RESUMO
In Africa and elsewhere, medicinal plants including Spilanthes uliginosa, Ocimum basilicum, Hyptis spicigera and Cymbopogon citratus are still widely used in the treatment of malaria and other ailments. The aim of the present study was to investigate in vivo antiplasmodial effect of ethanolic leaf extract of these plants in mice. Oral acute toxicity of the extracts was evaluated in mice using modified Lorke’s method and their in vivo anti-plasmodial effect against early infection, curative effect against established infection and prophylactic effect against residual infection were studied using total WBC count in chloroquine-sensitive Plasmodium berghei NK 65-infected mice. The oral median lethal dose of the extract in mice was determined to be greater than 2000 mg kg-1 body weight. The results indicated a significant (P<0.05) daily increase in the level of parasitaemia in the parasitized untreated groups and a significant (P<0.05) dose dependent decrease in the level of parasitaemia in the parasitized groups treated with varying doses of the various medicinal plants and the standard drug. Overall, the dose dependent effects were in the order of: 5mg/kg body weight of chloroquine > 800 mg/kg > 400 mg/kg > 200 mg/kg body weight of the plant extracts with the efficacy of the plants in the order of: H. Spicigera > O. basilicum > C. citratus > S. uliginosa (Sw) with minor variations. The implications of these results is that Spilanthes uliginosa, Ocimum basilicum, Hyptis spicigera and Cymbopogon citratus ethanolic leaf extracts posses potent antimalarial effects and may therefore serve as potential sources of safe, effective and affordable antimalarial drugs.