Delphatisine D and Chrysotrichumine A, two new diterpenoid alkaloids from Delphinium chrysotrichum

Chemical investigations of the aerial parts of Tibetan folk medicine Delphinium chrysotrichum resulted in the isolation of two new diterpenoid alkaloids, delphatisine D (1) and chrysotrichumine A (2), together with ten known diterpenoid alkaloids (3-12) and 3β,6α-dihydroxysclareolida (13). Delphatisine D (1) is a rare atisine-type alkaloid from genus Delphinium and is the C-15 epimer of spiramine C which bears an internal carbinolamine ether linkage (N-C-O-C) between C-7 and C-20. Chrysotrichumine A (2) is a rare natural C₁₉-diterpenoid alkaloid possessing a nitrone group between C-17 and C-19. Their structures were elucidated on the basis of extensive spectroscopic analysis. Compound 13 is a sesquiterpene first isolated from this genus. Compounds 1, 3-7 and 13 were investigated for cytotoxicity against human breast cancer cell lines of MCF-7 and MDA-MB-23, none of them presented significant activity except compound 7 which exhibited slight activity at 100 μM against MDA-MB-231, but did not reach the EC₅₀.