Mappianines A-E, structurally diverse monoterpenoid indole alkaloids from Mappianthus iodoides.

Five previously undescribed monoterpenoid indole alkaloids, mappianines A-E, along with twelve known analogues, were isolated from the stems of Mappianthus iodoides Hand.-Mazz. Their structures and absolute configurations were determined by spectroscopic analysis, single-crystal X-ray diffraction, and ECD calculations. The plausible biogenetic pathway of mappianine A was proposed. All the isolated compounds were evaluated for their cytotoxic effects on MGC-803, Bel-7404, A549, NCI-H460, and HepG2 cancer cell lines. Mappianine B, tetrahydroalstonine, β-carbolin-1-one, and 1,2,3,4-tetrahydronorharman-1-one displayed moderate cytotoxicity against all cell lines tested, with IC50 values ranging from 5.19 to 42.86 μM.