HPLC-DAD detection of changes in phenol content of red berry skins during grape ripening

With increasing concern for a demand from consumers for natural products, there is a wide interest in bioactive substances. The new frontier of dietary quality is the study and promotion of functional foods. Phenols are among the most important functional molecules. Red grape and red wine contain bioactive products as phenols. Changes occurring in the concentrations of phenols, such as hydroxycinnamic tartaric acids (hctas), flavonols, and anthocyanins in berry skins, were measured during growth and ripening of four red grape cultivars, Alicante, Black Malvasia, Nerello, and Prunesta (Vitis vinifera L.), cultivated in a coastal location of the Reggio Calabria Province (Southern Italy). These cultivars are the most popular and are considered to be the most suitable grape cultivars for cultivation in the Tyrrhenian side of the Reggio Calabria Province. Fractioning of three phenolic classes was conducted through the adsorbing resin Serdolit XAD-2. Each single phenolic fraction was analyzed by liquid chromatography with diode array detector (HPLC-DAD). Each cultivar presented a different chromatographic profile particularly for anthocyanins. The cultivar Nerello was distinguished from other for its high content of anthocyanins. The rate, at which the concentration of hctas, flavonols and anthocyanins increased, varied greatly among the cultivars. The hydroxycinnamic tartaric acid profile varied in the studied cultivars, in fact in Alicante, Black Malvasia and Prunesta cultivars, the predominant was trans-coumaroyl tartaric acid, while in Nerello cultivar, trans-caffeoyl tartaric acid was the most abundant. In addition, the results showed that amounts of phenolic compounds contained in grape skin changed throughout the grape ripening process.