Minquartia guianensis, popularly known as acariquara, was phytochemically investigated. The following triterpenes were isolated from the dichloromethane extract of leaves: lupen-3-one (1), taraxer-3-one (2) and oleanolic acid (3). The dichloromethane extract of branches yielded the triterpene 3β-methoxy-lup-20(29)-ene (4). The chemical structures were characterized by NMR data. Plant extracts, substance 3, squalene (5) and taraxerol (6), (5 and 6 previously isolated), were evaluated by in vitro assay against chloroquine resistant Plasmodium falciparum. The dichloromethane extract of leaves and the three triterpenes assayed have shown partial activity. Thus, these results demonstrated that new potential antimalarial natural products can be found even in partially active extracts.