Four new C 20 -diterpenoid alkaloids from Aconitum rotundifolium.

Four new C20 -diterpenoid alkaloids, rotundifosines D-G (1-4), along with eight known ones (5-12) were isolated from the whole plant of Aconitum rotundifolium Kar. & Kir. The structures of the compounds were elucidated on the basis of spectroscopic analyses, including HR-ESI-MS and 1D, 2D NMR. Rotundifosine F (3) is a rare C20 -diterpenoid alkaloid with quaternary ammonium salt. Alkaloids 1-4, 5, 6, 9, and 12 were evaluated for cytotoxicity against MCF-7, HCT-116 and HepG2 human cancer cell lines.