What Are Flavonoids?
Flavonoids were discovered by Nobel Prize-winning biochemist
Albert Szent-Gyorgi, who labeled them "vitamin P". He discovered that
they enhanced the function of vitamin C, improving absorption and
protecting it from oxidation. Flavonoids that have been shown to have
particularly beneficial properties include proanthocyanidins, green tea
polyphenols and soy isoflavones. Quercetin and its derivatives; the
citrus bioflavonoids, including quercitrin, rutin and hesperidin; have
also been fairly well studied.
They are responsible for the colors of many fruits and vegetables,
are found also in grains, nuts, leaves and flowers, and studies suggest
there value in the treatment of a number of disorders. They are
considered one of the most common biological constituents in plants.
They have a gentle, beneficial action on numerous physiological
processes in the body and may benefit the heart, blood vessels, liver,
immune system, connective tissue, adrenal glands, kidneys, musculature
and nervous system. Flavonoids may act as anti-oxidants,
"anti-allergics", anti-inflammatories, immunostimulating,
anti-hepatotoxic, anti-neoplastic and hypoglycemic along with numerous
other actions including stabilizing capillary permeability. Important
herbs containing flavonoids include milk thistle, hawthorn, echinacea
and bilberry. One possible chemical classification consists of PCO
(proanthocyanidins), quercetin, citrus bioflavonoids and green tea
polyphenols. The following is a description of three popular
flavonoids; quercetin, grape seed extract and green tea extract.
Quercetin serves as the backbone for other flavonoids, and is the
most active of the flavonoids. Many medicinal plants have a significant
quercetin content. It blocks mast cell and basophilic histamine
degranulation, inhibits xanthine oxidase (the enzymes producing uric
acid) and aldose reductase (the enzyme converting glucose into
sorbitol), decreases neutrophil lysosomal enzyme secretion, and
normalizes activity if phospholipase A2 and lipoxygenase. Although
human studies are limited, its physiological actions explain its use in
inflammatory and allergic conditions including asthma, hay fever,
rheumatoid arthritis, lupus, diabetes and cancer. Sorbitol is
implicated in the development of diabetic complications including
cataracts, neuropathy and retinopathy. Studies show decreased cataract
formation in the lens of diabetic animals. Its potential influence on
diabetes may also relate to enhanced insulin secretion, protection of
pancreatic beta cells from free-radical damage, and inhibition of
platelet aggregation. Quercitin has anti-viral action against a number
of different viruses, and inhibits a number of different cancers in
experimental models.
Proanthocyanidins (Procyanidins) is an important therapeutic class
of flavonoids extracted from grape seeds and maritime (Landes) pine.
When individual molecules bind together, the result is collectively
called procyanidolic oligomers (PCO). They have a broad range of
pharmacologic activity through increasing vitamin C levels, decreasing
capillary permeability and fragility, scavenging free radicals and
inhibiting destruction of collagen. The latter occurs through ability
to cross-link collagen fibers, preventing free-radical damage,
inhibiting enzymatic cleavage of collagen, and preventing the synthesis
and release of inflammatory mediators. PCO has approximately 50 times
the anti-oxidant activity of vitamin C or vitamin E. These influences,
along with other mechanisms, explain there benefit in venous and
capillary disorders, including venous insufficiency, capillary
fragility, diabetic retinopathy and macular degeneration. Studies show
that PCO also lowers cholesterol levels and can shrink arterial
cholesterol deposits.
Green tea is derived from the tea plant, Camellia sinensis, through
light steaming of the leaves. Allowing the leaves to oxidize produces
black tea. Green tea contains polyphenols, mainly flavonoids. They are
potent anti-oxidants as well as anti-cancer substances. They inhibit
the formation of carcinogenic substances such as nitrosamines, suppress
their activation, and detoxify them.
