Grape pomace is a potential source of natural antioxidant agents. Phenolic compounds and antioxidant and cardioprotective properties of fresh and fermented pomace extracts obtained from Vitis vinifera L. red variety Fetească neagră grown in Romania in 2015 were investigated. Grape pomace extracts total phenolic index, total tannins, total anthocyanins, proanthocyanidins, flavan-3-ol monomers, stilbenes, and DPPH free radical scavenger were measured. The effect of a seven-day pretreatment with grape pomace extracts on the isoprenaline-induced infarct-like lesion in rats was assessed by ECG monitoring, serum levels of creatine kinase, aspartate transaminase, and alanine transaminase. Total serum oxidative status, total antioxidant response, oxidative stress index, malondialdehyde, total thiols, and nitric oxide have been also assessed. Higher phenolic content and antioxidant activity were found in fermented pomace extracts when compared to fresh pomace extracts. Pretreatment with grape pomace extracts significantly improved cardiac and oxidative stress parameters. In conclusion, Fetească neagră pomace extracts had a good in vitro antioxidant activity due to an important phenolic content. In vivo, the extracts had cardioprotective effects against isoprenaline-induced infarct-like lesion by reducing oxidative stress, fresh pomace extracts having a better effect.

Grape pomace is a waste from wine industry which pollutes the environment. This by-product is considered a potential source of polyphenols, which were proven to be powerful antioxidants or natural coloring agents. The aim of this study was to quantify total polyphenols, total anthocyanins content and some stilbenes in grape pomace seed, skin and mixed flours from 'Fetească neagră' (cultivar for red wines) and 'Italian Riesling' (cultivar for white wines), grown in Miniș-Măderat vineyard, Romania. Flours were obtained by natural drying and ulterior grinding. One-way ANOVA and Tukey's post-hoc test were used.anthocyanins content was high in all the flours from 'Fetească neagră', with the highest concentration in skin flour (35.98 mg malvidin-3-O-glucoside/g dry weight). Stilbenes were also determined through HPLC methods. Cis-resveratrol was present in all forms of flour (0.90 to 10.14 μg/g dry weight), compared to its trans-isomer, which was not determined in 'Italian Riesling' seed and mixed flour. Trans-piceid was the most abundant stilbene and varied between 12.35 μg/g dry weight ('Italian Riesling' mixed flour) and 29.01 μg/g dry weight ('Fetească neagră' seed flour). The concentration of cis-piceid was similar among all forms of flour from 'Italian Riesling', while in 'Fetească neagră' seed flour (9.40 μg/g dry weight) it was present at a higher rate. Thus, results proved that 'Fetească neagră' flours are a better source of stilbenes than 'Italian Riesling' flours and seed flours from both varieties are richer in polyphenols than skin flours. Also, the concentration of anthocyanins in 'Fetească neagră' skin flour was high.

The aim of this study was to analyze the content of functional tannins in grape pomace skin, seed, and mixed flour, from Feteasca Neagra and Italian Riesling varieties. Results showed that all compounds were present in the highest concentration in grape pomace seed flours and the lowest in skin flours. The concentration of total tannins and total flavan-3-ol monomers in all flour samples ranged from 37.34 to 72.28 mg epicatechin/g dry weight and 0.57 to 3.13 mg/g dry weight, respectively. Among monomers, (+)-catechin was found in the highest concentration, except in Italian Riesling seed flours, where (-)-epicatechin was predominant. The mDP of proanthocyanidins in seed flour (7.15 to 8.07) is lower than that of skin flours (10.83 to 18.43) while the opposite was observed for %G. As a result, all Feteasca Neagra and Italian Riesling grape pomace flours, especially seed flour, could be used as sources of functional tannins in alimentary or pharmaceutical industry.

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