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Rat gastrointestinal tissues metabolize quercetin
Brigitte A Graf1, Clement Ameho, Gregory G Dolnikowski
1Antioxidants Research Laboratory, Jean Mayer U.S. Department of Agriculture Human Nutrition Research Center on Aging, Tufts University, Boston, MA.
The Journal of Nutrition
|December 21, 2005
Summary
Quercetin is extensively metabolized in the gastrointestinal tract and liver, forming various conjugates. These quercetin metabolites, not the parent compound, are likely responsible for its biological activity in vivo.
Area of Science:
- Biochemistry
- Pharmacology
- Nutritional Science
Background:
- Quercetin, a common dietary flavonoid, is found in various foods and supplements.
- Its in vivo bioactivity is hypothesized to stem from its metabolites rather than the parent compound.
Purpose of the Study:
- To investigate the pre- and postabsorptive metabolism of orally ingested quercetin.
- To compare the metabolite patterns in gastrointestinal (GI) tissues, contents, and internal tissues.
Main Methods:
- F344 rats were fed a diet containing 0.45% quercetin for 6 weeks.
- Metabolite patterns were analyzed in stomach, small intestine, cecum, colon, liver, kidney, and plasma using LC-MS/MS.
Main Results:
- GI contents primarily contained unmetabolized quercetin (94-100%).
- GI tissues showed extensive metabolism, with quercetin present as 11 different sulfated, glucuronated, and methylated conjugates.
- Internal tissues (liver, kidney, plasma) predominantly contained sulfated methyl-quercetin glucuronide.
Conclusions:
- Quercetin undergoes significant biotransformation within the gastrointestinal tract before absorption.
- The metabolite profiles vary distinctly across different GI tissues, indicating localized metabolic activity.
- Postabsorptive metabolism further modifies quercetin, with conjugates being the primary form found in systemic circulation.