Flavonoid biosynthesis explained

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.

Flavanoids can possess chiral carbons. Methods of analysis should take this element into account^[2] especially regarding bioactivity or enzyme stereospecificity.^[3]

Enzymes

The biosynthesis of flavonoids involves several enzymes.

• Anthocyanidin reductase
• Chalcone isomerase
• Dihydrokaempferol 4-reductase
• Flavone synthase
• Flavonoid 3'-monooxygenase
• Flavonol synthase
• Flavanone 3-dioxygenase
• Flavanone 4-reductase
• Leucoanthocyanidin reductase
• Leucocyanidin oxygenase
• Naringenin-chalcone synthase

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

Notes and References

1. Ververidis Filippos . 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. 10.1002/biot.200700084 . 17935117 . F .
2. https://archive.today/20120910232611/http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6X0P-4MCW9YC-3&_user=10&_coverDate=04/01/2007&_rdoc=1&_fmt=high&_orig=search&_sort=d&_docanchor=&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=a954cf0e4deadf9ba44c9ec0ec188b45 Methods of analysis and separation of chiral flavonoids. Jaime A. Yáñeza, Preston K. Andrewsb and Neal M. Journal of Chromatography B, Volume 848, Issue 2, 1 April 2007, Pages 159-181
3. https://archive.today/20120915044007/http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6T6R-4C47NMR-9&_user=10&_coverDate=12/31/2004&_rdoc=1&_fmt=high&_orig=search&_sort=d&_docanchor=&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=dcbc57e4c27eb0c8e9052a4e2e090dab A theoretical study of the conformational behavior and electronic structure of taxifolin correlated with the free radical-scavenging activity. Patrick Trouillas, Catherine Fagnère, Roberto Lazzaroni, Claude Calliste, Abdelghafour Marfak and Jean-Luc Duroux, Food Chemistry, Volume 88, Issue 4, December 2004, Pages 571-582