Repellent and mosquitocidal effects of leaf extracts of Clausena anisata against the Aedes aegypti mosquito (Diptera : Culicidae)

摘要

Mosquitoes are rapidly developing resistance to insecticidesthat millions of people relied on to protect themselvesfrom the diseases they carry, thereby creating a need todevelop new insecticides. Clausena anisata is used traditionallyas an insect repellent by various communities in Africaand Asia. For this study, the repellency and adulticidal activitiesof leaf extracts and compounds isolated from this plantspecies were evaluated against the yellow fever mosquito,Aedes aegypti. In the topical application assays, using totalbites as an indicator, repellency was dose dependent, withthe acetone crude extract (15 %) having 93 % repellence andthe hexane fraction (7.5 %) 67 % repellence after 3 h.Fractionation resulted in a loss of total repellence. Asmosquito-net treating agents, the acetone and hexane extractsof C. anisata, both at 15 %, had average repellences of 46.89± 2.95 and 50.13 ± 2.02 %, respectively, 3 h after exposure.The C. anisata acetone extract and its hexane fraction causedmosquito knockdown and eventually death when nebulisedinto the testing chamber, with an EC50 of 78.9 mg/ml (7.89 %) and 71.6 mg/ml (7.16 %) in the first 15 min afterspraying. C. anisata leaf extracts have potential to be includedin protection products against mosquitoes due to the repellentand cidal compounds contained therein.