Cytotoxic monoterpenoid indole alkaloids from the leaves and twigs of Tabernaemontana bovina

Phytochemical investigation of the leaves and twigs of Tabernaemontana bovina led to the isolation of 10 mon-oterpenoid indole alkaloids, including two new taberbovinines A (1) and B (2) along with eight known analogs: mehranine (3), 14 alpha,15 beta-dihydroxy-N-methylaspidospermidine (4), (16S*)-15-epi-E-isositsirikine (5), (16R*)-15-epi-E-isositsirikine (6), 16 R*-19,20-E-isositsirikine acetate (7), hecubine (8), voafinidine (9), and voa-cangarine (10). Taberbovinine B (2) represents the first case of an unusual ring C/D cleavage among the natural Corynanthe-type alkaloids. Compounds 2 and 8 exhibited weak cytotoxicity against five human cancer cell lines, including SK-LU-1, HepG2, MCF-7, SK-Mel-2, and LNCaP, with IC50 values ranging from 42.9 to 66.3 mu M, whereas compounds 4 inverted exclexpressionmexpressiontion 6 and 9 were cytotoxic toward MCF-7, SK-LU-1 and LNCaP cells, with IC50 values in a range of 51.6-93.3 mu M.

Automated summary

Phytochemical investigation of Tabernaemontana bovina leaves and twigs led to the isolation of 10 monoterpenoid indole alkaloids, including two new compounds. One of the new compounds, taberbovinine B, demonstrated an unusual ring C/D cleavage. Compounds 2 and 8 exhibited weak cytotoxicity against various cancer cell lines, while other compounds showed different levels of toxicity against specific cancer cells.