|Naresh Kumar, A.|
Submitted to: Vector-Borne and Zoonotic Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/8/2009
Publication Date: 1/7/2010
Citation: Kamalakannan, S., Madhiyzahagan, P., Naresh Kumar, A., Murugan, K., Barnard, D.R. 2010. Pedilanthus tithymaloides (Euphorbiaceae) leaf extract phytochemicals: Toxicity to the filariasis vector, Culex quinquefasciatus (Diptera: Culicidae).. Vector-Borne and Zoonotic Diseases. 10:817-820. Interpretive Summary: At present, the main threat to effective control of disease-transmitting mosquitoes is resistance to conventional synthetic insecticides in the vector populations. Botanical insecticides are an alternative to synthetic insecticides and are relatively safe, biodegradable, and often can be obtained from local sources. In this study, Bharathiar University (India) and Agricultural Research Service scientists evaluated phytochemicals from a type of spurge plant for toxicity to the eggs, larvae, and pupae of an important vector of filiariasis in India. The extract caused significant morbidity and mortality in immature mosquitoes in tests made in the laboratory and field. The reuslts of the study suggest that phytochemicals from spurge may provide an effective alternative/adjunct to conventional synthetic pesticides for mosquito control.
Technical Abstract: Ethanolic extract of Pedilanthus tithymaloides (Euphorbiaceae) leaves was tested for biological activiity against the eggs, larvae, and pupae of Culex quinquefasciatus. Significant (P <0.0001) mortality effects were observed in each life stage. In eggs, these effects ranged from 7 to 14% at the 2 to 6 ppm concentrations, respectively. In larvae, the same concentration range induced, respectively, 23 to 30% and 88% to 95% mortality in 4th-1st instars. In pupae, 2 to 6 ppm concentrations of leaf extract induced between 18 and 42% mortality. The median and 90% Lethal Concentrations (LC50/LC90) of extract for eggs, instars 1-4, and pupae were: 1.292/2.212, 0.360/0.625, 0.384/0.650. 0.395/0.672, 0.420/0.700, and 0.741//1.473, respectively. Qualitative analyses of the extract revealed the presence of flavinoids, steroids, and phenols but the absence of alkaloids, saponins, glycosides, tannins, and resins. The results indicate that Pedilanthus tithymaloides leaf extract exhibits significant biological activity against mosquitoes and warrant further study of this material for development and use as a natural product-based biocide for disease vector control.