Mosquito Repellent Activity and Toxicity of Flower Buds (Cloves) of Syzygium aromaticum Linn.

The repellent activity of methanolic extract of flower buds (clove) of Syzygium aromaticum Linn. and its different fractions was screened against the dengue fever and yellow fever mosquito, Aedes aegypti L. at 4% concentration under laboratory conditions using human subject. The extract and main ethyl acetate soluble fractions were the most effective and showed 80% repellency for 4 hours while petroleum ether soluble sub-fraction of latter fraction gave 72% repellency for 4 hours. These samples were 50-60% effective for 9 hours. The results were compared with standard mospel. Furthermore, in the present investigation toxicity of the extract and fractions of clove was determined against 4th instar larvae of Ae. aegypti by using WHO method. The extract, ethyl acetate soluble main fraction and petroleum ether soluble sub-fraction showed mortality with LC50 320, 240 and 160 ppm, respectively after 24 hours of exposure. It was observed that toxicity decreased with the increasing polarity of the fractions. These results were compared with standard neem formulation, biosal showing LC50 = 400 ppm against the same mosquito Ae. aegypti.