Digestion and absorption of phenolic compounds assessed by in vitro simulation methods. A review

Phenolic compounds are a group of key plant metabolites found abundantly in fruit and vegetables. Because of their antioxidant properties, they play a significant role in preventing various degenerative illnesses, tumours or cardiovascular disease. In nature, they are present in foods mainly as esters, glycosides and polymers which need to undergo enzymatic hydrolysis in the digestive tract or by the gut microflora before becoming absorbed. The biological properties of these phenolic compounds undergoing this degradation, are thus governed by their absorption as well as metabolism. Many methods are used to assess the rates and the degrees to which these substances are digested and absorbed, both in vivo and in vitro ones, where the former are the most reliable, although they suffer from various limitations. For this reason, many in vitro models have now arisen to simulate the function of human digestion in the attempt to faithfully re-create real-life conditions. Mechanisms of polyphenols absorption have been principally studied by intestinal epithelial cell models, in particular, those using the Caco-2 cell line.