Chemical Composition and In Vitro Antidiabetic Effect of Extracts from Ripe, Unripe, and Fermented Unripe Cornus mas L. Fruits

This study aimed to investigate the chemical composition, antioxidant activity, and in vitro antidiabetic properties of extracts obtained from ripe, unripe, and fermented (unripe) cornelian cherry (<i>Cornus mas</i> L.) fruits. Polyphenols were identified using UPLC-ESI-qTOF-MS/MS and quantified by HPLC-PDA. Antioxidant activity was evaluated using ABTS, DPPH, and FRAP assays, while enzyme inhibitory activity was determined for <i>α</i>-glucosidase and <i>α</i>-amylase. Additionally, the effects of <i>C. mas</i> extracts on insulin sensitivity in adipocytes were investigated. The study's results showed that each of the extracts tested contained varying proportions of substances with proven health-promoting properties. The extract from ripe fruits was characterized by the highest loganic acid content, whereas the extract from fermented unripe fruits contained a high amount of gallic acid, released through the hydrolysis of tannins during fermentation. The extract from unripe fruits exhibited the highest tannin content and the strongest antioxidant activity. All extracts inhibited <i>α</i>-glucosidase and <i>α</i>-amylase to a similar extent and improved insulin-stimulated glucose uptake in 3T3-L1 adipocytes without affecting <i>INSR</i> or <i>SLC2A4</i> expression. In conclusion, extracts from unripe and fermented <i>C. mas</i> fruits may represent promising agents for alleviating insulin resistance and preventing type 2 diabetes.