Once the sugars have been removed from the skeleton for absorption, flavonoids are further metabolized in the gut and subsequently in the liver and kidneys to produce a vast number of modified molecules, known as flavonoid secondary metabolites. This process involves further conjugation of the flavonoid through the joining of glucuronate, sulfate, or methyl groups. In the intestine, this process is controlled by enzymes produced by the gut bacteria that play an important role in
the metabolism of plant bioactive compounds