Xanthine Oxidase Inhibition and Anti-LDL Oxidation by Prenylated Isoflavones from Flemingia philippinensis Root

Xanthine oxidase is a frontier enzyme to produce oxidants, which leads to inflammation in the blood. Prenylated isoflavones from were found to display potent inhibition against xanthine oxidase (XO). All isolates ( - ) inhibited XO enzyme with IC ranging 7.8~36.4 μM. The most active isoflavones ( - , IC = 7.8~14.8 μM) have the structural feature of a catechol motif in B-ring. Inhibitory behaviors were disclosed as a mixed type I mode of inhibition with < . Binding affinities to XO enzyme were evaluated. Fluorescence quenching effects agreed with inhibitory potencies (IC s). The compounds ( - ) also showed potent anti-LDL oxidation effects in the thiobarbituric acid-reactive substances (TBARS) assay, the lag time of conjugated diene formation, relative electrophoretic mobility (REM), and fragmentation of apoB-100 on copper-mediated LDL oxidation. The compound protected LDL oxidation with 0.7 μM in TBARS assay, which was 40-fold more active than genistein (IC = 30.4 μM).