Review articleDietary flavonols: chemistry, food content, and metabolism
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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.
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