Two novel alkaloids with an unprecedented tricyclic skeleton, cassiarins A (1) and B (2), have been isolated from the leaves of Cassia siamea, and the structures were elucidated on the basis of spectroscopic data. Cassiarin A (1) showed a potent antiplasmodial activity.

Bioassay-guided purification from the seeds of Peganum harmala led to the isolation of harmine (1), harmaline (2), vasicinone (3), and deoxyvasicinone (4). Harmine (1) and harmaline (2) showed a moderate in vitro antiplasmodial activity against Plasmodium falciparum. Quinazoline alkaloid, vasicinone (3), showed a vasorelaxant activity against phenylephrine-induced contraction of isolated rat aorta.

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