Murota, Kaeko The University of Tokushima
Hotta, Azusa The University of Tokushima
Ido, Hikaru The University of Tokushima
Moon, Jae-Hak The University of Tokushima|Chonnam National University
Sekido, Keiko The University of Tokushima
Hayashi, Hiroki Kagome Co. Inc.
Inakuma, Takahiro Kagome Co.
Terao, Junji The University of Tokushima Tokushima University Educator and Researcher Directory KAKEN Search Researchers
Quercetin is a major dietary flavonoid found in onions and other vegetables. It is known that dietary quercetin is metabolized in the intestinal mucosa and the liver and is present as its glucuronide/sulfate conjugates with or without methylation. Although quercetin is known to possess strong antioxidant activity, there are only limited reports on the antioxidant activity of its metabolites. In this study, the antioxidant capacity of quercetin metabolites under physiological conditions was investigated. After consumption of cooked onion, more than 80% of quercetin metabolites were localized in the human plasma fraction containing concentrated serum albumin. Other lipoprotein fractions contained only small amounts of quercetin metabolites. Addition of quercetin 3-O-β-glucuronide to the lipoprotein-eliminated plasma fraction generated antioxidant activity against LDL oxidation in a dose-dependent manner. However, onion consumption failed to enhance the antioxidant activity of the lipoprotein-eliminated plasma fraction against LDL oxidation, probably because the amount of quercetin metabolites bound to albumin was less than the effective level in an ex vivo study. The physiological role of plasma albumin in retaining quercetin metabolites needs to be further clarified.
The Journal of Medical Investigation
Faculty of Medicine Tokushima University
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