Avaliação da actividade larvicida dos extractos e do óleo essencial das folhas de corymbia citriodora sobre as larvas do mosquito anopheles gambiae

Abstract

The worsening of the mosquitoes' resistance to insecticides, coupled with the reduced number of active compounds available for use in public health and the relatively low cost high level of synthetic insecticides, highlight the need for prospecting for research in order to provide alternative, safer and more accessible control measures against diseases vectorial This work aimed to evaluate the larvicidal activity of extracts ethanol, 25% ethanol and the essential oil of Corymbia citriodora leaves on the larvae of the third stage of development of the mosquito Anopheles gambiae, one of the main vectors of malaria parasites in Mozambique. The extracts were obtained by maceration using 96% ethanol as solvent, for 10 days, with stirring every two days, while the essential oil extracted quantitatively through the method of hydrodistillation using Clevenger apparatus. Preliminary phytochemical tests for identification of secondary metabolites were based on colorimetric reactions and precipitation. The physical-chemical analyzes of the essential oil were carried out to determination of density, refractive index, solubility in alcohol, color and appearance. At larvicidal activity, the toxicity of the ethanol extract, 25% ethanol extract and the essential oil on larvae of the third stage of Anopheles gambiae. Lethal concentration to kill 50% of the sample population (LC50), the 95% confidence interval was calculated through the methods of Reed-Muench and Pizzi respectively. The average income of essential oil extractions was 1.64% (w / w). Phytochemical tests carried out in the three extracts from Corymbia citriodora leaves revealed the presence of alkaloids, saponins, tannins, phenols and steroids / triterpenoids. The LC50 values ​​for the confidence interval at 95% of the ethanolic extract, 25% ethanolic and essential oil were 120.50 (± 2.23), 136.46 (± 2.22), and 93.11 (± 2.23) μg.ml-1 respectively. The results obtained indicate that the oil essential, as well as the ethanolic and ethanolic extracts 25% of Corymbia leaves citriodora are made up of substances that have larvicidal activity on the larvae of Anopheles gambiae.