The Food Matrix Protects Dark Chocolate Flavan-3-Ols and Onion Flavonols from Degradation During In Vitro Gastrointestinal Digestion

The bioaccessibility of flavonoids (namely, their release from the food matrix and their stability under gastrointestinal conditions) is pivotal in establishing their bioavailability and biological effects. Bioaccessibility is affected by several factors, including the food matrix. Previous studies suggested that flavonols and flavan-3-ols were higher in solid foods rather than in beverages. Therefore, this study investigated the bioaccessibility of red-skinned onion flavonols and dark chocolate flavan-3-ols during in vitro gastrointestinal digestion of whole foods and the corresponding phenolic compounds extracts, with the aim of ascertaining a possible food matrix effect. Results showed that the presence of the food matrix protected flavonols and flavan-3-ols from degradation during digestion. The bioaccessibility of total flavonols and flavan-3-ols determined by mass spectrometry was 79.0% and 80.8% for red-skinned onion and dark chocolate, respectively, whereas it was 57.5% and 47.3% for the corresponding extracts. Degradation of flavonols occurred mainly during intestinal digestion by deglycosylation and oxidative reactions, whereas for flavan-3-ols, it occurred during gastric digestion mainly by hydrolysis. Therefore, this study highlighted the importance of the food matrix in protecting flavonols and flavan-3-ols from degradation during digestion, underscoring the significance of consuming phenolic compounds in whole foods rather than supplements or extracts.