Fig. 1

The structures of the main classes of flavonoids. The major differences between the individual groups reside in the hydroxylation pattern of the ring-structure, the degree of saturation of the C-ring and the substitution of in the 3-position: a general structure of flavonoids, b structure of flavonols and flavones, c structure of flavanols, also referred as flavan-3-ols, d structure of anthocyanidins, e structure of flavanones and flavanonols and f structure of isoflavones