Antiprotozoal and cytotoxic screening of 45 plant extracts from Democratic Republic of Congo

Abstract

Aim of the study : To evaluate in vitro the antiprotozoal and cytotoxic activies of 80% methanol extract from 45 medicinal plants collected in Sankuru (Democratic Republic of Congo) against Trypanosoma brucei brucei, Trypanosoma cruzi and the chloroquine-sensitive Ghanaian strain of Plasmodium falciparum, and MRC-5 cell lines respectively. Material and methods : Differents extracts were obtained by maceration of each plant part used with 80% methanol for 24 h. The mixture was filtered and evaporated in vacuo to give corresponding dried extract. The activity against Trypanosoma brucei brucei and Trypanosoma cruzi were performed in 96 well tissue plates each containing 10 μl aqueous plant extract dilutions (100 to 0.01 μg/ml) with 10 μl of the parasite suspension cultured in Hirumi medium supplemented with 10% foetal calf serum, a solution of 2% penicillin/streptomycin (2% P/S) After 4 days incubation with Almar blueâ solution, fluorescence was measured at 500 nm emission and 530 nm excitation and results expressed as percentage reduction in parasite compared to control wells. The antiplasmodial activity of was assessed in vitro against the chloroquine-sensitive Ghanaian strain of Plasmodium falciparum cultured in RPMI-1640 medium by the lactate deshydrogenase assay in the presence of plant extracts (50 to 0.01 μg/ml). Cell-lines MRC-5 were cultured in MEM medium supplemented with 20 mM l-glutamine, 16.5 mM NaHCO 3, 5% foetal calf serum and 2% P/S solution. After 4 h incubation, cell proliferation/viability was spectrophotomecally assessed at 540 nm after addition of MTT. In each assay, the IC 50 value for each sample was derived by the drug concentration-response curves. Results : The extracts from Alcornea cordifolia leaves, Momordica charantia whole plant, Omphalocarpum glomerata, root bark and Piptadia africanum stem bark showed good antiprotozoal activity against Trypanosoma brucei brucei with IC 50 values from 0.7 to 7 μg/ml. Only Piptadenia africanum extract showed a pronounced antiprotozoal activity against Trypanosoma cruzi (IC 50 = 4.0 ± 06 μg/ml). The extracts from Alchornea cordifolia, Polyathia swaveleons stem bark, Sapium cornutum stem bark and Triclisia giletii stem bark exhibited a pronounced antiplasmodial activity against P. falciparum Ghanaian strain with IC 50 values ranging from 0.5 to 3.0 μg/ml. Piptadenia africanum extract was the most cytotoxic sample (CC 50 = 0.25 μg/ml) with poor selectivity against all selected protozoa (SI < 10) while other active extracts did not show a significant cytotoxic effect against MCR-5 cell-lines with good selectivity according to the case. Conclusion : These active plant extracts are selected for extensive studies leading to the isolation of active constituents.