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Nigeria Journal for Engineering
Data generated from the bioassays suggest potency of both methanolic and aqueous extract of Ageratum conyzoides and Guiera senegalensis against the larvae of Cx. quinquefasciatus, Ae. saegypti and An. Gambiae s.l. The efficacy of phytochemicals against mosquito larvae may vary significantly depending on plant species, plant parts used, solvent used during extraction as well as vector used for bioassay (Sukumar et al., 1991). It has been shown that the extraction of active biochemical from plants depends upon the polarity of the solvents used. Polar solvent will extract polar molecules and non-polar solvents extract non-polar molecules.It has been found that in most of the studies, solvent with minimum polarity have been used such as hexane, methanol, petroleum ether or that with maximum polarity such as aqueous/steam distillation. However, those bio-chemicals that were extracted using moderately polar solvents were also seen to give good results. Thus, different solvent types can significantly affect the potency of extracted plant compounds and there is difference in the chemo-profile of the plant species. Median lethal concentration (LC50) values obtained in this study (ranging between 42.53 and 112.49 ppm) compares favourably with other works done elsewhere. For instance, 53.60 ppm was reported from Solenostemmaargel against Cx. pipiens and Several other plants such as, Atlantia monophylla (20.26ppm)and Centella asiatic (50.67ppm) (Ghosh and Chandra,2006). Higher values of LC50 were obtained from Leaf of Solanum nigrum (107.01) and Azadirachta indica (560.32 ppm) (Mgbemena, 2010). The plants, A. conyzoides and G. senegalensis are excellent candidates of choice to be used as bio-friendly pesticides for their abundance especially period mestically. In addition G. senegalensis is a perennial shrub that is resistant to drought.
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