Malaria is one of the world's leading killer infectious diseases, with an estimated 300-500 million cases every year. It is caused by protozoan of the genus Plasmodium. In order to find antiplasmodial natural products, three plants were selected for bioguided isolation: Argemone mexicana, Licania octandra and Syzygium cumini. The alkaloids allocryptopine, berberine and protopine were isolated from A. mexicana traditional preparation and demonstrated to be active against P. falciparum. A quantitative NMR method was developed to determine the concentration of alkaloids in the decoction. From L. octandra hydroalcoholic leaf extract, flavonoids were isolated: myricetin and quercetin derivatives, as well as their aglycones were considered active against P. falciparum, while taxifolin and its derivative were not active. From S. cumini stem bark decoction, five compounds were isolated, including the new 3-O-methylellagic acid 3'-O-β-D-glucopyranoside. Only ellagic acid showed reduction of in vitro parasitaemia.