Phytochemical composition of crude extracts derived from Vernonia spp. and its larvicidal activity against Anopheles gambiae

Abstract

Abstract. Tarwish B, Ngeranwa JJN, Matasyoh JC. 2017. Larvicidal activity and phytochemical composition of crude extracts derived from Vernonia spp. against Anopheles gambiae. Bonorowo Wetlands 7: 108-116. This study aimed to elucidate the larvicidal activity of three species of Vernonia, i.e., Vernonia lasiopus, V. auriculifera, and V. galamensis, against the malaria vector Anopheles gambiae. Dried samples from leaves and roots of the three plants were sequentially extracted with hexane, chloroform, ethyl acetate, acetone, methanol, and water. Following rotor evaporation of the solvents, the extracts were subjected to phytochemical analysis and larvicidal assays against the third instar larvae of A. gambiae. The phytochemical screening revealed the presence of steroids, saponins, flavonoids, terpenoids, and cardiac glycosides in all extracts. Tannins were present in methanol and water extracts of all three plants and acetone extract of V. lasiopus roots, V. auriculifera root, and V. galamensis leaf. Phlobatannins were absent in all extracts. Percent mortality for different concentrations 125, 250, 500, 750, and 1000 ppm of the extracts was calculated and subsequently subjected to probit regression analysis to determine LC₅₀ and LC₉₀ values. The most active extract recorded was acetone root extract of V. galamensis with an LC₅₀ of 22.85. Vernonia auriculifera and V. lasiopus recorded the highest activity in acetone root extract and ethyl acetate root extract with an LC₅₀ value of 37.7 and 205.9, respectively. A one-Way ANOVA test was performed to compare the mean mortality of all tested groups. At all exposure hours except at 3 hours, the differences were significant. The Tukey post hoc tests indicated that the mortality rate for V. galamensis was substantially different from the mortality rates of V. lasiopus and V. auriculifera after 24 hours. This study underlines V. lasiopus, V. auriculifera, and V. galamensis as alternative sources of new, cheap, and readily available larvicides to control the mosquito vector A. gambiae. Further study is required to determine what secondary metabolites in Vernonia extracts are responsible for larvicidal activity.