Abstract:
The search for plant-derived antimalarial drugs has continued overtime as the choice for the treatment of malaria is highly limited due to drug resistance. Malaria is one of the most important infectious diseases in Nigeria and in tropical Africa at large as everyone is at risk of the infection. This study was carried out to evaluate the antiplasmodial activity of Alchornea laxiflora and Nauclea latifolia leaf extracts against Plasmodium berghei-infected mice. In vivo antimalarial assay on chloroquine-sensitive P. berghei-infected mice was carried out by oral administration of graded doses (200mg/kg, 400mg/kg and 600mg/kg) of methanolic and chloroform extracts using chloroquine and distilled water as positive and negative control respectively. Curative assay against established infection, suppressive activity against early infection and prophylactic potential in residual infection were tested against P. berghei-infected mice. Quantitative and qualitative phytochemical tests followed by functional group detection using Fourier transform infra-red spectrometry were carried out on the extracts. Nauclea latifolia and A. laxiflora displayed the highest curative activity of percentage chemosuppression of 98.59% and 98.36% at oral dose of 600mg/kg respectively. Lower doses, 200mg/kg and 400mg/kg of the chloroform extracts of N. latifolia and A. laxiflora also showed parasitemia suppression of 85.40% and 83.35% respectively. Chemosuppressive activity of chloroform extracts was lower than methanolic extracts. The entire extracts displayed dose-dependent significant (p ≤ 0.05) antiplasmodial activity as compared to the control. Residual antiplasmodial activity was highest in methanolic extract of N. latifolia (79.00% at 600mg/kg) and least in chloroform extract (23.77%) at 200mg/kg. Haematological analysis revealed an increase in packed cell volume, red blood cell, haemoglobin and white blood cell counts on dose-dependent manner in the treated mice compared to the negative control mice. Phytochemical test revealed the presence of saponins, alkaloids, tannins, phenols and flavonoids
while the Fourier transform infra-red spectrophotometric analysis of methanolic extracts showed five common functional groups namely: phenol, hydroxyl, carbon-hydrogen, carbonyl and aromatic groups of known antiplasmodial activity. Findings from this study show that crude leaf extracts of N. latifolia and A. laxiflora contained some chemical constituents that possibly can lead to antimalarial drug development as all the extracts in each model test showed a significant chemosuppression of P. berghei.
