Elsevier

Nutrition

Volume 18, Issue 1, January 2002, Pages 75-81
Nutrition

Review article
Dietary flavonols: chemistry, food content, and metabolism

https://doi.org/10.1016/S0899-9007(01)00695-5Get rights and content

Abstract

The flavonols belong to a large group of compounds called flavonoids, which are diverse in their chemical structure and characteristics. Fruits, vegetables, and beverages such as tea and red wine are major sources of flavonols in the human diet. The daily consumption of flavonols is difficult to estimate because values depend on accurate assessment of feeding habits and flavonol content in foods. Food sources, dietary intakes, and bioavailability of flavonols are strongly influenced by variations in plant type and growth, season, light, degree of ripeness, food preparation, and processing, all of which are discussed. In the past few years, a number of studies on the absorption and metabolism of flavonols in humans have been published and the findings from these studies are reviewed. We do not discuss the health effects of flavonols.

Section snippets

Synthesis and structure

The health effects of flavonols have been reviewed by others.1, 2 The flavonoids are a group of low-molecular-weight polyphenolic substances. They are formed from the combination of derivatives synthesized from phenylalanine (via the shikimic acid pathway) and acetic acid.3 The first step involves the formation of phenylalanine from phenylpyruvate. Phenylalanine is transformed to trans-cinnamic acid, which is then hydrolyzed to p-coumaric acid (C-9). The C-9 acids condense with three C-2

Flavonols in the human diet

It is important to bear in mind that reported dietary flavonoid intakes and food sources have been based mostly on the content of only three flavonols—quercetin, myricetin, and kaempferol—and two flavones—apigenin and luteolin. Therefore, total flavonoid intake and content in foods can be assumed to be greater than those reported. The following discussion of flavonoid food sources and intakes relates to the three flavonols and two flavones mentioned above, unless stated otherwise.

References (62)

  • C Ewald et al.

    Effect of processing on major flavonoids in processed onions, green beans, and peas

    Food Chem

    (1999)
  • U Justesen et al.

    Quantitative analysis of flavonols, flavones, and flavanones in fruits, vegetables and beverages by high-performance liquid chromatography with photo-diode array and mass spectrometric detection

    J Chromatogr A

    (1998)
  • S Häkkinen et al.

    Content of flavonols and selected phenolic acids in strawberries and Vaccinium speciesinfluence of cultivar, cultivation site and technique

    Food Res Int

    (2000)
  • C Manach et al.

    Quercetin is recovered in human plasma as conjugated derivatives which retain antioxidant properties

    FEBS Lett

    (1998)
  • A van der Sluis et al.

    Flavonoids as bioactive components in apple products

    Cancer Lett

    (1997)
  • S Nielsen et al.

    Human absorption and excretion of flavonoids after broccoli consumption

    Cancer Lett

    (1997)
  • J Conquer et al.

    Supplementation with quercetin markedly increases plasma quercetin concentration without effect on selected risk factors for heart disease in healthy subjects

    J Nutr

    (1998)
  • P.C.H Hollman et al.

    Absorption of dietary quercetin glycosides and quercetin in healthy ileostomy volunteers

    Am J Clin Nutr

    (1995)
  • T Walle et al.

    Quercetin glucosides are completely hydrolyzed in ileostomy patients before absorption

    J Nutr

    (2000)
  • M Olthof et al.

    Bioavailabilities of quercetin-3-glucoside and quercetin-4′-glucoside do not differ in humans

    J Nutr

    (2000)
  • A Day et al.

    Deglycosylation of flavonoid and isoflavonoid glycosides by human small intestine and liver β-glucuronidase activity

    FEBS Lett

    (1998)
  • A.J Day et al.

    Dietary flavonoid and isoflavone glycosides are hydrolysed by the lactase site of lactase phlorizin hydrolase

    FEBS Lett

    (2000)
  • C Manach et al.

    Bioavailability, metabolism and physiological impact of 4-oxo-flavonoids

    Nutr Res

    (1996)
  • E Oliveira et al.

    In vitro glucuronidation of kaempferol and quercetin by human UGT-1A9 microsomes

    FEBS Lett

    (2000)
  • G Kuhnle et al.

    Epicatechin and catechin are O-methylated and glucuronidated in the small intestine

    Biochem Biophys Res Commun

    (2000)
  • P Pietta et al.

    Identification of Gingko biloba flavonol metabolites after oral administration to humans

    J Chromatogr A

    (1997)
  • P.C.H Hollman et al.

    Absorption and disposition kinetics of the dietary antioxidant quercetin in man

    Free Radic Biol Med

    (1996)
  • Y Arai et al.

    Dietary intakes of flavonols, flavones and isoflavones by Japanese women and the inverse correlation between quercetin intake and plasma LDL cholesterol concentration

    J Nutr

    (2000)
  • G Duthie et al.

    Plant polyphenols in cancer and heart diseaseimplications as nutritional antioxidants

    Nutr Res Rev

    (2000)
  • W Heller

    Flavonoid biosynthesisan overview

  • J Kühnau

    The flavonoids, a class of semi-essential food componentstheir role in human nutrition

    World Rev Nutr Diet

    (1976)
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