Antiplasmodial Alkaloids from Desmos rostrata

Two new alkaloids, desmorostratine (1) and discretine N-oxide (2), were isolated from the stem bark of Desmos rostrata, together with five known alkaloids, discretine (3), dehydrodiscretine (4), pseudocolumbamine (5), predicentrine (6), and aristolactam All (7). The structures were established on the basis of spectroscopic data, including mass spectrometry and 2D-NMR. Compound 1 was cytotoxic against KB cells (IC50 2.4 mu M), while 2, 3, and 4 inhibited Plasmodium falciparum (IC50 of 4.2, 1.6, and 0.9 mu M, respectively).