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Research article2006Peer reviewedOpen access

Dietary flavonoids with a catechol structure increase alpha-tocopherol in rats and protect the vitamin from oxidation in vitro

Frank J, Budek A, Lundh T, Parker RS, Swanson JE, Lourenco CF, Gago B, Laranjinha J, Vessby B, Kamal-Eldin A

Abstract

To identify dietary phenolic compounds capable of improving vitamin E status, male Sprague-Dawleyrats were fed for 4 weeks either a basal diet ( control) with 2 g/kg cholesterol and an adequate content of vitamin E or the basal diet fortified with quercetin ( Q), (2)-epicatechin (EC), or (1)-catechin ( C) at concentrations of 2 g/kg. All three catechol derivatives substantially increased concentrations of alpha-tocopherol (alpha-T) in blood plasma and liver. To study potential mechanisms underlying the observed increase of alpha-T, the capacities of the Flavonoids to i) protect alpha-T from oxidation in LDL exposed to peroxyl radicals, ii) reduce alpha-tocopheroxyl radicals (alpha-T-.) in SDS micelles, and iii) inhibit the metabolism of tocopherols in HepG2 cells were determined. All flavonoids protected alpha-T from oxidation in human LDL ex vivo and dose-dependently reduced the concentrations of alpha-T-.. None of the test compounds affected vitamin E metabolism in the hepatocyte cultures. In conclusion, fortification of the diet of Sprague-Dawley rats with Q, EC, or C considerably improved their vitamin E status. The underlying mechanism does not appear to involve vitamin E metabolism but may involve direct quenching of free radicals or reduction of the alpha-T-. by the flavonoids

Published in

Journal of Lipid Research
2006, Volume: 47, number: 12, pages: 2718-2725 Publisher: AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC