Avaliação da atividade larvicida em Aedes Aegypti L. (Diptera: Culicidae) de óleos essenciais de espécies vegetais: um estudo de revisão e bioprospecção

Abstract

Dengue is considered the most important mosquito-borne viral disease in the world; it is endemic in over 100 countries, where 50-100 million are infected by dengue virus per year. As the dengue control is based on the combat of the primary vector of dengue, the mosquito Aedes aegypti L. (Diptera: Culicidae), one of the most effective ways to achieve this combat is by the use of synthetic chemicals, such as organophosphate temephos, against the mosquito larvae. However, the continued and repeated use of these products has contributed to the development of resistant strains. The occurrence of resistance can be figured out by researches to find out news plant-base insecticides, such as essential oils. Thus, this study aimed to perform a review of the essential oils with studies on the evaluation of the larvicidal activity against A. aegypti and to analyze the chemical composition and the larvicidal activity of essential oils from six plant species from Amazônia Legal maranhense. This dissertation was divided into two chapters; the chapter 1 consists of a review of the scientific papers which showed that 210 essential oils from 159 plant species have already been tested by their larvicidal potential and that more than 75% of these essential oils were considered active (LC50 < 100 mg/L). This study has further information such as the factors affecting the activity, structure-activity relationships, mechanisms of action, as well as the studies with the main compounds of these oils. The chapter 2 reports the experimental research to evaluate the larvicidal activity and chemical composition of essential oils extracted from six plants collected in the “Parque Nacional da Chapada das Mesas”, Maranhão, Brazil (Amazônia Legal maranhense). The oils were extracted by hydrodestilation, using a Clevenger apparatus and their compositions were analyzed by gas chromatography coupled to mass spectrometry (GC/MS). The larvicidal activity was performed according to the guidelines from the World Health Organization. The sesquiterpenes hydrocarbons were the major fraction of the essential oils from Eugenia patrisii Vahl, Eugenia piauhiensis Vellaff., Myrcia erythroxylon O. Berg, Psidium myrsinites DC., and Siparuna camporum (Tul.) A. DC.; whereas, Lippia gracilis Schauer essential oil showed the oxygenated monoterpenes as major compounds. Five of the six tested oils showed promising results for the development of products larvicides against A. aegypti larvae, showing LC50 value among 230 and 417 mg/L. From these results, it was possible to observe the need for standardization of methodologies for evaluation of larvicides against A. aegypti, the low number of patents and potential of oils from the “maranhense” flora to obtain products that can contribute to the control of dengue.