Plants produce many chemicals for various processes to help them survive and thrive. These can be aromatic compounds and pigments to create smells and colours to attract pollinators, antimicrobials to avoid invasions and various other reasons. Some are so potent they can be toxic if ingested but the majority are harmless and can have a very beneficial affect on the human body when consumed.
The benzopyrones are a group of compounds produced by many plants and whose members include coumarins and flavonoids. The terms 'flavonoids' and 'bioflavonoids' are used interchangeably and randomly but are actually the same.
They consist of water-soluble, crystalline
polyphenolic compounds and over 4000 have been discovered so far.
Flavonoids are the plant pigments found in many fruits and flowers. The common colours for these pigments are blue, purple, red and yellow and they are found in the cytoplasm and plastids of flowering plants. As opposed to other pigments such as betalains, chlorophylls or carotenoids, certain flavonoids play a role in fruit ripening and capturing certain variants of light within the UV spectrum.
In 1930, a new substance was isolated from oranges. At that time, it was believed to be a member of a new class of vitamins and was designated as vitamin P. Later on, it became clear that this substance was a flavonoid and it was named rutin, a flavone which is one of the subcategories of flavonoids.
All these compounds have ketone groups, which are oxygen atoms double-bonded (indicated by an O connected by two lines) to a carbon that is not at the end of a chain, and somewhere in the middle of the structure. If a molecule loses its ketone group, its name gets an A in place of an O. For example, flavonoid turns into flavanoid, and flavonol turns into flavanol. Hence the confusion over which is what and why!
If a flavonoid has a 5-carbon ring in the centre rather than the typical 6-carbon ring structure, it is known as an aurone.
Flavonoids are subdivided into different subgroups depending on the carbon of the C ring, on which the B ring is attached, and the degree of unsaturation and oxidation of the C ring.
Flavonoids all share one of three similar structural backbones and are broken down into:
Each of these categories are then broken down further.
Flavonoids with an open C ring are called chalcones.
Flavonoids in which B ring is linked in position 3 of the ring C are called isoflavones.
Flavonoids in which B ring is linked in position 4 are called neoflavonoids
Flavonoids in which the B ring is linked in position 2 can be further subdivided into several subgroups on the basis of the structural features of the C ring. These subgroups are called:
Flavanols (aka catechins)
Anthocyanidins with one or more sugar moieties (anthocyanidin glycosides) are called anthocyanins.
Proanthocyanidin oligomers formed from (+)-catechin and (-)-epicatechin subunits are called procyanidins.
Many of these flavonoid molecules, particularly the anthoxanthins, are the pigments that give some flower petals a yellow colour, while anthocyanins are often responsible for the red colour of buds and the purple-red colour of autumn leaves. Anthoxanthins are the flavonoids which are made up of flavones, flavonols and flavonones.
Lignans (resorcyclic acid lactones) are closely related to flavonoids and have similar properties.
Silymarin is a special type of flavonoid classified as a flavonolignan, part flavonoid and part lignan. Silymarin is made up of dihydrosilybin, isosilybin, silibinin, silychristin and silydianin and are found in plants from the thistle family such as globe artichokes and milk thistle. These flavonoids are particularly useful for healing and protecting the liver, treating diabetes and reducing the risk of prostate cancer. Silibinin, also inhibits proliferation and promotes cell-cycle arrest of human colon cancer.
Natural sources of chalcones in alphabetical order
Citrus fruit (skins)
Medicinal properties of chalcones
Chalcones are often responsible for the yellow pigment of many types of flowers such as daisies and sunflowers. They are a class of flavonoid compounds which are potent antioxidants, protecting cells from free radical damage, which is associated with accelerating the ageing process and with many disorders, including cancer, as well as degenerative diseases. They also suppress the excessive secretion of gastric juice in the stomach, which is often caused by stress and can lead to stomach ulcers.
In addition they help strengthen the immune system, regulate blood pressure and cholesterol and exhibit anti-viral and antibacterial activities. Chalcones have also been found to stimulate the production of Nerve Growth Factor (NGF), which is synthesised in minute amounts in the body and is essential in the development and survival of certain neurons (nerve cells) in the peripheral and central nervous system. NGF is believed to have the potential to alleviate Alzheimer's disease and peripheral neuropathy (a common neurological disorder resulting from damage to the peripheral nerves, which originate from the brain and spinal cord).
In an animal study conducted by the Biomedical Group, in Takara, Japan, there was a 20 per cent increase in NGF concentration after taking chalcone-rich ashitaba for just four days.
Phloretin, which is abundant in apples, inhibits the Escherichia coli bacteria.
Phloretin and phloridzin have shown, in studies, to have effective anti-cancer properties.
Any illness that ends with 'itis' is an inflammatory disease. Anthocyanidins exhibit powerful anti-inflammatory activity, and do it as well as drugs for the same purposes, without negative side effects.
Anthocyanidins can also decrease LDL-cholesterol, improve insulin sensitivity and lower blood pressure and reduce the risk of vascular dysfunction.
Anthocyanins can provide the following positive effects:
Maintains small blood vessel integrity by stabilising capillary walls and increases capillary permeability.