Consumption of a plant-based diet can prevent the development and
progression of chronic diseases associated with extensive
neovascularization, including solid malignant tumors. In previous
studies, we have shown that the plant-derived isoflavonoid genistein is
a potent inhibitor of cell proliferation and in vitro angiogenesis. In
the present study, we report that certain structurally related
flavonoids are more potent inhibitors than genistein. Indeed,
3-hydroxyflavone, 3',4'-dihydroxyflavone, 2',3'-dihydroxyflavone,
fisetin, apigenin, and luteolin inhibited the proliferation of normal
and tumor cells, as well as in vitro angiogenesis, at half-maximal
concentrations in the low micromolar range. We have previously
demonstrated that genistein concentrations in the urine of subjects
consuming a plant-based diet is 30-fold higher than in subjects
consuming a traditional Western diet. The wider distribution and the
more abundant presence of flavonoids in the plant kingdom, together
with the present results, suggest that flavonoids may contribute to the
preventive effect of a plant-based diet on chronic diseases, including
solid tumors.
Researchers have found that drinking at least one cup of tea a day
could cut the risk of heart attack by 44 %. The results are probably
due to flavonoids, vitamin-like nutrients that make blood cells less
prone to clotting. Flavonoids, powerful antioxidants, are found in
fruits and vegetables and are connected to the heart-healthy effect of
red wine. The study examined 340 men and women who had had heart
attacks and investigated their coffee and tea drinking habits over a
year. The question of how much tea to drink, and how strong it needs to
be brewed to achieve maximum benefits, was not determined.
This journal article discusses 'Crataegus oxycantha' (Hawthorne) and
its use in the treatment of cardiac conditions. It summarizes
information about the main constituents of Crataegus, its mechanisms of
action, clinical indications, dosage, drug nutrient interactions, and
toxicology. Crataegus appears to be an effective and low-risk
phytotherapeutic for patients with coronary heart disease,
atherosclerosis, hypertension, or hypercholesterolemia. It has been
shown to produce subjective and objective benefits in patients with
congestive heart failure. Its main constituents are flavonoids,
triterpene saponins, and a few cardioactive amines. However, the
primary cardiovascular protective activity of the plant is generally
attributed to its flavonoid content, particularly the oligomeric
proanthocyanadins.
Otto Daniel and colleagues from the Swiss Federal Office of Public
Health and the Swiss Federal Institute of Technology, both in Zürich,
study the toxic and beneficial human health effects of certain phenolic
compounds. These compounds are produced in plants to serve a number of
purposes, including repelling herbivores, pigmentation, protection
against UV light, and biocidal defense against bacteria and fungi.
External stimuli such as chemical stress from heavy metals and
pesticides can alter the chemical composition or quantities of phenolic
compounds in a plant; depending on its concentration, chemical
structure, and any external modulation, a given phenolic compound might
be either toxic or beneficial to humans. The scientists examined three
such compounds. Resveratrol, which is found in grapes and peanuts, has
been found to inhibit the synthesis of substances that cause blood
clotting, possibly offering protection against heart disease and
thrombosis. Flavonoids, which are found in almost every food or
beverage of plant origin, act as antioxidants, inhibit blood
coagulation, promote vasodilation, and have anti-inflammatory
effects--benefits that appear to outweigh their variable mutagenic
properties. Furanocoumarins, which are found in plants such as limes
and celery, can cause phototoxic burns but have also been harnessed for
use in psoralen UVA therapy, which is used to treat skin conditions
such as psoriasis and cutaneous T-cell lymphoma.
Flavonoids from different fruit sources vary in their
physical-chemical properties as antioxidants and partition to different
extents in biological tissues. After determining which flavonoids
inhibited low-density lipoprotein (LDL) oxidation in vitro,
investigators validated the hamster as a diet-responsive animal model
of atherosclerosis, in which the extent of disease is quantifiably
related to dietary antioxidant content. They then showed that
supplementation with tocopherol or ingestion of the monomeric flavonoid
catechin reduced the extent of atherosclerosis in hamsters on a
hypercholesterolemic diet. These studies were supported by fatty-acid
analyses in the Fatty Acids Subcore and LDL oxidation measurements in
the Antioxidants and Mass Spectrophotometry Core. Related studies
showed that polyphenolic flavonoids from grapes exhibit potent
vasorelaxing activities in isolated rabbit aortas, further suggesting
biologically important targets of action for this class of nutrients.
