Investigations of the absorption and metabolism of antioxidant flavonols

Abdul Aziz, Azlina (2000) Investigations of the absorption and metabolism of antioxidant flavonols. PhD thesis, University of Glasgow.

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Abstract

Flavonols are polyphenols, secondary plant metabolites commonly found in plants and foods of plant origin. They have widespread biological properties in the human body. The recent discovery of their potential antioxidant activities has prompted extensive research. Flavonols particularly quercetin are potent antioxidants with higher antioxidant properties than the well known antioxidant vitamins C and E. Several epidemiology studies have demonstrated a strong inverse association between flavonoid intake and risk of coronary heart disease. The association with cancer is less defined with only some studies showing an inverse association and others not. In view of their potential to act as antioxidants and prevent oxidative damage-related diseases, it is important to have an understanding of their bioavailability. Indeed, information of the absorption and metabolism of individual flavonols in man is limited. Previous investigations of their absorption have shown conflicting results. It was previously speculated that flavonol glycosides were not absorbed due to their conjugation to sugar molecules and that only the aglycones were transported into the blood stream. However, recent research has detected the presence of quercetin glycosides in plasma. These findings disagree with the earlier postulation that flavonol glycosides were not absorbed. In addition to absorption, the metabolism of flavonoids is another important area of research. As yet, little firai information is available on the fate of flavonols following absorption. The aim of the present study was to conduct further research on the absorption and metabolism of flavonols and to establish the influence of flavonol structure on the extent of their absorption and metabolism. Results obtained from this thesis can partially explain the seemingly low absorption of flavonol glycosides from the small intestine and their accumulation in plasma. The structure of flavonols, particularly the nature and position of the sugar moiety, has a major influence on their absorption and potential bioavailability. Furthermore, the substantial metabolism of flavonol glucosides by the liver may contribute to the low levels of the parent compounds detected in plasma and urine. Findings from this present study raised interesting health promotion possibilities as identification of the flavonol conjugates which will be highly absorbed into the bloodstream can be used to encourage the public to increase their intakes of flavonol-rich fruit and vegetables. Identification of the metabolites of flavonol metabolism with potential antioxidant activities can further contribute towards promoting the beneficial effects of increasing intakes of flavonol-rich foods. (Abstract shortened by ProQuest.).

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Additional Information: Adviser: Alan Crozier
Keywords: Biochemistry
Date of Award: 2000
Depositing User: Enlighten Team
Unique ID: glathesis:2000-73266
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 14 Jun 2019 08:56
Last Modified: 14 Jun 2019 08:56
URI: http://theses.gla.ac.uk/id/eprint/73266

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