Neutralises enzymes that destroy connective tissue, prevents oxidants from damaging connective tissue, and repair damaged proteins in the blood-vessel walls.
Promotes cardiovascular health by preventing oxidation of low-density lipoproteins (LDL) and protecting blood vessels walls from oxidative damage.
Reduces allergic reactions.
Supports healthy blood sugar levels.
Indirubin is an indole alkaloid that can be used to treat various diseases including granulocytic leukaemia, cancer, Alzheimer's disease and other inflammatory diseases.
Highest sources of anthocyanidins in alphabetical order
Beans (black and red)
Broccoli tops (purple)
Grapes (red and black)
Potatoes (red skinned)
Saw palmetto berries
Sweet potato (purple variety)
Note: One of the richest sources of anthocyanidins are maqui berries.
Regular consumption of flavan-3-ols has been shown to raise the 'good' HDL-cholesterol and lower total and LDL-cholesterol and blood pressure.
100 g of dark cocoa per day can significantly improve measures of pancreatic β-cell function and insulin sensitivity, along with cardiometabolic markers in glucose-intolerant and hypertensive subjects.
Three cups of black or green tea per day can significantly reduce the risk of ischemic strokes and breast, colon, lung, prostate and skin cancers. There are about 248 mg of flavonoids in green tea and 415 mg in black tea.
Note: Milk consumption has been shown to blunt the vascular benefits of tea flavonoids. Lemon juice is a better accompaniment as it is rich in vitamin C.
Natural sources of flavan-3-ols in alphabetical order
Natural sources of flavanones in alphabetical order
Citrus fruits (concentrated in skins and pith)
Note: Naringen is found in large amounts in grapefruit and may interact with medications, especially those in the calcium channel blocker family, increasing blood levels of the drugs. This may necessitate a reduction in drug dosages. See Medicinal properties of citrus bioflavonoids below.
Flavones have been proven in studies to assist with wound healing and the treatment of rheumatic arthritis and other inflammatory conditions.
Natural sources of flavones in alphabetical order
Bell peppers (red)
Prenylated flavonoids or prenylflavonoids are a sub-class of flavonoids. Prenylchalcones, prenylflavones, prenylflavonols and prenylflavanones are classes of prenylflavonoids. Chemically they have a prenyl group attached to their flavonoid backbone. Prenylation may increase the potential activity of its original flavonoid.
Types of prenylated flavonoids
Australone A found in the Chinese or Korean mulberry (Morus australis)
Furowanin A and B
Luteone found in the pods of Laburnum (Laburnum anagyroides)
Millewanins-F, G and H
Morusin the root bark of White mulberry (Morus alba)
7-O-Methylluteone found in the bark of the Flame tree (Erythrina burttii.
6-prenylnaringenin, 6-geranylnaringenin, 8-prenylnaringenin and isoxanthohumol found in hops and beer.
6,8-Diprenyleriodictyol, dorsmanin C and dorsmanin F can be found in the Mulberry (Dorstenia mannii).
Note: Of the prenylflavonoids, 8-prenylnaringenin is the most potent phytoestrogen known.
Horny goat weed (Epimedium wushanense) contains many flavonoids. 37 compounds were discovered in the underground and aerial parts of the plant. Among them, 28 compounds were prenylflavonoids. The predominant prenylated flavonoid, epimedin C, ranged from 1.4 to 5.1% in aerial parts and 1.0 to 2.8% in underground parts.
The Ceylon breadfruit (Artocarpus nobilis contains prenylated flavonoids in its root bark.
Wighteone (6-prenylgenistein), isowighteone (3′-prenylgenistein), and lupiwighteone (8-prenylgenistein) are genistein prenylated derivatives.
General health benefits of flavonoids
Flavonoids cannot be manufactured by the body and therefore can only be obtained through the diet.
Flavonoids have been widely recognised to affect a wide range of systems in the body and provide many
health benefits due to their following properties:
Regular consumption of flavonoids can assist with reducing occurrences of allergies and asthma
Flavonoids could be useful for iron deficiency (anaemia) since they help with the absorption of iron.
Because plants produce certain flavonoids to protect themselves against bacterial invasions they can have the same effect within the human body. Several flavonoids including apigenin, chalcones, galangin, flavanones, flavone and flavonol glycosides and isoflavones have been shown to possess potent antibacterial activity. Naringenin and sophoraflavanone G have intensive antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA) and Streptococci strains of bacteria.
Bones and joint disorders.
Flavonoids strengthen the bones and collagen which is the connective tissues in the body and can help with inflammatory conditions such as arthritis and rheumatism.
Many studies have been done to find out if flavonoids can be used to treat cancer and some have had favourable results in the treatment of breast, colon, lung, oral, pancreatic, prostate and skin cancers and leukaemia. Genistein is an isoflavone found in chick peas, legumes, red clover and soya beans that can reduce the risk of breast, pancreatic and prostate cancers. The flavonol, myricetin, can lower the risk of prostate cancer.
Flavonoids have been shown to help slow down the development of cataracts in the eyes.
Flavonoids have been shown to reduce insulin resistance and improve the balancing of blood sugar levels in diabetics.
