Coleus aromaticus leaf extract fractions: A source of novel ovicides, larvicides and repellents against Anopheles , Aedes and Culex mosquito vectors?

Abstract

Abstract Eco-friendly tools to manage mosquito young instar populations in an IPM framework are urgently required. Here, we analyzed six ethyl acetate and methanol fractions of Coleus aromaticus leaf extract using thin layer chromatography and GC–MS, in order to shed light on the main chemical constituents with toxicity on mosquitoes. The fractions were tested as ovicides, larvicides and repellents against the mosquito vectors Anopheles stephensi, Aedes aegypti and Culex quinquefasciatus. In GC–MS analysis, a total of nine compounds were identified in the methanolic extract composition, the main component was 11-octadecenoic acid, methyl ester. The highest larvicidal activity was observed for the methanol fraction 4 against Ae. aegypti, An. stephensi and Cx. quinquefasciatus with LC50 values of 23.90, 22.32 and 20.51 ppm. In the ovicidal experiments, 100% mortality was exterted by methanol fraction 4 tested at 40 ppm against Ae. aegypti, An. stephensi and Cx. quinquefasciatus. Furthermore, high repellence of methanol fraction 4 tested at 2.5 mg/cm2 was observed in “arm in cage” tests for at least 320 min. We hypothesized that 11-octadecenoic acid, methyl ester was the main constituent responsible for the mosquitocidal and repellent activity of C. aromaticus fractions.