Quercetin
Encyclopedia
Quercetin ˈkwɜrsɨtɨn, a flavonol, is a plant-derived flavonoid
found in fruits, vegetables, leaves and grains. It also may be used as an ingredient in supplements, beverages or foods.
widely distributed in nature. The name has been used since 1857, and is derived from quercetum (oak forest), after Quercus. It is a naturally-occurring polar auxin transport
inhibitor.
Foods rich in quercetin include black and green tea
(Camellia sinensis
; 2000–2500 mg/kg), caper
s (1800 mg/kg), lovage
(1700 mg/kg), apple
s (44 mg/kg), onion
, especially red onion
(191 mg/kg) (higher concentrations of quercetin occur in the outermost rings), red grapes, citrus fruit, tomato
, broccoli
and other leafy green vegetables, and a number of berries, including raspberry
, bog whortleberry
(158 mg/kg, fresh weight), lingonberry (cultivated 74 mg/kg, wild 146 mg/kg), cranberry
(cultivated 83 mg/kg, wild 121 mg/kg), chokeberry
(89 mg/kg), sweet rowan
(85 mg/kg), rowan
berry (63 mg/kg), sea buckthorn berry (62 mg/kg), crowberry
(cultivated 53 mg/kg, wild 56 mg/kg), and the fruit of the prickly pear
cactus. A recent study found that organically grown
tomatoes had 79% more quercetin than "conventionally grown".
A study by the University of Queensland
, Australia
has also indicated the presence of quercetin in varieties of honey
, including honey derived from eucalyptus
and tea tree
flower
s.
is converted to 4-coumaroyl-CoA in a series of steps known as the general phenylpropanoid
pathway using phenylalanine ammonia-lyase
, cinnamate-4-hydroxylase, and 4-coumaroyl-CoA-ligase. 4-Coumaroyl-CoA is added to three molecules of malonyl-CoA
to form tetrahydroxychalcone using 7,2’-dihydroxy-4’-methoxyisoflavanol synthase. Tetrahydroxychalcone is then converted into naringenin
using chalcone isomerase
. Naringenin is then converted into eriodictyol
using flavanoid 3’-hydroxylase. Eriodictyol is then converted into dihydroquercetin with flavanone 3-hydroxylase, which is then converted into quercetin using flavonol synthase
.
form of a number of other flavonoid glycoside
s, such as rutin
and quercitrin
, found in citrus
fruit, buckwheat
and onions. Quercetin forms the glycoside
s quercitrin
and rutin
together with rhamnose
and rutinose
, respectively. Likewise guaijaverin is the 3-O-arabinoside, hyperoside
is the 3-O-galactoside
, isoquercitin
is the 3-O-glucoside
, and spiraeoside
is the 4'-O-glucoside. CTN-986
is a quercetin derivative found in cottonseeds and cottonseed oil.
quercetin), as opposed to quercetin glycoside
s, is not a normal dietary component. In a bioavailability study in rats, radiolabelled quercetin-4'-glucoside was converted to phenolic acids as it passed through the gastrointestinal tract, producing compounds not monitored in several previous animal studies of aglycone quercetin. All but 4% of the radiolabel was recovered within 72 hours, with 69% recovered in urine.
Quercetin has neither been confirmed scientifically as a specific therapeutic for any condition nor been approved by any regulatory agency. The U.S. Food and Drug Administration has not approved any health claims for quercetin.
In another study also published in 2007 in the Archives of Pharmacal Research it was shown that quercetin, quercitrin and myricetin 3-O-beta-D-galactopyranoside displayed inhibition against HIV-1 reverse transcriptase, all with IC50 values of 60 microM.
In laboratory studies of cells in vitro
, quercetin produces changes that are also produced by compounds that cause cancer (carcinogens), but these studies do not report increased cancer in animals or humans.
From laboratory studies is conjecture that quercetin may affect certain mechanisms of cancer. An 8-year study found the presence of three flavonols — kaempferol
, quercetin, and myricetin
— in a normal diet was associated with 23% reduced risk of pancreatic cancer
, a rare but frequently fatal disease, in tobacco smokers. There was no benefit in subjects who had never smoked or had previously quit smoking.
In vitro, cultured skin and prostate cancer cells were suppressed (compared to nonmalignant cells) when treated with a combination of quercetin and ultrasound
.
In laboratory culture studies, quercetin increased the sensitivity of resistant colorectal tumors with microsatellite instability to the chemotherapy drug, 5-fluorouracil.
properties, and it is being investigated for a wide range of potential health benefits.
