Larvicidal potency of the extracts from Chlorella sp. against Aedes aegypti

Abstract Aedes aegypti is responsible for causing dengue in which the post infection risks are being reported to increase alarmingly. In this study various solvent extracts of microalgae were tested for their efficacy against the Dengue vector Aedes aegypti larvae. Chlorella sp. Genus confirmation was done to molecular level. Intracellular metabolites of chloroform and methanol extracts exhibited comparatively higher mortality in the dose dependent assay (91.2 and 50.1% respectively) to 3rd instar larvae. The lethal concentration (LC) of Chloroform extract (LC50 range within 116.82 and 159.20 ppm) was found efficient than methanol (LC50 range within 445.16 and 703.49 ppm). Lower larval instars were found to be more susceptible to the tested extracts. Chloroform extracts were purified using thin layer and column chromatography for separation and purification of compounds. Among the two fractions obtained the faster fraction had exhibited comparatively more larvicidal potency with a six fold increase in tested purified extract. Histopathology of dead larvae treated with column purified fractions showed severely affected region of the midgut, hindgut, brush border, epithelial cells and food bolus. The Gas chromatography Mass Spectral and Fourier Transform Infrared Spectroscopic analysis were carried out. The fractions revealed larvicidal compounds -hexadecanoic acid, oleic acid, β-sitosterol in both active fractions. A comparatively high larvicidal activity of the faster fraction could be attributed to the high % of hexadecanoic acid. Study concludes that partially purified fraction can be used as a potential and cost-effective biopesticide for the control of Aedes aegypti mosquitoes.