Four new C₁₉-diterpenoid alkaloids from Delphinium elatum

Diterpenoid alkaloids with remarkable chemical properties and biological activities are frequently found in plants of the genera Aconitum, Delphinium, and Garrya. Accordingly, several C₁₉-diterpenoid alkaloid components from Delphinium elatum cv. Pacific Giant, as well as their derivatives, exhibited cytotoxic activity against lung, prostate, nasopharyngeal, and vincristine-resistant nasopharyngeal cancer cell lines. Four new C₁₉-diterpenoid alkaloids, elapacigine (1), N-deethyl-N-formylpaciline (2), N-deethyl-N-formylpacinine (3), and N-formyl-4,19-secoyunnadelphinine (4), together with 11 known C₁₉-diterpenoid alkaloids were isolated in a phytochemical investigation on the seeds of D. elatum cv. Pacific Giant. Their structures were elucidated by extensive spectroscopic methods including NMR (1D and 2D), IR, and MS (HRMS). Three of the new C₁₉-diterpenoid alkaloids (2-4) and five of the known diterpenoid alkaloids were evaluated for cytotoxic activity against five human tumor cell lines.