Polyphenol Characterization and Antioxidant Activity of Grape Seeds and Skins from Sicily: A Preliminary Study

The interest in the consumption of health-promoting foods has led to identifying derivatives of the wine industry as products to increase the functional properties of different foods or todesign new functional foods. The main goal of this study is to characterize and valorize byproductsand wastes of Sicilian grapes as new sources of bioactive components, from the perspective of acircular economy and a biorefinery approach. In particular, this research investigated: 1. the totalphenolic content and antioxidant activities and 2. the phenolic profiles of free and bound fractionsof defatted grape seeds and red grape skins from Sicily. Defatted grape seeds (DGS) and red grapeskins (RGSK) are rich in phenolic compounds. Twenty biophenols were found in the defatted seedsand red grape skins. Particularly interesting were the results obtained after basic hydrolysis, whichallowed the release of biophenols from the matrix. The degreased grape seeds showed p-coumaricacid levels at 4641.65 µg g-1, gallic acid at 2649.23 µg g-1, and caffeic acid at 1474.13 µg g-1 , alongwith appreciable quantities of myricetin, epicatechin, and quercetin. As a sustainable approach, thereuse and the value added of the byproducts and wastes of grapes grown in Sicily is shown, whichmakes possible new applications in different fields, i.e., nutraceuticals.