Five new C-17/C-15 sesquiterpene lactone dimers from Carpesium abrotanoides

摘要

Five new unusual C-17/C-15 sesquiterpene lactone dimers, carabrodilactones A-E (1-5), along with four known common C-15/C-15 SLDs, carpedilactones A and B (6 and 7), faberidilactone A (8), and faberidilactone C (9), were isolated from the whole plants of Carpesium abrotanoides. The structures of 1-5 featured a flexible C-11/C-13' linked single bond between two sesquiterpene units and a tailed acetyl connected to the C-13 position. The preferential conformation of 1-5 was elucidated by the diagnostic NMR data of geminal proton of H-13. The biogenetic pathway of 1-5 was proposed to involve Stetter and Michael addition reactions. In addition, compound 1 exhibited significant cytotoxicities against the four cell lines (A549, HCT116, MDA-MB, and BEL7404 cells) with IC50 value in the range of 3.08-8.05 mu M, while compounds 2-5 showed weak cytotoxicities.