Flavones are a class of flavonoid

Flavonoid

Flavonoids , are a class of plant secondary metabolites....

s based on the backbone of 2-phenylchromen-4-one (2-phenyl-1-benzopyran

Benzopyran

Benzopyran is an polycyclic organic compound that results from the fusion of a benzene ring to a heterocyclic pyran ring. According to IUPAC nomenclature it is called chromene. There are two isomers of benzopyran depending on the orientation of the fusion of the two rings, resulting in 1-benzopyran...

-4-one) shown on the right.

Natural flavones include Apigenin

Apigenin

Apigenin is a flavone that is the aglycone of several glycosides. It is a yellow crystalline solid that has been used to dye wool. Apigenin may contribute to the chemopreventive action of vegetables and fruits...

 (4',5,7-trihydroxyflavone), Luteolin

Luteolin

Luteolin is a yellow crystalline compound. It is a flavonoid; to be specific, it is one of the more common flavones. From preliminary research, it is thought to play a role in the human body possibly as an antioxidant, a free radical scavenger, a promoter of carbohydrate metabolism, or an immune...

 (3',4',5,7-tetrahydroxyflavone) and Tangeritin

Tangeritin

Tangeritin is an O-polymethoxylated flavone that is found in tangerine and other citrus peels. Tangeritin strengthens the cell wall and protects it from invasion ....

 (4',5,6,7,8-pentamethoxyflavone), chrysin

Chrysin

Chrysin is a naturally occurring flavone chemically extracted from the blue passion flower . Honeycomb also contains small amounts. It is also reported in Oroxylum indicum or Indian trumpetflower.-Aromatase inhibition:...

(5,7-OH), 6-hydroxyflavone

6-Hydroxyflavone

6-Hydroxyflavone is a flavone, a type of chemical compound. It is one of the noncompetitive inhibitors of cytochrome P450 2C9. It is reported in leaves of Barleria prionitis Linn. ....

, baicalein

Baicalein

Baicalein is a flavone, a type of flavonoid, originally isolated from the roots of Scutellaria baicalensis. It is also reported in Oroxylum indicum or Indian trumpetflower...

 (5,6,7-trihydroxyflavone), scutellarein

Scutellarein

Scutellarein is chemical organic compound. It is a flavone that can be found in Scutellaria lateriflora.-Glycosides:The scutellarin is transformed by hydrolysis into scutellarein.-External links:*...

(5,6,7,4'-tetrahydroxyflavone), wogonin

Wogonin

Wogonin is an O-methylated flavone, a flavonoid-like chemical compound which was found in Scutellaria baicalensisThe glycosides of wogonin are known as wogonosides. For example, oroxindin is a wogonin glucuronide isolated from Oroxylum indicum...

 (5,7 -OH, 8 -OCH₃). Synthetic flavones are Diosmin

Diosmin

Diosmin is a semisynthetic phlebotropic drug , a member of the flavonoid family. It is an oral phlebotropic drug used in the treatment of venous disease, i.e., chronic venous insufficiency and hemorrhoidal disease , in acute or chronic hemorrhoids, in place of rubber-band ligation, in combination...

 and Flavoxate

Flavoxate

Flavoxate is an anticholinergic with antimuscarinic effects. Its muscle relaxant properties may be due to a direct action on the smooth muscle rather than by antagonizing muscarinic receptors.- Clinical uses :...

.

Intake and putative beneficial effects

Flavones are mainly found in cereals and herbs. In the West, the estimated daily intake of flavones is in the range 20–50 mg per day. In recent years, scientific and public interest in flavones has grown enormously due to their putative beneficial effects against atherosclerosis, osteoporosis, diabetes mellitus and certain cancers. Flavones intake in the form of dietary supplements and plant extracts has been steadily increasing.

Drug interactions

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

Organic chemistry

In organic chemistry

Organic chemistry

Organic chemistry is a subdiscipline within chemistry involving the scientific study of the structure, properties, composition, reactions, and preparation of carbon-based compounds, hydrocarbons, and their derivatives...

 several methods exist for the synthesis of flavones:

• the Allan-Robinson reaction
  Allan-Robinson reaction
  The Allan-Robinson reaction is the chemical reaction of o-hydroxyaryl ketones with aromatic anhydrides to form flavones .Note that if aliphatic anhydrides are used, coumarins can also be formed. -Mechanism:...
  
  
• the Auwers synthesis
  Auwers synthesis
  The Auwers synthesis is a series of organic reactions forming a flavonol from a coumarone. This reaction was first reported by Karl von Auwers in 1908....
  
  
• the Baker-Venkataraman rearrangement
  Baker-Venkataraman rearrangement
  The Baker–Venkataraman rearrangement is the chemical reaction of 2-acetoxyacetophenones with base to form 1,3-diketones.This rearrangement reaction proceeds via enolate formation followed by acyl transfer...
  
  
• the Algar-Flynn-Oyamada reaction
  Algar-Flynn-Oyamada reaction
  The Algar–Flynn–Oyamada reaction is a chemical reaction whereby a chalcone undergoes an oxidative cyclization to form a flavonol.-Reaction mechanism:...
  
  

Another method is the dehydrative cyclization of certain 1,3-diaryl diketones
this particular study making use of an ionic liquid

Ionic liquid

An ionic liquid is a salt in the liquid state. In some contexts, the term has been restricted to salts whose melting point is below some arbitrary temperature, such as . While ordinary liquids such as water and gasoline are predominantly made of electrically neutral molecules, ILs are largely made...

 solvent and microwave irradiation

Microwave chemistry

Microwave chemistry is the science of applying microwave irradiation to chemical reactions. Microwaves act as high frequency electric fields and will generally heat any material containing mobile electric charges, such as polar molecules in a solvent or conducting ions in a solid...

.

Wessely-Moser rearrangement

The Wessely-Moser rearrangement (1930) 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

Methoxy

In chemistry , methoxy refers to the functional group consisting of a methyl group bound to oxygen. This alkoxy group has the formula O–CH3.The word is used in organic nomenclature usually to describe an ether...

 groups to phenol

Phenol

Phenol, also known as carbolic acid, phenic acid, is an organic compound with the chemical formula C6H5OH. It is a white crystalline solid. The molecule consists of a phenyl , bonded to a hydroxyl group. It is produced on a large scale as a precursor to many materials and useful compounds...

 groups. It also has synthetic potential for example:

This rearrangement reaction

Rearrangement reaction

A rearrangement reaction is a broad class of organic reactions where the carbon skeleton of a molecule is rearranged to give a structural isomer of the original molecule. Often a substituent moves from one atom to another atom in the same molecule...

 takes place in several steps: A ring opening to the diketone

Diketone

A diketone is a molecule containing two ketone groups. The simpliest diketone is diacetyl, also known as 2,3-butanedione. Diacetyl, acetylacetone, and hexane-2,5-dione are examples of 1,2-, 1,3-, and 1,4-diketones, respectively...

, B bond rotation with formation of a favorable acetylacetone

Acetylacetone

Acetylacetone is an organic compound that famously exists in two tautomeric forms that rapidly interconvert. The less stable tautomer is a diketone formally named pentane-2,4-dione. The more common tautomer is the enol form. The pair of tautomers rapidly interconvert and are treated as a single...

-like phenyl-ketone interaction and C hydrolysis of two methoxy groups and ring closure.