PHYTOCHEMICAL STUDY AND EVALUATION OF LARVICIDAL ACTIVITY OF THE ESSENTIAL OILS OFCYMBOPOGON CITRATUS (D.C.) STAPF. AND CYMBOPOGON GIGANTEUS CHIOV. ON ANOPHELES GAMBIAE S.L.

This study evaluates the larvicidal activity of essential oils extracted from the leaves of Cymbopogon citratus DC. Stapf. and the stems with leaves and inflorescences of Cymbopogon giganteus Chiov. Towards the larvae of Anopheles gambiaes.l., the main vector of malaria. The essential oils were obtained by hydrodistillation using a Clevenger-type apparatus, then analysed by gas chromatography (GC) and by gas chromatography coupled with mass spectrometry (GC-MS). Larvicidal tests were carried out according to the WHO protocol (1985). The highest extraction yields were recorded with C. citratus (1.91%), followed by C. giganteus (0.46%). GC and GC-MS analysis revealed that the essential oil of C. citratusis mainly composed of a-citral (44.8%) and B-citral (32.7%). The essential oil of C. giganteus was not chemically characterized in this study. Larvicidal bioassays demonstrated significant activity of the two essential oils on An. gambiaelarvae. The essential oil of C. giganteus was found to be the most active (LD50 = 70.13 ppm), followed by that of C. citratus (LD50 = 114.36 ppm). Although these essential oils are less powerful than deltamethrin (LD50 = 2.3 ppm), used as a reference product, they appear to bepromisnig alternatives for the development of more sustainable insecticides. These results also provide scientific justification for the traditional use of aromatic plants in Niger as mosquito repellents.