Table 4.

Examples of pharmacologically relevant classes of flavonoids

Class	Basic structure	Typical rich food source	Example	Comment
Flavanolsa		Soy flour, red wine, green tea, grape, wine, cocoa, apricot, beans	Catechin, epicatechin	The intake of flavanol‐rich foods (such as Cocoa flavonols) has been evaluated in relation to cardiovascular healthb
Flavanones		Citrus fruits (Tomás‐Barberán and Clifford, 2000)	Hesperetin, Naringenin	Flavanones and flavanones‐rich botanical extracts have been a subject of great interest for scientific research for as a possible emerging treatment for diabetes and its complications and cardiovascular protectionc
Flavones		Green leafy spices, for example, Parsley	Apigenin, Luteolin	Flavones can contribute to plant tissue colour, if they occur in high concentrations or are complexed with metal ions. Flavones participate in taste.
Flavonols		Nearly ubiquitous in foods, for example, quercetin. Main sources include yellow onion, curly kale and leek.	Kaempferol, Myricetin Quercetin	The most abundant flavonoid assumed with the diet is the flavonol quercetin
Isoflavonoids		Soybeans, soy foods and legumes	Daidzein, Genistein	lsoflavonoids are a distinct class of flavonoids with estrogenic activity. They are found almost exclusively in legumes, particularly soybeans. Isoflavonoid‐containing preparations are promoted for alleviating menopausal symptoms
Proanthocyanidins		The foods with the highest levels of total proanthocyanidins are, in decreasing order, ground cinnamon, sorghum (sumac bran), dry grape seed, unsweetened baking chocolate, raw pinto beans, sorghum (high‐tannin whole grain), choke berries, red kidney beans, hazelnuts and pecan nutsd	Pycnogenol proanthocyanidin A‐2 (in hawthorn berry)	Also named condensed tannins, represents the most abundant plant‐derived polyphenols. Proanthocyanidins are responsible for the astringent taste of fruits. Potential areas of medical interest include the prevention of cardiovascular and metabolic disorders.
Anthocyanidins		Red, purple and blue Berries (e.g. blackberry, strawberry, blueberry), aubergine, red wine	Cyanidin, Delphinidin, peonidin	Anthocyanins produce the blue and red coloration of berry fruits, cherries and plums, eggplant, red cabbage and radishes. Fruit anthocyanins content usually increases as the fruit matures

General information, including chemistry and occurrence, has been extracted from Peterson and Dwyer (1998); Samuelsson (1999); Beecher (2003); Manach et al. (2004); D'Archivio et al. (2007); Cui and Duke (2015);

^aFlavanols may exist both as monomer (catechins) and polymer (proanthocyanidins) form;

^bLin et al. (2016); Vlachojannis et al. (2016);

^cChanet et al. (2012);

^dDixon et al., 2005; Gu et al., 2004.