New alkaloids from Aconitum taipaicum and their cytotoxic activities.

Three new aconitine-type C19-diterpenoid alkaloids, taipeinines A-C (1-3), were isolated from the roots of Aconitum taipaicum. The chemical structures of these three compounds were established as (1α,6α,8α,14α,16α)-20-ethyl-8,14-dihydroxy-1,6,16-trimethoxy-4-(methoxymethyl)-aconitane (1), (1α,6α,8α,14α,16β)-20-ethyl-8,14-dihydroxy-1,6,16-trimethoxy-4-(methoxymethyl)-aconitane (2) and (1α,6α,8α,14α,16α)-20-ethyl-1,8,14-trihydroxy-6,16-dimethoxy-4-(methoxymethyl)-aconitane (3), respectively, on the basis of spectroscopic analyses, mainly MS, 1D and 2D NMR. The cytotoxic activities of these compounds were also assayed, and the results were quite impressive.