Diterpenoid alkaloids from two species of Delphinium

Four new compounds (1-4) were isolated from the whole plants of two species of Delphinium, including two C₂₀-diterpenoid alkaloids, umbrodines A and B (1 and 2), and a dibenzoxazepinone, umbrolide A (3) from Delphinium umbrosum Hand.-Mazz. and a C₂₀-diterpenoid alkaloid, kingiadine (4) from Delphinium kingianum Bruhl. ex Huth. Ten known diterpenoid alkaloids were also isolated. Their structures were elucidated via HR-ESIMS, IR, and NMR data. Lycoctonine (11) and delectinine (12) exhibited appreciable cardiac activity. Furthermore, 11 and 12 showed cardioprotective effects against doxorubicin-induced toxicity in H9c2 cells, with the maximum protection rates of 61.63% and 51.18%, respectively.