Quercetin has been reported to be of use in alleviating symptoms of pollinosis. An enzymatically modified derivative was found to alleviate ocular but not nasal symptoms of pollinosis.
A study with rats showed that quercetin effectively reduced immediate-release niacin (vitamin B3) flush, in part by means of reducing prostaglandin D2
production. A pilot clinical study of four humans gave preliminary data supporting this.
Quercetin may have properties of a calcineurin
inhibitor, similar to cyclosporin A and tacrolimus, according to one laboratory study.
because of its potential anti-inflammatory or mast cell
inhibitory properties shown in laboratory studies.
, but only for short periods (fewer than 8 weeks). Effects of quercetin on exercise tolerance in mice have been associated with increased mitochondrial biogenesis
. In mice, an oral quercetin dose of 12.5 to 25 mg/kg increased gene expression
of mitochondrial biomarkers and improved exercise endurance.
It has also been claimed that quercetin reduces blood pressure in hypertensive and obese subjects in whom LDL cholesterol levels were also reduced.
An in vitro study showed quercetin and resveratrol
combined inhibited production of fat cells.
A 12-week study of 941 adults found that supplements of 500 to 1000 milligrams of quercetin with vitamin C and niacin did not cause any significant difference in body mass or composition and had no significant effect on inflammatory markers, diagnostic blood chemistries, blood pressure, and blood lipid profiles.
), as quercetin competitively binds to bacterial DNA gyrase. Whether this inhibits or enhances the effect of fluoroquinolones is not certain.
AHFS Drug Information (2010) identifies quercetin as an inhibitor of CYP2C8
, and specifically names it as a drug with potential to have harmful interactions with taxol/paclitaxel. As paclitaxel is metabolized primarily by CYP2C8, its bioavailability
may be increased unpredictably, potentially leading to harmful side-effects.
Quercetin is described as an inhibitor
of CYP2C9
. Quercetin is an inhibitor and inducer
of CYP3A4
(in other words, it reduces the enzyme's activity in the short term, but the body responds by producing more of it). CYP2C9 and CPY3A4 are members of the cytochrome P450 mixed-function oxidase system, and as such are enzyme
s involved in the metabolism of xenobiotics in the body. In either case, quercetin may alter serum levels and, therefore, effects of drugs metabolized by these enzymes.
Flavonoid
Flavonoids , are a class of plant secondary metabolites....
found in fruits, vegetables, leaves and grains. It also may be used as an ingredient in supplements, beverages or foods.
Occurrence
Quercetin is a flavonoidFlavonoid
Flavonoids , are a class of plant secondary metabolites....
widely distributed in nature. The name has been used since 1857, and is derived from quercetum (oak forest), after Quercus. It is a naturally-occurring polar auxin transport
Polar auxin transport
Polar auxin transport is the regulated transport of the plant hormone auxin in plants. It is an active process, the hormone is transported in cell-to-cell manner and one of the main features of the transport is its directionality...
inhibitor.
Foods rich in quercetin include black and green tea
Tea
Tea is an aromatic beverage prepared by adding cured leaves of the Camellia sinensis plant to hot water. The term also refers to the plant itself. After water, tea is the most widely consumed beverage in the world...
(Camellia sinensis
Camellia sinensis
Camellia sinensis is the species of plant whose leaves and leaf buds are used to produce Chinese tea. It is of the genus Camellia , a genus of flowering plants in the family Theaceae. White tea, green tea, oolong, pu-erh tea and black tea are all harvested from this species, but are processed...
; 2000–2500 mg/kg), caper
Caper
Capparis spinosa, the caper bush, is a perennial winter-deciduous species that bears rounded, fleshy leaves and large white to pinkish-white flowers. A caper is also the pickled bud of this plant...
s (1800 mg/kg), lovage
Lovage
Lovage is a tall perennial plant, the sole species in the genus Levisticum, in the family Apiaceae, subfamily Apioideae, tribe Apieae.-Distribution:...
(1700 mg/kg), apple
Apple
The apple is the pomaceous fruit of the apple tree, species Malus domestica in the rose family . It is one of the most widely cultivated tree fruits, and the most widely known of the many members of genus Malus that are used by humans. Apple grow on small, deciduous trees that blossom in the spring...
s (44 mg/kg), onion
Onion
The onion , also known as the bulb onion, common onion and garden onion, is the most widely cultivated species of the genus Allium. The genus Allium also contains a number of other species variously referred to as onions and cultivated for food, such as the Japanese bunching onion The onion...
