Indole alkaloids from three species of the Ervatamia genus: E. officinalis, E. divaricata, and E. divaricata Gouyahua

Six new indole alkaloids, 14,15-didehydro-10,11-dimethoxy-16-epivincamine (1), 14,15-didehydro-10-hydroxy-11-methoxy-16-epivincamine (2), 14,15-didehydro-10,11-dimethoxyvincamine (3), 14,15-didehydro-10-hydroxy-11-methoxyvincamine (4), 19,20-didehydro-6alpha-hydroxyervatamine (5), and dehydroxyervataminol (6), along with 36 known indole alkaloids, were isolated from three species, E. officinalis, E. divaricata, and E. divaricata Gouyahua, of the Ervatamia genus. The structures of these alkaloids were characterized on the basis of spectroscopic methods and chemical correlation. The in vitro cytotoxic activities of all the alkaloids except 7, 18, 27, 38, 40, and 44 against the tumor cell lines P-388 murine leukemia and A-549 human lung carcinoma were evaluated. Only the dimeric indole alkaloids showed cytotoxic activities.