Secondary Metabolites of Hypericum L. Species as Xanthine Oxidase Inhibitors

Nine Hypericum species (H. barbatum, H. hirsutum, H. linarioides, H. olympicum, H. perforatum, H. rochelii, H. rumeliacum, H. tetrapterum and H. umbellatum) collected in Serbia were assayed for inhibitory potential against xanthine oxidase in vitro, on the commercial enzyme, and compared with allopurinol. Seven studied Hypericum species (H. barbatum, H. rochelii, H. rumeliacum, H. umbellatum, H. perforatum, H. tetrapterum and H. olympicum) inhibit commercial xanthine oxidase with an IC50 below 100 mu g/mL. H. barbatum exerted the most potent inhibitory effect (IC50 = 31.84 +/- 6.64 mu g/mL), followed closely by H. perforatum (IC50 = 37.12 +/- 4.06 mu g/mL).