Bioavailability of quercetin in humans and the influence of food matrix comparing quercetin capsules and different apple sources.

The objective of the four-way cross-over pilot study was the investigation of quercetin bioavailability after ingestion of apple quercetin incorporated in different matrices and quercetin dihydrate capsule. Six healthy volunteers were given a standard diet supplemented with 71μmol quercetin equivalents from vacuum impregnated apple chips, apple peel extract capsules and apple peel. Quercetin dihydrate capsules were used as control. The vacuum impregnated apple chips were enriched with a quercetin rich apple peel extract. The ingestion of vacuum impregnated apple chips, apple peel extract capsules and apple peel resulted in similar plasma quercetin and plasma total flavonol concentrations compared to the quercetin dihydrate capsule. With regard to the bioavailabilities of all quercetin treatments, a reduced release from vacuum impregnated apple chips can be excluded. The apple peel matrix which is rich in indigestible dietary fibers impacted the profile of the plasma flavonol time curve similar to poor soluble quercetin dihydrate. Finally, the quercetin bioavailability of vacuum impregnated apple chips (AUC: 104±24μmol·min∙L) as functional food was similar to the supplementation with apple peel extract capsules (AUC: 87±27μmol∙min∙L).