Bioactive compounds of inhibiting xanthine oxidase from Selaginella labordei.

Four flavone compounds were isolated from the effective fractions inhibiting xanthine oxidase (XOD) of the medicinal plant Selaginella labordei with anti-virus activity, and the structures were elucidated as 4'-methylether robustaflavone (1), robustaflavone (2), eriodictyol (3) and amentoflavone (4). The 50% inhibitory concentration (IC(50)) of the three compounds of inhibiting XOD were 61.0, 0.199, 16.0 and 32.0 mg L(-1), respectively. All of these compounds were isolated from the species for the first time, and eriodictyol was found from Selaginellaceae for the first time. Among these compounds, robustaflavone has been reported as an effective compound against the hepatitis B virus.