Two new megastigmanes from Chinese traditional medicinal plant Sedum sarmentosum

To discover new bioactive compounds from nature plants, a primary screening of traditional Chinese medicines had been taken. The screening results showed that a EtOAc extract of Sedum sarmentosum displayed a certain degree of cytotoxic activity and bioassay-directed isolation of EtOAc extract gave two new megastigmanes, (6S,9R)-2-hydroxy-4-(2,6,6-trimethyl-4-oxo-cyclohex-2-enyl)-butyric acid (1) and (6S,9R)-2-hydroxy-4-(2,6,6-trimethyl-4-oxo-cyclohex-2-enyl)-butyric acid methyl ester (2) together with seven known flavonoids. The chemical structures of 1 and 2 were elucidated on the basis of detailed 1D, 2D NMR and MS data. When tested against HepG2 and Hep3B hepatocellular carcinoma cell lines, compounds 1-9 showed weak anti-HCC activity. In addition, in vitro antioxidant activities of 1-9 were evaluated by ABTS radical cation-scavenging assay. 1 and 2 exhibited weak activity with per micromoles equivalent to 0.039 and 0.042 μM of Trolox, respectively. The flavonoid component, quercetin (9) showed the highest antioxidant activities with per micromoles equivalent 0.67 μM of Trolox.