Amaranthus oleracea and Euphorbia hirta: natural potential larvicidal agents against the urban Indian malaria vector, Anopheles stephensi Liston (Diptera: Culicidae)

Malaria control in developing countries is based largely on vector eradication by the use of mosquito larvicides which is an ideal method for controlling mosquito and the related epidemics. On account of ecohazardous nature, nontarget specificity of chemical insecticides and evidences of developing resistance against them in the exposed species, currently, importance of secondary plant metabolites has been acknowledged. Insecticides of plant origin are environmentally safe, degradable, and target specific. In view of this fact, the present work highlights the larvicidal property of extracts of Amaranthus oleracea and Euphorbia hirta against the third instar larvae of Anopheles stephensi, the urban malaria vector. LC50 values for the carbon tetrachloride fraction of A. oleracea against larvae are 17,768.00 and 13,780.00 ppm after 24 and 48 h of exposure accordingly. For the methanol extract of the same, LC50 values are 15,541.00 and 10,174.00 ppm after 24 and 48 h of exposure. In the case of petroleum ether extract, LC50 values after 24 and 48 h of exposure are 848.75 and 311.50 ppm. LC50 values for carbon tetrachloride extracts of E. hirta against the larvae are 11,063.00 and 10,922.00 ppm after 24 and 48 h of exposure, respectively. For methanol extract of the same extract, the LC50 values are 19,280.00 and 18,476.00 ppm after 24 and 48 h of exposure. In the case of petroleum ether extract, LC50 values after a 24- and 48-h exposure period are 9,693.90 and 7,752.80 ppm. The results obtained for petroleum extracts of A. oleracea are encouraging and there are probabilities that the active principle contained in this extract may be more effective than its crude form and may serve as ecofriendly mosquito larvicide.