Mosquitocidal and phytochemical properties of loranthes pentandrus linn. (loranthaceae) against malarial vector, anopheles stephensi and filarial vector, culex quinquefasciatus (diptera:culicidae)

K. Krishnappa and K. Elumalai

Background & objectives: Vector and vector-borne diseases have become a challenging problem to public health in these days as it has social and economical impact especially in subtropical and tropical countries. Mosquitoes have mainly been controlled with synthetic insecticides in the last fifty years. However, one major drawback with the use of these chemical insecticides is that these are non-selective and could be harmful to other organisms in the environment. Plant products have been used traditionally by human communities in many parts of the world against the vectors and the other pest insects. To determine the larvicidal, ovicidal and adulticidal activity of hexane, diethyl ether, dichloromethane, ethyl acetate and methanol leaf extract of Indian saprophytic plant, Loranthes pentandrus Linn. (Loranthaceae) were investigated against malarial vector, Anopheles stephensi and filarial vector, Culex quinquefasciatus and different extracts were subjected to phytochemical analysis.Methods: Twenty five early 4th instar larvae of A. stephensi and C. quinquefasciatus were exposed to various concentrations (100-500 ppm) and were assayed in the laboratory by using the protocol of WHO 2005. The larval mortality was observed after 24 h of treatment. The ovicidal activity was determined against A. stephensi and C. quinquefasciatus mosquitoes at various concentrations ranging from 100-500 ppm under the laboratory conditions. The hatch rates were assessed 48 h after treatment. The adulticidal activity of the extracts was assessed by the method of WHO (1981). Freshly moulted adult mosquitoes (0–24h old; fed with sugar with multivitamin and blood-starved). The mortality was observed every 15min for 3 h exposure period. Adulticidal activity was calculated by counting dead mosquito from the introduced mosquito. Any mosquito was considered to be dead if did not move when prodded repeatedly with a soft brush and qualitative analyses of the phytochemicals were carried out by method of Harbone (1998). Results: Lethal concentration of larvae, LC50 value of hexane, diethyl ether, dichloromethane, ethyl acetate and methanol extract of L. pentandrus against Anopheles stephensi and Culex quinquefasciatus were 265.88, 262.82, 256.58, 259.20, 270.93, 266.53, 258.85, 247.60, 234.33 and 234.08ppm respectively. It has been noticed that the higher concentrations of L. pentandrus methanol and ethyl acetate extracts possesses strong ovicidal activity at 400 and 500ppm concentration against An. stephensi and C. quinquefasciatus, no egg hatchability was recorded. In the same way, methanol extracts showed maximum ovicidal activity followed by dichloromethane, diethyl ether and hexane against selected vector mosquitoes. Lethal concentration of adulticidal activity, the LC50 values of hexane, diethyl ether, dichloromethane, ethyl acetate and methanol extracts of L. pentandrus against An. stephensi and C. quinquefasciatus, adult in 24 h were 266.04, 267.13, 263.57, 306.85, 257.45, 268.53, 249.52, 256.23, 235.88 and 243.73ppm, respectively. Preliminary phytochemical analysis of L. pentandrus showed the presence of resins, fats/oil, glycoside, steroids, alkaloids, saponin, tanin, flavonoids and terpenoids. Conclusion: The present investigation lead the path of exploration of L. pentandrus for eradication of selected medically important human vector mosquitoes, thereby, gaining a real momentum to include this plant product for intense vector control programme.

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