CHEMICAL ANALYSIS AND EVALUATION OF THE LARVICIDAL ACTIVITY OF ESSENTIAL OILS AND CRUDE EXTRACTS OF LEUCAS MARTINISENCIS L. AND CROTON ZAMBESICUS MUELL. ON ANOPHELES GAMBIAE GILES

The aim of the present study was to evaluate the larvicidal activities of essential oils and crude organic (petroleum ether, chloroform, ethyl acetate and methanol) and aqueous extracts of Leucas martinisencis L. (whole plant) and Croton zambesicus Muell. (fruits), two aromatic plants of Niger on Anopheles gambiae Giles. GC and GC/MS analysis showed that β?caryophylene (43,86 %) and α?humulene (19,93 %) were the main constituents of the sesquiterpenic essential oil of L. martinisencis while two sesquiterpenic compounds β ?elemol (13,23 %) and β ?eudesmol (10,50 %) were found as the main constituents of the essential oil of C. zambesicus which was a monoterpenic one. Phytochemical analysis of the crude organic and aqueous extracts revealed the presence of terpenes and sterols, tannins and polyphenols, saponosides and alkaloids in the two plants and flavonoids in C. zambesicus. The larvicidal tests showed that the essential oil of L. martinisencis was more active than that of C. zambesicus with DL50 values of respectively 0,050 g/L and 0,083 g/L, but the two essential oils were less active than deltamethrine, the reference larvicide. Of the crude organic and aqueous extracts, only the ethereal extracts of the two plants and the chloroformic extract of L. martinisencis showed larvicidal activities after 48 hours of exposure. These results support the use of the two aromatic plants as larvicide against Anopheles larvae.