Everything about Bioflavonoid totally explained
The term
flavonoid refers to a class of
plant secondary metabolites. According to the
IUPAC nomenclature, they can be classified into:
Flavonoids are most commonly known for their
antioxidant activity. However, it's now known that the health benefits they provide against cancer and heart disease are the result of other mechanisms. Flavonoids are also commonly referred to as
bioflavonoids in the media – the terms are largely equivalent and interchangeable, for most flavonoids are biological in origin.
Biosynthesis
Flavonoids are synthesized by the
phenylpropanoid metabolic pathway in which the
amino acid phenylalanine is used to produce
4-coumaroyl-CoA
, anti-microbial and anti-
cancer activity.
Consumers and food manufacturers have become interested in flavonoids for their medicinal properties, especially their potential role in the prevention of cancers and
cardiovascular disease. The beneficial effects of fruit, vegetables, and tea or even red wine have been attributed to flavonoid compounds rather than to known
nutrients and
vitamins.
Health benefits aside from antioxidant values
In 2007, research conducted at the
Linus Pauling Institute and published in
Free Radical Biology and Medicine indicates that inside the human body, flavonoids themselves are of little or no direct antioxidant value. Unlike in the controlled conditions of a test tube, flavonoids are poorly absorbed by the human body (less than 5%), and most of what is absorbed is quickly metabolized and excreted from the body.
The huge increase in antioxidant capacity of blood seen after the consumption of flavonoid-rich foods isn't caused directly by the flavonoids themselves, but most likely is due to increased uric acid levels that result from expelling flavonoids from the body.
Important flavonoids
Quercetin
Quercetin is a flavonoid and, to be more specific, a flavonol (see below), that constitutes the
aglycone of the
glycosides
rutin and
quercitrin. In studies, quercetin is found to be the most active of the flavonoids, and many medicinal plants owe much of their activity to their high quercetin content. Quercetin has demonstrated significant anti-inflammatory activity because of direct inhibition of several initial processes of
inflammation. For example, quercetin inhibits both the production and release of
histamine and other allergic/inflammatory
mediators. In addition, it exerts potent antioxidant activity and
vitamin C-sparing action. It has been found to be anti-cancer. Quercetin can be found in the herbal products based on
Hawthorn, which are used for acute symptoms of
congestive heart failure. One study that people who ate quercetin-rich foods at least four times a week, on average, were 51% less likely to have lung cancer than those who ate none.
Epicatechin
Epicatechin improves blood flow and thus seems good for
cardiac health.
Cocoa, the major ingredient of dark
chocolate, contains relatively high amounts of epicatechin and has been found to have nearly twice the antioxidant content of
red wine and up to three times that of
green tea in in-vitro tests. But in the test outlined above it now appears the beneficial antioxidant effects are minimal as the antioxidants are rapidly excreted from the body.
Oligomeric proanthocyanidins
Proanthocyanidins extracts demonstrate a wide range of pharmacological activity. Their effects include increasing
intracellular vitamin C levels, decreasing capillary permeability and fragility, scavenging oxidants and free radicals, and inhibiting destruction of
collagen, the most abundant protein in the body.
Important dietary sources
Good sources of flavonoids include all
citrus fruits, berries,
ginkgo biloba,
onions,
parsley,
legumes,
tea (especially
white and
green tea),
red wine,
seabuckthorn, and
dark chocolate (with a
cocoa content of seventy percent or greater).
Citrus
The citrus bioflavonoids include
hesperidin (a glycoside of
hesperetin),
quercitrin,
rutin (two
glycosides of
quercetin), and
tangeritin. In addition to possessing antioxidant activity and an ability to increase intracellular levels of
vitamin C, rutin and
hesperidin exert beneficial effects on
capillary permeability and
blood flow. They also exhibit some of the anti-allergy and anti-inflammatory benefits of quercetin. Quercetin can also inhibit
reverse transcriptase, part of the replication process of
retroviruses. The therapeutical relevance of this inhibition hasn't been established.
Hydroxyethylrutosides (HER) have been used in the treatment of capillary permeability, easy
bruising,
hemorrhoids, and
varicose veins.
Ginkgo
Leaf extract from the
Ginkgo tree is widely marketed as an herbal supplement. The active ingredients are flavoglycosides.
Tea
Green tea flavonoids are potent
antioxidant compounds, thought to reduce incidence of cancer and heart disease. The major flavonoids in green tea are the
kaempferol and
catechins (catechin, epicatechin, epicatechin gallate, and
epigallocatechin gallate (EGCG)).
In producing teas such as
oolong tea and
black tea, the leaves are allowed to
oxidize, during which
enzymes present in the tea convert some or all of the catechins to larger molecules.
White tea is the least processed of teas and is shown to present the highest amount of catechins known to occur in
camellia sinensis. However, green tea is produced by steaming the fresh-cut
leaf, which inactivates these enzymes, and oxidation doesn't significantly occur.
Wine
Grape skins contain significant amounts of flavonoids as well as other polyphenols. Both red and white wine contain flavonoids; however, since red wine is produced by fermentation in the presence of the grape skins, red wine has been observed to contain higher levels of flavonoids, and other polyphenolics such as
resveratrol.
Dark chocolate
Flavanoids exist naturally in cacao, but because they can be bitter, they're often removed from chocolate, even the dark variety.
Subgroups
Over 5000 naturally occurring flavonoids have been characterized from various plants. They have been classified according to their chemical structure, and are usually subdivided into the following subgroups (for further reading see
Flavones
:Flavones use the 2-phenylchromen-4-one skeleton.
:Examples: Luteolin, Apigenin, Tangeritin
Flavonols
:Flavonols or 3-hydroxyflavones use the 3-hydroxy-2-phenylchromen-4-one skeleton.
:Examples: Quercetin, Kaempferol, Myricetin, Fisetin, Isorhamnetin, Pachypodol, Rhamnazin
Flavanones
:Flavanones use the 2,3-dihydro-2-phenylchromen-4-one skeleton.
:Examples: Hesperetin, Naringenin, Eriodictyol, Homoeriodictyol.
3-Hydroxyflavanones or 2,3-dihydroflavonols
:3-Hydroxyflavanones use the 3-hydroxy-2,3-dihydro-2-phenylchromen-4-one skeleton.
:Examples: Dihydroquercetin, Dihydrokaempferol
Isoflavones
Isoflavones
:Isoflavones use the 3-phenylchromen-4-one skeleton.
:Examples: Genistein, Daidzein, Glycitein
Flavan-3-ols and Anthocyanidins
Flavan-3-ols
:Flavan-3-ols use the 2-phenyl-3,4-dihydro-2H-chromen-3-ol skeleton.
:Examples: Catechins (Catechin (C), Gallocatechin (GC), Catechin 3-gallate (Cg), Gallocatechin 3-gallate (GCg)), Epicatechins (Epicatechin (EC), Epigallocatechin (EGC), Epicatechin 3-gallate (ECg), Epigallocatechin 3-gallate (EGCg))
Anthocyanidins
:Anthocyanidins are the aglycones of anthocyanins. Anthocyanidins use the flavylium (2-phenylchromenylium) ion skeleton
:Examples: Cyanidin, Delphinidin, Malvidin, Pelargonidin, Peonidin, Petunidin
Availability through microorganisms
A number of recent research articles have demonstrated the efficient production of flavonoid molecules from genetically-engineered microorganisms.
Further Information
Get more info on 'Bioflavonoid'.
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