Flavonoids from Cyclopia genistoides and Their Xanthine Oxidase Inhibitory Activity.

The present paper reports the chemical analysis of the methanolic extracts of fermented and non-fermented Cyclopia genistoides herbs and an investigation of the xanthine oxidase inhibitory activity of the isolated constituents. Chemical analysis of the leaves and stems of C. genistoides yielded the isolation and identification of two benzophenone glucosides, iriflophenone 2-O-β-glucopyranoside (1) and iriflophenone 3-C-β-glucopyranoside (2), two pterocarpans, (6aR,11aR)-(-)-2-methoxymaackiain (5) and (6aR,11aR)-(-)-maackiain (6), along with the flavanones liquiritigenin (9) and hesperetin (10), the flavone diosmetin (11), the isoflavones afrormosin (7) and formononetin (8), piceol (3), and 4-hydroxybenzaldehid (4). Among the eleven compounds, nine are reported for the first time from this species, and six from the genus Cyclopia. These compounds, together with previously isolated secondary metabolites of this species, were tested for xanthine oxidase inhibitory activity. The 5,7-dihydroxyflavones luteolin and diosmetin significantly inhibited the enzyme in vitro, while hesperetin (10) and 5,7,3',5'-tetrahydroxyflavone exerted weak activity.