Obtenção e avaliação da atividade larvicida da nanoemulsão do óleo essencial de Hyptis suaveolens (L.) Poit. sobre Aedes aegypti e Culex quinquefasciatus (Diptera: Culicidae)

Abstract

Growing interest in ecofriendly alternatives of vector control is observed worldwide. On this context, aqueous nanoemulsions appear as promising delivery-systems of bioactive larvicidal agents, including low polar natural products from plant origin. Our study aimed to generate an oil in water nanoemulsion using the essential oil extracted from the leaves of Hyptis suaveolens and evaluate its larvicidal potential against Aedes aegypti larvae. Gas chromatograph analysis revealed that 1,8 - cineole was the major compound, corresponding to 26.34% of the relative composition. The second analysis showed a predominance of monoterpenes with RT lower than 15 minutes. A low mean droplet size, which remained around 150 nm, was observed even after seven days of storage. The average size of droplets was ≤200nm. The estimated values of LC50 and LC90 after 24h were 202.66 (152.508 - 321.745) ppm and 339.618 (253.747-616.336) ppm for Aedes aegypti, respectively. The larvicidal action against Culex quinquefasciatus showed values of LC50 = 102.41 (77.5253 - 149.14) ppm and 70.8105 (44.5282 - 109.811) ppm, for 24 and 48 hours, respectively. The mortality in the control with surfactant was below 9%. The scanning micrographs showed changes in the integument of the larvae. The absence of a heating step on the nanoemulsion preparation and utilization of a conventional magnetic stirrer can be considered an advantage in terms of costs of the preparation. Moreover, the surfactant which was used is biodegradable and no organic solvent was used, making this a green nanostructure system. Thus, the present study provides valuable information concerning nanobiotechnology of larvicidal agents from plant origin, opens perspectives for viable preparation of these novel systems with great potential to be used in integrative practices of disease vector control