New serratene triterpenoids from Palhinhaea cernua and their cytotoxic activity

Four new serratene triterpenoids, 3β,21β,24-trihydroxyserrat-14-en-24-(4'-hydroxybenzoate) (1), 3β,21α,24-trihydroxyserrat-14-en-3-(4'-hydroxybenzoate) (2), 3β,14α,15α,21α-tetrahydroxyserrat-14-en-3-(3'-methoxyl-4'-hydroxybenzoate) (3), and 3β,14α,15α,21α-tetrahydroxyserrat-14-en-21-acetyl-3-(4'-hydroxybenzoate) (4), together with two known ones, 5 and 6, were isolated from whole plants of Palhinhaea cernua. The structures of these new compounds were elucidated by spectroscopic methods. All the six compounds were tested for their in vitro cytotoxicity against three human cancer cell lines (K562, SMMC-7721, and SGC7901). Compound 5 showed cytotoxicity against the three test cell lines with IC₅₀ values of 20.3, 34.0, and 22.5 ug/mL, respectively. Compound 1 showed slight cytotoxicity against K562 cell lines with IC₅₀ value of 56.1 ug/mL, while no obvious inhibitory effects were detected for other compounds.