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The occurrence and content of some polyphenols and the antioxidant activity of compounds present in grape berries, stems and leaves of <i>Vitis vinifera</i> L. were evaluated. Three white and three blue varieties of grapevine were investigated. The contents were determined of <i>trans</i>-resveratrol, <i>trans</i>-piceid, caftaric acid, tryptophan, catechin, epicatechin, total polyphenols, and flavanols, both in healthy material and in the samples of the plant material infested with microorganisms (<i>Botryotinia fuckeliana</i> Whetzel anamorph <i>Botrytis cinerea</i> Pers.; Uncinula necator (Schw.) Burr; <i>Plasmopara viticola</i> (Berk. & M.A. Curtis) Berl & De Toni). The antioxidant activity of the extracts obtained was determined by different methods: FRAP (Ferric Reducing Antioxidant Power), DPPH (2,2-diphenyl-1-picrylhydrazyl radical) and TAC-PCL (Total Antioxidant Capacity of Photochemiluminescence). The content of <i>trans</i>-resveratrol varied between 0.3–2.3 mg/kg and 0.7–12.1 mg/kg in non-infested and infested grape berries, respectively. The content of <i>trans</i>-piceid between 0.6–2.9 mg/kg and 1.5–6.3 mg/kg in non-infested and infested grape berries, respectively. The content of trans-resveratrol varied between 2.5–10.3 mg/kg and 3.7–20.9 mg/kg in healthy and in infected leaves, respectively. The content <i>trans</i>-piceid varied between 11.3–58.4 mg/kg and 18.5–60.9 mg/kg in the healthy and in the infected leaves, respectively. The highest content of trans-resveratrol was found in stems (16.3–276.3 mg/kg). In young lateral shoots, the highest levels of <i>trans</i>-piceid (12.6–99.7 mg/kg) and caftaric acid (474–2257 mg/kg) were determined. The infested grape berries showed a higher antioxidant activity, which was most closely correlated with the content of total polyphenols (correlation coefficient = 0.8336–0.9952).

Totušek J., Tříska J., Lefnerová D., Strohalm J., Vrchotová N., Zendulka O., Průchová J., Chaloupková J., Novotná P., Houška M. (2011): Contents of sulforaphane and total isothiocyanates, antimutagenic activity, and inhibition of clastogenicity in pulp juices from cruciferous plants. Czech J. Food Sci., 29: 548-556.The consumption of Cruciferous vegetables is important for the prevention of cancerous diseases, particularly colorectal cancer. The effects of technological treatments (freezing, pasteurisation, high-pressure treatment) on the content of isothiocyanates, considered to be the active substance, were observed in single-species vegetable juices prepared from cruciferous vegetables (broccoli, cauliflower, Brussels sprouts, white and red cabbage). The contents of sulforaphane and total isothiocyanates were studied relative to the temperature, action period, and time delay after juice pressing. Sulforaphane and total isothiocyanates were determined by HPLC. Sulforaphane content in various parts of fresh broccoli was also assessed. Antimutagenic activity of the juices (frozen, pasteurised, and high-pressure treated) was evaluated using the Ames test and the following mutagens: AFTB1 (aflatoxin B1), IQ (2-amino-3-methyl-3H-imidazo-[4,5-f]quinoline), and MNU (2-nitroso-2-methylurea). Clastogenicity inhibition of the mutagens, in response to broccoli juice, as well as of pure sulforaphane, was observed using an in vivo experiment (the micronucleus test). It was shown that in terms of sulforaphane content, it is best to let broccoli juice stand for 60 min after pressing and pH adjustment. Sulforaphane content does not change under heating to 60°C. Its content decreases considerably (compared to fresh juice) with heating to higher temperatures than 60°C. High-pressure treatment preserves mutagenic inhibition to the same degree as juices freezing.

Abstract:The effects of the pressing technology and clarification of white grape musts on concentrations of phenolic compounds and their antioxidative capacity were investigated. Four different varieties were processed by hydraulic or pneumatic pressing technologies. In the individual stages of pressing and after the application of different doses of the clarification agent, must samples were analysed for the content of polyphenols and the antioxidative capacity. The highest concentrations of caftaric acid were estimated in the musts made by hydraulic pressing from grapes of Welschriesling variety. On the other hand, musts made from grapes of Grüner Veltliner showed the highest contents of trans-piceid in both variants of pressing. The values of antioxidative capacity of the must samples analysed were not significantly different. The influence of clarification on the changes of phenolic substances in young red wines of Saint Laurent variety was also studied. Six various clarifiers were tested as applied in two different doses. Polyvinylpolypyrrolidone caused the highest losses of trans-resveratrol in the course of red wine clarification. The concentrations of catechin, epicatechin, and total anthocyanins as well as the colour parameters of red wines were influenced at most by the application of egg white.

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