, especially red onion
Red onion
Red onions, sometimes called purple onions, are cultivars of the onion with purplish red skin and white flesh tinged with red.These onions tend to be medium to large in size and have a mild to sweet flavor. They are often consumed raw, grilled or lightly cooked with other foods, or added as color...
(191 mg/kg) (higher concentrations of quercetin occur in the outermost rings), red grapes, citrus fruit, tomato
Tomato
The word "tomato" may refer to the plant or the edible, typically red, fruit which it bears. Originating in South America, the tomato was spread around the world following the Spanish colonization of the Americas, and its many varieties are now widely grown, often in greenhouses in cooler...
, broccoli
Broccoli
Broccoli is a plant in the cabbage family, whose large flower head is used as a vegetable.-General:The word broccoli, from the Italian plural of , refers to "the flowering top of a cabbage"....
and other leafy green vegetables, and a number of berries, including raspberry
Raspberry
The raspberry or hindberry is the edible fruit of a multitude of plant species in the genus Rubus, most of which are in the subgenus Idaeobatus; the name also applies to these plants themselves...
, bog whortleberry
Bilberry
Bilberry is any of several species of low-growing shrubs in the genus Vaccinium , bearing edible berries. The species most often referred to is Vaccinium myrtillus L., but there are several other closely related species....
(158 mg/kg, fresh weight), lingonberry (cultivated 74 mg/kg, wild 146 mg/kg), cranberry
Cranberry
Cranberries are a group of evergreen dwarf shrubs or trailing vines in the subgenus Oxycoccus of the genus Vaccinium. In some methods of classification, Oxycoccus is regarded as a genus in its own right...
(cultivated 83 mg/kg, wild 121 mg/kg), chokeberry
Chokeberry
Aronia, the chokeberries, are two to three species of deciduous shrubs in the family Rosaceae, native to eastern North America. They are most commonly found in wet woods and swamps. Chokeberries are cultivated as ornamental plants and also because they are very high in antioxidant pigment...
(89 mg/kg), sweet rowan
Rowan
The rowans or mountain-ashes are shrubs or small trees in genus Sorbus of family Rosaceae. They are native throughout the cool temperate regions of the Northern Hemisphere, with the highest species diversity in the mountains of western China and the Himalaya, where numerous apomictic microspecies...
(85 mg/kg), rowan
Rowan
The rowans or mountain-ashes are shrubs or small trees in genus Sorbus of family Rosaceae. They are native throughout the cool temperate regions of the Northern Hemisphere, with the highest species diversity in the mountains of western China and the Himalaya, where numerous apomictic microspecies...
berry (63 mg/kg), sea buckthorn berry (62 mg/kg), crowberry
Crowberry
Crowberry is a small genus of dwarf evergreen shrubs that bear edible fruit. They are commonly found in the northern hemisphere, from temperate to subarctic climates, and also in the Southern Andes of South America and on the South Atlantic islands of South Georgia, the Falklands and Tristan da...
(cultivated 53 mg/kg, wild 56 mg/kg), and the fruit of the prickly pear
Opuntia
Opuntia, also known as nopales or paddle cactus , is a genus in the cactus family, Cactaceae.Currently, only prickly pears are included in this genus of about 200 species distributed throughout most of the Americas. Chollas are now separated into the genus Cylindropuntia, which some still consider...
cactus. A recent study found that organically grown
Organic farming
Organic farming is the form of agriculture that relies on techniques such as crop rotation, green manure, compost and biological pest control to maintain soil productivity and control pests on a farm...
tomatoes had 79% more quercetin than "conventionally grown".
A study by the University of Queensland
University of Queensland
The University of Queensland, also known as UQ, is a public university located in state of Queensland, Australia. Founded in 1909, it is the oldest and largest university in Queensland and the fifth oldest in the nation...
, Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
has also indicated the presence of quercetin in varieties of honey
Honey
Honey is a sweet food made by bees using nectar from flowers. The variety produced by honey bees is the one most commonly referred to and is the type of honey collected by beekeepers and consumed by humans...
