Absorption pathway of dietary flavonoids: the potential roles of the lymphatic transport in the intestine

Flavonoids are one of the major phytochemicals in the diet and have attracted much attention to potentially prevent various diseases. Dietary flavonoid aglycons enter the intestinal epithelial cells and metabolized by the phase II enzymes producing the corresponding conjugated metabolites. The bioavailability of flavonoids affects their physiological function. Recently, we found dietary flavonoids are absorbed not only via the portal vein but also via the intestinal lymphatic pathways. The small intestine is the primary tissue to absorb most dietary nutrients, and the lymphatic system is generally used to absorb lipids and lipophilic vitamins as the form of chylomicrons. In the case of lipophilic drugs, the lymphatic transport pathway makes the medicine avoid the first-pass metabolism in the liver and deliver the drugs as more active form to the target tissues. In this review, the several reports on the lymphatic transport of flavonoids are summarized, mainly in the cause of quercetin and its derivatives. In addition, the potential of physiological importance of lymphatic flavonoid absorption will be discussed.