ker Gawler) (Myoporaceae) and Stemodia grossa Benth. (Scrophulariaceae) showed the greatest activity with inhibitions of 84, 61 and 57%, respectively, at 50 microg/ml, with four other species having more than 40% inhibitory activity at this concentration.