Indole alkaloids from Muntafara sessilifolia with antiplasmodial and cytotoxic activities

Four vobasinyl-iboga bisindole and one 2-acyl monomeric indole alkaloids were isolated from the stem bark of Muntafara sessilifolia along with eleven known compounds. Their structures and relative stereochemistry were elucidated on the basis of spectroscopic data including 1D and 2D NMR and mass spectrometry (MS). All isolated compounds were evaluated in vitro for antiplasmodial activity against the chloroquine-resistant strain FcB1 of Plasmodium falciparum, and for cytotoxicity against the human lung cell line MRC-5 and the rat skeletal muscle cell line L-6. 3'-Oxo-tabernaelegantine A exhibited antiplasmodial activity (4.4 μM IC(50)) associated with non-significant cytotoxicity (selectivity index of 48). Tabernaelegantine B and D displayed the highest cytotoxicity with IC(50) values of 0.47 and 1.89 μM on MRC-5 cells, and 0.42 and 2.7 μM on L-6 cells, respectively.