Inibição da tripsina de bicho-mineiro do cafeeiro por um fator não-protéico presente em extratos de folhas de mamona

Abstract

RESUMOInibidores de tripsina representam uma estratégia de controle de insetos e, por isso, a identificação e caracterização desses inibidores são etapas muito importantes para que novas formas de controle de pragas sejam desenvolvidas. Os inibidores de tripsina atuam na digestão primária de proteínas e comprometem o processo digestivo por completo, reduzindo a disponibilidade de aminoácidos ao inseto. A incorporação de inibidores de tripsina na dieta de insetos-praga é uma forma de controle cuja eficácia foi verificada por diferentes autores. Este projeto foi conduzido a fim de se observar a eficiência de extratos de folhas de mamona na inibição "in vitro" de proteinases do tipo tripsina do bicho-mineiro do cafeeiro. Após testes realizados com os extratos de folhas de mamona não-fervidos e fervidos com e sem a adição de -mercaptoetanol 0,2% (v/v) e mediante precipitações com acetona, verificou-se que o inibidor é uma molécula termoresistente e não-protéica. Desta forma, iniciou-se um processo de purificação da molécula inibidora por meio de cromatografia de adsorção com posterior análise em espectrômetro de massas. Os resultados dos testes de inibição indicaram a presença de um inibidor de tripsina eficaz contra o bicho-mineiro do cafeeiro nos extratos de folhas de mamona capaz de inibir 2,48 + 0,15 UTI, o que representa aproximadamente 40% de inibição. Em testes realizados com tripsina bovina observou-se que o extrato de folhas de mamona não apresenta poder de inibição sobre essa enzima.Termos para indexação: Bicho-mineiro do cafeeiro, inibição de tripsina, mamona. ABSTRACTTrypsin inhibitors stand for a strategy of insect control and, therefore, the identification and characterization of these inhibitors are very important steps for new forms of pest control to be developed. Trypsin inhibitors act in the primary digestion of proteins and endanger the digestive process wholly, reducing the availability of aminoacids to the insect. The incorporation of trypsin inhibitors in the diet of pest insects is a control form whose efficacy was verified by different authors. In order to observe the efficiency of castor bean leaf extracts in inhibiting trypsin-like enzymes of the coffee leaf miner, an experiment was carried out with the purpose of observing an "in vitro" inhibition phenomenon. The results of the trypsin inhibition tests with normal and boiled with and without -mercaptoethanol 0.2% (v/v) castor bean leaf extracts and the results of the acetone precipitation process indicated that the inhibitor is a heat-resistant molecule and it is not a protein. This way, the purification process was made by adsorption chromatography with later analysis in mass spectrometer. The reached results indicated that the presence of a trypsin inhibitor of the coffee leaf miner in the castor bean leaf extracts is capable of inhibiting 2.48 + 0.15 UTI, which stands for about 40% of inhibition. Tests performed with bovine trypsin indicated that the castor bean leaf extract have no inhibiting power on this enzyme.

Biochemical Analysis of a Castor Bean Leaf Extract and its Insecticidal Effects Against Spodoptera frugiperda (Smith) (Lepidoptera: Noctuidae)

“…The castor bean Ricinus communis (Euphorbiaceae) has shown a great potential as a source of insecticidal molecules against several insects (Roark 1947, Upasani et al 2003, Rahuman et al 2008, Elimam et al 2009Rossi et al 2010, Zahir et al 2011, including species of Spodoptera (Ramos-López et al 2010. Therefore, we aimed to verify the effects of an aqueous extract of leaves of castor bean by evaluating the food utilization (nutritional indices), larval development, and survival of S. frugiperda fed on different concentrations of the tested extract.…”

In-Vitro Effects of Ricinus Communis Seed Kernel Extract On Some Antioxidant And Hydrolytic Enzymes In Nymph And Adult Zonocerus Variegatus (Grasshopper)

“…Briefly, an aliquot of 0.2 ml of the diluted insect homogenate was added to 2.5 ml of 0.05M carbonate buffer (pH 10.2) to equilibrate in the spectrophotometer. Then, 0.2 ml of the extract RCSKE (15,30,45,60, 75, 90 and 105µg/ml) followed by 0.3ml of freshly prepared 0.3M adrenaline (substrate) were added to the mixture. Similar concentrations of commercial cypermethrin and chlorpyrifos were separately used for comparison with the extract.…”

“…The activity of Acetylcholinesterase (AChE) in insect homogenates was determined following the methods described by Ellman [43], and Nachmansohn and Neumann [44] with modification. The reaction mixture contained 2.6 ml phosphate buffer (0.1M, pH 7.4), 0.1 ml Ellman's reagent (DTNB), 0.4 ml insect homogenate and 0.3 ml of the extract RCSKE (15,30,45,60, 75, 90 and 105µg/ml). This was followed by addition of 0.1 ml of acetylthiocholine iodide solution (substrate) to the reaction mixture, to initiate the reaction.…”

“…According to some studies castor oil has been widely applied in folklore medicine and manufacturing of lubricants, paints and cosmetics [11;12]. Certain studies have investigated the insecticidal effects of castor oil against several insects including termites [12], Cosmopolites sordidus [13], Musca domestica (housefly) [14], Spodoptera frugiperda [15,16] and Callosobruchus chinensis [17]. Furthermore, ricin [18], ricinine [19], epicatechin [20] and certain fatty acids [21] present in castor have been described to exhibit insecticidal properties against insects.…”

Extrato de Coffea racemosa como alternativa no controle do bicho-mineiro do cafeeiro

“…Em decorrência, existe uma grande demanda por novas alternativas para o controle desse inseto, dentre as quais se destaca a possibilidade de se empregarem produtos de origem natural. Nesse sentido, são inúmeros os relatos, em literatura, da aplicação de produtos naturais para o controle de pragas agrícolas (Almeida et al, 2006;Mendonça et al, 2006;Gonçalves-Gervásio & Vendramim, 2007;Oliveira et al, 2007;Pereira et al, 2008;Santiago et al, 2008;Silva et al, 2008;Lima et al,2009;Rossi et al, 2010).…”