The ethanolic leaf extract of Cassia obtusifolia was investigated for their larvicidal and oviposition deterrence effects against Anopheles stephensi. Concentrations ranging from 25 to 125 mg/l were assessed at 24 h post-treatment against late third instar larvae. The leaf extract had significant larvicidal effect with LC(50) and LC(90) values were 52.2 and 108.7 mg/l, respectively. In oviposition behaviour study, four different concentrations ranging from 100 to 400 mg/l were studied against gravid female mosquitoes. The results of oviposition study indicated that the leaf extract showed concentration dependent oviposition deterrent activity. At higher concentration (400 mg/l) showed 92.5% effective repellency against oviposition, followed by 300, 200 and 100 mg/l showed 87.2%, 83.0% and 75.5%, respectively. The larvicidal and oviposition deterrent effect of C. obtusifolia against A. stephensi make this plant product promising as an alternative to synthetic insecticide in mosquito control programs.

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The bioactivity of four flavonoid compounds, namely poncirin, rhoifolin, naringin and marmesin, from Poncirus trifoliata was studied against the Aedes aegypti. Larvicidal assays were conducted to evaluate the 24 h LC(50) and LC(90) values of the flavonoid compounds. The lethal concentration (LC(50) and LC(90)) values ranged from 0.082 to 0.122 mg/l and 0.152 to 0.223 mg/l, respectively. The result of ovicidal test suggests that the ovicidal activity of the flavonoid compounds was influenced by the concentration of flavonoid compounds and age of the eggs. The result of oviposition test showed that the four flavonoid compounds exhibited oviposition-deterrent activity against gravid female mosquitoes. Oviposition decreased with an increase in concentration of flavonoid compounds. A laboratory test was carried out to evaluate protection period and percentage of repellency of four compounds diluted in ethanol (10 mg/l). The compound rhoifolin provided maximum 365.0 +/- 12.0 min protection and also 100.0% +/- 0.0 repellency against mosquito bite followed by poncirin, marmesin and naringin. None of the 25 volunteers of either sex exposed to 10% (w/v) flavonoid compounds (4-h patch test) showed a positive skin irritant reaction. All of the tested compounds proved to have various activities against different life stages of A. aegypti. Therefore, flavonoid compounds from P. trifoliata can be a potential candidate for use in the development of commercial mosquitocidal products that may be an alternative to conventional synthetic chemicals, particularly in integrated vector control applications.

The present finding suggest that the C. indica leaf essential oil provided an excellent potential for controlling An. stephensi mosquito at earlier stage of their life cycle.