This research studies in detail the contents of phenolic compounds determined by the Folin-Ciocalteu reagent and the antioxidant activities determined by the TEAC (Trolox equivalent antioxidant capacity), DPPH (using diphenyl-p-picrylhydrazyl radical), and FRAP (ferric reducing antioxidant power) methods, and their correlations for used standards with these methods (catechine, gallic acid, caffeic acid, ferulic acid, Trolox, ascorbic acid, and ferrous sulfate) and extracts from several species of commonly consumed vegetables were studied in detail. The comparison of absolute values of absorption coefficients for used standards and for individual methods allows one to choose optimal common standards for methods to be compared. The procedures applied for the same sets of the extracts using identical calibration procedures and common standards allowed better comparison of the results obtained by the TEAC, DPPH, and FRAP methods. The values of content of phenolic substances and total antioxidant activity of the sets of samples correlate very well for all used methods. The very high values of antioxidant activity were found in intensely colored vegetables (red cabbage, red onion, etc.), and the values were very low in watery vegetables such as potato, marrow, and cucumber.

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Stratil P., Kubáň V., Fojtová J. (2008): Comparison of the phenolic content and total antioxidant activity in wines as determined by spectrophotometric methods. Czech J. Food Sci., 26: 242-253.Folin-Ciocalteu reagent (FCM) and Price and Butler method (PBM) were used for spectrophotometric determination of the total content of phenolic compounds in 29 wines (8 white, 21 red). The average contents of phenolic compounds determined by FCM and PBM were 108 (90-119) and 105 (90-129) for white wines, and 1545 (874-2262) and 547 (306-816) mg/l of gallic acid equivalents (GAE) for red wines, respectively. The reason for the lower PBM values in red wines is the higher reactivity in PBM of phenolic compounds, especially of gallic acid generally used as a standard in the above methods. The higher reactivity of the standard means that the measured absorbance of the sample responds to a lower concentration. The average total antioxidant activities determined by TEAC (Trolox Equivalent Antioxidant Capacity), FRAP (Ferric Reducing Antioxidant Power), and DPPH (using diphenyl-p-picrylhydrazyl radical) were 5.14 (4.30-6.14), 1.43 (0.86-2.14), and 0.71 (0.61-0.81) of Trolox equivalents (TE) and 26.44 (13. 9-34.4), 9.43 (4.92-13.9), and 5.52 (2.91-8.62) mmol/l TE for white and red wines, respectively. Almost the same molar absorptivities with TEAC and DPPH methods were found while with FRAP method it was somewhat higher (about 1.56-times). The ratio of the values determined by FRAP and DPPH methods for white and red wines were 2.0 and 1.7, respectively. The TEAC values were 2.8-and 4.8-fold higher than those determined by FRAP and DPPH methods, respectively. The radical ABTS •+ used in TEAC method is therefore the most reactive and responds to the highest number of hydroxyl groups of the phenolic compounds of wines.

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Recent findings concerning the significance of alpha 1-fetoprotein (AFP) as a tool for clinical diagnosis and monitoring of tumor diseases are reviewed briefly. The applicability of this protein marker to the early diagnosis of patients at carcinogenic risk is discussed. In addition, experimental data obtained with a model of chemical hepatocarcinogenesis are reported. The increase of proliferative activity in precancerous liver tissue preceded AFP production under experimental conditions with azodyes and aflatoxin B1 as carcinogens. Immunohistochemical analysis of the relation of AFP to changes of cell populations and to liver tissue rearrangement led to the conclusion that AFP-producing cells cannot be precursors of malignant hepatocytes; however, AFP appeared to be linked to dividing hepatocytes at a certain step of cell differentiation regardless of the stages of precancerous development. A decrease in the rate of nuclear RNA synthesis was observed in both precancerous and tumor tissues. A possible analogy between the early phase of AFP production in animal carcinogenesis and that in human carcinogenesis is considered.

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