A b s t r a c t A r t i c l e I n f oThe management of breeding sites is one of the preventive measures against malaria. However, in view of the environmental damage caused by the various chemical insecticides used for this purpose and especially the resistances developed by Anopheles gambiae (the main vector) with respect to these synthetic chemical compounds, we have proposed implementing of extracts plants. Thus, organic solvents with a gradient of polarities such as nhexane, dichloromethane and methanol-water were used to extract the phytochemical compounds present in the leaves of Elaeis oleifera and Launaea taraxacifolia. The three different extracts obtained for each plant were tested on 3rd stage larvae from two genotypes of Anopheles gambiae: the Kisumu strain of Kenyan origin and the wild strain from the breeding sites of Cotonou. Phytochemical analysis revealed that in addition to tannins, flavonoids, anthocyanins, leuco-anthocyanins and triterpenes which are present in both plants, Elaeis oleifera also contains mucilages and alkaloids. The hydro-methanolic extracts were found to be the most active on the two origins of larvae with lethal concentrations LC 50 of 448.01 ppm in 24 hrs and 51.38 ppm in 48 hrs of exposure for the Kisumu strain; 4199.63 ppm and 1456.44 ppm in 24 hrs and 48 hrs respectively for the wild population for Elaeis oleifera. In addition, Launaea taraxacifolia appeared much more interesting and displayed almost identical activities on the two larval origins with LC 50 of 182.68 ppm and 135.13 ppm respectively in 24 hrs and 48 hrs for Kisumu larvae and 157.36 ppm in 24 hrs then 116.88 ppm in 48 hrs for wild larvae. It is therefore concluded that Launaea taraxacifolia can be used for bio-larvicide production in integrated malaria vector control.

Objective: One of the measures used to prevent malaria is the management of breeding sites. For preventive and ecologically profitable control, the use of bio-larvicides made from active plant extracts would be an asset for the control of malaria vectors, in particular Anopheles gambiae. Advances in pharmacognosy have revealed the benefits of several phytochemicals with very rich and varied therapeutic effects. Among the latter, oleanolic acid (OA) is quite remarkable because of its various and multiple properties, much of which is demonstrated with the leaves of Launaea taraxacifolia. Methods: After a liquid-liquid fractionation with different organic solvents of the hydro-methanolic extract of Launaea taraxacifolia, we obtained three fractions named Fhex (hexane fraction), FDCM (dichloromethane fraction) and FHM (hydro-methanolic fraction) which were tested on 3rd instar Anopheles gambiae larvae. Results: Fhex proved to be the most active with LC50 of 120.11 ppm and 69.50 ppm respectively in 24 and 48 hours of contact. We then developed a new method of Ultra-Violet High Performance Liquid Chromatography (HPLC / UV) method and determined the quantity of oleanolic acid in the Fhex and FDCM fractions to be respectively 0.46% and 0.23% . Conclusion: Launaea taraxacifolia has a larvicidal potential due to the presence of oleanolic acid whose inhibitory effect against Anopheles gambiae larvae.