Table 1.

Structure of the main flavonoid compounds. Based on their structural differences, flavonoids can be divided into flavones, flavonols, flavanones, isoflavonoids, flavanols, and anthocyanins. Flavonoids whose epigenetic action is detailed in the text are in bold.

	Chemical Structure	Bonds	Compounds
FLAVONES		Double bond between C2-C3 and a ketone in C4 of the C ring.	Apigenin Luteolin Morin Tricin
FLAVONOLS		Hydroxylic group, a double bond between C2-C3 and a ketone in C ring.	Quercetin Myrecitin Fisetin Kaempferol
FLAVANONES		Lack the double bond between C2-C3 in C ring; only hydroxyl and methoxy groups as substituents.	Silibinin Naringenin Hesperdin
ISOFLAVONOIDS		Large diversity of structure in the C ring. The B ring is attached at C3 rather C2 of the C ring.	Genistein DaidzeinGlycitein
FLAVANOLS OR CATECHINS		No double bond of C2-C3 in the hydroxyl group in position 3.	EGCG Epicatechin Epicatechin-3-gallate
ANTHOCYANINS		Flavylium cation binding hydroxyl groups and/or methoxy group(s) in R₁, R₂, and R₃ position.	Delphinidin Cyanidin PeonidinN