Flavonoids are among the best candidates for mediating the
protective effect of diets rich in fruits and vegetables with respect
to colorectal cancer. To gain additional information about their growth
effects on colorectal tumors and their cellular mechanisms of action, a
series of related flavonoids was added to cultures of colonic tumor
cells. Most compounds induced growth inhibition and cell loss at
concentrations of 1-100 microM, relative effectivity being quercetin
> apigenin > fisetin > robinetin and kaempferol.
Thornton reports on research indicating that nuts may actually
improve heart health, regardless of other risk factors such as weight,
blood pressure, exercise, or gender. This may spring from the nature of
the fat in nuts, which is both monounsaturated and polyunsaturated.
These are the healthy forms of fat, found in such foods as olive and
canola oils. In addition, nuts contain Omega-3 fatty acids, and are
nutritionally dense with such nutrients as vitamin E, folic acid,
niacin, copper, potassium, and magnesium. According to Thornton, nuts
also contain flavonoids and isoflavones, compounds thought to prevent
cancer and cardiovascular disease. Finally, since nuts have a high
satiety factor, most people find a small amount filling, which
contributes to weight loss.
Flavonoids were discovered by Nobel Prize-winning biochemist
Albert Szent-Gyorgi, who labeled them "vitamin P". He discovered that
they enhanced the function of vitamin C, improving absorption and
protecting it from oxidation. Flavonoids that have been shown to have
particularly beneficial properties include proanthocyanidins, green tea
polyphenols and soy isoflavones. Quercetin and its derivatives; the
citrus bioflavonoids, including quercitrin, rutin and hesperidin; have
also been fairly well studied.
They are responsible for the colors of many fruits and vegetables,
are found also in grains, nuts, leaves and flowers, and studies suggest
there value in the treatment of a number of disorders. They are
considered one of the most common biological constituents in plants.
They have a gentle, beneficial action on numerous physiological
processes in the body and may benefit the heart, blood vessels, liver,
immune system, connective tissue, adrenal glands, kidneys, musculature
and nervous system. Flavonoids may act as anti-oxidants,
"anti-allergics", anti-inflammatories, immunostimulating,
anti-hepatotoxic, anti-neoplastic and hypoglycemic along with numerous
other actions including stabilizing capillary permeability. Important
herbs containing flavonoids include milk thistle, hawthorn, echinacea
and bilberry. One possible chemical classification consists of PCO
(proanthocyanidins), quercetin, citrus bioflavonoids and green tea
polyphenols. The following is a description of three popular
flavonoids; quercetin, grape seed extract and green tea extract.
Quercetin
Quercetin serves as the backbone for other flavonoids, and is the
most active of the flavonoids. Many medicinal plants have a significant
quercetin content. It blocks mast cell and basophilic histamine
degranulation, inhibits xanthine oxidase (the enzymes producing uric
acid) and aldose reductase (the enzyme converting glucose into
sorbitol), decreases neutrophil lysosomal enzyme secretion, and
normalizes activity if phospholipase A2 and lipoxygenase. Although
human studies are limited, its physiological actions explain its use in
inflammatory and allergic conditions including asthma, hay fever,
rheumatoid arthritis, lupus, diabetes and cancer. Sorbitol is
implicated in the development of diabetic complications including
cataracts, neuropathy and retinopathy. Studies show decreased cataract
formation in the lens of diabetic animals. Its potential influence on
diabetes may also relate to enhanced insulin secretion, protection of
pancreatic beta cells from free-radical damage, and inhibition of
platelet aggregation. Quercitin has anti-viral action against a number
of different viruses, and inhibits a number of different cancers in
experimental models.
