RESUMO
Background: Infectious diseases are the worst problem in tropical and subtropical regions of the world. The Nupe ethnic group from Nigeria has been using the leaves of Abrus precatorius for treatment of malaria and various forms of cancers. However studies have shown that the plant has antimicrobial and anti-cancer activities. In this study the crude methanolic extract, methanolic, ethyl acetate, chloroform and n-hexane fractions of Abrus precatorius leaf were tested In vitro against chloroquine and pyrimethamine resistant Plasmodium falciparum K1, Trypanosoma brucei rhodesiense, Trypanosoma cruzi, Leishmania donovoni and rat skeletal myoblasts (L-6 cells). Methods: The leaf ingredients were extracted and separated via methanol, ethyl acetate, chloroform and n-hexane solvents using column chromatography. In vitro activity against erythrocytic stages of P. falciparum was determined by a modified [3H]-hypoxanthine incorporation assay. In vitro activities against T. brucei rhodesiense, T. cruzi and L. donovoni and cytotoxicity against L6 cells line were assayed. Regression analysis was adopted for computation of the 50% inhibitory concentrations. The antiprotozoan activity of the extracts was qualified as active when IC50 value was less than 50 g/ml. The extract that showed selectivity index higher than 3.29 was considered to have potential for safer therapy. Results: n-hexane fraction showed the best antiplasmodial activity with inhibitory concentration (IC50) value of 12.1 g/ml followed by chloroform fraction (23.0 g/ml), crude methanolic extract (30.4 g/ml) and ethyl acetate fraction (45.9 g/ml) with selectivity index of 3.66, 1.90, 2.18 and 3.29 respectively. Chloroform fraction showed the best activity against T. brucei rhodesiense with IC50 value of 17.9 g/ml and selectivity index of 2.44 and followed by n-hexane fraction with IC50 (34.5 g/ml) and selectivity index of 1.28. Conclusion: Since leaf extract has significant antiplasmodial, antitrypanosomal and antileshmanial activities in vitro, bioassay guided isolation of the active principles can be done with a view to discovering novel drugs for the treatment of malaria, trypanosomiasis and leishmaniasis.