LARVICIDAL AND ENZYME INHIBITORY EFFECTS OF ACALYPHA FRUTICOSA (F.) AND CATHARANTHUS ROSEUS L (G) DON. LEAF EXTRACTS AGAINST CULEX QUINQUEFASCIATUS (SAY.) (DIPTERA: CULICIDAE)

Abstract

ABSTRACTObjective: The prime objective of this study is to evaluate the larvicidal and enzyme inhibitory effects of Acalypha fruticosa and Catharanthus roseusleaf extracts against Culex quinquefasciatus.Methods: Insecticidal susceptibility tests were carried out using the World Health Organization standard method, and the mortality was observedafter 24 hrs exposure.Results: The tested extracts showed a significant larvicidal activity depending on the dose of the plant extracts. However, maximum larval mortalitywas detected in ethyl acetate extract of A. fruticosa with a lethal concentration (LC50) value of 253.08 ppm and (LC90) value of 455.40 ppm followedby hexane extract of C. roseus with LC50 value of 645.33 ppm and LC90 value of 1452.88 ppm against the larvae of C. quinquefasciatus. In control, therewere five different fractions of α-carboxylesterases resolved in the gel with the mobilities ranging between 0.14 and 0.66. β-carboxylesterase isozymeprofile of larvae treated with hexane extract of A. fruticosa showed higher enzyme activities by way of intense staining of fractions both at 1/4 and1/10 LC50 value of 48 hrs treatments. A. fruticosa ethyl acetate extract, and C. roseus hexane extract exposed larvae indicated increased quantitiesof β-Est4/5 isozymes in the concentration of 1/4 and 1/10 of LC50 value of 24 hrs treatment when compared to control. The protein quantity in themajority of treatments decreased compared to control.Conclusion: The results revealed that the organic leaf extract of A. fruticosa and C. roseus had significant larvicidal and enzyme inhibitory effectsagainst C. quinquefasciatus.Keywords: Acalypha fruticosa, Catharanthus roseus leaves extract, β-carboxylesterase, Culex quinquefasciatus, Lethal concentration50.