Hanultarin, a cytotoxic lignan as an inhibitor of actin cytoskeleton polymerization from the seeds of Trichosanthes kirilowii

A new lignan derivative, hanultarin, was isolated and structure-determined. It inhibited the polymerization of the actin cycloskeleton and also showed cytotoxic effect against human lung carcinoma A549 and other cell lines. Bioactivity-directed fractionation of extracts from the seeds of Trichosanthes kirilowii led to the isolation of (−)-1- O-feruloylsecoisolariciresinol (2), named hanultarin, In addition, four known lignans were also isolated, including (−)-secoisolariciresinol (1), 1,4- O-diferuloylsecoisolariciresinol (3), (−)-pinoresinol (4), and 4-ketopinoresinol (5). Their structures were elucidated on the basis of spectroscopic data. Compounds 2 and 3 exhibited strong cytotoxic effects against human lung carcinoma A549 cells, melanoma SK-Mel-2 cells, and mouse skin melanoma B16F1 cells with IC 50 ranges of 3–13 μg/mL. Compound 2 showed an inhibitory effect on the polymerization of the actin cytoskeleton in normal epidermal keratinocyte (HaCaT cells), suggesting unique biological properties of compound 2 compared to those of the other isolates.