Four New Diterpenoid Alkaloids from the Roots of Aconitum carmichaelii

Aconitum carmichaelii Debeaux is a widely used traditional Chinese medicine and an important source of clinical drugs, of which the parent and lateral roots are known as 'Chuanwu' and 'Fuzi', respectively. Four new C₁₉ -diterpenoid alkaloids, carmichasines A - D (1 - 4), were isolated from the roots of Aconitum carmichaelii, together with twelve known compounds (5 - 16). Their structures were elucidated via spectroscopic analyses, including HR-ESI-MS, IR, and NMR. Carmichasine A (1) is the first natural C₁₉ -diterpenoid alkaloid possessing a cyano group. Most of the diterpenoid alkaloids isolated were C₁₉ -category, which might provide further clues for understanding the chemotaxonomic significance of this plant. The cytotoxicity of the new compounds was also investigated against several human cancer cell lines, including MCF-7, HCT116, A549, and 786-0, and none of them showed considerable cytotoxic activity.