Winemaking industry produces large amounts of by-products (grape pomace or marc) every year, making necessary a sustainable management of such waste. Among red wines, Tannat variety possesses a unique polyphenolic profile. Consequently, the study of the bioactive properties of its by-product and the extraction optimization of its bioactive compounds is of great interest to state its health promoting potential. In this study, different extraction processes were tested: maceration with ethanol (95 %), ultrasound assisted ethanolic extraction optimization with surface methodology, ultrasound assisted aqueous extraction and hydro-alcoholic-acid extraction (EHAA). Using this last extraction procedure higher polyphenolic content (11.459±1.048 g GAE/100g of dry extract), monomeric anthocyanins (2.030±0.085 g Cyd/100g of dry extract), antioxidant capacity (0.474±0.036 mg/mL for ABTS and 0.715±0.063 µmol TE/mg of dry extract for ORAC-FL), -glucosidase (IC50 888.5±79.3 µg/mL) and pancreatic lipase inhibition capacity (IC50 2431.0±79.9 µg/mL) was found on Tannat grape skin. Considering as a whole, these results may imply a great antidiabetic and antiobesity potential. Moreover, EHAA showed to have anti-inflammatory capacity (IC50 587 µg/mL) on RAW 264.7 cells. In summary, EHAA possesses great potential as a functional ingredient for prevention and/or treatment of chronic diseases.

Diabetes pathogenesis encompasses oxidative stress, inflammation, insulin malfunctioning and partial or total insulin secretion impairment, which leads to a constant hyperglycemia. Polyphenols are known to possess bioactive properties, being Tannat grape skin a natural and sustainable source of these compounds. The present study aimed to find out the bioaccessibility of health-promoting molecules composing a multifunctional extract from Tannat grape skin obtained under hydro-alcoholic-acid conditions. The identification of phenolic compounds in the samples was performed by ultra-high performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS). Subsequently, the samples were in vitro digested mimicking the human oral gastrointestinal conditions and the bioactivity of the digest (antioxidant, anti-inflammatory and modulation of glucose metabolism) was assessed. Effect on glucose metabolism was estimated by measuring carbohydrases activity and the functionality of glucose transporters of small intestine cells in presence and absence of the digested extract. Flavonoids, phenolic acids and phenolic alcohols were the major phenol compounds detected in the extract. The bioaccessible compounds protected the intestinal cells and macrophages against the induced formation of reactive oxygen species (ROS) and nitric oxide (NO). In addition, glucose transporters were inhibited by the digested extract. In conclusion, the bioaccessible compounds of the extract, including phenols, modulated key biochemical events involved in the pathogenesis of diabetes such as oxidative stress, inflammation and glucose absorption. The extract was effective under prevention with co-administration conditions supporting its potential for either reducing the risk or treating this disease.