Alkaloids from Aconitum brachypodum and their network-based analysis of chemotaxonomic value

Twenty alkaloids were isolated from the whole herb of Aconitum brachypodum Diels. (Ranunculaceae), a famous medicinal plant in China, including thirteen diterpenoid alkaloids (1-13), five isoquinoline alkaloids (14-18), and two benzamide alkaloids (19-20), whose structures were elucidated on the basis of NMR and MS analyses. Among them, thalifoline (15) has not previously been isolated from the Aconitum genus, and ten alkaloids (6-7, 9, 11, 14, and 16-20) have not previously been found in this species. The structural features of the isolated diterpenoid alkaloids support the middle transitional state of this species within subgenus Aconitum. In addition, the distribution of the isolates at the species level within the genus Aconitum was presented via network analysis, which showed that some of the isolates, such as 2, 6, 9, 11, and 13 with a limited distribution in the genus exhibited certain potential chemotaxonomical values.