- International Journal of Pure and Applied Zoology (2014) Volume 2, Issue 2

Phytochemicals and Larvicidal Activity of Plectranthus Glandulosus (Lamiaceae) Leaf Extracts Against Anopheles Gambiae, Aedes Aegypti and Culex Quinquefasciatus (Diptera: Culicidae)

Mosquitoes transmit diseases, causing millions of human deaths every year. Due to the huge consequences of synthetic insecticides, plants may be alternative sources of mosquito control agents. The present study assessed the phytochemicals and larvicidal activity of different solvent leaf extracts of Plectranthus glandulosus against three major vector mosquitoes, viz. Anopheles gambiae, Aedes aegypti and Culex quinquefasciatus. Twenty five early fourth instar larvae of each mosquito species were exposed to various concentrations ranging from 125- 1000 ppm of methanol crude extract (MCE), hexane (HF), chloroform (CF), ethyl acetate (EAF) and methanol fractions (MF), from 250-2000 ppm of water extract (AE) and 2000 ppm of DDVP. The WHO standard protocol was followed. The larval mortality was observed 24 h post-exposure. The LC50 and LC90 values were determined by probit analysis. The qualitative phytochemical analysis revealed the presence of Alkaloids, Terpenoids, Steroids, Saponins, Tannins and Phenolic Compounds, Lipids, Fats and Fixed Oils. Among all solvent extracts and fractions tested, the maximum efficacy was observed in HF against all target mosquito species with LC50 values of 17.11, 89.08 and 610.40 ppm against An. gambiae, Ae. aegypti and Cx. quinquefasciatus, respectively. MCE, CF and EAF against An. gambiae were also effective with LC50 values of 167.85, 201.50 and 76.21 ppm, respectively. The results of the leaf extracts and fractions of P. glandulosus are promising as good mosquito larvicides against An. gambiae, Ae. aegypti and Cx. quinquefasciatus. This is a new eco-friendly approach that may replace the chemical DDVP for vector control programs.

Author(s): Y.S.P. Danga, E.N. Nukenine, L. Younoussa1 and C.O. Esimone

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