We found a match
Your institution may have rights to this item. Sign in to continue.
- Title
Antioxidant properties of major metabolites of quercetin.
- Authors
Dueñas, Montserrat; Surco-Laos, Felipe; González-Manzano, Susana; González-Paramás, Ana; Santos-Buelga, Celestino
- Abstract
Dietary flavonoids have been related to health promotion, which has been attributed in part to their antioxidant properties as demonstrated in many in vitro studies. However, in the human organism most flavonoids are little bioavailable and largely transformed to different metabolites that are crucial to explain the health effects associated with their dietary intake, although little is known about their biological activities. Quercetin is a majority flavonoid in the human diet that has been commonly used in studies on the flavonoid and health relationships. In this study, the antioxidant activity of different conjugated metabolites of quercetin (quercetin 3′- O-sulphate, quercetin 4′- O-sulphate, quercetin 3- O-glucuronide and isorhamnetin 3- O-sulphate) prepared in the laboratory, and of some phenolic acids that may result from its colonic degradation, was investigated by two in vitro assays (ABTS and FRAP assays). As expected, substitution of the hydroxyl groups of quercetin by the conjugating substituents resulted in a decrease in the antioxidant activity with regard to the parent compound. Despite this, the conjugated metabolites still retained significant antioxidant activity and behave as significantly better radical scavengers and reducing compounds than usually recognized antioxidants like α-tocopherol. Greater antioxidant activity of the metabolites was found in the ABTS assay, conducted at pH 7.4, suggesting that quercetin derivatives could act as potential radical scavengers in physiological conditions. Similarly, antioxidant activity significantly higher than α-tocopherol was also found in the ABTS assay for 3,4-dihydroxyphenylacetic, 3-methoxy-4-hydroxyphenylacetic and 3-(3,4-dihydroxyphenyl)propionic acids, described as products of the colonic degradation of quercetin. Phenylacetic acids were more active than benzoic and phenylpropionic acids, and the activity increased with the number of phenolic hydroxyls in the molecule; methoxylated derivatives showed, in general, lower activity than the equivalent O-dihydroxylated forms but greater than that of the monohydroxylated precursor. The results obtained are expected to contribute to the understanding of the mechanisms involved in the biological effects associated with the intake of flavonoid-rich diets.
- Subjects
FLAVONOIDS; ANTIOXIDANTS; METABOLITES; QUERCETIN; GLUCURONIDES; SULFATES; HEALTH promotion; DIET
- Publication
European Food Research & Technology, 2011, Vol 232, Issue 1, p103
- ISSN
1438-2377
- Publication type
Article
- DOI
10.1007/s00217-010-1363-y