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Plantas medicinais tropicais e mediterrânicas compropriedades biocidas no controlo de insetos vetores de agentes patogénicos
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Resumo(s)
As parasitoses e as arboviroses têm um impacto social e económico considerável, em particular nos países tropicais e subtropicais. Problemas financeiros e de gestão, assim como as alterações ambientais, a resistência dos vetores aos inseticidas e dos agentes patogénicos aos fármacos, o aumento e respetiva mobilidade da população humana contribuíram não só para o incremento da prevalência de doenças transmitidas por vetores, como também para a sua emergência ou reemergência em novas regiões.
O progressivo aumento de resistências nos insetos vetores tem levado à restrição progressiva da aplicação de inseticidas químicos e/ou à introdução de novos compostos sintéticos.
O presente estudo surgiu da necessidade de desenvolver novas medidas de controlo vetorial, mais seguras para o ambiente, e consistiu na avaliação das propriedades biocidas de plantas medicinais tropicais e mediterrânicas, (Sambucus nigra, Melia azedarach, Azadirachta indica, Foeniculum vulgare e Mentha pulegium), bem como na avaliação da sua utilidade no controlo dos culicídeos vetores de agentes patogénicos da malária e arboviroses, nomeadamente, Anopheles arabiensis e Aedes aegypti, em Cabo Verde.
Este trabalho englobou um conjunto de ações, nomeadamente a colheita, o processamento e o rastreio sobre alvos biológicos, de extratos vegetais e óleos essenciais (OE). Foram realizados extratos brutos de folhas de S. nigra, M. azedarach e A. indica com solventes de diferentes polaridades. Estes extratos foram posteriormente analisados por Cromatografia em Camada Fina e fracionados por Cromatografia em Coluna. Os OEs de M. pulegium e de F. vulgare, obtidos por hidrodestilação das partes aéreas ou por via comercial foram caraterizados qualitativamente e quantitativamente por Cromatografia Gasosa e Espetrometria de Massa e confirmada a identificação dos seus constituintes por Ressonância Magnética Nuclear.
Os bioensaios inseticidas foram efetuados de acordo com os testes padronizados da Organização Mundial de Saúde. Os resultados foram analisados estatisticamente com recurso aos programas Microsoft Excel ® 2010 e SPSS® para Windows e aos testes estatísticos considerados relevantes.
Quanto às três primeiras plantas referidas apenas o extrato de S. nigra revelou atividade em larvas do 3º estádio de Ae. aegypti. Estas são também mais suscetíveis ao OE de F. vulgare (amostras de Cabo Verde e Portugal respetivamente CL50= 23,3 e 28,2 μlL-1) comparativamente ao óleo de M. pulegium (amostras de Cabo Verde e Portugal respetivamente CL50= 136,1 e 107,3 μlL-1). Embora não se tenham registado diferenças altamente significativas entre as plantas em estudo, é de salientar que as concentrações necessárias para eliminar 50, 90 e 99% da população são menores quando se aplica o OE de F. vulgare. Quanto ao An. arabiensis optou-se por avaliar apenas o OE de F. vulgare, não tendo sido observadas diferenças significativas comparativamente a Ae. aegypti. Os resultados de bioensaios com os compostos ativos de ambas as espécies vegetais evidenciaram a existência de efeitos sinergistas. Os adultos demonstraram maior sensibilidade ao OE de F. vulgare de Cabo Verde. Este estudo permitiu uma caraterização química e avaliação de atividade de plantas de regiões geográficas que ainda não tinham sido estudadas com resultados bastante promissores.
