Flavones: What They Are, What They're Used For, and What Their Properties Are... (2024)

Flavones are flavonoids that maintain their skeleton but with a different molecular arrangement (isomerization). They have an unsaturated 3-C chain and a double bond between C-2 and C-3, similar to Flavonols and akin in the synthesis of chalcones, another type of flavonoid, but unlike the latter, flavones do not have a hydroxyl group at position 3.

What are flavones?

They are natural yellow pigments with potent antioxidant properties. They belong to the group of plant secondary metabolites with a chemical structure of 2-phenyl-1-benzopyran-4-one, which categorizes flavones as a subset of flavonoids.

Flavones are found in fruits, vegetables, and spices that can be taken as dietary supplements or as part of daily food intake. They possess medicinal properties and benefits, serving as a nutritional supplement to protect the body against free radicals and inflammation.

Plants containing flavones use them along with carotenoids and chlorophyll to perform various functions. One of these functions is to achieve a stronger and more vibrant coloration in aerial parts such as leaves and flowers and as a pesticide agent that plants use to repel potentially harmful insects. They have fungicidal effects (anti-fungal) and also promote root growth in plants.

But the interest and importance of flavones lie in their properties for humans.

Properties of flavones for human health

As we have indicated, this type of yellow pigment is naturally present in plants. Animals and humans must ingest them through food, as this is the key to obtaining all their benefits:

• Cardiovascular protectors.
• Neuroprotective.
• Anticancer.
• Anti-inflammatory.

There is evidence that the consumption of flavones may protect against cardiovascular and neuropathological diseases. Although the data from studies are based on experiments with neuron cultures in vitro, the results indicate that flavones have neuronal antioxidant properties, as demonstrated in models of Parkinson’s disease and focal cerebral ischemia. However, there are no studies that delve into groups of people with these pathologies, so it is unknown whether they could have the same benefits as other flavonoids such as isoflavones and anthocyanins.

Flavones and flavonoids

Flavonoids are a class of metabolites widely distributed in the plant kingdom. They have many properties in living organisms and can be classified into several subgroups such as anthocyanins, chalcones, Flavonols, flavandiols, aurones, and also flavones, which are flavonoids.
All this classification derives from the chemical structure of the flavonoid. Although there are 7 classified groups, when the molecular skeleton has modifications, Flavonols can also be classified into other subgroups. However, those mentioned in this section are the most important due to their nutraceutical interest, that is, their medicinal properties from natural ingredients («nutrition» and «pharmaceutical»).

Types of flavones

The Best Flavones

• Chrysin

• Apigenin

• Luteolin

• Naringenin

• Vitexin

• Baicalein

• Acacetin

• Lonicerina

• Velutina

Apigenin reduces inducible nitric oxide production (iNOS). Decreases prostaglandin.The properties of apigenin, a flavone, act by inhibiting nitric oxide synthase, reducing nitric oxide (NO) formation, prostaglandin, and COX-2. It inhibits phosphorylation of signal transducer and activator of transcription (STAT)-1, leading to reduced levels of interleukin (IL)-6 and tumor necrosis factor-alpha (TNF-α).

It has other interactions in metabolism, potentially providing anti-inflammatory effects, with its potential to reduce inflammatory diseases being evaluated. Plants with apigenin C-glucosides, isovitexin, and vitexin can contribute to inhibiting COX-2 mRNA expression. An example of this is the legume Mung bean, which has nutraceutical interest.

Luteolin is a very common flavone in edible plants and aromatic spices. Luteolin can be found in artichokes (Cynara scolymus), pomegranates (Punica granatum), and spices such as rosemary (Rosmarinus officinalis).The flavonoid Luteolin belongs to the subgroup of flavones. It has anti-inflammatory effects and works in the prevention of neurodegenerative diseases. Its mechanism of action inhibits chronic inflammation of macrophages and adipocytes.

Macrophages are cells responsible for digesting foreign particles in the body. They are part of the immune system and destroy germs, viruses, and bacteria that can cause infection in the human body.

Adipocytes are cells that form adipose or fatty tissue and store energy from nutrients, being very useful for maintaining the body’s vitality.

The importance of Luteolin in preventing inflammation in these types of cells is enormous. It prevents the deterioration of the immune system and allows, by defending the body against pathogens, the nutrients to be utilized normally.

The 6-C-glucoside of Luteolin inhibits thromboxane synthesis in platelet aggregation (blood clotting), and the flavones spinosin, vecenin-2, and isovitexin have anti-inflammatory effects.

On the other hand,velutinahas anti-inflammatory effects related to the inhibition of TNF-α and IL-6 in macrophages. It is capable of blocking IκB degradation and is thought to contribute to the blockade of MAPK p38 phosphorylation and induced cell apoptosis.

In addition,baicalein is a flavone present in medicinal plants such as Scutellaria baicalensis, Scutellaria, and Oroxylum indicum trees. Its scientific name is 5,6,7-trihydroxyflavone and also corresponds to the flavonoid genus. It is an aglycone or non-glycidic group of baicalin, being one of the most active flavones.
The properties of baicalein are modulators of GABA (gamma-aminobutyric acid) receptors, a neurotransmitter that functions in the neurons of the cerebral cortex. Baicalein can modify the nervous system response and neuronal communication, having effects such as anxiolytic and muscle relaxant.

