Flavones

Flavones (from Latin flavus "yellow") are a class of flavonoids based on the backbone of 2-phenylchromen-4-one (2-phenyl-1-benzopyran-4-one) (as shown in the first image of this article).[1][2]

Flavones are common in foods, mainly from spices, and some yellow or orange fruits and vegetables.[1] Common flavones include apigenin (4',5,7-trihydroxyflavone), luteolin (3',4',5,7-tetrahydroxyflavone), tangeritin (4',5,6,7,8-pentamethoxyflavone), chrysin (5,7-dihydroxyflavone), and 6-hydroxyflavone.[1]

Intake and elimination

The estimated daily intake of flavones is about 2 mg per day.[1] Following ingestion and metabolism, flavones, other polyphenols, and their metabolites are absorbed poorly in body organs and are rapidly excreted in the urine, indicating mechanisms influencing their presumed absence of metabolic roles in the body.[1][3]

Drug interactions

Flavones have effects on CYP (P450) activity,[4][5] which are enzymes that metabolize most drugs in the body.

Biosynthesis

The biosynthesis of flavones proceeds from the phenylpropanoid pathway, which uses L-phenylalanine as a starting point.[6] Phenylalanine ammonia lyase facilitates the deamination of L-phenylalanine to (E)-cinnamate,[6] which is then oxidized by cinnamate 4-hydroxylase to yield p-Coumaric acid.[7] Coenzyme A is attached to the carboxylate facilitated by 4-Coumarate-CoA ligase, forming (Coumaroyl-CoA).[6] A chalcone synthase then facilitates a series of condensation reactions in the presence of 3 malonyl CoA ending with a ring-forming Claisen condensation yielding a chalcone (naringenin chalcone is shown), [8] which is subsequently isomerized by chalcone isomerase resulting in a flavanone (naringenin is shown).[9] It is at this point that the flavanone can undergo further modifications (such as glycosylation or methylation at the various points of the backbone. The subsequent modified flavanones are then transformed into flavones by flavone synthase, which generates a double bond between the C-2 and C-3 positions (the synthesis of apigenin is shown).[10]

Organic chemistry

In organic chemistry several methods exist for the synthesis of flavones:

Another method is the dehydrative cyclization of certain 1,3-diaryl diketones.[11]

Wessely–Moser rearrangement

The Wessely–Moser rearrangement (1930)[12] has been an important tool in structure elucidation of flavonoids. It involves the conversion of 5,7,8-trimethoxyflavone into 5,6,7-trihydroxyflavone on hydrolysis of the methoxy groups to phenol groups. It also has synthetic potential for example:[13]

This rearrangement reaction takes place in several steps: A ring opening to the diketone, B bond rotation with formation of a favorable acetylacetone-like phenyl-ketone interaction and C hydrolysis of two methoxy groups and ring closure.