Grape Seed Extract
Proanthocyanidins (Procyanidins) is an important therapeutic class
of flavonoids extracted from grape seeds and maritime (Landes) pine.
When individual molecules bind together, the result is collectively
called procyanidolic oligomers (PCO). They have a broad range of
pharmacologic activity through increasing vitamin C levels, decreasing
capillary permeability and fragility, scavenging free radicals and
inhibiting destruction of collagen. The latter occurs through ability
to cross-link collagen fibers, preventing free-radical damage,
inhibiting enzymatic cleavage of collagen, and preventing the synthesis
and release of inflammatory mediators. PCO has approximately 50 times
the anti-oxidant activity of vitamin C or vitamin E. These influences,
along with other mechanisms, explain there benefit in venous and
capillary disorders, including venous insufficiency, capillary
fragility, diabetic retinopathy and macular degeneration. Studies show
that PCO also lowers cholesterol levels and can shrink arterial
cholesterol deposits.
Green Tea Extract
Green tea is derived from the tea plant, Camellia sinensis, through
light steaming of the leaves. Allowing the leaves to oxidize produces
black tea. Green tea contains polyphenols, mainly flavonoids. They are
potent anti-oxidants as well as anti-cancer substances. They inhibit
the formation of carcinogenic substances such as nitrosamines, suppress
their activation, and detoxify them.
Consumption of a plant-based diet can prevent the development and
progression of chronic diseases associated with extensive
neovascularization, including solid malignant tumors. In previous
studies, we have shown that the plant-derived isoflavonoid genistein is
a potent inhibitor of cell proliferation and in vitro angiogenesis. In
the present study, we report that certain structurally related
flavonoids are more potent inhibitors than genistein. Indeed,
3-hydroxyflavone, 3',4'-dihydroxyflavone, 2',3'-dihydroxyflavone,
fisetin, apigenin, and luteolin inhibited the proliferation of normal
and tumor cells, as well as in vitro angiogenesis, at half-maximal
concentrations in the low micromolar range. We have previously
demonstrated that genistein concentrations in the urine of subjects
consuming a plant-based diet is 30-fold higher than in subjects
consuming a traditional Western diet. The wider distribution and the
more abundant presence of flavonoids in the plant kingdom, together
with the present results, suggest that flavonoids may contribute to the
preventive effect of a plant-based diet on chronic diseases, including
solid tumors.
Researchers have found that drinking at least one cup of tea a day
could cut the risk of heart attack by 44 %. The results are probably
due to flavonoids, vitamin-like nutrients that make blood cells less
prone to clotting. Flavonoids, powerful antioxidants, are found in
fruits and vegetables and are connected to the heart-healthy effect of
red wine. The study examined 340 men and women who had had heart
attacks and investigated their coffee and tea drinking habits over a
year. The question of how much tea to drink, and how strong it needs to
be brewed to achieve maximum benefits, was not determined.
This journal article discusses 'Crataegus oxycantha' (Hawthorne) and
its use in the treatment of cardiac conditions. It summarizes
information about the main constituents of Crataegus, its mechanisms of
action, clinical indications, dosage, drug nutrient interactions, and
toxicology. Crataegus appears to be an effective and low-risk
phytotherapeutic for patients with coronary heart disease,
atherosclerosis, hypertension, or hypercholesterolemia. It has been
shown to produce subjective and objective benefits in patients with
congestive heart failure. Its main constituents are flavonoids,
triterpene saponins, and a few cardioactive amines. However, the
primary cardiovascular protective activity of the plant is generally
attributed to its flavonoid content, particularly the oligomeric
proanthocyanadins.
Otto Daniel and colleagues from the Swiss Federal Office of Public
Health and the Swiss Federal Institute of Technology, both in Zürich,
study the toxic and beneficial human health effects of certain phenolic
compounds. These compounds are produced in plants to serve a number of
purposes, including repelling herbivores, pigmentation, protection
against UV light, and biocidal defense against bacteria and fungi.
