Table 6.

Main determinants of polyphenols bioavailability.

Factor	Main Mechanism
Class of polyphenols	The bioavailability is determined by the class of polyphenols and ranks as follows: phenolic acids > isoflavones > flavonols > catechins > flavanones > proanthocyanidins > anthocyanins.
Differences in chemical structure within the polyphenol class	Changes in physicochemical properties: solubility, ability to polymerize, and ability to enter reactions of conjugation.
Small intestine	Hydrolysis of most glycosides—aglycone absorbed by enterocytes, conjugation reactions, methylation, glucuronidation, and sulfation.
Liver	Aglycone-conjugation reactions: methylation, glucuronidation, and sulfation; part of the products goes back to the intestine with bile; part is excreted with urine; the majority enter other organs and tissues through the bloodstream.
Colon	Metabolism by bacterial enzymes to fewer complex compounds, absorption by colonocytes, and part of the ingested polyphenol dose are excreted with feces.
Food matrix	Can protect polyphenols from degradation. The food matrix changes caused by diet modification can affect gut microbiota and improve or decrease bioavailability depending on their composition.