Common flavones
Flavones and their structure [14]
Name Structure R3 R5 R6 R7 R8 R2' R3' R4' R5' R6'
Flavone backbone – – – – – – – – – –
Primuletin – –OH – – – – – – – –
Chrysin – –OH – –OH – – – – – –
Tectochrysin – –OH – –OCH3 – – – – – –
Primetin – –OH – – –OH – – – – –
Apigenin – –OH – –OH – – – –OH – –
Acacetin – –OH – –OH – – – –OCH3 – –
Genkwanin – –OH – –OCH3 – – – –OH – –
Echioidinin – –OH – –OCH3 – –OH – – – –
Baicalein – –OH –OH –OH – – – – – –
Oroxylin A – –OH –OCH3 –OH – – – – – –
Negletein – –OH –OH –OCH3 – – – – – –
Norwogonin – –OH – –OH –OH – – – – –
Wogonin – –OH – –OH –OCH3 – – – – –
Liquiritigenin[15] – – – –OH – – – –OH – –
Naringenin[15] – –OH – –OH – – – –OH – –
Geraldone – – – –OH – – –OCH3 –OH – –
Tithonine – – – –OCH3 – – –OH –OCH3 – –
Luteolin – –OH – –OH – – –OH –OH – –
6-Hydroxyluteolin – –OH –OH –OH – – –OH –OH – –
Chrysoeriol – –OH – –OH – – –OCH3 –OH – –
Diosmetin – –OH – –OH – – –OH –OCH3 – –
Pilloin – –OH – –OCH3 – – –OH –OCH3 – –
Velutin – –OH – –OCH3 – – –OCH3 –OH – –
Norartocarpetin – –OH – –OH – –OH – –OH – –
Artocarpetin – –OH – –OCH3 – –OH – –OH – –
Scutellarein – –OH –OH –OH – – – –OH – –
Hispidulin – –OH –OCH3 –OH – – – –OH – –
Sorbifolin – –OH –OH –OCH3 – – – –OH – –
Pectolinarigenin – –OH –OCH3 –OH – – – –OCH3 – –
Cirsimaritin – –OH –OCH3 –OCH3 – – – –OH – –
Mikanin – –OH –OCH3 –OCH3 – – – –OCH3 – –
Isoscutellarein – –OH – –OH –OH – – –OH – –
Zapotinin – –OH –OCH3 – – –OCH3 – – – –OCH3
Zapotin – –OCH3 –OCH3 – – –OCH3 – – – –OCH3
Cerrosillin – –OCH3 –OCH3 – – – –OCH3 – –OCH3 –
Alnetin – –OH –OCH3 –OCH3 –OCH3 – – – – –
Tricetin – –OH – –OH – – –OH –OH –OH –
Tricin – –OH – –OH – – –OCH3 –OH –OCH3 –
Corymbosin – –OH – –OCH3 – – –OCH3 –OCH3 –OCH3 –
Nepetin – –OH –OCH3 –OH – – –OH –OH – –
Pedalitin – –OH –OH –OCH3 – – –OH –OH – –
Nodifloretin – –OH –OH –OH – – –OCH3 –OH – –
Jaceosidin – –OH –OCH3 –OH – – –OCH3 –OH – –
Cirsiliol – –OH –OCH3 –OCH3 – – –OH –OH – –
Eupatilin – –OH –OCH3 –OH – – –OCH3 –OCH3 – –
Cirsilineol – –OH –OCH3 –OCH3 – – –OCH3 –OH – –
Eupatorin – –OH –OCH3 –OCH3 – – – –OCH3 –OH –
Sinensetin – –OCH3 –OCH3 –OCH3 – – – –OCH3 –OCH3 –
Hypolaetin – –OH – –OH –OH – –OH –OH – –
Onopordin – –OH – –OH –OCH3 – –OH –OH – –
Wightin – –OH – –OCH3 –OCH3 –OCH3 –OH – – –
Nevadensin – –OH –OCH3 –OH –OCH3 – – –OCH3 – –
Xanthomicrol – –OH –OCH3 –OCH3 –OCH3 – – –OH – –
Tangeretin – –OCH3 –OCH3 –OCH3 –OCH3 – – –OCH3 – –
Serpyllin – –OH – –OCH3 –OCH3 –OCH3 –OCH3 –OCH3 – –
Sudachitin – –OH –OCH3 –OH –OCH3 – –OCH3 –OH – –
Acerosin – –OH –OCH3 –OH –OCH3 – –OH –OCH3 – –
Hymenoxin – –OH –OCH3 –OH –OCH3 – –OCH3 –OCH3 – –
Gardenin D – –OH –OCH3 –OCH3 –OCH3 – –OH –OCH3 – –
Nobiletin – – –OCH3 –OCH3 –OCH3 –OCH3 – –OCH3 –OCH3 – –
Scaposin – – –OH –OCH3 –OH –OCH3 – –OCH3 –OCH3 –OH
Name Structure R3 R5 R6 R7 R8 R2' R3' R4' R5' R6'

Research

In one preliminary 2021 study, flavone intake was associated with lower odds of subjective cognitive decline after adjustment for age, total energy intake, major nondietary factors, and specific dietary factors.[16]

