Tabercarpamines A-J, apoptosis-inducing indole alkaloids from the leaves of Tabernaemontana corymbosa

A total of 10 new indole alkaloids, tabercarpamines A-J (1-10), were isolated from the leaves of Tabernaemontana corymbosa. Tabercarpamines C-F (3-6) are rare C-14/C-15-seco-tabersonine-type monoterpenoid indole alkaloids, and 5 and 6 are the first examples with a lactone linkage between C-14 and C-20. The structures of these alkaloids were elucidated using spectroscopic methods, and the absolute configurations of 1 and 2 were determined using the ECD exciton chirality method. In addition, an MTT assay was used to examine the growth-inhibitory effects of all new isolates and of two known isolates on MCF-7, HepG2, and SMMC-7721 cells; 1 exhibited significant inhibitory effects against these three human cancer cell lines with IC50 values of 8.54, 3.31, and 6.76 μM, respectively. Additionally, the results from the annexin-V/PI double-staining assay indicated that 1 might inhibit the proliferation of HepG2 cells by inducing apoptosis.