Abstract
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.
Highlights
Malaria is a parasitic disease, one of the main vectors of which is Anopheles gambiae
We evaluated the mortality of A. gambiae larvae in contact with fractions derived from the active hydro-methanolic extract of L. taraxacifolia
The hydro-methanolic mixture is the solvent which produced the largest quantity by mass of fraction (81.63%). These results are in accordance with the nature of the L. taraxacifolia extract which has been fractionated and which is obtained from the same mixture of solvents but in varying proportions
Summary
Malaria is a parasitic disease, one of the main vectors of which is Anopheles gambiae. Despite the ever-increasing use of insecticide-treated bed nets, the number of malaria cases was estimated at 212 million and 429,000 associated deaths in 2015 [1]. Preventive control measures lean more and more toward mosquito control through larval control. The use of insecticides of natural origin made from active plant extracts against mosquito larvae emerges a good alternative for the control of malaria vectors. Advanced phytochemical researches have revealed the presence of several bioactive compounds with varied therapeutic effects. Oleanolic acid (OA, Fig. 1) is quite renowned for diverse pharmacological properties
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