Mosquito larvicidal activity of Enhalus acoroides (L.f) royle and Halophila ovalis (R. br) hook. f. against the deadly vectors Aedes aegypti and Culex quinquefasciatus

Mosquitoes act as vectors to induce various dreadful diseases which continue to cause fatal effect on human beings. Aedes aegypti (Ae. aegypti) is one among the vectors which causes yellow fever, dengue and chikungunya, and Culex quinquefasciatus (C. quinquefasciatus) is another which can cause lymphatic filariasis, a widely distributed tropical disease across the world. In line with the larvicidal activity of sea grasses against the disease vectors, the present contribution has been focused. Two seagrasses namely Enhalus acoroides (L.f) Royle (E. acoroides) and H. ovalis (R.Br) Hook.f. (H. ovalis) collected from the Mandapam Coast, Rameswaram, Tamil Nadu located in South India were washed, shade dried, blended and made in to a fine powder. Sea grass extracts of different concentrations from 62.5 ppm to 500 ppm were prepared in the ratio 1:3 (w/v) using hexane, dichloromethane and ethanol as solvents. The results showed that the hexane extract (500 ppm) of E. acoroides exhibited the larvicidal activity of 62% against the Ae. aegypti after 24 h whereas its ethanol extracts (500 ppm) showed 50% of larvicial activity against C. quinquefasciatus. It could be inferred that the H. ovalis displayed a lesser larvicidal potentiality against Ae. aegypti than that of E. acoroides. The FT Infra-Red characterization of E. acoroides was carried out for the identification of various functional groups. The presence of about 11 organic compounds in E. acoroides was analysed using GC – MS. The significant role of solvents’ polarity in enabling the bioactive compounds to combat against two different mosquito vectors has been discussed. Statistical data such as LC50 (concentration of compound that kills 50% of larva), LC90 (concentration of compound that kills 90% of larva), correlation coefficient (r), χ2 and p values are calculated and discussed.