Pedilanthus tithymaloides (Euphorbiaceae) leaf extract phytochemicals: toxicity to the filariasis vector Culex quinquefasciatus (Diptera: Culicidae).

An ethanolic extract of Pedilanthus tithymaloides L. (Euphorbiaceae) leaves was tested for biological activity against the eggs, larvae, and pupae of Culex quinquefasciatus. Significant mortality effects were observed in each life stage. In eggs, these effects ranged from 7% to 14% at the 0.013-0.040% concentrations, respectively. In larvae, the same concentration range induced, respectively, 30-95% and 23-88% mortality in first to fourth instars. In pupae, 0.013-0.040% concentrations of leaf extract induced between 18% and 42% mortality. Fitted probit-mortality curves for larvae indicated the median and 90% lethal concentrations (LC(50)/LC(90)) of extract for instars 1-4 to be 0.024/0.042, 0.025/0.043, 0.026/0.045, and 0.028/0.047, respectively. Qualitative analyses of the extract revealed the presence of flavonoids, phenols, and steroids but the absence of alkaloids, glycosides, resins, saponins, and tannins. The results indicate that Pe. tithymaloides leaf extract exhibits significant biological activity against immature stages of Cx. quinquefasciatus and warrants further study for development and use as a natural product-based biocide in disease vector control.