Five New C₁₉ -Diterpenoid Alkaloids from Delphinium tianshanicum W.T.Wang

Five new diterpenoid alkaloids, tianshanitines A-E (1 - 5), along with ten known compounds (6 - 15), were isolated from the EtOH extracts of the whole plant of Delphinium tianshanicum W.T.Wang. Their structures were determined based on extensive spectroscopic analyses, including 1D- and 2D-NMR, HR-ESI-MS, and the structure of tianshanitine C (3) was confirmed by X-ray diffraction analysis. Tianshanitine A (1) is the first example of natural diterpenoid alkaloid containing a benzoyl group at C(1) position. Tianshanitine B (2) is a rare natural diterpenoid alkaloid bearing a OH group at C(16) position. Compounds 1 - 5, 6, 8, 10, 12 and 14 were evaluated for cytotoxicity against HCT116, MCF-7 and HepG2 human cancer cell lines.