Bioactive Compounds, What is a Flavonoid?

Bioactive Compounds, What is a Flavonoid?

In the grouping of ‘Bioactive plant compounds’, polyphenols are one of the most important in terms of medicinal and health benefits. Polyphenols are also known as phenols because they are essentially lots of different clusters of the basic phenol rings.1 Based on difference in molecular structure (namely the number of phenol rings they have and the structural elements that bind these rings to each other) polyphenols can be divided into categories, which include a particularly helpful group of polyphenols called flavonoids.

Fabulous Flavonoids

Flavonoids are a large and diverse group of bioactive compounds, known as phytonutrients or phytochemicals that come under the banner of Polyphenols and can be categorised further into flavonols; flavones; isoflavones; flavanones; anthocyanins; and flavanols (catechins and proanthocyanidins). Within the flavanol subgroup there are further classifications. Each individual subgroup and each type of flavonoid has a unique and particular range of functions, health benefits and specific plant source.2 This particular group of plant bioactive compounds have been identified as possessing huge benefits to human health, best known for their antioxidant and anti-inflammatory health benefits. Flavonoids are present in practically every fruit and vegetable and are, in fact, the largest group of phytonutrients; there are more than 6,000 different identified types of flavonoid and they are the polyphenol most consumed in the human diet.

Chemical structure

Flavonoids are water-soluble and grow in cell vacuoles. Their basic molecular structure is two benzene rings bonded to a three carbon chain that forms a closed pyran ring.3

Sources of Flavonoids

Flavonoids are abundant in a whole range of fruits and vegetables. Great sources include berries, leeks, ginger, grapefruit, carrots, apples, onions, broccoli, cabbage, kale, tomatoes, lemons, parsley, buckwheat and legumes. Coffee, tea, chocolate, a range of spices, herbs and red wine are also bursting with health-giving flavonoids.

Bountiful Health Benefits

Countless studies have shown that a diet rich in phytonutrients is good for human health. Flavonoids have so much beneficial potential because they can act as a powerful antioxidant; able to neutralise free radicals, limiting damage to cells and other body tissue. Flavonoids can also possess anti-inflammatory and anti-aging capabilities.4 Research has also identified a link between these particular polyphenols and the prevention of diseases brought about by ‘oxidative stress’, for instance, cancer and cardiovascular and neurodegenerative diseases. Flavonoids have been studied for their ability to potentially improve the quality of blood vessel walls.5 Flavonoids are also valuable in terms of supporting the nervous system.6 In addition to this, it’s thought that flavonoids can regulate the activity of certain enzymes and cell receptors. Research has also shown that flavonoids could help to regulate blood flow in the brain, which could result in improved cognitive function.7 Flavonoids can be especially effective in combination with other phytonutrients and antioxidant vitamins and minerals, having a synergistic effect by increasing the overall antioxidant properties.8

Bioactivity and Bioavailability

Every plant possesses a unique biochemical structure. The levels of active ingredients present in individual plants can differ depending on various factors, such as where the plant is grown and the presence of fertilisers, for example. And the production of these complex bioactive compounds in plants is stimulated and sensitive to factors such as light, oxygen and heat, producing notable differences in bioactive concentration. These external factors affect the nutritional or medicinal properties of polyphenols, resulting in a higher flavonol content of one type of fruit, for example, compared to another. The antioxidant properties of flavonoids contained in certain types of fruit or plant will vary, for instance, depending on the season it’s harvested, how it’s processed and the specific variety.