References
  1. "Flavonoids". Micronutrient Information Center, Linus Pauling Institute, Oregon State University, Corvallis, OR. November 2015. Retrieved 30 March 2018.
  2. "Flavone". ChemSpider, Royal Society of Chemistry. 2015. Retrieved 30 March 2018.
  3. David Stauth (5 March 2007). "Studies force new view on biology of flavonoids". EurekAlert!; Adapted from a news release issued by Oregon State University.
  4. Cermak R, Wolffram S (Oct 2006). "The potential of flavonoids to influence drug metabolism and pharmacokinetics by local gastrointestinal mechanisms". Curr Drug Metab. 7 (7): 729–744. doi:10.2174/138920006778520570. PMID 17073577.
  5. Si D, Wang Y, Zhou YH, et al. (March 2009). "Mechanism of CYP2C9 inhibition by flavones and flavonols". Drug Metab. Dispos. 37 (3): 629–34. doi:10.1124/dmd.108.023416. PMID 19074529. S2CID 285706. Archived 2008-12-17 at the Wayback Machine
  6. Ferrer JL, Austin MB (2008). "Structure and function of enzymes involved in the biosynthesis of phenylpropanoids". Plant Physiol. Biochem. 46 (3): 356–370. doi:10.1016/j.plaphy.2007.12.009. PMC 2860624. PMID 18272377.
  7. Mizutani M, Ohta D, Sato R (1997). "Isolation of a cDNA and a genomic clone encoding cinnamate 4-hydroxylase from Arabidopsis and its expression manner in plants". Plant Physiology. 113 (3): 755–763. doi:10.1104/pp.113.3.755. PMC 158193. PMID 9085571. S2CID 10059931.
  8. Ferrer JL, Jez JM (1999). "Structure of chalcone synthase and the molecular basis of plant polyketide biosynthesis". Nat. Struct. Biol. 6 (8): 775–784. doi:10.1038/11553. PMID 10426957. S2CID 23408591.
  9. Jez JM, Bowman ME (2000). "Structure and mechanism of the evolutionarily unique plany enzyme chalcone isomerase". Nat. Struct. Biol. 7 (9): 786–791. doi:10.1038/79025. PMID 10966651. S2CID 22198011.
  10. Martens S, Mithofer A (2005). "Flavones and flavone synthases". Phytochemistry. 66 (20): 2399–2407. doi:10.1016/j.phytochem.2005.07.013. PMID 16137727.
  11. Sarda SR, Pathan MY, Paike VV, Pachmase PR, Jadhav WN, Pawar RP (2006). "A facile synthesis of flavones using recyclable ionic liquid under microwave irradiation". Arkivoc. xvi (16): 43–8. doi:10.3998/ark.5550190.0007.g05. hdl:2027/spo.5550190.0007.g05.
  12. Wessely F, Moser GH (December 1930). "Synthese und Konstitution des Skutellareins". Monatshefte für Chemie. 56 (1): 97–105. doi:10.1007/BF02716040. S2CID 95833443.
  13. Larget R, Lockhart B, Renard P, Largeron M (April 2000). "A convenient extension of the Wessely-Moser rearrangement for the synthesis of substituted alkylaminoflavones as neuroprotective agents in vitro" (PDF). Bioorg. Med. Chem. Lett. 10 (8): 835–8. doi:10.1016/S0960-894X(00)00110-4. PMID 10782697.
  14. Harborne, Jeffrey B.; Marby, Helga; Marby, T. J. (1975). The Flavonoids - Springer. doi:10.1007/978-1-4899-2909-9. ISBN 978-0-12-324602-8. S2CID 33487001.
  15. Dewick, Paul M. (2009). "The Shikimate Pathway: Aromatic Amino Acids and Phenylpropanoids". Medicinal Natural Products. A Biosynthetic Approach. Chichester, UK: John Wiley & Sons. pp. 137–186. doi:10.1002/9780470742761.ch4. ISBN 978-0-470-74276-1.
  16. Yeh, Tian-Shin; Yuan, Changzheng; Ascherio, Alberto; Rosner, Bernard A.; Willett, Walter C.; Blacker, Deborah (2021-09-07). "Long-term Dietary Flavonoid Intake and Subjective Cognitive Decline in US Men and Women". Neurology. 97 (10): e1041–e1056. doi:10.1212/WNL.0000000000012454. ISSN 0028-3878. PMC 8448553. PMID 34321362.
  • Flavones at the U.S. National Library of Medicine Medical Subject Headings (MeSH)
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