The metabolism of anthocyanins.

Anthocyanins are the largest group of water-soluble pigments in the plant kingdom. As with other polyphenols, they express antioxidant activity in vivo. Anthocyanins are associated with reduced risk of some several diseases, such as atherosclerosis and diabetes. Their beneficial health effects depend on the efficiency of their absorption. The intake of anthocyanins from the gastrointestinal lumen into the blood is likely to occur through the epithelium of the stomach, intestine and colon. The mechanisms of absorption differ from site to site, and they depend on the structure of the molecules that are absorbed. In plasma, anthocyanins can be found in their intact form, or as the corresponding phenolic acids and aldehydes, and also as methyl, sulfate and glucuronyl conjugates. Although aglycones can exist in plasma for short times, they are prone to degrade due to their instability; however, binding with proteins might preserve their intact structures. The plasma concentrations of anthocyanins are low, and efficient transport is crucial for their accessibility to tissues. Anthocyanins can cross the blood-brain barrier. However, besides their reduction of oxidative stress, the mechanisms behind their influence on neuronal activity are not completely understood. In this mini-review, we provide a short overview of the bioavailability, metabolic products, and transport processes of anthocyanins.