Efeito de extratos de açaí (Euterpe oleracea Mart) e pitanga (Eugenia uniflora L) sobre a atividade de catalase e GST em cérebro e hepatócito de ratos visando a proteção contra agentes citotóxicos

Abstract

There are several xenobiotic compounds capable of directly impairing the body's function or inducing the formation of reactive oxygen species (ROS). The necessary process for xenobiotic elimination occurs mainly with the participation of biotransformation enzymes, as Glutathione S-transferase (GST). ROS, on the other hand, are eliminated by other mechanisms that may also involve the action of enzymes, such as catalase. Bioactive compounds present in vegetables, especially fruits, are constantly reported to have antioxidant action and to act directly on the cell or to act as modulators of both biotransformation enzymes and ROS metabolism. In this study, we aimed to verify how compounds present in Acai and Pitanga extracts influence the activity of GST, its mu isoform and the cerebral and hepatic catalase of rats; also, to evaluate the possibility of the extracts of these fruits becoming promising alternatives to increase the protection capacity of the organism against potentially cytotoxic agents. Extracts of the two fruits were obtained; the crude extract was obtained by extracting compounds in distilled water and the ether (ethyl ether), alcoholic (in ethanol, using solid residue resulting from obtaining the ether extract) and aqueous (in distilled water, using solid residue resulting from the etheric and alcoholic extract) fractionated extracts. These extracts were tested in enzymatic assays of rat GST and cytosolic brain and hepatic catalase of rats, and the results were compared with control assays performed in the absence of extracts. Kinetic studies of the assays were performed in the presence and absence of extracts at various substrate concentrations, such as Michaelis-Menten curves and the enzyme behavior evaluated. It was possible to observe the modulatory capacity of the compounds present in the extracts obtained from the two fruits, depending on the compound, the enzyme and / or isoform. Both GST and catalase were activated or inhibited by the different extracts tested. Inactivations were more recurrent, and for GST occurred mostly in mixed form for both acai and pitanga extracts; however, competitive inhibition was found for crude brain pitanga extract indicating that the compounds present in this extract inhibited the enzyme without a direct bound to the active site. For hepatic GST, the raw acai extract promoted noncompetitive inhibition, presenting direct interaction of the compounds with the active site. Increased GST activity was observed with the açai ether extract in the brain and the alcoholic extract of pitanga in the liver. For catalase, increased activity was observed with crude açai extract in brain and crude pitanga extract for both cerebral and hepatic catalase. The results obtained with these extracts allow to relate them to the increase of the cellular capacity of biotransformation and decrease of the concentration of xenobiotic compounds in the organism, as well as to the reduction of the possibility of oxidative stress occurrence. Given that the fruit consumption is similar to the crude extract obtained in this work, the increased catalase activity provided by these extracts was one of the most important results obtained from the perspective of reducing ROS.