Bioassay-guided isolation of antimalarial triterpenoid acids from the leaves of Morinda lucida

The EtOH, CH2Cl2, and petroleum ether extracts from Morinda lucida Benth. leaves have been shown to exhibit an in vitro antiplasmodial activity against a chloroquine-sensitive Plasmodium falciparum strain with IC50 values 5.7 +/- 1.3, 5.2 +/- 0.8, and 3.9 +/- 0.3 mu g/mL, respectively. In vivo, at a daily oral dose of 200 mg/kg body weight, they produced at least 62.5%, 67.5%, and 72.2% reduction of parasitemia in mice infected with Plasmodium berghei berghei, respectively. A bioassay-guided fraction of the most active petroleum ether extract resulted in the isolation of two known triterpenic acids as ursolic acid 1 and oleanolic acid 2. In vitro, 1 and 2 exhibited an antiplasmodial activity with IC50 values of 3.1 +/- 1.3 and 15.2 +/- 3.4 mu g/mL, respectively. In vivo, at a daily dose of 200 mg/kg body weight, they produced 97.7% and 37.4% chemosuppression, respectively. However, all tested samples were inactive in vitro against chloroquine-resistant Plasmodium falciparum (K1) at the highest tested concentration of 25 mu g/mL.