Importance of grape phenols in the human diet.

Polyphenols are secondary metabolites of plants and are generally involved in defense against ultraviolet radiation or aggression by pathogens. The phenolic compounds, present in vegetables and fruits and their juices possess antioxidant activity that may have beneficial effects on human health. Moreover, they are responsible for certain organoleptic properties intimately related to wine quality, particularly color, astringency and bitterness. Proanthocyanidins and flavanols are located in the skin and seeds of grapes, and are transferred to the must/wine during the maceration step of winemaking. Numerous studies have shown that long term consumption of diets rich in plant polyphenols offer protection against development of cancers, cardiovascular diseases, osteoporosis, neurodegenerative diseases and diabetes. Red wine is a very rich source of flavonoids, particularly the class called flavanols. Flavonoids represent a large group of low molecular weight compounds with high antioxidant properties. The purpose of this study was to evaluate the skins and seeds phenolic composition of three native Romanian wine grape varieties (Fetească regală, Fetească albă and Fetească neagră). The grapes were collected at technological maturity from three different growing zones of Transylvania (Romania) in 2011. Spectrophotometric methods were used to measure the absorbance at 280 nm (A280), the flavanols reactive to vanillin and the proanthocyanidin indices in the skin and seed extracts. Among white varieties, the proanthocyanidins and flavanols concentrations in the skins were significantly higher in the Fetească regală variety. Furthermore, we assessed the distinct characteristics of Fetească neagră variety linked to their phenolic composition, and compared these characteristics with those of Pinot noir grapes. According to A280, the red varieties contained more total skin polyphenols. Fetească neagră was identified as a promising variety to be exploited in the future for its particular phenolic characteristics.