Bioactive compounds in grape cane extracts from different Vitis vinifera cultivars.

Grape canes from Italian Vitis vinifera L. cultivars: "Aglianico", "Fiano", and "Greco" were used for extraction of bioactive compounds at different pH (1÷13). The total phenolic content and the Radical Scavenging Activity (RSA) were measured in order to establish the most effective extraction pH among those tested. "Greco" grape canes gave the highest amount of phenolic compounds at every pH, ranging from 42.7 mg Gallic Acid Equivalents (GAE)/g Dry Extract (DE) (pH 1.00) to 104.3 mg GAE/g DE (pH 13.00). The RSA ranged from 12.5% ("Aglianico" pH 13.00) to 18.4% ("Greco" pH 1.00). Gallic acid, protocatechuic acid, catechin, ferulic acid, resveratrol, p-coumaric acid, and ellagic acid were detected in different amounts. The results of this study demonstrated that the alkaline pH (13.00) allowed the best yield of phenolic compounds for all the cultivars, as the total content was more than double of the value obtained by extraction at pH 1.00. However, the RSA had an opposite trend, because the acid extracts were slightly more antioxidant than the alkaline ones. The HPLC analysis showed that grape canes from different cultivars possessed a distinguishing quantitative phenolic profile, strongly affected by the extraction pH.