Tanaconitine (1), a novel Aconitum alkaloid with a C29 skeleton, together with six known diterpenoid alkaloids, was isolated from the roots of Aconitum tanguticum. The structure of 1 was elucidated to be 17-dehydroxyl-3′a(cis-1′-methyl-3′,3′a,7′, 7′a-tetrahydro-1H-indol-6′(2H)-one)-naviculine A by spectroscopic analysis. © 2011 Phytochemical Society of Europe.