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.