Changes in Polyphenolic Content and Antioxidant Activity of Grapes cv Vranac During Ripening

Abstract

This study characterised and evaluated the phenolic composition and antioxidant activity of the red wine grape Vranac (Vitis vinifera L.) from the southern Serbian vineyard region during grape ripening. Polyphenol composition at different harvest dates was determined by HPLC-DAD analysis. Antioxidant activity was estimated by DPPH assay. The study demonstrates that the Vranac variety represents important sources of dietary antioxidants. The results show that (+)-catechin, (-)-epicatechin and procyanidin dimer B2 were the most prevalent in the seeds, and quercetin and malvidin glucosides in the grape skins. All grape extracts were shown to have high radical-scavenging activity. Strong correlations between radical-scavenging activity and polyphenols suggest that the phenolic composition of the Vranac variety contributes significantly to the antioxidant capacities of grape extracts. During grape ripening there were significant changes in physiological properties and phenolic content, and it is important to determine optimal harvest time, which will ensure grapes with very good quality parameters (in our study at the 30th day after véraison).

Phenolic Compounds and Bioactivity of Healthy and Infected Grapevine Leaf Extracts from Red Varieties Merlot and Vranac (Vitis vinifera L.)

“…Total phenolics, hydroxycinnamoyl tartaric acids, and flavonols in selected extracts were quantified using the spectrophotometric method described previously [19]. The results are expressed as milligrams (mg) gallic acid equivalents (GAE) for total phenols, mg caffeic acid equivalents (CAE) for total hydroxycinnamoyl tartaric acids, and mg quercetin equivalents (QE) for total flavonols per gram (g) extract dry matter (DM).…”

“…The samples were separated on an AgilentEclipse XDB C-18 4.6×150 mm column, 5 μm particle size, controlled at 30°C. The solvent system consisted of A: formic acid/water (5:95, v/v) and B: acetonitrile/formic acid/water (80:5:15, v/v) and the elution gradient was as described previously [19]. The injection volume was 5 μL and the flow rate was 0.8 mL/min.…”

The determination of bioactive ingredients of grape pomace (Vranac variety) for potential use in food and pharmaceutical industries

“…Total anthocyanins were also determined spectrophotometrically [12]. Malvidin-3-glucoside was employed as a calibration standard and the results were expressed as mg malvidin-3-glucoside equivalents (ME) per g of the extract DM.…”

“…The column (Agilent-Eclipse XDB C-18 4.6 × 150 mm) was thermostated at 30 °C. The solvents A: formic acid/water (5:95 v/v) and B: acetonitrile/formic acid/water (80:5:15 v/v) were used and the elution gradient were previously described [12]. The injection volume was 5 µL and the flow rate was 0.9 mL/min.…”

“…Determination of the Radical Scavenging Activity The antioxidant activity of all investigated extracts was estimated by determining the radical scavenging activity (RSA, %) of the extracts by the DPPH test previously described [12]. The antioxidant activities of the investigated extracts were expressed as median efficient concentrations (EC50).…”