, including honey derived from eucalyptus
Eucalyptus
Eucalyptus is a diverse genus of flowering trees in the myrtle family, Myrtaceae. Members of the genus dominate the tree flora of Australia...
and tea tree
Melaleuca
Melaleuca is a genus of plants in the myrtle family Myrtaceae known for its natural soothing and cleansing properties. There are well over 200 recognised species, most of which are endemic to Australia...
flower
Flower
A flower, sometimes known as a bloom or blossom, is the reproductive structure found in flowering plants . The biological function of a flower is to effect reproduction, usually by providing a mechanism for the union of sperm with eggs...
s.
Biosynthesis
PhenylalaninePhenylalanine
Phenylalanine is an α-amino acid with the formula C6H5CH2CHCOOH. This essential amino acid is classified as nonpolar because of the hydrophobic nature of the benzyl side chain. L-Phenylalanine is an electrically neutral amino acid, one of the twenty common amino acids used to biochemically form...
is converted to 4-coumaroyl-CoA in a series of steps known as the general phenylpropanoid
Phenylpropanoid
The phenylpropanoids are a diverse family of organic compounds that are synthesized by plants from the amino acid phenylalanine. Their name is derived from the six-carbon, aromatic phenyl group and the three-carbon propene tail of cinnamic acid, which is synthesized from phenylalanine in the first...
pathway using phenylalanine ammonia-lyase
Phenylalanine ammonia-lyase
In enzymology, a phenylalanine ammonia-lyase is an enzyme that catalyzes the chemical reactionHence, this enzyme has one substrate, L-phenylalanine, and two products, trans-cinnamic acid and ammonia....
, cinnamate-4-hydroxylase, and 4-coumaroyl-CoA-ligase. 4-Coumaroyl-CoA is added to three molecules of malonyl-CoA
Malonyl-CoA
Malonyl-CoA is a coenzyme A derivative.-Functions:It plays a key role in chain elongation in fatty acid biosynthesis and polyketide biosynthesis....
to form tetrahydroxychalcone using 7,2’-dihydroxy-4’-methoxyisoflavanol synthase. Tetrahydroxychalcone is then converted into naringenin
Naringenin
Naringenin is a flavanone, a type of flavonoid, that is considered to have a bioactive effect on human health as antioxidant, free radical scavenger, anti-inflammatory, carbohydrate metabolism promoter, and immune system modulator. It is the predominant flavanone in grapefruit.-Biological...
using chalcone isomerase
Chalcone isomerase
In enzymology, a chalcone isomerase is an enzyme that catalyzes the chemical reactionHence, this enzyme has one substrate, a chalcone, and one product, a flavanone....
. Naringenin is then converted into eriodictyol
Eriodictyol
Eriodictyol is a bitter-masking flavanone, a flavonoid extracted from Yerba Santa , a plant native to North America...
using flavanoid 3’-hydroxylase. Eriodictyol is then converted into dihydroquercetin with flavanone 3-hydroxylase, which is then converted into quercetin using flavonol synthase
Flavonol synthase
In enzymology, a flavonol synthase is an enzyme that catalyzes the chemical reactionThe 3 substrates of this enzyme are dihydroflavonol, 2-oxoglutarate, and O2, whereas its 4 products are flavonol, succinate, CO2, and H2O....
.
Glycosides
Quercetin is the aglyconeAglycone
An aglycone is the non-sugar compound remaining after replacement of the glycosyl group from a glycoside by a hydrogen atom. The spelling aglycon is sometimes encountered .Classes of phytochemicals found in the aglycone and glycosides forms :...
form of a number of other flavonoid glycoside
Glycoside
In chemistry, a glycoside is a molecule in which a sugar is bound to a non-carbohydrate moiety, usually a small organic molecule. Glycosides play numerous important roles in living organisms. Many plants store chemicals in the form of inactive glycosides. These can be activated by enzyme...
s, such as rutin
Rutin
Rutin, also called rutoside, quercetin-3-O-rutinoside and sophorin, is a citrus flavonoid glycoside found in buckwheat, the leaves and petioles of Rheum species, and asparagus...
and quercitrin
Quercitrin
Quercitrin is a glycoside formed from the flavonoid quercetin and the deoxy sugar rhamnose. It is a constituent of the dye quercitron. It can be found in Tartary buckwheat ....
