Bioavailability of Quercetin

Quercetin is generally present as quercetin glycoside in nature and involves quercetin aglycone conjugated to sugar moieties such as glucose or rutinose. Quercetin has been reported to exhibit antioxidative, anti-carcinogenic, anti-inflammatory, anti-aggregatory and vasodilating effects. Unfortunately, quercetin bioavailability is generally poor and several factors affect its bioavailability. Quercetin bioavailability varies widely between individuals. Gender may affect quercetin bioavailability, but there is no clear evidence. There has been little research looking for the effects of age and vitamin C status on bioavailability of quercetin supplements, but there is no research seeking out the effects of age and vitamin C status on bioavailability of food-derived quercetin. Presence of sugar moieties increases bioavailability and differences in quercetin-conjugated glycosides affect bioavailability. For instance, onion-derived quercetin, which is mainly quercetin glucoside, is more bioavailable than apple-derived quercetin, which contains quercetin rhamnoside and quercetin galactoside. Quercetin is lipophilic compound, thus dietary fat enhances its bioavailability. Nondigestible fiber may also improve quercetin bioavailability. Quercetin bioavailability is greater when it is consumed as an integral food component. This study reviews and discusses factors affecting quercetin bioavailability.