Development of topical mosquito repellent emulgels containing zanthoxylum limonella essential oils

Vector-borne diseases caused by Aedes aegypti and other mosquitoes have become a global health problem. Zanthoxylum limonella essential oils, one of the rich sources of limonene, have a potential mosquito repellent effect. In this current study, the essential oils were successfully extracted from clusters of dried fruits by steam distillation method. The percentage yield of the essential oils was 6 %v/w. GC-MS results suggested that the essential oils composed mainly of five peaks where limonene was found as a major volatile constituent. GC-FID result showed that the concentration of limonene was 71.07 %w/w. The essential oils were prepared as microcapsules using the extrusion method involving emulsification and crosslinking processes where sodium alginate was employed as polymer matrix and calcium alginate as a crosslinking agent. The calcium alginate microcapsules of essential oils were obtained by employing sodium alginate (1.5%), Span 20 (3%) and essential oils (20%). The microcapsules obtained were ≤200 μm in diameter. The percentage yield and percentage entrapment efficiency of alginate microcapsules were 67.29±2.5 %w/w and 29.96±1.65 %w/w, respectively. The microcapsules of essential oils and free essential oils were separately prepared in the emulgels. The emulgels containing microcapsules of essential oils or free essential oils, jojoba oil, cremophorRH 40 and carbopol 940 were whitish milky cream with lemon-like odor. 5% vanillin was also added into the emulgels as a fixative. The emulgels were found as stable under centrifugation at 6000 rpm for 8 cycles with no phase separation. There were no changes in appearance, color, odor, pH and viscosity after emulgels were subjected to 6 cycles of heating-cooling cycle. Moreover, the emulgels showed pseudoplastic behavior throughout the heating-cooling cycle test. The physically stable emulgel preparations were subjected to mosquito repellency test on human volunteers. The emulgel preparations containing essential oils (18%) and vanillin (5%) showed 3.1-3.4 hours of protection against Ae. aegypti. The emulgel was stored at 30˚C, 75% RH and 40˚C, 75% RH for 12 weeks and determined the amount of limonene and vanillin. The results showed that limonene and vanillin were stable for 8 weeks at 30˚C. Therefore, emulgel containing Zanthoxylum limonella essential oils was a potential mosquito repellent for general public use.