Assessment of selected medicinal plants indigenous to West Africa for antiprotozoal activity

Abstract

The disease burden of protozoal infections is enormous in West Africa and other developing regions of the world. Malaria is one of the most important parasitic disease in tropical areas caused by protozoans of the genus Plasmodium and more than a third of the world's population (about two billion people) lives in malaria-endemic areas. Leishmaniasis and trypanosomiasis are other parasitic protozoan infections caused by protozoan of the genus Leishmania and Trypanosoma respectively. The development of resistance to available antiprotozoal drugs has necessitated the search for new and effective compounds. Plant-based products with long history of traditional use in treating infectious diseases can be explored in this regard. To evaluate in vitro the antiplasmodial, antileishmanial and anti-trypanosomal activities of fractions of 18 medicinal plants belonging to 14 different families. Fractions (hexane, chloroform and methanol) of eighteen medicinal plants belonging to fourteen families, with historical use as traditional antiprotozoal therapy were screened in vitro for activity against chloroquine-sensitive and chloroquine-resistant strains of Plasmodium falciparum , Leishmania donovani (promastigotes, axenic amastigotes and intracellular amastigotes in THP1 cells) and Trypanosoma brucei brucei , using standard procedures. The methanol fraction of Corchorus walcottii showed selective antileshimanial activity against intracellular L. donovani amastigotes with an IC 50 average of 5.94 µg/ml. Methanol fraction of Cassia obtusifolia , methanol and chloroform fractions of Corchorus walcotti and methanol fraction of Vitex grandifolia exhibited activity against T. brucei brucei blood stage trypamastigotes with IC 50 values of 5.88, 5.73, 7.29 and 8.73 (µg/ml) respectively. Methanol fractions of Crotalaria mucronata and Pseudocedrela kotschyi, with the chloroform fraction of Launaea taraxacifolia showed >50% growth inhibition against chloroquine-sensitive (D6) strain of P. falciparum with values as 60%, 73% and 52%. At concentrations of 15.8667 µg/mL, the most active fractions antimalarial activity was exhibited by methanol extracts of Pseudocedrela kotschyi (IC 50 = 29.7 µg/mL (D6) S.I = 1 µg/ml (W2) S.I = 1.3) and Crotalaria mucronata (IC 50 = 46.45 µg/mL (D6) S.I > 1.0, 46.86 µg/mL (W2) S.I = 1.0) and chloroform extract of Launaea taraxicifolia (IC 50 = 21.55 µg/mL (D6) S.I >2.2, 18.0 µg/mL (W2) S.I >2.6). The results showed that the methanol extracts of Pseudocedrela kotschyi and, Crotalaria mucronata with chloroform extract of Launaea taraxicifolia may contain useful antimalarial leads. Cassia obtusifolia, Corchorus walcottii and Vitex grandifolia may be promising candidates for isolation of antiprotozoal compounds which could serve as new lead structures for development of new drugs against these neglected tropical (leshmanasis and trypanosomiasis) diseases and may provide scientific support for the traditional use of these plants against protozoal related treatments. • Plant-based products with long history of traditional use in treating infectious diseases was explored in this regard. • In vitro evaluation of the antiplasmodial, antileishmanial and anti-trypanosomal activities of 18 medicinal plants belonging to 14 different families. • Some fractions exhibited selective antileishmanial and anti-trypanosomal activities. • Some medicinal plants may be promising candidates for isolation of antiprotozoal compounds. • This study provides scientific support for the traditional use of some of these medicinal plants against protozoal related treatments.