Atividade larvicida e caracterização molecular dos princípios ativos de Magonia pubescens St.Hil. (Sapindaceae) e de Copaifera reticulata Ducke (Leguminosae), visando ao controle de Aedes aegypti
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2004-12-02
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Universidade Federal de Goiás
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Dengue is an acute viral disease of great importance to the public health, and its high incidence in the tropical countries is intimately related to the presence of the main vector, the mosquito Aedes aegypti. Throughout the years, attempts to control the vector have been based on the application of synthetic chemical insecticides, which have already began to produce undesirable effects. The modification of the susceptibility and the emergence of generations resistant mosquitoes besides fast proliferation stimulated studies about the activity of natural products on the larvae of A. aegypti, as an alternative measure for control. In this work, phytochemicals studies were accomplished by larvicidal activity of the plants Magonia pubescens St. Hil. (Sapindaceae) and Copaifera reticulata Ducke (Leguminosae), with the purpose of isolating fractions and/or pure substances with insecticide potential. After collection of peels of the M. pubescens stem and C. reticulata oil-resin in natura, extracts obtained were submitted to bioassays, guided-purification and structural identification. For the larvicidal activity assays, 3rd instar larvae of A. aegypti were used. They were obtained from cyclic colony maintained by ten years, at 28±1°C, 80±5% of relative humidity and 12 h photoperiod. Twenty larvae were used for each concentration and the bioassays were carried out in 5 replicate, in an acclimatized ambient similar to colony growth. Control assays were conducted using the same number of larvae in a dimethylsulphoxide and distilled water solution. The mortality of larvae was measured after 24 and 48 h. Fractions, subfractions and pure substances with larvicidal activity, obtained from those procedures, were monitored chemically through thin layer chromatography and analyzed by 1H nuclear magnetic resonance and 13C, and gas chromatography coupled to mass spectrometry. The identified active substance in the M. pubescens was a tannin (C45H36O18 and molecular mass of 864.77 Da) which presented LC50 of 3.1 ppm; from the C. reticulata the acid 3-acetoxi-labda-8(17),13-dien-15-oic was isolated (C22H34O4, and molecular mass of 362 Da) with LC50 of 0.8 ppm. These two active substances presented lethal concentrations with potential use in the actions to control of the A. aegypti.
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SILVA, H. H. G. da. Atividade larvicida e caracterização molecular dos princípios ativos de Magonia pubescens St.Hil. (Sapindaceae) e de Copaifera reticulata Ducke (Leguminosae), visando ao controle de Aedes aegypti. 2004. 79 f. Tese (Doutorado em Medicina Tropical e Saúde Publica) - Universidade Federal de Goiás, Goiânia, 2004.