Fig. 4.

Direct inhibitory effects of aglycons and their glycosides on xanthine oxidase activity in vitro. Data on direct XO inhibitions in vitro are expressed as means from two individual experiments. IC50 values were calculated by curve fitting of at least six different concentrations of test samples as described in Materials and methods. Allopurinol was adopted as a positive control drug. IC50 values are shown in Fig. a (allopurinol, quercetin, rutin), b (luteolin, orientin, isoorientin) and c (apigenin, vitexin, isovitexin), respectively