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  • The metabolism of dietary polyphenols and the relevance to circulating levels of conjugated metabolites.

The metabolism of dietary polyphenols and the relevance to circulating levels of conjugated metabolites.

Free radical research (2003-02-21)
Andreas R Rechner, Gunter Kuhnle, Henglong Hu, Andrea Roedig-Penman, Maarten H van den Braak, Kevin P Moore, Catherine A Rice-Evans
ABSTRACT

Berry extracts rich in anthocyanins have been linked to protective effects including the modulation of age-related neurological dysfunction and the improvement of the resistance of red blood cells against oxidative stress in vitro. In this study the bioavailability, metabolism and elimination of polyphenols from blackcurrant juice, rich in anthocyanins, flavonols, and hydroxycinnamates, were investigated. The four major native anthocyanidin glycosides of blackcurrant juice, delphinidin-3-glucoside, delphinidin-3-rutinoside, cyanidin-3-glucoside and cyanidin-3-rutinoside, were detected and identified in low amounts by HPLC and LC-MS in plasma and urine post-ingestion. Elimination of the anthocyanins was fast (maximum excretion after 1 h) and plasma levels (0-128.6 nmol/l) and total urinary exretion (0.07-1.35 mg; 0.007-0.133% of the dose ingested) were low. Most significantly, of the hydroxycinnamates, conjugated and free ferulic, isoferulic, p-coumaric, sinapic and vanillic acids were identified in plasma and urine, using GC-MS techniques. Quercetin and kaempferol (as glucuronides) and the proposed colonic metabolite of quercetin, 3-hydroxyphenylacetic acid, were detectable in a minority of subjects. Increased daily urinary hippuric, 4-hydroxyhippuric and 3-hydroxyhippuric acid levels were also observed post-ingestion in all volunteers.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Vanillic acid, purum, ≥97.0% (HPLC)
Sigma-Aldrich
Vanillic acid, 97%
Sigma-Aldrich
Vanillic acid, ≥97%, FG
Sigma-Aldrich
3-Hydroxyphenylacetic acid, ≥99%
Supelco
Vanillic acid, certified reference material, TraceCERT®, Manufactured by: Sigma-Aldrich Production GmbH, Switzerland
Sigma-Aldrich
3-Hydroxy-4-methoxycinnamic acid, predominantly trans, 97%
Sigma-Aldrich
3-Hydroxyhippuric acid, ≥95% (NMR)
Supelco
Delphinidin chloride, analytical standard