Quercetin Bioavailability And Biotransformation Are Inversely Related To Vitamin C Status In College‐Aged Adults

Dietary quercetin (Q) may reduce the risk of cardiovascular disease (CVD), but little is known about its bioavailability. We conducted a pharmacokinetics study to define whether antioxidant status affects Q bioavailability in young adults. Participants (n = 8M/5F) ingested 1095 mg Q aglycone with a standardized meal. Then, plasma antioxidants [ascorbic acid (AA), tocopherols, uric acid, carotenoids], Q and its methylated metabolites isorhamnetin (I) and tamarixetin (T) were measured at timed intervals for 24 h. Q bioavailability (AUC 0‐24 h 308–1738 μM x min) and maximum concentrations (C max 0.4–2.8 μM) exhibited high inter‐subject variability. AUC 0‐24 h and C max of I and T were also highly variable (120–750 and 33–787 μM x min; 0.1–0.9 and 0.1–1.2 μM, respectively). AA, but no other antioxidants, was inversely related to Q AUC 0‐24 h and Q C max ( P <0.05; r = −0.63 to −0.49). AA was also negatively related to AUC 0‐24 h of I + T ( P <0.05, r = −0.58) and tended to inversely relate to C max of I + T ( P =0.06; r = −0.46), suggesting that low AA status increases Q bioavailability and biotransformation. AA was also inversely related to myeloperoxidase ( P <0.05, r = −0.56), a proinflammatory enzyme that increases CVD risk. These data suggest that low AA status increases Q bioavailability, possibly through a proinflammatory mechanism that increases its intestinal absorption. Grant Funding Source : Donaghue Nutrition Research Program