5,6-dihydroxypyranoflavone, a New Flavonoid with an Oxidized Prenyl Group from Dietary Plant Citrus hystrix.

Citrus hystrix has been widely used as beverages, traditional condiments and folk medicines. In this study, 5,6-dihydroxypyranoflavone (1), a new flavonoid with an oxidized prenyl group, and three known phenols (2-4), were separated from the leaves of this plant. Their structures were elucidated using comprehensive spectroscopic data including 1D NMR, 2D NMR and mass spectral analysis. Additionally, 5,6- dihydroxypyranoflavone (1) exhibited moderate antioxidant effect against DPPH and ABTS free radicals with IC50 values of 18.28 ± 0.36 and 12.46 ± 0.82 μM, respectively. The results suggested that the dietary plant Citrus hystrix could be considered as a potential source of natural antioxidants. [ABSTRACT FROM AUTHOR]