Cytotoxic serratane triterpenes from Diphasiastrum complanatum with a hydroxy group at C-27

Four serratane-type triterpenes ( 1- 4) were isolated from D. COMPLANATUM. Their chemical structures were elucidated as 14alpha,15alpha,20beta,21beta,24,27alpha,29-heptahydroxyserrat-3-one ( 1), 3beta,14alpha,15alpha,20beta,21beta,24,27alpha,29-octahydroxyserratane ( 2), 3alpha,14alpha,20beta,21beta,24,27alpha,29-heptahydroxyserratane ( 3) and 3beta,14alpha,21beta,24,27alpha-pentahydroxyl-serratane-29-yl ( E)- P-coumarate ( 4) by spectroscopic methods (MS, 1D and 2D NMR) and X-ray crystallography. Interestingly, the most characteristic methylene (C-27) of the serratane ring C was oxidized to a methine. Compound 4 showed significant cytotoxic activity against the human leukemia K562/S and the doxorubicin-resistant K562/R cell lines, but the other compounds were inactive.