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The acute and chronic affect of the feed of coffee (Coffea arabica, L.) on the antioxidant capacity of rats


A main risk factor for several degenerative diseases is the excessive presence of free radicals and reactive species caused by oxidative stress. These species are part of the normal metabolic pathways, but their excess can promote reactions resulting in degeneration of biological systems and molecules. Exogenous antioxidant compounds besides the endogenous enzymatic system help the organisms in the defense against oxidative stress and all diseases related to it. Studies have been demonstrating that some phenolic acids are involved in this defensive routine, acting as antioxidants and as transcriptional factors for the synthesis of phase II enzymes like superoxide dismutase, glutathione peroxidase and catalase, that are the main responsible for the antioxidant capacity of organisms. These phenolic acids act through an indirect mechanism, activating the enzymes MAPK, PI3K and PKC that phosphorylate the enzyme Nrf2, which acts as a direct transcriptional factor for the mentioned phase II enzymes. Objectives: This project has the main objective to evaluate the effect of the feed of coffee (acute and chronic) on the antioxidant capacity of rats. The specific objectives are: a) measure the total phenolic compounds, the main phenolic acids and the antioxidant capacity of regular and decaffeinated coffee, using the one with better in vitro antioxidant characteristic for all in vivo tests; b) determine the period of maximum biological response after an oral and acute feed of coffee; c) quantify the dose/response relationship after an oral and acute feed of coffee; d) evaluate the effect on the plasmatic antioxidant capacity and on the hepatic concentration of the transcriptional factor Nrf2 after a chronic feed of coffee (15 days). Methods: Regular and decaffeinated coffee will be analyzed to quantify total phenolic compounds (Folin-Ciocalteau), main phenolic acids (HPLC) and the antioxidant capacity (ORAC and crocin) to identify which one present better in vitro antioxidant characteristics, to be used for all in vivo tests. Male Wistar rats with 20010 grams of body weight will be submitted to an equalization diet with low phenolic contend for 3 days. Then, they will be divided in 13 groups with 6 animals in each group by the systematic casual sampling method. Group 1 (chronic control) will be feed during 15 days with commercial ration and water, being sacrificed after this period for the analysis of the plasmatic antioxidant capacity (ORAC, crocin and phase II antioxidant enzymes) and the hepatic concentration of the transcriptional factor Nrf2. Besides commercial ration and water, group 2 will receive a single daily dose of coffee for 15 days, being sacrificed after that to run the same analysis. Group 3 (acute control) will be sacrificed right after the equalization period, to determine basal plasmatic antioxidant capacity of rats. Groups 4 to 8 will receive a single dose of coffee, equal for all groups, being sacrificed in 1-hour intervals after feeding, to determine the period of maximum response of the plasmatic antioxidant capacity. Groups 9 to 13 will receive a single dose, with different concentration of coffee for each group, being sacrificed after the period of maximum response determined in the previous item to verify the dose/response relationship of the already mentioned plasmatic parameters. All coffee feed will be done by gavages. All analysis will be done in triplicate. Mathematic methods will be used to verify statistically significant differences between control groups and the ones submitted to all different nutritional stimuli. (AU)

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