Nanoemulsion of Ocotea indecora (Shott) Mez essential oil : larvicidal effects against Aedes aegypti .

Abstract

The widespread use of insecticide can lead to the resistance of the Aedes aegypti mosquito and adverse effects on non-target organisms, such as humans, other animals, and insects. In this sense, nanotechnology associated with natural products is a promising alternative to obtaining safer and more sustainable insecticide formulations against this vector. Therefore, in this research, we developed and optimized a nanoemulsion with essential oil from Ocotea indecora (Shott) Mez leaves and evaluated its larvicidal properties against Ae. aegypti larvae. In addition, oral toxicity assays were performed to test the nanoemulsion safety of the non-target organism Apis mellifera. The major constituent found was sesquirosefuran (81.4 %). The nanoemulsions were prepared by the low-energy method by phase inversion and characterized by the dynamic light scattering technique. The most suitable surfactant mixture was in hydrophilic-lipophilic balance 14.22, presenting droplets size of 122.8 nm and polydispersity index of 0.262. Then a 23 factorial design was realized to optimize the formulation suggesting the variables conditions of 1:1 of essential oil (5 % w/w) and surfactants at 500 rotations per minute. This led to

spherical nanoemulsions with mean size and PdI of 105.3 nm and 0.263, respectively. The optimized nano- emulsion presented stability when stored at room temperature and refrigerated for up to one year. The LC50

values against Ae. aegypti larvae were 61.4, and 26.8 μg/mL after, 48, and 144 h, respectively. Scanning electron micrography showed morphological body alterations on the larvae Ae. aegypti treated with the nanoemulsion.

Regarding the ecotoxicological evaluation, the nanoemulsion showed no toxicity against Apis mellifera. There- fore, this work demonstrated a simple method to obtain O. indecora nanoemulsion as an environmental-friendlier

alternative to the Aedes aegypti control.