Three new carabrane sesquiterpenoid derivatives from the whole plant of Carpesium abrotanoides L.

Dicarabrols B and C ( 1 and 2 ), two new carabrane sesquiterpenoid dimers, along with one new carabrane sesquiterpenoid ( 3 ) were isolated from the whole plant of Carpesium abrotanoides L. Their full structures were established by extensive analysis of HRESI-MS and NMR spectroscopic data, and time-dependent density functional theory (TDDFT) electronic circular dichroism (ECD) calculations. Dicarabrol B possesses a novel C30 skeleton featuring a methylene-tethered bridge between two sesquiterpene moieties while dicarabrol C manifests the unique linkage of a cyclopentane ring in the molecule. Dicarabrol C exhibited potent inhibitory effects on HL−60 cells with IC50 value of 3.7 μM.