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The small intestine can both absorb and glucuronidate luminal flavonoids
J P Spencer1, G Chowrimootoo, R Choudhury
1International Antioxidant Research Centre, Guy's King's and St. Thomas's School of Biomedical Sciences, London, UK.
FEBS Letters
|September 11, 1999
Summary
Flavonoid and hydroxycinnamate metabolism in the rat jejunum and ileum shows that glycosylation influences absorption. Glucuronidation is key for reducing phenolics, while aglycones dominate for less reducing compounds.
Area of Science:
- Pharmacokinetics and Drug Metabolism
- Gastrointestinal Physiology
- Natural Product Chemistry
Background:
- Flavonoids and hydroxycinnamates are plant-derived phenolic compounds with potential health benefits.
- Their absorption and metabolism in the gastrointestinal tract are crucial for bioavailability and efficacy.
- Glycosylation, the attachment of sugar moieties, significantly impacts the physicochemical properties and biological fate of these compounds.
Purpose of the Study:
- To investigate the perfusion and metabolism of flavonoids and hydroxycinnamates in an isolated rat jejunum and ileum model.
- To determine the influence of glycosylation on the subsequent metabolic pathways of these phenolic compounds.
- To elucidate the role of the jejunum and ileum in the Phase II metabolism, specifically glucuronidation, of ingested phenolics.
Main Methods:
- Utilized an isolated rat intestine model to study the perfusion of various flavonoids and hydroxycinnamates.
- Analyzed the absorbed compounds to identify metabolites and quantify parent compounds.
- Investigated the role of gut microflora by demonstrating glucuronidation independent of microbial activity.
Main Results:
- Flavone and flavonol glucosides undergo significant glucuronidation during transfer across the jejunum and ileum, independent of gut microflora.
- Quercetin-3-glucoside and rutin were primarily absorbed unmetabolized, indicating differential metabolic handling.
- Highly reducing phenolics were predominantly absorbed as glucuronides (96.5%+/-4.6), whereas monophenolic hydroxycinnamates and B-ring flavonoids showed higher aglycone levels (88.1%+/-10.1) post-absorption.
Conclusions:
- The jejunum and ileum possess the enzymatic machinery, including UDP-glucuronyl transferase and glycosidases, for direct phenolic glucuronidation.
- Glycosylation status critically influences the absorption and metabolic fate of dietary phenolics in the small intestine.
- Absorption of reducing phenolics favors glucuronidation, while less reducing phenolics are absorbed mainly as aglycones.
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