Another function of baicalein is to function as an antagonist of estrogen receptors, also called antiestrogen, meaning it can have applications for inhibiting the growth of cancer cells.

It also stimulates cognitive function, benefiting memory and problems related to amnesia in cases of neurodegeneration.

Baicalin can be used in combination with catechin (flavan-3-ols or flavanols) as a drug for osteoarthritis. The commercial name of the patented product is Flavocoxid.

In the case of naringenin, it has properties to inhibit the clustering of abnormal glandular formations in the lining of the colon and rectum (crypt foci). It is a beneficial flavone for preventing colorectal polyps and cancer formation. Along with apigenin, naringenin increases apoptosis of luminal colon mucosal cells (induced cell death) in ranges from 78 to 97%, respectively.

Loniceraflavanone it is a flavone glucoside called Luteolin 7-neohesperidoside. The interest in this flavonoid lies in its anti-inflammatory and pain-relieving effects. Loniceraflavanone can be obtained from plants such as Veronicastrum, possessing anti-arthritic properties.

Foods Rich in Flavones and Medicinal Plants

Most purple-colored fruits and vegetables contain many flavones, although there are also other foods with flavones such as the following:

• Parsley.
• Celery.
• Mung bean (Vigna radiata).
• Acai Berry (Euterpe oleracea).
• Scutellaria baicalensis.
• Scutellaria lateriflora.
• Oroxylum indicum (Indian Trumpet Flower).
• Veronicastrum.
• Apples (Malus x domestica).
• Rice.
• Wheat.
• Thyme.
• Kale.
• French beans.
• Onions.
• Lettuce.
• Tomatoes.
• Apricot.
• Sweet pepper.

Other flavonoids have the ability to provide dark or violet color to plants, and although flavones also contribute to the tone of plant parts, they are primary pigments of cream and white-colored flowers.
However, with the addition of anthocyanins, flowers can achieve a blue color, protecting plants from solar radiation (UVB).

In the case of Acai, there are some anti-inflammatory results due to the content of flavones and other phytochemicals present in its composition. But as with other beneficial health effects, more samples and studies are needed to complement the current information, which, although promising about the properties of flavones in acai, are not sufficient.

Natural apigenin can be obtained from foods such as parsley, wheat sprouts, oranges, chamomile, and tea.

Excess of Flavones

The increase of flavones in the body can be excreted through urination. Metabolism processes and eliminates them along with other waste products contained in urine, similar to other polyphenols.

Contraindications

• Drugs with CYP (cytochrome P450) activity.
• Use of anti-inflammatories.
• Anxiolytics.
• Muscle relaxants.

Flavones have influence on the activity of cytochrome P450 enzymes, so it is recommended to monitor their intake as they could alter essential functions of the body.
There may be other interactions with medications and dietary supplements. The contraindications of flavones are still being studied due to their broad-spectrum effects.

When flavones are taken through food, there is no risk as long as the dosage is appropriate, although side effects may occur due to hypersensitivity to polyphenols and flavonoids.

Synthesis of Flavones

Flavones can be synthesized through several chemical methods, with the most commonly used being the following:

• Allan-Robinson reaction.
• Auwers synthesis.
• Baker-Venkataraman rearrangement.
• Algar – Flynn – Oyamada reaction.
• Dehydrating cyclization of 1,3-diaryl diketones.

References

• Flavones: Food Sources, Bioavailability, Metabolism, and Bioactivity, Gregory L Hostetler Robin A Ralston Steven J Schwartz. Advances in Nutrition, Volume 8, Issue 3, 1 May 2017, Pages 423–435, 05 May 2017.
• Hollman PCH. Absorption, bioavailability, and metabolism of flavonoids. Pharm Biol.
• Manach C, Scalbert A, Morand C, Remesy C, Jimenez L. Polyphenols: food sources and bioavailability. Am J Clin Nutr 2004; 79:727–47.
• Manach C, Williamson G, Morand C, Scalbert A, Remesy C. Bioavailability and bioefficacy of polyphenols in humans. I. Review of 97 bioavailability studies. Am J Clin Nutr 2005; 81:230S–242S.
• Williamson G, Manach C. Bioavailability and bioefficacy of polyphenols in humans. II. Review of 93 intervention studies. Am J Clin Nutr 2005; 81:243S–255S.
• Martens S, Mithöfer A. Flavones and flavone synthases. Phytochemistry 2005; 66:2399–407.
• Justesen U, Knuthsen P, Leth T. Quantitative analysis of flavonols, flavones, and flavanones in fruits, vegetables and beverages by high-performance liquid chromatography with photo-diode array and mass spectrometric detection. J Chromatogr A 1998; 799:101–10.
• Jennings A, Welch AA, Spector T, Macgregor A, Cassidy A. Intakes of anthocyanins and flavones are associated with biomarkers of insulin resistance and inflammation in women. J Nutr 2014; 144:202–8.