O-methylated flavonoid explained

The O-methylated flavonoids or methoxyflavonoids are flavonoids with methylations on hydroxyl groups (methoxy bonds). O-methylation has an effect on the solubility of flavonoids.

Enzymes

O-methylated flavonoids formation implies the presence of specific O-methyltransferase (OMT) enzymes which accept a variety of substrates.^[1] Those enzymes mediate the O-methylation on a specific hydroxyl group, like on 4' (example in Catharanthus roseus^[2]) or 3' (example in rice^[3]) positions. Those positions can be ortho, meta, para and there can be a special 3-O-methyltransferase for the 3-OH position. Calamondin orange (Citrus mitis) exhibits all of those activities.^[4]

Plant enzymes

• Apigenin 4'-O-methyltransferase
• 8-hydroxyquercetin 8-O-methyltransferase
• Isoflavone 4'-O-methyltransferase
• Isoflavone 7-O-methyltransferase
• Isoliquiritigenin 2'-O-methyltransferase
• Isoorientin 3'-O-methyltransferase
• Kaempferol 4'-O-methyltransferase
• Luteolin O-methyltransferase
• Methylquercetagetin 6-O-methyltransferase
• 3-methylquercetin 7-O-methyltransferase
• Myricetin O-methyltransferase
• Quercetin 3-O-methyltransferase
• Vitexin 2"-O-rhamnoside 7-O-methyltransferase

Animal enzyme

• Catechol-O-methyl transferase

O-methylated anthocyanidins

• 5-Desoxy-malvidin
• Capensinidin
• Europinidin
• Hirsutidin
• Malvidin
• Peonidin
• Petunidin
• Pulchellidin
• Rosinidin
• ^[5]

O-methylated flavanols

• Meciadanol (3-O'methyl catechin)

O-methylated flavanones

• Hesperetin
• Homoeriodictyol
• Isosakuranetin
• Sakuranetin
• Sterubin

O-methylated flavanonols

• Dihydrokaempferide

O-methylated flavonols

of kaempferol

• Kaempferide

of myricetin

• Annulatin
• Combretol
• Europetin
• Laricitrin (3'-O-Dimethylmyricetin)
• 5-O-methylmyricetin
• Syringetin (3',5'-O-Dimethylmyricetin)

of quercetin

• Ayanin
• Azaleatin
• Isorhamnetin
• Ombuin
• Pachypodol
• Retusin (quercetin-3,7,3',4'-tetramethyl ether)
• Rhamnazin
• Rhamnetin

other

• Eupatolitin
• Natsudaidain

O-methylated flavones

• Acacetin
• Chrysoeriol
• Diosmetin
• Nepetin
• Nobiletin
• Oroxylin-A
• Sinensetin
• Tangeritin
• Thevetiaflavone
• Wogonin

O-methylated isoflavones

• Biochanin A
• Calycosin
• Formononetin
• Glycitein
• Irigenin
• 5-O-methylgenistein
• Pratensein
• Prunetin
• Psi-tectorigenin
• Retusin
• Tectorigenin

See also

• C-methylated flavonoid

Notes and References

1. 10.1016/j.jbiotec.2005.04.004 . Regiospecific methylation of naringenin to ponciretin by soybean O-methyltransferase expressed in Escherichia coli . 2005 . Kim . Dae Hwan . Kim . Bong-Gyu . Lee . Youngshim . Ryu . Ji Young . Lim . Yoongho . Hur . Hor-Gil . Ahn . Joong-Hoon . Journal of Biotechnology . 119 . 2 . 155–62 . 15961179.
2. 10.1016/j.phytochem.2004.02.010 . Flavonoid methylation: a novel 4′-O-methyltransferase from Catharanthus roseus, and evidence that partially methylated flavanones are substrates of four different flavonoid dioxygenases . 2004 . Schroder . G . Phytochemistry . 65 . 8 . 1085–94 . 15110688 . Wehinger . E . Lukacin . R . Wellmann . F . Seefelder . W . Schwab . W . Schröder . J.
3. 10.1016/j.phytochem.2005.11.022 . Flavonoid 3′-O-methyltransferase from rice: CDNA cloning, characterization and functional expression . 2006 . Kim . Bong-Gyu . Lee . Youngshim . Hur . Hor-Gil . Lim . Yoongho . Ahn . Joong-Hoon . Phytochemistry . 67 . 4 . 387–94 . 16412485.
4. 10.1016/0031-9422(80)85102-8 . O-methylation of flavonoids by cell-free extracts of calamondin orange . 1980 . Brunet . Gunter . Ibrahim . Ragai K. . Phytochemistry . 19 . 5 . 741–6.
5. 10.1016/S0031-9422(00)82884-8 . Comparative biochemistry of the flavonoids-IV.: Correlations between chemistry, pollen morphology and systematics in the family plumbaginaceae . 1967 . Harborne . J.B. . Phytochemistry . 6 . 10 . 1415–28.