Cytotoxic monoterpenoid indole alkaloids from Alstonia yunnanensis Diels.

The ethanol extract of the aerial parts of Alstonia yunnanensis Diels afforded five new monoterpenoid indole alkaloids, alstiyunnanenines A-E (1-5), along with one known compound, alstoniascholarine I (6). The structures of the isolated compounds were established based on 1D and 2D (1H-1H COSY, HMQC, and HMBC) NMR spectroscopy, in addition to high resolution mass spectrometry. The isolated compounds were tested in vitro for cytotoxic potential using eight tumor cell lines. As a result, alkaloids 4-6 exhibited cytotoxicities against all tested tumor cell lines, especially against osteosarcoma cell lines (SOSP-9607, MG-63, Saos-2, M663) with IC50 values<6μM.