Aleksandra Radovanovic

Free radical scavenging activity and anthocyanin profile of Cabernet Sauvignon wines from the Balkan region.

The present study is focused on anthocyanin derivatives characterizing the antioxidant activity of Cabernet Sauvignon wines produced from different vineyard regions in the Balkans. These bioactive compounds were quantified with a high performance liquid chromatography (HPLC)-diode array detection (DAD) method. The antiradical activity was estimated by the ability of the wine to scavenge the stable 2,2`-diphenyl-1-picrylhydrazyl free radical (DPPH•). The results show that the total anthocyanin content varied from 205.88 to 1940.28 mg/L, depending on agroclimatic factors and the enological practices of the corresponding vineyard region. The most prominent antocyanin in all investigated Cabernet Sauvignon wines was malvidin-3-O-monoglucoside, which accounted for 50.57% of total content, followed by its acetyl derivatives, 15.45%, and p-coumaryl derivatives 5.66%. The relationship between the anthocyanin derivatives and free radical scavenging activity is discussed. A high correlation between total anthocyanin content and DPPH· scavenging ability of tested wines was confirmed (r2 = 0.9619). The significant correlations were obtained between antiradical activity and the sum of 3-monoglucoside (r2 = 0.95594), the sum of 3-acetyl-3-glucoside (r2 = 0.9728) and the sum of p-coumaryl-3-glucoside (r2 = 0.8873) of wine samples. It can be concluded that, the anthocyanin composition can be used as biochemical marker for the authenticity of red grape cultivar and their corresponding single-cultivar wine.

Changes in polyphenolic content and antioxidant activity of grapes cv Vranac during ripening.

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 veraison).

Phenol composition, DPPH radical scavenging and antimicrobial activity of cornelian cherry (Cornus mas) fruit and leaf extracts

Fruit is rich in different phenolic compounds which are recognized as potential natural medicaments and have been used in folk medicine for centuries. In order to evaluate phenol composition, cornelian cherry (Cornus mas) fruit and leaf extracts were subjected to the spectrophotometric and HPLC analysis. The radical scavenging activity was estimated using DPPH test and antimicrobial activity by disc diffusion and microwell dilution tests. All extracts showed high phenol content from 89.89 ± 0.45 to 117.34 ± 1.40 mg f gallic acid equivalents GAE/g extract dry matter DM but different composition of phenol compounds. Flavonols, anthocyanins, flavan-3-ols and phenolic acids were the main phenol classes found in the investigated fruit and leaf extracts. All extracts showed significant radical scavenging activity and a correlation with total phenol content (R2 = 0.9832). Significant antimicrobial activity was found against Gram-positive, followed by Gram-negative strains, and yeast in all tested extracts. Cornelian cherry fruit and leaf extracts, rich in phenolic content, with significant antiradical and antimicrobial activity, can be used as additives in food and medicaments. [Projekat Ministarstva nauke Republike Srbije, br. 34012, br. 31020 and br 176006 and EU, FP7 - Regpot - 2007- 3-01, the project «Chromlab-Antioxidant», No. 204756]