Flavonoid biosynthesis
From Wikipedia, the free encyclopedia
Flavonoids are synthesized by the phenylpropanoid metabolic pathway in which the amino acid phenylalanine is used to produce 4-coumaroyl-CoA.[1] This can be combined with malonyl-CoA to yield the true backbone of flavonoids, a group of compounds called chalcones, which contain two phenyl rings. Conjugate ring-closure of chalcones results in the familiar form of flavonoids, the three-ringed structure of a flavone. The metabolic pathway continues through a series of enzymatic modifications to yield flavanones → dihydroflavonols → anthocyanins. Along this pathway, many products can be formed, including the flavonols, flavan-3-ols, proanthocyanidins (tannins) and a host of other various polyphenolics.[2]
Flavanoids can possess chiral carbons. Methods of analysis should take this element into account[3] especially regarding bioactivity or enzyme stereospecificity.[4]
Enzymes
The biosynthesis of flavonoids involves several enzymes.
Backbone
- 4-Coumaroyl-CoA chalcone (naringenin chalcone)
- Naringenin chalcone flavanone (naringenin).
Path to cyanidin:
- flavanone 3'-hydroxyflavonoid (eriodictyol)
- eriodictyol dihydroflavonol (taxifolin)
- taxifolin leucocyanidin
- leucocyanidin cyanidin
Path to (–)-epicatechin:
- cyanidin (–)-epicatechin
Path to (+)-catechin:
Path to flavones:
Path to flavonols:
Path to 3-deoxyanthocyanidins:
- flavanone flavan-4-ol
- (Process analogous to taxifolin → cyanidin follows)