Flavonoids: Classification, Chemistry and Examples
Introduction to Flavonoids
Flavonoids are group of plant polyphenolic secondary metabolites showing common three ring structure.
Flavonoid is named from the latin word flavus meaning yellow which is their colour in nature.
The flavonoids have aroused considerable interest recently because of their potential effect on human health as well as their
role in plant metabolism.
Medicinal Properties of Flavonoids
Flavonoids have been reported to have:
antiviral
antitumor
antiallergic
anti-platelet
anti-inflammatory and
antioxidant and so many other
activities.
Classifcation and Chemistry of Flavonoids
Flavonoids are majorly classified into six, depending on the Carbon of the C ring on which B ring is attached, and the degree of unsaturation and oxidation of the C ring. Classification of Flavonoids
If B ring is linked in position 3 of the C ring, it is an Isoflavone. B ring attached at position 2 of C ring, it is a flavones, flavanone, flavonol, flavanol or anthocyanidin. B ring attached at position 4 of C ring, it is a Neoflavonoid.
Flavonoids basic structure is a skeleton of diphenylpropane, namely, two benzene rings (ring A and B, see figure) linked by a three carbon chain that forms a closed pyran ring (heterocyclic ring containing oxygen,the C ring) with benzenic A ring.
Therefore, their structure is also referred to as C6-C3-C6. In most cases, B ring is attached to position 2 of C ring, but it can also bind in position 3 or 4; this, together with the structural features of the ring B and the patterns of glycosylation and hydroxylation of the three rings, makes the flavonoids one of the larger and more diversified groups of phytochemicals. Flavonoids Structure
