Pch. Hollman et al., ABSORPTION AND DISPOSITION KINETICS OF THE DIETARY ANTIOXIDANT QUERCETIN IN MAN, Free radical biology & medicine, 21(5), 1996, pp. 703-707
Quercetin is a dietary antioxidant that prevents oxidation of low-dens
ity lipoproteins in vitro by scavenging of free oxygen radicals. Its i
ntake was inversely associated with coronary heart disease mortality i
n Dutch elderly men. However, data on absorption of quercetin in man a
re scarce and contradictory. We studied the time course of the plasma
quercetin concentration in two subjects after ingestion of fried onion
s containing quercetin glucosides equivalent to 64 mg of quercetin agl
ycone. Peak plasma levels of 196 ng/ml were reached after 2.9 h, with
a half-life of absorption of 0.87 h. The half-life of the distribution
phase was 3.8 h, and of the subsequent elimination phase 16.8 h. Afte
r 48 h the plasma concentration was about 10 ng/ml. We conclude that q
uercetin glucosides from onions are absorbed and are eliminated slowly
throughout the day. Thus, the dietary antioxidant quercetine could in
crease the antioxidant capacity of blood plasma.