Mosquito Repellent Actions of the Essential Oils of Cymbopogon citratus, Cymbopogon nardus and Eucalyptus citriodora: Evaluation and Formulation Studies

Abstract

Essential oils extracted by steam distillation from Cymbopogon citratus (DC.) Stapf, Cymbopogon nardus (L.) Rendle and Eucalyptus citriodora Hook were evaluated for their repellent effects against Anopheles arabiensis mosquitoes under laboratory conditions. Blended oils, ointments and cream formulations of the oil of C. nardus in different bases were also evaluated. At 10 % and 20 % concentrations, all the oils showed a minimum of 90 % and 95 % relative protection, respectively, soon after application. These were not significantly different in efficacy from NN-diethyl-meta-toluamide (DEET), P<0.05. Afterwards however, only C. nardus oil produced more than 70 % protection for 3 h and 4 h at a concentration of 10 % and 20 %, respectively. Combinations of 10 % or 20 % of each of the oils of C. citratus and C. nardus gave better protection than their individual effects. In the presence of the oil of E. citriodora, the effects of C. citratus and C. nardus were significantly reduced at both concentrations. The oil of C. nardus in oleaginous ointment (i.e. Vaseline) provided above 80 % relative protection for as long as 4 h which was better than the effect of the 20 % oil, P<0.05. Similarly, the oil in hydrophilic ointment, 1:1 w/w blend of PEG 4000 and PEG 600, gave better repellent effect than the 20 % oil (P<0.05). However, the effect of the o/w cream was not statistically different from the 20 % oil, P>0.05. The blends of C. citratus and C. nardus oils and the ointment formulations of the oil of C. nardus showed improvement on the percentage of protection of the oil of C. nardus. However, both the blending and the formulations did not improve the duration of protection. In addition, both the percentage and duration of protection were not as good as DEET, P<0.05. This study demonstrated the potential of essential oil of C. nardus as topical repellent against An. arabiensis.