Flavonoid biosynthesis

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]

Flavonoid Biosynthesis Diagrams

Biosynthesis of catechin

A biochemical diagram showing the class of flavonoids and their source in nature through various inter-related plant species.

Flavanoids can possess chiral carbons. Methods of analysis should take this element into account[3] especially regarding bioactivity or enzyme stereospecificity.[4]

## Contents

* 1 Enzymes
* 1.1 Backbone
* 1.2 Methylation
* 1.3 Glycosylation
* 1.4 Further acetylations
* 2 References

## Enzymes

The biosynthesis of flavonoids involves several enzymes.

### Backbone

* 4-Coumaroyl-CoA Template:Underoverset chalcone (naringenin chalcone)
* Naringenin chalcone Template:Underoverset flavanone (naringenin).

Path to cyanidin:

* flavanone Template:Underoverset 3'-hydroxyflavonoid (eriodictyol)
* eriodictyol Template:Underoverset dihydroflavonol (taxifolin)
* taxifolin Template:Underoverset leucocyanidin
* leucocyanidin Template:Underoverset cyanidin

Path to (–)-epicatechin:

* cyanidin Template:Underoverset (–)-epicatechin

Path to (+)-catechin:

* leucocyanidin Template:Underoverset (+)-catechin

Path to flavones:

* Flavone synthase

Path to flavonols:

* dihydroflavonol Template:Underoverset flavonol

Path to 3-deoxyanthocyanidins:

* flavanone Template:Underoverset flavan-4-ol
* (Process analogous to taxifolin → cyanidin follows)

### Methylation

* Apigenin 4'-O-methyltransferase
* Luteolin O-methyltransferase
* Quercetin 3-O-methyltransferase

### Glycosylation

* Anthocyanidin 3-O-glucosyltransferase
* Flavone 7-O-beta-glucosyltransferase
* Flavone apiosyltransferase
* Flavonol-3-O-glucoside L-rhamnosyltransferase
* Flavonol 3-O-glucosyltransferase

### Further acetylations

* Isoflavone-7-O-beta-glucoside 6"-O-malonyltransferase

## References

1. ↑ Ververidis Filippos, F; Trantas Emmanouil; Douglas Carl; Vollmer Guenter; Kretzschmar Georg; Panopoulos Nickolas (October 2007). "Biotechnology of flavonoids and other phenylpropanoid-derived natural products. Part I: Chemical diversity, impacts on plant biology and human health". Biotechnology Journal 2 (10): 1214–34. doi:10.1002/biot.200700084. PMID 17935117.
2. ↑ Liu, Weixin; Feng, Yi; Yu, Suhang; Fan, Zhengqi; Li, Xinlei; Li, Jiyuan; Yin, Hengfu (2021). "The Flavonoid Biosynthesis Network in Plants". International Journal of Molecular Sciences 22 (23). doi:10.3390/ijms222312824. PMID 34884627.
3. ↑ Yáñez, Jaime A.; Andrews, Preston K.; Davies, Neal M. (April 2007). "Methods of analysis and separation of chiral flavonoids". Journal of Chromatography B 848 (2): 159–181. doi:10.1016/j.jchromb.2006.10.052. PMID 17113835. http://www.sciencedirect.com/science/article/pii/S1570023206008671.
4. ↑ Trouillas, Patrick; Fagnère, Catherine; Lazzaroni, Roberto; Calliste, Claude; Marfak, Abdelghafour; Duroux, Jean-Luc (December 2004). "A theoretical study of the conformational behavior and electronic structure of taxifolin correlated with the free radical-scavenging activity". Food Chemistry 88 (4): 571–582. doi:10.1016/j.foodchem.2004.02.009. http://www.sciencedirect.com/science/article/pii/S0308814604001608.

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Types of flavonoids

Flavonoids|

| Anthoxanthins|

| Flavones|

* Apigenin, Chrysin, et.c.

|

Flavonols|

* Quercetin, Kaempferol, et.c.

Isoflavones|

* Daidzein, Genistein, Orobol et.c.

Neoflavonoids|

* Dalbergichromene

Flavans|

| Flavan|

* Luteoliflavan

|

Flavan-3-ols
(flavanols)|

* Catechin, Gallocatechol, et.c.

Flavan-4-ols
(flavanols)|

* Apiforol, Luteoforol, et.c.

Flavan-3,4-diols|

* Leucocyanidin, Leucodelphinidin, et.c.

Flavanones|

* Hesperidin
* Naringenin
* Eriodictyol

Flavanonols|

* Taxifolin
* Aromadendrin, et.c.

Anthocyanidins|

| 3-deoxyanthocyanidins|

* Cyanidin, Delphinidin, et.c.

|

3-hydroxyanthocyanidin|

* Apigeninidin, Guibourtinidin, et.c.

Aurones|

* Aureusidin
* Leptosidin

Chalcones|

| Chalcones|

* Butein, Isoliquiritigenin, et.c.

|

Dihydrochalcone|

* Phloretin

Miscellaneous|

* List of phytochemicals in food
* C-methylated flavonoids
* O-methylated flavonoids
* Furanoflavonoids
* Pyranoflavonoids
* Prenylflavonoids
* Methylenedioxy
* Castavinols

Flavonoid biosynthesis

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