Factors such as heat, light and oxygen can all bring about passive oxidation which can change the chemical compounds and alter the molecular nature of the polyphenols present in the plant. For example, when Green tea is subjected to oxidation most of the catechins present are converted into theaflavins and thearubigins, which is essentially how Green tea becomes Black tea. Other examples can be seen in the reduction in the flavonoid content of onions when stored at room temperature and the loss of flavonoids when food is heated, such as when vegetables are boiled. Flavonoids are often found mainly in the skins and outer layers of fruits and vegetables so damaged or cut fruit or vegetables will begin to lose their flavonoid content immediately, changing the potency and medicinal effect.9

The Flavonoid Subgroups


Flavonols are one of the more common types of flavonoid and can be found in broccoli, onions, brussel sprouts, kale, berries, apples, tea and beans. Quercetin and Kaempferol are particular types of flavonol found in lots of vegetables, fruits, leaves, and grains. Both are rich with anti-inflammatory goodness and regarded as particularly effective antioxidants, helping to reduce the risk of fatal disease.

Quercetin powder. Quercetin is a water soluble plant pigment classed as a bioflavonoid. Natural sources of Quercetin include green tea, onions, apples, berries, Ginkgo Biloba and buckwheat tea. Quercetin can be used as an ingredient in supplements, beverages, or foods. Quercetin has antihistamine properties and is used to treat hay fever and hives. It’s valued too for its anti-inflammatory action and ability to protect cells from damage. The benefit of taking this in powder form is that it is very versatile and can be used as a nutritious addition to a shake or food.

Ginkgo Biloba tablets. Ginkgo Biloba is a rich source of the flavonol Kaempferol. The active compounds of the Biloba seeds are called Ginkgolides and Bilobalides. These compounds provide a beneficial list of therapeutic actions, namely their effects on cognitive function. This ample source of kaempferol is thought to help maintain mental well being and memory function, while helping to protect against cognitive decline, typically associated with the ageing process. This benefit is brought about by contributing to normal circulation to the brain, and thus increasing brain performance and reactivity. In addition, Ginkgo Biloba has been linked with beneficial effects to the ears and eyes, particularly for the elderly generation. Ginkgo is rich in antioxidants, that scavenge potentially damaging free radicals, protect cellular integrity, reduce oxidation and ill health. Oxford Vitality’s Ginkgo Biloba comes in a manageable and easy to swallow 8mm tablet in a variety of six different sizes to suit your needs.10


Natural sources of flavones include fiery peppers, celery, various leaves, parsley and an assortment of other herbs. Flavones are praised for their general antioxidant properties and also have the effect of slowing down and delaying the metabolizing of drugs. Luteolin and Apigenin are examples of specific flavones. Luteolin is present in lots of different plants including fruits, vegetables, and medicinal herbs. Apigenin is present in several herbs including chamomile, lemon balm, vervain, yarrow, parsley, thyme, and peppermint. Other sources include red wine and tomato sauce.


These unique flavonoids are found in rich abundance in soybeans and soy products, and also various legumes. Specific isoflavones includes genistein, glycitein and daidzein. Isoflavones are classed as phytoestrogens, which means they are biocompounds with the same function as the hormone estrogen. Isoflavones have been identified as being capable of reducing the threat of cancers related to hormones, such as prostate cancer, breast cancer and endometrial cancer. This particular group of flavonoids are also believed to have positive benefits as a treatment for the symptoms menopause.11


Flavanones: Citrus fruits are a rich source of flavanones Types of flavanones include hesperetin, eriodictyol and naringenin. These special flavonoids are linked to cardiovascular health, thought to promote relaxation and cited for their powerful antioxidant and anti-inflammatory benefits.


Anthocyanins are a special and diverse type of flavonoid which help to keep our hearts healthy. Types of anthocyanins include malvidin, pelargonidin, peonidin and cyanidin. Good sources of anthocyanins include pomegranates, red, purple and blue berries; plums; red wine; and red and purple grapes. Anthocyanins are adept at stopping the oxidation of cholesterol, helping to prevent high blood pressure and generally beneficial for vascular health. They have amazing antioxidant value, preventing free radical damage, protecting the immune system and reputed to protect against a host of diseases. Anthocyanins are also thought to be particularly beneficial for promoting healthy skin and to the health of the eye by protecting the microvascular systems. Anthocyanins have also been cited as helpful in preventing the onset of diabetes.12 Anthocyanins are considered to have anti-inflammatory, antiviral, and anti-cancer properties and particularly effective for the treatment of colds and urinary tract infections.13 The powerful antioxidant properties of anthocyanins assist the body to burn more fat, increasing metabolism, meaning anthocyanins can work well in supporting weight loss, as part of a healthy balanced lifestyle.

