Quercetin, but not its glycosides, is absorbed from the rat stomach

Absorption and metabolism of quercetin, isoquercitrin (quercetin 3-O-glucose), and rutin (quercetin 3-O-glucose-rhamnose) were investigated in rats after in situ gastric administration (15 mumol/L) for 30 min. At the end of the experiment, 38% of the initial dose of quercetin had disappeared. Quercetin was rapidly absorbed by the stomach, and was recovered in the bile 20 min after infusion (4.07 +/- 0.10 mumol/L). The administration of rutin and isoquercitrin indicated that these glycosides were not hydrolyzed nor absorbed by this tissue. In conclusion, when flavonols are present in the diet as aglycons, they could be partly absorbed in the stomach, in contrast to their glycosidic forms which are not absorbed.