Antimalarial quassinoids: past, present and future.

This review is a compilation of the investigations reported to date on the sources, isolation, chemistry and antimalarial activities of natural quassinoids and their synthetic and semisynthetic analogs. It also provides an analysis of the in vitro structure-activity relationship of quassinoids for further evaluation in animal models. The introduction of non-nitrogenous antimalarial drugs has created a new era of malaria chemotherapy to treat Plasmodium falciparum strains that are resistant to existing nitrogenous drugs and the rising incidence of the deadly cerebral malaria. Many antimalarial quassinoids are discovered from simaroubaceous plants that are used traditionally to treat fever and malaria, thereby reiterating the critical role of ethnopharmacology as a rich source of novel drug discovery.