Controle de vetores em saúde ambiental: atividade larvicida de óleo essencial de Croton rhamnifolioides encapsulado em nanossistema polimérico frente ao mosquito Aedes aegypti

Abstract

Aedes aegypti is the mosquito with the greatest dispersion in urban areas of the world and of great importance for medicine because it is a vector of four serotypes of flavivirus, the causative agent of classical dengue fever. There is no vaccine for dengue, its main forms of control being the combat measures, eliminating the sites where the oviposition of the host occurs and its development. This control is carried out through applications of insecticides, larvicides and repellents. However, the frequent use of these products has caused resistance to mosquitoes transmitting dengue. Several researches have been carried out in order to find substances of plant origin that can serve as an alternative for the control of dengue. In this sense, medicinal plants have shown promise for their larvicidal, insecticidal and deterrent action, which, combined with new technologies, enables new products that are not harmful to the environment. Controlled release systems of the principle are alternatives that can increase the period of application of the larvicide to be tested, guaranteeing a greater time of action. Such systems containing essential oil present themselves as important strategies for the control of this vector. Thus, the aromatic plants, through their essential oils, obtained through their secondary metabolism, are presented as viable to combat this mosquito. Therefore, the objective of this work was to evaluate the larvicidal activity of essential oil extracted from aerial parts of pure Croton rhamnifolioides and in formulations of nanocapsules against larvae in the L3 phase of Aedes aegypti. The essential oil was extracted from the leaves by hydrodistillation using an adapted Clevenger apparatus. The essential oils were analyzed by gas chromatography coupled to a mass spectrometer (CG / MS). Formulations containing concentrations ranging from 40 to 80 μg / mL of pure essential oil and polycaprolactone nanocapsules ranging from 30 to 80 μg / mL with the encapsulated essential oil were produced. The larvicidal assays were performed using 20 larvae per test in a beaker containing 100 ml of distilled water, with triplicate being performed at the pre-established concentrations for each dosage, according to the protocol established by the World Health Organization. , LC50 values ranging from 26.3 μg / mL to 52.2 μg / mL and LC90 ranging from 37.8 μg / mL to 68.7 μg / mL were obtained for pure oil. For the encapsulated oil the LC50 value was 63.4 μg / mL and the CL90 was 104.8 μg / mL. Pure oil was considered strongly active (LC50 <50 μg / mL) against A. aegypti larvae and moderately active (LC50 <100 μg / mL) for the encapsulated oil. Taking into account the prospecting of the essential oil tested, we can affirm that it presented itself as strongly active against the larvae of the Aedes aegypti mosquito. This suggests that the oil of this plant species may be an alternative in combating the vector of dengue, reducing the impact on the environment and the health of the population, however further research is needed, since the oil presents several variables that need to be controlled . Further studies are also required in the method of encapsulating the oil with the synthetic polymers so that a more suitable release profile can be determined