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United States Department of Agriculture

Agricultural Research Service

Title: Flavonoids in Foods

Author
item Beecher, Gary

Submitted to: Antioxidants International Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: January 4, 1999
Publication Date: N/A

Interpretive Summary: In addition to nutrients, most foods contain a large number of other organic compounds, some of which may be beneficial to human health. One class of these components is the flavonoids, a subclass of polyphenols. Most fruits that are red or purple, such as red grapes, cherries and blueberries, have substantial quantities of anthocynanidins. Many of these same foods also contain flavonols, primarily quercetin. Catechins are present in red grapes and red wine as well as other red fruits. Citrus foods and juices contain hesperetin and naringenin as well as quercetin. Onions have the highest concentration of quercetin, about 300 mg/kg food. Some green vegetables also contain quercetin or kaempferol. Teas have high concentrations of catechins and small amounts of quercetin. Most flavonoids in foods are conjugated to a carbohydrate; the type of carbohydrate and its linkage varies. Several types of dimers, trimers and polymers of flavonoids are present in many foods. There is a dearth of comprehensive data on the flavonoid content of foods due primarily to the lack of a simple analytical system that will measure all of the prominent food flavonoids in a single run. Development of such a system, comprehensive analysis of foods, and subsequent summarization of food flavonoid data into a convenient database will provide the appropriate tools to ascertain the impact of dietary flavonoids on health maintenance and disease prevention.

Technical Abstract: Many commonly consumed fruits, vegetables and beverages contain various classes of flavonoids and in varying quantities. Most fruits that are red or purple, such as red grapes, cherries and blueberries, have substantial quantities of several anthocynanidins. Many of these same foods also contain flavonols, primarily quercetin. Catechins (flavan-3-ols) are present in red grapes and their processed product, red wine, as well as other red fruits, such as apples. Citrus foods and juices have a unique class of flavonoids, flavanones (hesperetin and naringenin), as well as quercetin. Onions have the highest concentration of quercetin (about 300 mg/kg food) of any common food that has been analyzed. Other vegetables that contain quercetin or kaempferol, but at much lower quantities, include broccoli and kale. Teas provide high concentrations of catechins and small amounts of the flavonol, quercetin.. Most flavonoids in foods are conjugated to a carbohydrate moiety; the type of carbohydrate and its linkage to flavonoids is varied which leads to many different molecular structures. A variety of dimers, trimers, oligomers and polymers of flavonoids are present in many foods. There is a dearth of comprehensive data on the flavonoid content of foods. This is due primarily to the lack of a single, robust analytical system that will measure all of the prominent food flavonoids, as aglycones, in a single run. Development of such a system, comprehensive analysis of foods, and subsequent summarization of food flavonoid data into a convenient database

Last Modified: 4/17/2014
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