Advance on the absorption, metabolism, and efficacy exertion of quercetin and its important derivatives

Quercetin, a dietary flavonol, has been used as potential ingredient in food supplements to promote health. Its health effects are closely related to its bioavailability and further depend on its absorption, metabolism and excretion in vivo. Here, wesystematically summarized the absorption andmetabolism of quercetin in human intestine, liver, and kidney, highlighting the transport and metabolic pathways, intermediate metabolites, and circulation channels involving quercetin. The bioactivities of quercetin on theintestine, liver, and kidneywere also considered. In general, except for passive diffusion, different transporters (e.g., SGLT1,OATPs, andMRPs) participate in the transport of quercetin and its metabolites across biological barriers. Quercetin undergoes phase II metabolism after absorption by the intestine and is finally excreted into bile through liver or urine through kidney. Quercetin can protect the intestinal barrier and modulate the microflora. Moreover, its antioxidant, anti-inflammatory, and anti-fibrotic activities protect the liver and kidney.