Accumulation of quercetin conjugates in blood plasma after the short-term ingestion of onion by women.
Quercetin is a typical flavonoid present mostly as glycosides in plant foods; it has attracted much attention for its potential beneficial effects in disease prevention. In this study, we examined human volunteers after the short-term ingestion of onion, a vegetable rich in quercetin glucosides. The subjects were served diets containing onion slices (quercetin equivalent: 67.6-93.6 mg/day) with meals for 1 wk. Quercetin was only found in glucuronidase-sulfatase-treated plasma, and its concentration after 10 h of fasting increased from 0.04 +/- 0.04 microM before the trial to 0.63 +/- 0.72 microM after the 1-wk trial. The quercetin content in low-density lipoprotein (LDL) after glucuronidase-sulfatase treatment corresponded to <1% of the alpha-tocopherol content. Human LDL isolated from the plasma after the trial showed little improvement of its resistance to copper ion-induced oxidation. It is therefore concluded that conjugated metabolites of quercetin accumulate exclusively in human blood plasma in the concentration range of 10(-7) approximately 10(-6) M after the short-term ingestion of vegetables rich in quercetin glucosides, although these metabolites are hardly incorporated into plasma LDL.
Department of Nutrition, School of Medicine, The University of Tokushima, Japan.
J H
JH
Moon
R
R
Nakata
S
S
Oshima
T
T
Inakuma
J
J
Terao
D000328:Adult; D002338:Carotenoids / Q000032:analysis; D008076:Cholesterol, HDL / Q000097:blood; D008078:Cholesterol, LDL / Q000097:blood / Q000737:chemistry / Q000378:metabolism; D003300:Copper / Q000494:pharmacology; D004435:Eating / Q000502:physiology*; D005215:Fasting / Q000097:blood; D005260:Female; D006027:Glycosides / Q000032:analysis; D006801:Humans; D007477:Ions; D008077:Lipoproteins, LDL / Q000737:chemistry; D019697:Onions / Q000737:chemistry; D010084:Oxidation-Reduction / Q000187:drug effects; D011794:Quercetin / Q000032:analysis / Q000097:blood*; D013997:Time Factors; D014810:Vitamin E / Q000032:analysis
D008076:Cholesterol, HDL; D008078:Cholesterol, LDL; D006027:Glycosides; D007477:Ions; D008077:Lipoproteins, LDL; D014810:Vitamin E; D002338:Carotenoids; D003300:Copper; D011794:Quercetin