Flavonoids

Flavonoids, a ubiquitous group of plant secondary metabolites with a 15-carbon structure (two phenyl rings and a heterocyclic ring; C6-C3-C6) are an indispensable component of traditional medicines, current nutraceuticals, and functional foods. They are the most abundant polyphenols in the human diet.

Dietary flavonoids are found in tea, berry fruit, citrus and other fruit and legumes. There are more than 6,000 identified flavonoids which have been classified into six major subgroups, outlined in the table below.

Flavonoid Subgroup	Specific Flavonoids	Food Sources
Flavonols	Quercetin, kaempferol myricetin, isorhamnetin	Onions, apples, leafy vegetables, berries
Flavones	Luteolin, apigenin	Parsley, hot peppers, celery, artichokes, spices
Flavanones	Hesperetin, naringenin, eriodictyol	Citrus fruits and citrus juices
Flavan-3-ols	Catechins, epigallocatechins, theaflavins	Tea, chocolate, tree fruits, grape seed
Anthocyanidins	Cyanidin, delphinidin, malvidin, pelargonidin, peonidin, petunidin	Most berries, cowpeas
Isoflavones	Daidzein, genistein, glycitein	Soybeans, soyfoods