Flavones

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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]

Molecular structure of the flavone backbone with numbers

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 eliminationEdit

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 interactionsEdit

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

BiosynthesisEdit

 
Synthesis of apigenin to depict general flavone 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 chemistryEdit

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 rearrangementEdit

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 flavonesEdit

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
Oroxylon –OH –OCH3 –OH
Negletein –OH –OH –OCH3
Norwogonin –OH –OH –OH
Wogonin –OH –OH –OCH3
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'

ResearchEdit

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.[15]

ReferencesEdit

  1. ^ a b c d e "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.
  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.[1]
  6. ^ a b c Ferrer JL, Austin MB (2008). "Structure and function of enzymes involved in the biosynthesis of phenylpropanoids". Plant Physiol. Biochem. 46: 356–370. doi:10.1016/j.plaphy.2007.12.009.
  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: 755–763. doi:10.1104/pp.113.3.755.
  8. ^ Ferrer JL, Jez JM (1999). "Structure of chalcone synthase and the molecular basis of plant polyketide biosynthesis". Nat. Struct. Biol. 6: 775–784. doi:10.1038/11553.
  9. ^ Jez JM, Bowman ME (2000). "Structure and mechanism of the evolutionarily unique plany enzyme chalcone isomerase". Nat. Struct. Biol. 7: 786–791. doi:10.1038/79025.
  10. ^ Martens S, Mithofer A (2005). "Flavones and flavone synthases". Phytochemistry. 66: 2399–2407. doi:10.1016/j.phytochem.2005.07.013.
  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.
  12. ^ Wessely F, Moser GH (December 1930). "Synthese und Konstitution des Skutellareins". Monatshefte für Chemie. 56 (1): 97–105. doi:10.1007/BF02716040.
  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". 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.
  15. ^ 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.

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