Bioavailability of anthocyanins and derivatives

Anthocyanins are naturally occurring compounds widespread in plant-derived foodstuffs and therefore abundant in human diet. There are evidences regarding the positive association of their intake with healthy biological effects displayed in vivo. This review aims to highlight some aspects regarding anthocyanins bioavailability; these include a short introductory part of anthocyanin chemistry, stability, occurrence and intake. This first part is followed by a more detailed one concerning the main topic of the review that includes the bioavailability and metabolism of anthocyanins. Special attention is given to the contribution of the gastric mucosa to anthocyanin absorption as the result of the high content of intact anthocyanins (20–25%) detected is plasma few minutes after intake. The contribution of intestinal tissue and the microbiota impact in anthocyanin absorption and bioactivity is also highlighted. Despite the biological activities that have been associated with these compounds, anthocyanins appear to be rapidly absorbed and eliminated, reaching only low maximal concentrations in plasma and urine. Some possible critical factors that may contribute to this paradox were also explored including the ability of a compound to cross membranes, the effect of pH, digestive enzymes, biliary acids and microbiota, the lack of sensitivity of the analytical method, the possible ingestion of pigments (anthocyanin derivatives, especially in the case of red wine) and the influence of the food matrix. Generally, the bioavailability of anthocyanins is presumed but whether the effect is due to the native compounds or other forms, which mechanism are involved or which factors have crucial impact on bioavailability still remain underexplored.