Flavone glycosides sugar moieties

Flavonoids occur in a variety of structural forms. They are phenolic compounds with a basic C6-C3-C6 skeleton. The two phenyl rings may be linked by an open three carbon chain (chalcones), or by the three carbon chain formed into a five-membered (aurones) or the more usual six-membered heterocyclic ring (flavones and flavonols) (Fig. 2 and 3). Conveniently, the 3000 different flavonoids are divided into some 12 classes according to the oxidation level of the central Cs-unit. Most flavonoids occur in vivo as glycosides that may have an aliphatic or aromatic acyl substituent on the sugar moieties. Other flavonoids are conjugated with sulphate groups, and some flavonoids occur as dimers, trimers, and polymers. 

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