Health benefits of winemaking by-products: in vitro study of the phenolic profile and potential healthy properties

Introduction: the wine sector plays a significant role in the international agri-food industry, with the winemaking process leading to the generation of considerable amounts of by-products. Among these by-products, grape pomace, is one of the most abundant resources, mainly finding application in the production of distillates, fertilizers, and animal feed. In recent years, an increasing number of companies have started a circular economy model, which aims to extend the lifecycle of products and to valorize food waste and by-products. In this context, which includes the valorization of food waste and by-products, grape pomace is raising growing interest both for its nutritional properties and potential health benefits. From grape pomace, it is possible to extract functional compounds such as polyphenols, that can be used for food, feed and cosmetic formulations. Although several scientific studies report the possible positive effects of polyphenols on the cardiovascular system and oxidative stress, knowledge regarding their impact on postprandial glycemia modulation is still limited. Purpose: the aim of this study was to compare different in vitro methods to evaluate the phenolic profile and antioxidant capacity of grape pomace obtained from different vitis vinifera l. Varieties. The efficacy of the extracts to influence enzymes generally involved in glucose metabolism and glycemia regulation was also investigated. Methods: different in vitro methods were applied and compared, including: 1) folin-ciocalteu assay to evaluate the total polyphenol content, 2) differential ph test to evaluate the total anthocyanin content, 3) dpph (2,2-diphenyl-1-picrylhydrazyl) assay to evaluate antioxidant activity, and 4) vanillin assay for the quantification of total proanthocyanidin content. After the preliminary characterization of the samples, the inhibitory capacity of the extracts was evaluated by applying assays for the inhibition of dipeptidyl peptidase iv (dpp-iv), pancreatic alpha-amylase, and alpha-glucosidase. Results: spectrophotometric methods proved useful in obtaining initial insights into the phenolic composition of grape samples and generally showed satisfactory correlation with antioxidant activity. In particular, grape pomace, especially when containing seeds, generally represents a valuable source of polyphenols with noticeable antioxidant activity and promising inhibitory activity on dipeptidyl peptidase iv (dpp-iv), pancreatic alpha-amylase, and alpha-glucosidase, which are involved in the regulation of post-prandial glycemia. Conclusions: preliminary results indicate that winemaking by-products can represent a valuable source of bioactive compounds suitable for use in dietary supplements or other functional products, further emphasizing their potential contribution to sustainable practices within the wine sector.