, found in citrus
Citrus
Citrus is a common term and genus of flowering plants in the rue family, Rutaceae. Citrus is believed to have originated in the part of Southeast Asia bordered by Northeastern India, Myanmar and the Yunnan province of China...
fruit, buckwheat
Buckwheat
Buckwheat refers to a variety of plants in the dicot family Polygonaceae: the Eurasian genus Fagopyrum, the North American genus Eriogonum, and the Northern Hemisphere genus Fallopia. Either of the latter two may be referred to as "wild buckwheat"...
and onions. Quercetin forms the glycoside
Glycoside
In chemistry, a glycoside is a molecule in which a sugar is bound to a non-carbohydrate moiety, usually a small organic molecule. Glycosides play numerous important roles in living organisms. Many plants store chemicals in the form of inactive glycosides. These can be activated by enzyme...
s quercitrin
Quercitrin
Quercitrin is a glycoside formed from the flavonoid quercetin and the deoxy sugar rhamnose. It is a constituent of the dye quercitron. It can be found in Tartary buckwheat ....
and rutin
Rutin
Rutin, also called rutoside, quercetin-3-O-rutinoside and sophorin, is a citrus flavonoid glycoside found in buckwheat, the leaves and petioles of Rheum species, and asparagus...
together with rhamnose
Rhamnose
Rhamnose is a naturally occurring deoxy sugar. It can be classified as either a methyl-pentose or a 6-deoxy-hexose. Rhamnose occurs in nature in its L-form as L-rhamnose . This is unusual, since most of the naturally occurring sugars are in D-form...
and rutinose
Rutinose
Rutinose is the disaccharide also known as 6-O-L-rhamnosyl-D-glucose that is present in some flavonoid glycosides. It is prepared from rutin by hydrolysis with the enzyme rhamnodiastase....
, respectively. Likewise guaijaverin is the 3-O-arabinoside, hyperoside
Hyperoside
Hyperoside is a chemical compound. It is the 3-O-galactoside of quercetin. It is a medicinally active compound that can be isolated from Drosera rotundifolia, from the Stachys plant, from Prunella vulgaris, from Rumex acetosella, Cuscuta Chinensis seeds and from St John's wort.In Rheum nobile and R...
is the 3-O-galactoside
Galactoside
A galactoside is a glycoside containing galactose. The H of the OH group on carbon-1 of galactose is replaced by an organic moiety.Depending on whether the glycosidic bond lies "above" or "below" the plane of the galactose molecule, galactosides are classified as α-galactosides or β-galactosides....
, isoquercitin
Isoquercitin
Isoquercitin is a chemical compound. It can be isolated from mangoes and from Rheum nobile, the Noble rhubarb or Sikkim rhubarb, a giant herbaceous plant native to the Himalaya. Quercetin glycosides are also present in tea....
is the 3-O-glucoside
Glucoside
A glucoside is a glycoside that is derived from glucose. Glucosides are common in plants, but rare in animals. Glucose is produced when a glucoside is hydrolysed by purely chemical means, or decomposed by fermentation or enzymes....
, and spiraeoside
Spiraeoside
Spiraeoside is a chemical compound. It can be isolated from flowers of Filipendula ulmaria or from the garden onion .Spiraeoside is the 4'-O-glucoside of quercetin....
is the 4'-O-glucoside. CTN-986
CTN-986
CTN-986 is a quercetin derivative found in cottonseeds and cottonseed oil. It has antidepressant properties and has been shown to stimulate neurogenesis in the hippocampus. The neurogenesis appears to be mediated by activation of the 5-HT1A receptor. Co-administration with the 5-HT1A antagonist...
is a quercetin derivative found in cottonseeds and cottonseed oil.
Effects of consumption by humans and other animals
Quercetin itself (aglyconeAglycone
An aglycone is the non-sugar compound remaining after replacement of the glycosyl group from a glycoside by a hydrogen atom. The spelling aglycon is sometimes encountered .Classes of phytochemicals found in the aglycone and glycosides forms :...
quercetin), as opposed to quercetin glycoside
Glycoside
In chemistry, a glycoside is a molecule in which a sugar is bound to a non-carbohydrate moiety, usually a small organic molecule. Glycosides play numerous important roles in living organisms. Many plants store chemicals in the form of inactive glycosides. These can be activated by enzyme...
s, is not a normal dietary component. In a bioavailability study in rats, radiolabelled quercetin-4'-glucoside was converted to phenolic acids as it passed through the gastrointestinal tract, producing compounds not monitored in several previous animal studies of aglycone quercetin. All but 4% of the radiolabel was recovered within 72 hours, with 69% recovered in urine.
Quercetin has neither been confirmed scientifically as a specific therapeutic for any condition nor been approved by any regulatory agency. The U.S. Food and Drug Administration has not approved any health claims for quercetin.
