BIOAVAILABILITY OF THE DIETARY ANTIOXIDANT FLAVONOL QUERCETIN IN MAN

Quercetin, a dietary antioxidant flavonoid, has anticarcinogenic prope rties. We quantified the absorption of quercetin in ileostomists. Abso rption was 52 +/- 5% for quercetin glucosides from onions, 17 +/- 15% for quercetin rutinoside, and 24 +/- 9% for quercetin aglycone. The pl asma quercetin concentration in subjects with an intact colon, after i ngestion of fried onions, apples and pure quercetin rutinoside, decrea sed slowly with elimination half-lives of about 25 h. Thus, repeated d ietary intake of quercetin will lead to accumulation in plasma. The re lative bioavailability of quercetin from apples and rutinoside was one -third of that from onions. Absorption kinetics and bioavailibility mi ght be determined by the type of glycoside. Dietary quercetin could in crease the antioxidant capacity of blood plasma. (C) 1997 Elsevier Sci ence Ireland Ltd.