Larvicidal activity of Copaifera sp. (Leguminosae) oleoresin microcapsules against Aedes aegypti (Diptera: Culicidae) larvae.

Studies have demonstrated the potential of Copaifera sp. oleoresin to control Aedes aegypti proliferation. However, the low water solubility is a factor that limits its applicability. Thus, the micro- or nanoencapsulation could be an alternative to allow its use in larval breeding places. The purpose of this study was to evaluate if achievable lethal concentrations could be obtained from Copaifera sp. oleoresin incorporated into polymers (synthetic or natural) and, mainly, if it can be sustained in the residual activity compared to the pure oil when tested against the A. aegypti larvae. Microcapsules were prepared by the process of emulsification/precipitation using the polymers of cellulose acetate (CA) and poly(ethylene-co-methyl acrylate) (PEMA), yielding four types of microcapsules: MicPEMA1 and MicPEMA2, and MicCA1 and MicCA2. When using only Copaifera sp. oleoresin, the larvicidal activity was observed at concentrations of LC50 = 48 mg/L and LC99 = 149 mg/L. For MicPEMA1, the LC50 and LC99 were 78 and 389 mg/L, respectively. Using MicPEMA2, the LC50 was 120 mg/L and LC99 > 500 mg/L. For microcapsules MicCA1 and MicCA2, the LC50 and LC99 were 42, 164, 140, and 398 mg/L, respectively. For a dose of 150 mg/L of pure oleoresin, the residual activity remained above 20% for 10 days, while the dose of 400 mg/L remained above 40% for 21 days. The MicPEMA1 microcapsules showed a loss in residual activity up to the first day; however, it remained in activity above 40% for 17 days. The microcapsules of MicCA1 showed similar LC50 of pure oil with 150 mg/L.

Larvicidal effect of dried leaf extracts from Pinus caribaea against Aedes aegypti (Linnaeus, 1762) (Diptera: Culicidae) / Efeito larvicida dos extratos de folhas secas de Pinus caribaea contra Aedes aegypti (Linnaeus, 1762) (Diptera: Culicidae)

In this study, the larvicidal activity of dried leaf extracts from Pinus caribaea Morelet against Aedes aegypti was evaluated for the first time. Pinus caribaea extracts were obtained by macerating dried leaves in alkaline hydroethanol, ethanol and acetone solutions followed by evaporation under reduced pressure. The lignin content was quantified using the thioglycolic acid complexation method. Lethality bioassays (LC50 and LC90) were carried out in accordance with the recommendations of the World Health Organization. The results showed that the acetone extract from Pinus caribaea was more active, and that larvicidal activity was associated with lignin concentration.

Neste trabalho foi avaliada pela primeira vez a atividade larvicida contra Aedes aegypti de extratos obtido a partir de folhas secas de Pinus caribae. Os extratos de Pinus caribaea foram obtidos a partir da maceração de folhas secas em solução hidroetanólica alcalina, etanol e acetona, seguido de evaporação sob pressão reduzida. O teor de lignina foi quantificado usando o método de complexação com ácido tioglicóliclo. Os ensaios de letalidade foram conduzidos de acordo com a recomendação da Organização Mundial da Saúde. Os resultados demonstraram que o extrato obtido com acetona foi mais ativo, e a atividade larvicida esta associada com a concentração de ligninas.