The Impact of Gastrointestinal Modifications, Blood-Brain Barrier Transport, and Intracellular Metabolism on Polyphenol Bioavailability: An Overview

Polyphenols are found ubiquitously in plants, and epidemiological studies suggest an association between their regular consumption and a reduced risk of a number of chronic diseases; such as cardiovascular disease, specific forms of cancer, and neurodegenerative disease. The mechanisms by which polyphenols express these beneficial properties appear to involve their interaction with cellular signaling pathways and related machinery that mediate cell function under both normal and pathological conditions. Thus, their effectiveness and mechanisms of action in vivo will be dependent on the extent of their biotransformation. Native polyphenols in the diet are subjected to extensive metabolism following oral ingestion, in the upper gastrointestinal tract and in the colon, and after reaching the circulation, further intracellular metabolism in target tissues may occur. Additionally, the blood-brain barrier's crossing ability will influence their effect in the brain. This chapter will give an overview of how the polyphenols' bioavailability is influenced by gastrointestinal modifications, blood-brain barrier transport, intracellular metabolism, and the impact on their mechanisms of action.