New antiproliferative germacranolides from Carpesium divaricatum .

Six new highly oxygenated (2-7) and one known (1) germacranolides were isolated from the whole plant of Carpesium divaricatum . The planar structures and relative configurations of the new compounds were determined by detailed spectroscopic analysis. The absolute configurations of 1 and 3 were established by circular dichroism (CD) and X-ray crystallographic analyses, and the stereochemistry of the new compounds 2 and 4-6 were determined by similar CD data to 1 and 3, respectively. All isolates were evaluated for their antiproliferative activities against three human tumor cell lines, and compounds 3 and 6 show antiproliferative activities against HeLa and Hep G2 cells with IC 50 values of 4.13-8.37 μM. Intensive mechanism study showed that 3 caused cell-cycle arrest at the S/G2 phase and induced apoptosis in Hep G2 cells through a mitochondria-related pathway.