External stimuli such as chemical stress from heavy metals and
pesticides can alter the chemical composition or quantities of phenolic
compounds in a plant; depending on its concentration, chemical
structure, and any external modulation, a given phenolic compound might
be either toxic or beneficial to humans. The scientists examined three
such compounds. Resveratrol, which is found in grapes and peanuts, has
been found to inhibit the synthesis of substances that cause blood
clotting, possibly offering protection against heart disease and
thrombosis. Flavonoids, which are found in almost every food or
beverage of plant origin, act as antioxidants, inhibit blood
coagulation, promote vasodilation, and have anti-inflammatory
effects--benefits that appear to outweigh their variable mutagenic
properties. Furanocoumarins, which are found in plants such as limes
and celery, can cause phototoxic burns but have also been harnessed for
use in psoralen UVA therapy, which is used to treat skin conditions
such as psoriasis and cutaneous T-cell lymphoma.
Flavonoids from different fruit sources vary in their
physical-chemical properties as antioxidants and partition to different
extents in biological tissues. After determining which flavonoids
inhibited low-density lipoprotein (LDL) oxidation in vitro,
investigators validated the hamster as a diet-responsive animal model
of atherosclerosis, in which the extent of disease is quantifiably
related to dietary antioxidant content. They then showed that
supplementation with tocopherol or ingestion of the monomeric flavonoid
catechin reduced the extent of atherosclerosis in hamsters on a
hypercholesterolemic diet. These studies were supported by fatty-acid
analyses in the Fatty Acids Subcore and LDL oxidation measurements in
the Antioxidants and Mass Spectrophotometry Core. Related studies
showed that polyphenolic flavonoids from grapes exhibit potent
vasorelaxing activities in isolated rabbit aortas, further suggesting
biologically important targets of action for this class of nutrients.
Flavonoids are among the best candidates for mediating the
protective effect of diets rich in fruits and vegetables with respect
to colorectal cancer. To gain additional information about their growth
effects on colorectal tumors and their cellular mechanisms of action, a
series of related flavonoids was added to cultures of colonic tumor
cells. Most compounds induced growth inhibition and cell loss at
concentrations of 1-100 microM, relative effectivity being quercetin
> apigenin > fisetin > robinetin and kaempferol.
Thornton reports on research indicating that nuts may actually
improve heart health, regardless of other risk factors such as weight,
blood pressure, exercise, or gender. This may spring from the nature of
the fat in nuts, which is both monounsaturated and polyunsaturated.
These are the healthy forms of fat, found in such foods as olive and
canola oils. In addition, nuts contain Omega-3 fatty acids, and are
nutritionally dense with such nutrients as vitamin E, folic acid,
niacin, copper, potassium, and magnesium. According to Thornton, nuts
also contain flavonoids and isoflavones, compounds thought to prevent
cancer and cardiovascular disease. Finally, since nuts have a high
satiety factor, most people find a small amount filling, which
contributes to weight loss.
- Flavonoids, Farmacopia LLC
- Fotsis T, Pepper MS,
Et al. Flavonoids, dietary-derived inhibitors of cell proliferation and
in vitro angiogenesis. Cancer Res; 57(14):2916-21 1997 - Ross, E. Tea may cut heart-attack risk 44 %. San Jose Mercury News. July 9, 1999.
- Crataegus Oxycantha. Common Name: Hawthorne. Alternative Medicine Review. 3(2): 138-139. April 1998.
- Environmental Health Perspectives Volume 107, Number 2, February 1999
- Scientific Advances/Accomplishments - University of California-Davis Clinical Nutrition Research Unit
- Richter
M; Ebermann R; Marian B. Quercetin-induced apoptosis in colorectal
tumor cells: possible role of EGF receptor signaling. Nutr Cancer
1999;34(1):88-99 - Thornton, J. Health Nuts. Cooking Light. p.96-101,154. March 1999.
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