Avaliação da atividade larvicida da nanoemulsão do óleo essencial das raízes de Philodendron fragrantissimum (Hook) G.Don (Araceae) contra Aedes aegypti (Linnaeus 1762) (Diptera: Culicidae)

Abstract

The mosquito of the species Aedes aegypti is the cause of the transmission of diseases like dengue fever, yellow fever, chikungunya and zika. It causes a high mortality rate in the world, especially in tropical countries, and it is a public health problem. Currently, looking for substances that control the vector, is and increasing interest. The essential oils of plants, for example, reduce the toxic effects on the environment and the resistance that some insects present against synthetic products. However, the oils are poorly soluble in water and the nanoemulsions are viable alternatives, since they are able to disperse in aqueous medium. This study aimed to evaluate the larvicidal activity of the essential oil nanoemulsion of Philodendron fragrantissimum (Hook.) G.Don on A. aegypti. The plant material was identified and the exsicata deposited in the amapaense herbarium (HAMAB). The extraction of the oil from the root of P. fragrantissimum was done by means of the hydrodistillation technique in Clevenger apparatus. The identification of the substances that are in the essential oil was made by gas chromatography coupled to a GC / MS mass spectrometer. The nanoemulsions were prepared by a low energy input method. The final mass was 4 g and were composed of 2.5% (w / w) of essential oil of P. fragrantissimum; 2.5% (w / w) surfactant (s) and 95% (w / w) water. To perform the larvicidal test, they were diluted to 3.125ppm; 12.5ppm; 25ppm; 50ppm; 100ppm; and 150ppm. The larvae of A. aegypti (Rockfeller strain) used in the experiments were taken from the Institute of Arthropoda Laboratory of the Federal University of Amapá. Bioassays of larvicidal activity followed the standard protocol recommended by the World Health Organization (WHO), performed in quintuplet with 10 larvae in each repetition, and mortality was verified after 24 and 48 hours of exposure. The anticholinesterase activity was performed according to the method described by Ellman et al. (1961). The essential oil of P. fragrantissimum allowed to identify 27 constituents and the major substances were β-Bisabolene (40.44%), α-Pinene (23.69%), β-Pinene (7.20%), α-Bisabolene (6.59%) and β-Farnesene (5.29%). The essential oil nanoemulsion of P. fragrantissimum showed a low average droplet size and showed a potential larvicide against A. aegypti species. The estimated lethal concentration values of CL50 and CL90 after 24h were 55.07ppm (42.44 - 75.36ppm) and 86.70ppm (68.73 - 129.87), respectively. The essential oil of P. fragrantissimum presented moderates inhibition of the acetylcholinesterase enzyme with the IC 50 = 251.9 μg / mL. The larvae of the species studied were susceptible to the composition of the essential oil. Such results may be useful in promoting research for vector control of mosquitoes based on active compounds from plant species as an alternative to synthetic larvicides