Free and bound polar phenols in Corinthian currants (Vitis vinifera L., var. Apyrena)

Abstract

Corinthian currant is a Greek dried fruit that accounts for approximately 3% of the dried vine fruit worldwide production; its consumption has been associated with health benefits in rodents and humans. In this study, Corinthian currant was evaluated for its free and bound polar phenol content; samples from six Greek cultivation regions were analyzed. Among others, ten compounds were identified for the first time as components of the Corinthian currant free polar phenol profile, using UHPLC-ESI/MS; Caftaric acid predominated (10.59 mg/100 g) followed by miquelianin (5.41 mg/100 g). Two procedures, both combining acid and alkaline hydrolysis but in reverse order, were comparatively evaluated for the release of bound phenols from the fruit matrix; both approaches were proven adequate for the Corinthian currant bound phenol determination. Phenolic acids and flavonoids constituted the Corinthian currant bound polar phenol fraction. p-Hydroxybenzoic acid was the major constituent of both the acid (6.81 mg/100 g) and the subsequent alkaline (4.85 mg/100 g) hydrolysates. Bound polar phenols may provide various health-promoting properties and this is the first study to investigate the bound phenols of Corinthian currant and apply an efficient method for their release.