In vitro screening for antiplasmodial activity of isoquinoline alkaloids from Brazilian plant species

In the search for new antimalarial agents, nine Brazilian plant species were selected, from the Annonaceae (6), Menispermaceae (2) and Siparunaceae (1) families naturally occurring at the cerrado and Atlantic rainforest regions, in order to investigate their in vitro antiplasmodial activity. The ethanol and the alkaloid extracts were tested against K1, chloroquine-resistant, and Palo Alto, chloroquine-sensitive, strains of Plasmodium falciparum. The majority of the alkaloid extracts were more active than the ethanol ones, with IC50 ranging 0.3–8.2 μg/mL. The crude Guatteria australis alkaloids were the most active against K1 with an IC50 = 0.3 μg/mL. The most promising total alkaloid fractions for further bioguided isolation are those with the IC50 ≤ 5 μg/mL: G. australis, Cissampelos ovalifolia and Duguetia lanceolata.