Himalaflavone A-E, five new flavonoids from Oxybaphus himalaicus

Five previously undescribed flavonoids (1–5) and ten known ones (6–15) were isolated from the roots of Oxybaphus himalaicus. Their structures were elucidated by spectroscopic experiments including NMR, HRESIMS and ECD. The cytotoxic activities of all isolated compounds were assayed against human lung carcinoma A549 cells and human hepatocellular carcinoma HepG2 cells in vitro. Compound 11 displayed the most powerful inhibitory effect with IC50 values of 19.47 ± 0.28 μM against A549 and 52.6 ± 0.38 μM against HepG2, respectively.