Evaluation of mosquito repellent, larvicidal and mosquitocidal activities of essential oil and monoterpene alcohols from leaves of Acronychia pedunculata

AbstractThe essential oil from leaves of Acronychia pedunculata was obtained by hydro distillation and the chemical composition was determined by GC and GC-MS. Monoterpenes alcohols were isolated by preparative GC. Further, the oil and isolated compounds were screened for mosquito repellent, larvicidal and mosquitocidal activities against three species, Aedes aegypti, Anopheles stephensi and Culex quinquefasciatus. Laboratory bioassay showed that leaf oil at 36.11, 39.24 and 44.39 mg/ml of could induce 90% mortality in the larvae, excellent mosquitocidal activity with LD50 of 1.8, 2.3 and 2.8 ×10-3 mg/cm-3 respectively for A. aegypti, A. stephensi and C. quinquefasciatus. While, Malathion, a positive control sample caused 90% mortality at 1.79, 1.93 and 2.26 mg/ml for the three species of mosquitoes. Repellency was tested by knockdown and arm-in cage tests and compared favourably with prallethrin and DEET. The sample with 3% essential oil showed highest mortality rate of 96% while 99% mortality rate was observed with the prallethrin. Arm-in-cage test revealed that the potent repellent activity of the oil with RD50 values of 25.8, 29.3 and 32.4 ×10-3 mg/cm-2 for the three mosquito species respectively while, DEET, a widely used insect repellent displayed RD50 of 20.3 - 21.6×10-3 mg/cm-. Monoterpene alcohols, isofenchol, isopulegol and isothujanol were isolated and all the compounds demonstrated significant repellent, larvicidal and mosquitocidal activities on all the tested organisms. The results indicate the potential repellent and larvicidal activities of oil and isolated compounds which can be further developed into lead molecules and can be employed in various mosquito control programmes.