Flavonoids

Flavonoids are a group of phytonutrients found in all plants on the planet. Functions of these chemicals in plants include UV protection, defense against invasive pathogens, pigmentation, and signaling in symbiosis. This group of chemicals can be broken down further into subgroups based on the makeup of their chemical structures. In foods, flavonoids are full of natural antioxidants and can be found in a multitude of food types.

Chemical structures

Six subgroups of Flavonoids separated by chemical structure

All flavonoids consist of phenolic and pyrane rings and are generally insoluble. [2] Flavonoids differ in the arrangement of hydroxyl, methoxy, and glycosidic groups around a flavin backbone and from there form subgroups that include more specific chemicals. [4]

Flavones -Apigenin, Luteolin

Flavanones -Hesperetin, Naringenin, Eriodictyol

Flavonols -Quercetin, Kaempferol, Myricetin, Isorhamnetin

Flavan-3-ols -Catechins, Epicatechins, Epicatechin3-gallate, Epigallocatechin, Epigallocatechin 3-gallate, Gallocatechin, Theaflavin, Theaflavin 3-3’-digallate, Theaflavin 3’-gallate, Theaflavin 3-gallate, Thearubigins

Anthocyanidins -Cyanidin, Delphinidin, Malvidin, Pelargonidin, Peonidin, Petunidin

Presence in foods

Flavonoids are present in many foods including blueberries, cocoa beans, strawberries, and aloe vera plants

Flavonoids have been discovered to play a big role in the presence of antioxidants in common food sources. The five subgroups of flavonoids above exist as antioxidants within a multitude of common food items. [4]

Flavonols are found heavily in black tea and raw onions as well as in beer, coffee, and tomatoes. [4] Bee pollen has also found to contain flavonols. [5]

Dried and raw parsley contains more than 14,000 mg of flavones per gram of the plant. Flavones are also found in sweet, green, and hot chili peppers in addition to oranges and watermelons.

Regular and decaffeinated black tea accounts for an overwhelming amount of flavan-3-ols consumed by humans, joined by peaches, pears, and bananas.

Flavanones are mainly found in oranges and grapefruit juice along with lemons and tangerines.

Anthocyanidins are commonly found in blueberries, strawberries, bananas, and cherries.

References

[4] Bhagwat, S., Haytowitz, D.B. Holden, J.M. (Ret.). 2014. USDA Database for the Flavonoid Content of Selected Foods, Release 3.1. U.S. Department of Agriculture, Agricultural Research Service. Nutrient Data Laboratory Home Page: http://www.ars.usda.gov/nutrientdata/flav

[5] Kyle, J.A.M. et al. Flavonoids, chemistry, biochemistry and applications. In Flavonoids in Foods. Anderson, O.M. et al., Ed. CRC Press, Boca Raton, Fl. 2006