Acai tablets,

Regarded as an exceptionally powerful antioxidant and possessing potential anti-inflammatory activities, the acai berry is a really helpful bioactive compound. The high levels of polyphenols, anthocyanins, flavonoids and carotenoids make the acai a significant antioxidant source. Studies have shown that the high content of anthocyanins plays an antiproliferative role on different cancer cells. Moreover, scientists observed that other berries rich in anthocyanins do not have similar inhibitory activity, demonstrating the unique benefits of acai consumption.14 This nicely highlights how the unique chemical makeup of each distinct type of flavonoid is correlative to the unique medicinal properties each type holds and what a complex and multifarious group of bioactive compounds flavonoids are.

Bilberry tablets. Goji Berry tablets and Grape seed tablets: Bilberry, Goji Berry, and Grape Seed extracts contain a fantastic amount of flavonoids; which fall into the category of anthocyanins. Try pairing acai with Green tea for extra antioxidative power; Studies have shown that some plants containing large quantities of phenolics and flavonoids, such as Acai and Bilberry, when combined with Green tea can synergistically enhance antioxidant activity.15

Flavanols (catechins and proanthocyanidins).

Flavanols: These can be split into three main types; catechins which are also known as monomers; dimers and polymers. Flavanols are present in grapes, berries, apples, teas, cocoa, fava beans and red wine. Dimers, which are linked to lowering cholesterol, are present in black tea. Catechins have been linked to some amazing health benefits such as relieving the symptoms of chronic fatigue syndrome. Catechins possess powerful antioxidant properties and have been linked with cardiovascular and neurological health.

Green tea Tablets.

Green tea is a wonderful natural source of Flavanols. It’s an effective antioxidant recognised for its anti-inflammatory, anti-thrombogenic and anti-hypertensive qualities. The flavanols contained in Green tea are catechins, of which EGCG is thought to be the most magical. As a health supplement, Green tea extract can provide many of the essential minerals and vitamins vital to optimum human health. Plant polyphenols often have high levels of astringency which can be felt as that dry mouth sensation and bitter taste. A bonus of the Green tea tablets is you get to ‘pass’ on this experience and cut straight to the chase of getting the goodness.16

Follow the Flavonoids

This hugely diverse group of bioactive compounds belonging specifically to plants has the potential to have such an amazing effect on so many aspects of human health; most notably their antioxidative properties, anti-inflammatory action; benefits to heart health and anti-cancer capabilities.

Including more fruits and vegetables in our diets generally is advisable, but taking a little more interest in what we’re getting nutritionally from the food we’re eating, so that we are providing our bodies with as many varieties of flavonoid and other phytonutrients as possible, is a brilliant way forward.

Polyherbal combinations of medicinal plants; and interaction between individual enzymes or active compounds; can act in a synergistic manner, providing an increased activity against a disease or maximise the beneficial health-giving properties. Supporting a varied, healthy diet with the right combination of dietary supplements, such as a selection which provide a range of different types of polyphenol, will help to ensure the bases are covered and we’re getting as many of our bioactive compounds as possible.

Good combinations are the flavonol rich Quercetin powder, paired with Grape seed tablets, which are full of flavonoids that fall into the subgroup anthocyanins. Try combining these with other polyphenol rich supplements, such as rosehip tablets or Astaxanthin tablets, which are packed with carotenoids. Carotenoids have rich antioxidant properties, especially when combined with other phytonutrients and antioxidant minerals and vitamins, increasing the bioavailability of the health-giving goodness they possess.


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