Ten vobasinyl-ibogan type bisindole alkaloids, including three new ones, tabercorines A-C (1-3), and a new natural product, 17-acetyl-tabernaecorymbosine A (4), were isolated from the twigs and leaves of Tabernaemontana corymbosa. Their structures were elucidated on the basis of spectroscopic data, and the NMR data of 17-acetyl-tabernaecorymbosine A (4) was assigned and reported for the first time. The absolute configurations of 1-4 were determined by CD exciton chirality method. All new compounds were evaluated for in vitro cytotoxicity against various human cancer cell lines. Compounds 1 and 4 showed significant inhibitory effects with IC50 values comparable to those of cisplatin.
Keywords: Bisindole alkaloids; Cytotoxicity; Tabercorines A–C; Tabernaemontana corymbosa.
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