author(s)
Simon Pierre Yinyang Danga, Oumarou Bibi Farouck Aboubakar, Honore Menga Tissebe Ndouwe, Bouladji Yonki, David Ngadvou, Charles Okechukwu Esimone and Elias Nchiwan Nukenine

abstract
Malaria remains one of the deadly diseases in Africa in general and Cameroon in particular. Synthetic insecticides have been used to kill its mosquito vector and so to prevent the disease. Though very efficient, those insecticides showed their limits. Plants can be used as alternative mosquitocidal agents as they are made up of several bioactive chemicals. This project aimed at evaluating the larvicidal activity of n-hexane, chloroform, ethyl acetate and methanol fractions of stem bark and root of Nauclea latifolia and Ekebergia senegalensis and the leaf of Clerodendrum splendens against 4^th instar larvae of Anopheles gambiae, the major malaria vector mosquito. The World Health Organization standard protocol for mosquito larval tests was used. Twenty five 4^th instar larvae were treated with 125 to 1000 ppm of methanol crude extract, n-hexane, chloroform and ethyl acetate and methanol fractions as well as 500 ppm of Diclorvos. Dead larvae were registered 24 h post-exposure. The LC₅₀ and LC₉₀ values were determined by Probit analysis. n-hexane fractions of N. latifolia stem bark and root and E. senegalensis root were the most active. They globally killed all exposed larvae at all concentrations as compared to the synthetic insecticide (Diclorvos). As for C. splendens leaf, n-hexane fraction was still the most active followed by ethyl acetate fraction, with LC₅₀ values of 250.7 and 363.2 ppm, respectively. Our findings reveal that n-hexane is the ideal solvent that can be used to extract the most toxic compounds from the three above mentioned plants. However, further studies need to be done in order to identify the bio-efficient chemicals responsible of the toxicity through the bio-guided fractionation.