Atividade larvicida do óleo essencial de Croton blanchetianus contra Aedes aegypti (Diptera: Culicidae)

Abstract

Aedes aegypti is an insect that belongs in the Culicidae family, popularly known as mosquitoes. The culicidae is an important family in the medical aspect, because they are vectors that transmit arboviruses and diseases such as: zika, chikungunya and urban yellow fever. The main preventive measure against arboviruses is to do a chemical control on the vectores. However, these measures became limited because Aedes aegypti fast microevolution against the insecticides commonly used. Considering the toxic potential and the vector's resistance towards pesticides, vegetal compounds are an excellent alternative to Aedes aegypti control. On endemic countries and with a wild diversity of plants like in Brazil, the search for new methods of control are of great importante. Among the plants that constitute the Caatinga, the Croton genre has a lot of species known. In Brazil, Croton is popularly known as marmeleiro, where some of its representatives are used to treat diseases like diabetes, malaria, digestive problems and some symptoms like fever. Futhermore, previous studies already indicate that the essential oil of some species from the Croton genre have larvicidal activity against medically important mosquitoes. That way, the objective of this work is to avaliate the larvicidal potential of the essential oil of Croton blanchetianus in different concentrations against A. aegypti. The extraction of oil from C. blanchetianus was carried out by the hydrodistillation process and the chemical characterization was carried out by gas chromatography associated with mass spectrometry. For that, WHO standardized tests were carried out, larvae in the 3rd instar were exposed to different concentrations of the essential oil of C. blanchetianus: 20mg/mL, 12.5mg/mL 10mg/mL and 5mg/mL. Readings were done 24h, 48h and 72h after so as to avaluate larvae motility. The chemical description of the essential oil of C. blanchetianus showed the presece of espatulenol as the majoritary component (20,03%), biciclogermacrene (5,92%), caryophyllene oxide (5,81%) and eucaliptol (5,62%). The larvicida essays showed that there was a mortality in all concentrations tested. The morphohistologycal analysis revealed that the exposition to the oil caused changes in the midgut of the insect, it was also possible to identify the emergence of vacuoles and detachment of epithelial cells from the basement membrane.