Abstract
Human onchocerciasis has devastating pathological effects and the control relies on community directed treatment with ivermectin. However, ivermectin is only microfilaricidal and threatened by potential resistance in the parasite among other limitations. Allanblackia floribunda and Symphonia globulifera, with reported antiparasitic activity, were tested for anti-onchocerca activity and toxicity. The activity of methanol extracts of the stem barks were determined on Onchocerca ochengi adult male worms and microfilariae by motility reduction and adult female worms using MTT/Formazan assay. Cytotoxicity of extracts was assessed on monkey kidney epithelial cells, LLCMK2. Acute toxicity was investigated in mice and biochemical changes in the liver and kidney were assessed. High and moderate activities were recorded for S. globulifera and A. floribunda extracts with IC(50) values of 4.37 and 37.4 µg/mL respectively. Both extracts were not cytotoxic (CC(50) > 130 µg/mL), and no significant changes (p > 0.05), were recorded for the liver enzymes (alanine aminotransferase and aspartate aminotransferase) and the kidney function parameters (creatinine and urea). This study has revealed that S. globulifera and A. floribunda possess high and moderate anti-onchocerca activities respectively with a low risk of toxicity, hence could be exploited in traditional medicine as an alternative treatment for onchocerciasis. Both plants are potential sources of efficacious anti-onchocerca natural products which should be isolated and also studied.