Pch. Hollman et al., RELATIVE BIOAVAILABILITY OF THE ANTIOXIDANT FLAVONOID QUERCETIN FROM VARIOUS FOODS IN MAN, FEBS letters, 418(1-2), 1997, pp. 152-156
Quercetin is a strong antioxidant and a major dietary flavonoid. Epide
miological studies suggest that consumption of quercetin protects agai
nst cardiovascular disease, but its absorption in man is controversial
. We?ie fed nine subjects a single large dose of onions, which contain
glucose conjugates of quercetin, apples, which contain both glucose a
nd non-glucose quercetin glycosides, or pure quercetin-3-rutinoside, t
he major quercetin glycoside in tea, Plasma levels were then measured
over 36 h, Bioavailability of quercetin from apples and of pure querce
tin rutinoside was both 30% relative to onions, Peak levels were achie
ved less than 0.7 h after ingestion of onions, 2.5 h after apples and
9 h after the rutinoside. Half-lives of elimination were 28 h for onio
ns and 23 h for apples. We conclude that conjugation with glucose enha
nces absorption from the small gut, Because of the long half-lives of
elimination, repeated consumption of quercetin-containing foods will c
ause accumulation of quercetin in blood. (C) 1997 Federation of Europe
an Biochemical Societies.