The Metabolism of Dietary Polyphenols and the Relevance to Circulating Levels of Conjugated Metabolites

• Published in: Free radical research Vol. 36; no. 11; pp. 1229 - 1241
• Main Authors: Rechner, Andreas R., Kuhnle, Gunter, Hu, Henglong, Roedig-Penman, Andrea, van den Braak, Maarten H., Moore, Kevin P., Rice-Evans, Catherine A.
• Format: Journal Article
• Language: English
• Published: England Informa UK Ltd 2002; Taylor & Francis
• Subjects: Absorption; Adult; Anthocyanins; Anthocyanins - blood; Anthocyanins - pharmacokinetics; Anthocyanins - urine; Biological Availability; Biotransformation; Blackcurrant; Chromatography, High Pressure Liquid; Diet; Female; Flavonoids; Flavonols; Fruit; Gastric Juice - metabolism; Glucuronides - metabolism; Humans; Hydroxycinnamates; Male; Mass Spectrometry; Metabolism; Phenols - metabolism; Polymers - metabolism
• ISSN: 1071-5762; 1029-2470
• DOI: 10.1080/246-1071576021000016472

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 excretion (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.