Antiviral
In a 2007 study that assessed the anti-Hepatitis B effects of Hyperoside, and that was published in the Acta Pharmacologica Sinica, it was shown that Hyperoside (which is the 3-O-galactoside of quercetin) is a strong inhibitor of HBsAg and HBeAg secretion in 2.2.15 cells.In another study also published in 2007 in the Archives of Pharmacal Research it was shown that quercetin, quercitrin and myricetin 3-O-beta-D-galactopyranoside displayed inhibition against HIV-1 reverse transcriptase, all with IC50 values of 60 microM.
Cancer
The American Cancer Society says while quercetin "has been promoted as being effective against a wide variety of diseases, including cancer," and "some early lab results appear promising, as of yet there is no reliable clinical evidence that quercetin can prevent or treat cancer in humans." In the amounts consumed in a healthy diet, quercetin "is unlikely to cause any major problems or benefits."In laboratory studies of cells in vitro
In vitro
In vitro refers to studies in experimental biology that are conducted using components of an organism that have been isolated from their usual biological context in order to permit a more detailed or more convenient analysis than can be done with whole organisms. Colloquially, these experiments...
, quercetin produces changes that are also produced by compounds that cause cancer (carcinogens), but these studies do not report increased cancer in animals or humans.
From laboratory studies is conjecture that quercetin may affect certain mechanisms of cancer. An 8-year study found the presence of three flavonols — kaempferol
Kaempferol
Kaempferol is a natural flavonol, a type of flavonoid, that has been isolated from tea, broccoli, Delphinium, Witch-hazel, grapefruit,cabbage, kale, beans, endive, leek, tomato, strawberries, grapes, brussels sprouts, apples and other plant sources. Kaempferol is a yellow crystalline solid with a...
, quercetin, and myricetin
Myricetin
Myricetin is a naturally occurring flavonol, a flavonoid found in many grapes, berries, fruits, vegetables, herbs, as well as other plants. Walnuts are a rich dietary source. Trace amounts can be found as glycosides. It is one of the phenolic compounds present in red wine.Myricetin has antioxidant...
— in a normal diet was associated with 23% reduced risk of pancreatic cancer
Pancreatic cancer
Pancreatic cancer refers to a malignant neoplasm of the pancreas. The most common type of pancreatic cancer, accounting for 95% of these tumors is adenocarcinoma, which arises within the exocrine component of the pancreas. A minority arises from the islet cells and is classified as a...
, a rare but frequently fatal disease, in tobacco smokers. There was no benefit in subjects who had never smoked or had previously quit smoking.
In vitro, cultured skin and prostate cancer cells were suppressed (compared to nonmalignant cells) when treated with a combination of quercetin and ultrasound
Ultrasound
Ultrasound is cyclic sound pressure with a frequency greater than the upper limit of human hearing. Ultrasound is thus not separated from "normal" sound based on differences in physical properties, only the fact that humans cannot hear it. Although this limit varies from person to person, it is...
.
In laboratory culture studies, quercetin increased the sensitivity of resistant colorectal tumors with microsatellite instability to the chemotherapy drug, 5-fluorouracil.
Inflammation
Several laboratory studies show quercetin may have anti-inflammatoryAnti-inflammatory
Anti-inflammatory refers to the property of a substance or treatment that reduces inflammation. Anti-inflammatory drugs make up about half of analgesics, remedying pain by reducing inflammation as opposed to opioids, which affect the central nervous system....
properties, and it is being investigated for a wide range of potential health benefits.
Quercetin has been reported to be of use in alleviating symptoms of pollinosis. An enzymatically modified derivative was found to alleviate ocular but not nasal symptoms of pollinosis.
A study with rats showed that quercetin effectively reduced immediate-release niacin (vitamin B3) flush, in part by means of reducing prostaglandin D2
Prostaglandin D2
Prostaglandin D2 is a prostaglandin that binds to the receptor PTGDR, as well as CRTH2. It is a major prostaglandin produced by mast cells – recruits Th2 cells, eosinophils, basophils. In mammalian organs, large amounts of PGD2 are found in the brain, in mast cells and found nowhere else...
production. A pilot clinical study of four humans gave preliminary data supporting this.
