Larvicidal efficacy of the mature leaf extract of Cajanus cajan against the vector of Japanese encephalitis

Abstract

Vector borne diseases can be controlled by managing the mosquito population. So the present study was done to evaluate larvicidal activities of Cajanus cajan mature leaf extracts against the Japanese encephalitis vector Culex vishnui. Crude and three different solvent extracts of C. cajan leaves were applied for larvicidal bioassay against the all instars larvae of Cx. vishnui. For statistical justifications log probit, regression and ANOVA analyses were performed. Non-target organisms were also evaluated against crude and ethyl acetate solvent extract of mature leaves. The IR analysis and GC-MS analyses were carried out to find out the active ingredient. 0.5% concentration of crude extract showed highest larval mortality after 72 h of exposure. Amongst the three tested solvent extracts namely n-Hexane, ethyl acetate and chloroform: methanol (1:1 v/v), ethyl acetate extract exhibited the most potent larvicidal activity. In ethyl acetate extract 100% mortality was found in 100 ppm concentration against 1st instar larvae after 72 h of exposure. Chemical characterization revealed that the active ingredient belongs to the flavonoids group of compound which might be responsible for larval toxicity. However, the bioassay against the non-target organisms revealed that, they were mostly safe to the extracts. The results support that C. cajan mature leaves can be used as an ecofriendly larvicidal agent against the Cx. vishnui in near future.