Effect of niloticin,a protolimonoid isolated from Limonia acidissima L. (Rutaceae) on the immature stages of dengue vector Aedes aegypti L. (Diptera: Culicidae)

The aim of the present study was to evaluate the mosquitocidal activity of fractions and a compound niloticin from the hexane extract of Limonia acidissima L. leaves on eggs, larvae and pupae of Aedes aegypti L. (Diptera: Culicidae). In these bioassays, the eggs, larvae and pupae were exposed to concentrations of 2.5, 5.0, 7.5 and 10.0 ppm for fractions and 0.5, 1.0, 1.5 and 2.0 ppm for compound. After 24 h, the mortality was assessed and the LC₅₀ and LC₉₀ values were calculated for larvae and pupae. Per cent ovicidal activity was calculated for eggs after 120 h post treatment. Among the sixteen fractions screened, fraction 8 from the hexane extract of L. acidissima generated good mosquitocidal activity against Ae. aegypti. The LC₅₀ and LC₉₀ values of fraction 8 were 4.11, 8.04 ppm against Ae. aegypti larvae and 4.19, 8.10 ppm against Ae. aegypti pupae, respectively. Further, the isolated compound, niloticin recorded strong larvicidal and pupicidal activities. The 2 ppm concentration of niloticin showed 100% larvicidal and pupicidal activities in 24 h. The LC₅₀ and LC₉₀ values of niloticin on Ae. aegypti larvae were 0.44, 1.17 ppm and on pupae were 0.62, 1.45 ppm, respectively. Niloticin presented 83.2% ovicidal activity at 2 ppm concentration after 120 h post treatment and niloticin exhibited significant growth disruption and morphological deformities at sub lethal concentrations against Ae. aegypti. The structure of the isolated compound was identified on the basis of single XRD and spectral data (¹H NMR and ¹³C NMR) and compared with literature spectral data. The results indicate that niloticin could be used as a potential natural mosquitocide.