Quercetin may have properties of a calcineurin
Calcineurin
Calcineurin is a protein phosphatase also known as protein phosphatase 3, PPP3CA, and calcium-dependent serine-threonine phosphatase, and formerly known as protein phosphatase 2B . It activates the T cells of the immune system and can be blocked by drugs...
inhibitor, similar to cyclosporin A and tacrolimus, according to one laboratory study.
Fibromyalgia
Quercetin may be effective in the treatment of fibromyalgiaFibromyalgia
Fibromyalgia is a medical disorder characterized by chronic widespread pain and allodynia, a heightened and painful response to pressure. It is an example of a diagnosis of exclusion...
because of its potential anti-inflammatory or mast cell
Mast cell
A mast cell is a resident cell of several types of tissues and contains many granules rich in histamine and heparin...
inhibitory properties shown in laboratory studies.
Metabolic syndrome
Quercetin has been shown to increase energy expenditure in ratsLaboratory rat
A laboratory rat is a rat of the species Rattus norvegicus which is bred and kept for scientific research. Laboratory rats have served as an important animal model for research in psychology, medicine, and other fields.- Origins :...
, but only for short periods (fewer than 8 weeks). Effects of quercetin on exercise tolerance in mice have been associated with increased mitochondrial biogenesis
Mitochondrial biogenesis
Mitochondrial biogenesis is the process by which new mitochondria are formed in the cell. Mitochondrial biogenesis is activated by numerous different signals during times of cellular stress or in response to environmental stimuli...
. In mice, an oral quercetin dose of 12.5 to 25 mg/kg increased gene expression
Gene expression
Gene expression is the process by which information from a gene is used in the synthesis of a functional gene product. These products are often proteins, but in non-protein coding genes such as ribosomal RNA , transfer RNA or small nuclear RNA genes, the product is a functional RNA...
of mitochondrial biomarkers and improved exercise endurance.
It has also been claimed that quercetin reduces blood pressure in hypertensive and obese subjects in whom LDL cholesterol levels were also reduced.
An in vitro study showed quercetin and resveratrol
Resveratrol
Resveratrol is a stilbenoid, a type of natural phenol, and a phytoalexin produced naturally by several plants when under attack by pathogens such as bacteria or fungi....
combined inhibited production of fat cells.
A 12-week study of 941 adults found that supplements of 500 to 1000 milligrams of quercetin with vitamin C and niacin did not cause any significant difference in body mass or composition and had no significant effect on inflammatory markers, diagnostic blood chemistries, blood pressure, and blood lipid profiles.
Monoamine-oxidase inhibitor
Quercetin has also been shown to have MAO inhibiting activity which may explain some of it's pharmacological properties.Drug interactions
Quercetin is contraindicated with some antibiotics; it may interact with fluoroquinolones (an antibioticAntibiotic
An antibacterial is a compound or substance that kills or slows down the growth of bacteria.The term is often used synonymously with the term antibiotic; today, however, with increased knowledge of the causative agents of various infectious diseases, antibiotic has come to denote a broader range of...
), as quercetin competitively binds to bacterial DNA gyrase. Whether this inhibits or enhances the effect of fluoroquinolones is not certain.
AHFS Drug Information (2010) identifies quercetin as an inhibitor of CYP2C8
CYP2C8
Cytochrome P4502C8 , a member of the cytochrome P450 mixed-function oxidase system, is involved in the metabolism of xenobiotics in the body.- CYP2C8 Ligands :...
, and specifically names it as a drug with potential to have harmful interactions with taxol/paclitaxel. As paclitaxel is metabolized primarily by CYP2C8, its bioavailability
Bioavailability
In pharmacology, bioavailability is a subcategory of absorption and is used to describe the fraction of an administered dose of unchanged drug that reaches the systemic circulation, one of the principal pharmacokinetic properties of drugs. By definition, when a medication is administered...
may be increased unpredictably, potentially leading to harmful side-effects.
Quercetin is described as an inhibitor
Enzyme inhibitor
An enzyme inhibitor is a molecule that binds to enzymes and decreases their activity. Since blocking an enzyme's activity can kill a pathogen or correct a metabolic imbalance, many drugs are enzyme inhibitors. They are also used as herbicides and pesticides...
of CYP2C9
CYP2C9
Cytochrome P450 2C9 is a protein that in humans is encoded by the CYP2C9 gene.- Function :CYP2C9 is an important cytochrome P450 enzyme with a major role in the oxidation of both xenobiotic and endogenous compounds. CYP2C9 makes up about 18% of the cytochrome P450 protein in liver microsomes...
