Combined larvicidal efficacy of rhinacanthin-c, luteolin, quercetin, and binary mixtures of rhinacanthus nasutus, andrographis paniculata and vernonia cinerea extracts against aedes aegypti mosquito

Abstract

© 2018 Association of Agricultural Technology in Southeast Asia. All Rights Reserved. Phytochemicals have been shown to possess insecticidal activities against insects and mosquitoes. We tested toxicities of the mixtures of Rhinacanthus nasutus, Andrographis paniculata and Vernonia cinerea extracts together with their major compounds against Aedes aegypti mosquito, collected from Nakhon Pathom, Thailand. The mosquitoes were observed tolerant to pyrethroids and had increased activities of detoxification enzymes compared to the susceptible Bora strain, indicating detoxicification system could be responsible for tolerance to pyrethroid insecticides. Among the extracts, R. nasutus hexane extract showed the highest larvicidal activity toward Ae. aegypti fourth-instar larvae (LC50=68.52 μg/ml). Synergism in toxicity was observed on binary mixtures of R. nasutus with A. paniculata hexane fraction and of R. nasutus hexane with V. cinerea ethyl acetate fraction. Mixtures of rhinacanthin-C and luteolin or quercetin flavonoids, the major compounds of R. nasutus and V. cinerea, respectively, revealed potent larvicidal activity. Effect of those extracts and compounds against detoxification enzyme activities suggested that the observed larvicidal synergism might be due to the combination of insecticidal property of rhinacanthin-C and inhibition of insecticide detoxification enzymes by the respective phytochemical compounds. This study should have an implication in development of eco-friendly strategy in resistance mosquito vector control.