Flavonoids help to increase bile production which can help alleviate some digestive issues.
If infected by herpes, foods rich in vitamin C and flavonoids, consumed three times a day at least, will help and can prevent outbreaks and cold sores.
High blood pressure and LDL cholesterol
Regular consumption of flavonoids can reduce LDL cholesterol and increase HDL cholesterol levels and therefore prevent arterial plaques from forming. It can also enable a reduction of cardiovascular risk markers by lowering systolic and diastolic blood pressure. Apigenin has been shown in studies to prevent LDL oxidation which can help to prevent atherosclerosis.
Because of their ability to reduce inflammation and help the body eliminate potentially toxic and cancer-causing chemicals, flavonoids can be advantageous to those with Alzheimer's, dementia. fibromyalgia, multiple sclerosis, Parkinson's disease and similar inflammatory conditions.
Injuries and pain
Flavonoids are effectively used in the treatment of sport injuries due to their pain relieving properties. They can be used to relieve back pain and pains in the legs and can lessen the symptoms of prolonged bleeding such as a low serum calcium.
Menstruation and menopausal problems
Isoflavones are phytoestrogens that can help to alleviate menstrual and menopausal symptoms.
Flavonoids contained in berries have a positive effect against Parkinson’s disease and may help to improve the memory in elderly people. Flavonoids found in chocolate, tea and wine have shown, in studies, to have beneficial effects on the brain, possibly in the protection against cerebral vascular disorders, cognitive impairments and subsequent stroke and dementias. They also showed improvements in global cognitive function in elderly individuals over 70 years of age.
Poor circulation and strokes
Flavonoids help with dilating and strengthening the blood vessels and keeping them elastic and flexible. They also increase the strength of capillaries and regulate their permeability and for this reason are good additions to the diet for those prone to having a stroke.
Apigenin, baicalein, biochanin A, kaempferol, luteolin and naringenin have been shown to inhibited the influenza virus development.
Flavonoids and vitamin C
Flavonoids enhance the action of vitamin C and prolong the effectiveness of it so, for this reason, they should always be taken together and most natural foods, that provide vitamin C, also provide flavonoids. They work together to help maintain the thin walls of the capillaries, therefore preventing bleeding or bruising.
They assist vitamin C in keeping collagen, the intercellular "cement" in healthy condition; are essential for the proper absorption and use of vitamin C and prevents vitamin C from being destroyed in the body by oxidation. They are beneficial in hypertension; help to heal ruptures in connective tissues and they can help to build a protective barrier against infections.
Citrus bioflavonoids may help reduce allergic reactions, cholesterol levels and inflammation, benefit people with diabetes and prevent cancer. They have also been tried, with some success, for treating lymphedaema (arm swelling) following breast cancer surgery.
Note: Tangeretin should be avoided if tamoxifen is being taken for breast cancer as it can reduce the effectiveness of this drug.
Diosmin and hesperidin may be helpful for haemorrhoids and for individuals that bruise easily or suffer with nose bleeds.
Diosmin, hesperidin and rutin, may be helpful for chronic venous insufficiency, a condition in which the veins in the legs begin to weaken.
The ‘Sweetie fruit’ is a citrus bioflavonoid-rich hybrid of grapefruit and pommelo and has shown some promise in reducing high blood pressure but can interact with certain medications. See the Cautionary note below.
The major flavonoids found in citrus fruits, diosmin, hesperidin, oxerutins and quercetin, are very beneficial. to maintaining good health Quercetin is a very highly concentrated in citrus fruits.
The flavanones found in citrus fruits
The flavones found in citrus fruits
The flavonols found in citrus fruits
NOTE: In citrus fruits, flavonoids are mostly concentrated in the peel and white pith material just beneath peel.
CAUTION: According to new research, it is not the flavonoids in grapefruit that interact dangerously with some drugs, it is the furanocoumarins. Some medications, such as those for cholesterol and hypertension, are affected by furanocoumarins so that they enter the bloodstream too quickly.
Furanocoumarins influence the function of certain enzymes along the gastrointestinal tract or in the liver, and these interactions influence the rate at which certain medications can be broken down or removed from the body. Much of the past attention had focused on felodipine (marketed as Plendil), a popular medication for treating hypertension. When this occurs, the level of the blood pressure lowering medication in the body becomes too high, by as much as a five-fold increase.
Thus, blood pressure may fall too low, causing symptoms of light-headedness, dizziness, weakness or even fainting. It does not take much grapefruit or grapefruit juice to make this happen, especially if it is consumed on a regular basis. There is great individual variability, however, on who will and who will not be reactors.
Another group of medications that interact with the grapefruit are the “statins,” which are now widely prescribed to lower blood cholesterol levels. There are many other medications, however, that also interact with grapefruits. A partial list (using drug generic names) includes
See more about coumarins and furanocoumarins
Find out more about some of the natural sources of flavonoids
Because the various flavonoids been named so similarly they are constantly confused and misspelt.
Common misspellings for bioflavonoids include bioflavinoids, bioflavanoids, flavinoids, flavanoids, falvanoids, flavenoids, flavinoids, falvinoids, bioflavanoid.
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