Evaluation of chemical composition and larvicidal activity of Coleus aromaticus essential oil, its major compound carvacrol against Aedes aegypti, Culex quinquefasciatus and Anopheles stephensi (Diptera: Culicidae)

Authors: S Govindaraju, C Karthik and P Indra Arulselvi
Vectors are living organisms that can transmit infectious diseases between humans or from animals to humans. Mosquitoes are the best known disease vector that transmits dengue, malaria, lymphatic filariasis and chikungunya. Globally, these major diseases record significant mortality in human and other livestock. Further, due to the high resistance towards chemical insecticides, the mosquito control is now facing a challenge. Phyto-insecticides may help as an alternative to vector (mosquito) control. The major objective of this study was to find out the toxicity of essential oil and carvacrol extracted from Coleus aromaticus against Aedes aegypti, Culex quinquefasciatus and Anopheles stephensi. The phytoconstituents of the essential oil were analyzed by Gas chromatography-mass chromatography (GC-MS) thereby 13 compounds were identified including carvacrol, Dodecane, Tritetracontane and stigamosterol. The larvicidal activity of essential oil and carvacrol were tested with the concentration of 10, 20, 30, 40 and 50µg/ml respectively. The toxicity was observed after 24 hours of treatment. The essential oil had a significant toxic effect against Cx. quinquefasciatus, Ae. aegypti and An. stephensi with LC50 and LC90 of 16.84256 (11.45 - 20.71); 48.83991 (43.31 - 57.63), 20.57808 (15.62 - 24.11); 54.75958 (48.24 - 65.42), 23.25586 (18.95 - 26.78); 56.42830 (48.88 - 66.99)µg/ml, whereas carvacrol had 35.67071 (32.565 - 39.228); 64.64680 (57.834 - 75.209), 38.20320 (35.062 - 42.004); 77.93745 (68.746 - 93.804), 40.55376 (36.975 - 45.237); 72.03935 (63.484 - 86.023) µg/ml respectively. There is no observation of mortality in control. The result indicated that essential oil of C. aromaticus and its isolates carvacrol have a potential application in controlling of Cx. quinquefasciatus, Ae. aegypti and An. stephensi instead of synthetic chemicals.

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