Parasitoses and arboviroseshave a considerable economic and social impact, particularly in tropical and subtropical countries. Financial and management problems, as well as environmental changes, vectors resistance to insecticides and of pathogens to drugs, the crescent density of human population and of their mobility, contributed not only to increase the prevalence of vector-borne diseases, but also to their reemergence or emergence in new regions. The progressive increase of insects’ resistance to known insecticides has led to the progressive restriction of the application of chemical insecticides and/or the introduction of new synthetic compounds.The present study arose from the need of developing new vector control measures, environmentally safe, and consists on the evaluation of biocidal properties of medicinal tropical and Mediterranean plants (Sambucus nigra, Melia azedarach, Azadirachta indica, Foeniculum vulgareand Mentha pulegium) and on their quantification, on mosquitoes vectors of pathogens causing malaria and arboviruses, namely Aedes aegyptiand Anopheles arabiensisfrom Cape Verde.A set of actions are included in this work, like the harvesting, processing and screening of plant extracts and essential oils (EO) on biological targets. Crude extracts from leaves of S. nigra,M. azedarachand A. indicawere performed with solvents with different polarities. These extractswere subsequently analyzed by Thin Layer Chromatography and fractionated by Column Chromatography. The EOs of M. pulegiumand F. vulgare, obtained by steam distillation of leaves and the aerial parts were characterized qualitatively and quantitatively by Gas Chromatography and Mass Spectrometry and confirmed by identification of its constituents by Nuclear Magnetic Ressonance.Insecticide bioassays were conducted according to standardized tests of the World Health Organization. The results were statistically analyzed using the program Microsoft Excel 2010 and SPSS ® for Windows ® and the statistical tests considered relevant.From the first threeplants mentioned only the S. nigraextracts showed activity against the 3rd stage larvae of Ae. aegypti. These larvae were also more susceptible to EO of F. vulgare(samples from Cape Verde and Portugal respectively LC50 = 23.3 and 28.2 μlL-1) than those of M. pulegium(samples from Cape Verde and Portugal having LC50= 136.1 and 107.3 l μlL-1, respectively). Although there were no significant differences between the plants studied, it was noted that concentrations required to eliminate 50, 90and 99% of the larvae populations are lower when applying the EOof F. vulgare. For Anopheles arabiensiswe choose to evaluate only the EO of F. vulgare, and no significant differences were observed between these results and those obtained against Ae. aegypti. The results of the bioassay with the active compounds isolated from M. pulegiumand F. vulgareevidenced the existence of synergistic effects. Adults showed greater sensitivity to OE F. vulgarefrom Cape Verde. This study allowed the chemical characterization and activity assessment of plants from two different geographic regions that were not studied before with highly promising results.
Parasitoses and arboviroseshave a considerable economic and social impact, particularly in tropical and subtropical countries. Financial and management problems, as well as environmental changes, vectors resistance to insecticides and of pathogens to drugs, the crescent density of human population and of their mobility, contributed not only to increase the prevalence of vector-borne diseases, but also to their reemergence or emergence in new regions. The progressive increase of insects’ resistance to known insecticides has led to the progressive restriction of the application of chemical insecticides and/or the introduction of new synthetic compounds.The present study arose from the need of developing new vector control measures, environmentally safe, and consists on the evaluation of biocidal properties of medicinal tropical and Mediterranean plants (Sambucus nigra, Melia azedarach, Azadirachta indica, Foeniculum vulgareand Mentha pulegium) and on their quantification, on mosquitoes vectors of pathogens causing malaria and arboviruses, namely Aedes aegyptiand Anopheles arabiensisfrom Cape Verde.A set of actions are included in this work, like the harvesting, processing and screening of plant extracts and essential oils (EO) on biological targets. Crude extracts from leaves of S. nigra,M. azedarachand A. indicawere performed with solvents with different polarities. These extractswere subsequently analyzed by Thin Layer Chromatography and fractionated by Column Chromatography. The EOs of M. pulegiumand F. vulgare, obtained by steam distillation of leaves and the aerial parts were characterized qualitatively and quantitatively by Gas Chromatography and Mass Spectrometry and confirmed by identification of its constituents by Nuclear Magnetic Ressonance.Insecticide bioassays were conducted according to standardized tests of the World Health Organization. The results were statistically analyzed using the program Microsoft Excel 2010 and SPSS ® for Windows ® and the statistical tests considered relevant.From the first threeplants mentioned only the S. nigraextracts showed activity against the 3rd stage larvae of Ae. aegypti. These larvae were also more susceptible to EO of F. vulgare(samples from Cape Verde and Portugal respectively LC50 = 23.3 and 28.2 μlL-1) than those of M. pulegium(samples from Cape Verde and Portugal having LC50= 136.1 and 107.3 l μlL-1, respectively). Although there were no significant differences between the plants studied, it was noted that concentrations required to eliminate 50, 90and 99% of the larvae populations are lower when applying the EOof F. vulgare. For Anopheles arabiensiswe choose to evaluate only the EO of F. vulgare, and no significant differences were observed between these results and those obtained against Ae. aegypti. The results of the bioassay with the active compounds isolated from M. pulegiumand F. vulgareevidenced the existence of synergistic effects. Adults showed greater sensitivity to OE F. vulgarefrom Cape Verde. This study allowed the chemical characterization and activity assessment of plants from two different geographic regions that were not studied before with highly promising results.
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Palavras-chave
Aedes aegypti Ciências Biomédicas Parasitologia Médica Anopheles Controlo vetorial Plantas medicinais