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Although numerous reports are available concerning the larvicidal potential of essential oils, very few investigations have focused on their mechanisms of action. In the present study, we have investigated the chemical composition of the leaf oil of Croton rhamnifolioides during storage and its effects on oviposition and survival of larvae of the dengue fever mosquito Aedes aegypti. In addition, we have established a possible mechanism of action for the larvicidal activity of the essential oil. GC-MS analyses revealed marked differences in the composition of oil that had been freshly isolated and that of a sample that had been stored in a sealed amber-glass vial under refrigeration for three years. However, both fresh and stored oil exhibited substantial larvicidal activities with LC50 values of 122.35 and 89.03 ppm, respectively, and oviposition deterrent effects against gravid females at concentrations of 50 and 100 µg·mL . These results demonstrate that the larvicidal effect of the essential oil was unchanged during three years of storage even though its chemical composition altered. Hence, the essential oil could be used in the preparation of commercial products. In addition, we observed that the trypsin-like activity of mosquito larvae was OPEN ACCESSMolecules 2014, 19 16574 inhibited in vitro by the essential oil of C. rhamnifolioides, suggesting that the larvicidal effect may be associated with inhibition of this enzyme.

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RESUMONo presente trabalho, foi realizado o estudo químico de plantas medicinais comercializadas no Mercado Público de Casa Amarela, Recife-PE. Por meio de questionários, foi possível conhecer as plantas medicinais comercializadas e possíveis processos de secagem das plantas frescas, executados pelos feirantes. Pela análise dos resultados, foram escolhidas três plantas para o presente estudo e, ainda, pode-se constatar que os feirantes perdem grandes quantidades de plantas comercializadas originalmente frescas, por falta de um processo de secagem que favoreça a conservação. Para o estudo do teor, índice de refração e composição química do óleo essencial de suas folhas frescas e secas, foram selecionadas Rosmarinus officinalis L., Ocimum basilicum L. e Chenopodium ambrosioides L. As folhas frescas foram secas naturalmente à temperatura ambiente. Os óleos foram extraídos e observou-se que, independentemente de obtidos das folhas frescas ou secas, mantiveram bons teores, semelhantes índices de refração e os mesmos componentes químicos majoritários. Assim, o processo de secagem mostrou-se vantajoso, podendo representar uma importante contribuição ao processo de conservação destas plantas medicinais. PALAVRAS-CHAVE: plantas medicinais, secagem natural, princípio ativo, qualidade MEDICINAL PLANTS MARKETED IN MERCADO PÚBLICO DE CASA AMARELA -RECIFE -PE: PRESERVATION INFLUENCE ON THE CHEMICAL COMPOSITION OF ESSENTIAL OIL ABSTRACTIn this study, we performed the chemical study of medicinal plants traded in the Mercado Público de Casa Amarela, Recife-PE. Through questionnaires, it was possible to know the marketed medicinal plants and possible drying processes of fresh plants, run by merchants. Examining the results, three plants were chosen for this study, and also can be seen that the vendors lose large amounts of fresh plants marketed originally, for lack of a drying process promoting conservation. To study the content, and refractive index of the essential oil composition of their fresh and dried leaves were selected Rosmarinus officinalis L. Ocimum basilicum L. and Chenopodium ambrosioides L. Fresh leaves are naturally dried at room temperature. The oils were extracted and it was found that, regardless of the obtained fresh or dried leaves, maintained good yields similar refractive indices and controlling the same chemical components. Thus, the drying process proved advantageous and may represent an important contribution to the conservation process of these plants.