There is an urgent need for the development of effective anti-malarial drugs due to emergence of resistant strains of P. falciparum. Medicinal plants represent a plethora of compounds to achieve this feat. The stem and leaf extracts of Alstonia boonei and Carapa procera are used in various traditional medicines for the treatment of malaria. In the present study, the petroleum ether and hydro-alcoholic extracts of these two plants were tested in vitro on choloroquine sensitive (3D7) strains of Plasmodium falciparum for their anti-malarial activity. Growth inhibition was determined in vitro by counting GIEMSA-stained parasites by light microscopy. The petroleum ether extract of the leaves and stem bark of A. boonei were both inactive (IC50Ã?â?¹Ã?Æ?100 μg/ml). Their soxhlet ethanol extracts were also inactive with IC50 Ã?â?¹Ã?Æ?100 μg/ml. However, the leaf extract, obtained by cold maceration, showed weak activity (IC50 = 71.24 μg/ml) whereas that of the stem was 88.15 μg/ml. The petroleum ether extract of the stem bark of C. procera inhibited the growth of the chloroquine sensitive (3D7) Plasmodium falciparum parasite with IC50 value of 19.52 μg/ml and the soxhlet extracted ethanol extract giving IC50 = 11.41 μg/ml. Column chromatography of the bioactive soxhlet ethanol extract afforded fractions with significant antimalarial activities (IC50Ã?â?¹Ã?â??10μg/ml).The present study has revealed that the leaves and stem bark of A. boonei show weak antiplasmodial activity. Extracting the constituents of A. boonei by cold maceration retains considerable antiplasmodial activity. The stem bark of C. procera however, showed significant antiplasmodial activity. Chromatographic fractionation afforded more potent antiplasmodial fractions.
