The metabolism of dietary polyphenols and the relevance to circulating levels of conjugated metabolites |
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Authors: | Rechner Andreas R Kuhnle Gunter Hu Henglong Roedig-Penman Andrea van den Braak Maarten H Moore Kevin P Rice-Evans Catherine A |
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Institution: |
a Antioxidant Research Group, Wolfson Centre for Age-Related Diseases, Guy's, King's and St. Thomas's School of Biomedical Sciences, King's College London, Guy's Campus, Hodgkin Building--3rd floor, London SE1 9RT, UK.
b Nutritional Healthcare R & D, GlaxoSmithKline, Royal Forest Factory, Coleford, Gloucestershire GL16 8JB, UK.
c Centre for Hepatology, Department of Medicine, Royal Free Campus, Royal Free and University College Medical School, London NW3 2PF, UK. |
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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 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. |
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Keywords: | Blackcurrant Anthocyanins Hydroxycinnamates Flavonols Absorption Metabolism |
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