. Quercetin is an inhibitor and inducer
Enzyme inhibitor
An enzyme inhibitor is a molecule that binds to enzymes and decreases their activity. Since blocking an enzyme's activity can kill a pathogen or correct a metabolic imbalance, many drugs are enzyme inhibitors. They are also used as herbicides and pesticides...
of CYP3A4
CYP3A4
Cytochrome P450 3A4 , a member of the cytochrome P450 mixed-function oxidase system, is one of the most important enzymes involved in the metabolism of xenobiotics in the body. CYP3A4 is involved in the oxidation of the largest range of substrates of all the CYPs. As a result, CYP3A4 is present in...
(in other words, it reduces the enzyme's activity in the short term, but the body responds by producing more of it). CYP2C9 and CPY3A4 are members of the cytochrome P450 mixed-function oxidase system, and as such are enzyme
Enzyme
Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...
s involved in the metabolism of xenobiotics in the body. In either case, quercetin may alter serum levels and, therefore, effects of drugs metabolized by these enzymes.
External links
- UMM Quercetin Info Page (University of Maryland Medical CenterUniversity of Maryland Medical CenterThe University of Maryland Medical Center is a teaching hospital with 705 beds based in Baltimore, Maryland, that provides the full range of health care to people throughout Maryland and the Mid-Atlantic region. It gets more than 35,000 inpatient admissions and 165,000 outpatient visits each year...
Website)
See also
- Flavonol 3-sulfotransferaseFlavonol 3-sulfotransferaseIn enzymology, a flavonol 3-sulfotransferase is an enzyme that catalyzes the chemical reactionThus, the two substrates of this enzyme are 3'-phosphoadenylyl sulfate and a flavonol, whereas its two products are adenosine 3',5'-bisphosphate and flavonol 3-sulfate...
- Phenolic compounds in winePhenolic compounds in wineThe phenolic compounds - natural phenol and polyphenols - in wine include a large group of several hundred chemical compounds that affect the taste, color and mouthfeel of wine. These compounds include phenolic acids, stilbenes, flavonols, dihydroflavonols, anthocyanins, flavanol monomers and...
- PhytochemicalPhytochemicalPhytochemicals are biologically active chemical compounds that occur naturally in plants . Phytochemicals are the molecules responsible for the color and organoleptic properties . For example, the deep purple color of blueberries and the smell of garlic...
- Quercetin 2,3-dioxygenaseQuercetin 2,3-dioxygenaseIn enzymology, a quercetin 2,3-dioxygenase is an enzyme that catalyzes the chemical reactionThus, the two substrates of this enzyme are quercetin and O2, whereas its 3 products are 2--4,6-dihydroxybenzoate, CO, and H+....
- Quercetin 3-O-methyltransferaseQuercetin 3-O-methyltransferaseIn enzymology, a quercetin 3-O-methyltransferase is an enzyme that catalyzes the chemical reactionThus, the two substrates of this enzyme are S-adenosyl methionine and 3,5,7,3',4'-pentahydroxyflavone, whereas its two products are S-adenosylhomocysteine and...
- Quercetin-3-sulfate 3'-sulfotransferaseQuercetin-3-sulfate 3'-sulfotransferaseIn enzymology, a quercetin-3-sulfate 3'-sulfotransferase is an enzyme that catalyzes the chemical reactionThus, the two substrates of this enzyme are 3'-phosphoadenylyl sulfate and quercetin 3-sulfate, whereas its two products are adenosine 3',5'-bisphosphate and quercetin 3,3'-bissulfate.This...
- Quercetin-3-sulfate 4'-sulfotransferaseQuercetin-3-sulfate 4'-sulfotransferaseIn enzymology, a quercetin-3-sulfate 4'-sulfotransferase is an enzyme that catalyzes the chemical reactionThus, the two substrates of this enzyme are 3'-phosphoadenylyl sulfate and quercetin 3-sulfate, whereas its two products are adenosine 3',5'-bisphosphate and quercetin 3,4'-bissulfate.This...
- Quercetin-3,3'-bissulfate 7-sulfotransferaseQuercetin-3,3'-bissulfate 7-sulfotransferaseIn enzymology, a quercetin-3,3'-bissulfate 7-sulfotransferase is an enzyme that catalyzes the chemical reactionThus, the two substrates of this enzyme are 3'-phosphoadenylyl sulfate and quercetin 3,3'-bissulfate, whereas its two products are adenosine 3',5'-bisphosphate and quercetin...