HOME

TheInfoList



OR:

Catechin is a
flavan-3-ol Flavan-3-ols (sometimes referred to as flavanols) are a subgroup of flavonoids. They are derivatives of flavans that possess a 2-phenyl-3,4-dihydro-2''H''-chromen-3-ol skeleton. Flavan-3-ols are structurally diverse and include a range of comp ...
, a type of
secondary metabolite Secondary metabolites, also called specialised metabolites, toxins, secondary products, or natural products, are organic compounds produced by any lifeform, e.g. bacteria, fungi, animals, or plants, which are not directly involved in the norma ...
providing antioxidant roles in
plant Plants are predominantly photosynthetic eukaryotes of the kingdom Plantae. Historically, the plant kingdom encompassed all living things that were not animals, and included algae and fungi; however, all current definitions of Plantae exclu ...
s. It belongs to the subgroup of
polyphenol Polyphenols () are a large family of naturally occurring organic compounds characterized by multiples of phenol units. They are abundant in plants and structurally diverse. Polyphenols include flavonoids, tannic acid, and ellagitannin, some o ...
s called
flavonoids Flavonoids (or bioflavonoids; from the Latin word ''flavus'', meaning yellow, their color in nature) are a class of polyphenolic secondary metabolites found in plants, and thus commonly consumed in the diets of humans. Chemically, flavonoids ...
. The name of the catechin chemical family derives from ''
catechu ( or ) is an extract of acacia trees used variously as a food additive, astringent, tannin, and dye. It is extracted from several species of '' Acacia'', but especially '' Senegalia catechu'' (''Acacia catechu''), by boiling the wood in w ...
'', which is the tannic juice or boiled extract of ''Mimosa catechu'' (''
Acacia catechu ''Senegalia catechu'' is a deciduous, thorny tree which grows up to in height. The plant is called ''khair''
in H ...
'' L.f).


Chemistry

Catechin possesses two
benzene ring Benzene is an organic chemical compound with the molecular formula C6H6. The benzene molecule is composed of six carbon atoms joined in a planar ring with one hydrogen atom attached to each. Because it contains only carbon and hydrogen atom ...
s (called the A- and B-rings) and a
dihydropyran In organic chemistry, dihydropyran refers to two heterocyclic compounds with the formula C5H8O: * 3,4-Dihydro-2''H''-pyran *3,6-dihydro-2''H''-pyran Nomenclature In IUPAC names, "dihydro" refers to the two added hydrogen atoms needed to remove o ...
heterocycle (the C-ring) with a hydroxyl group on carbon 3. The A-ring is similar to a
resorcinol Resorcinol (or resorcin) is an organic compound with the formula C6H4(OH)2. It is one of three isomeric benzenediols, the 1,3-isomer (or '' meta''-isomer). Resorcinol crystallizes from benzene as colorless needles that are readily soluble i ...
moiety while the B-ring is similar to a
catechol Catechol ( or ), also known as pyrocatechol or 1,2-dihydroxybenzene, is a toxic organic compound with the molecular formula . It is the ''ortho'' isomer of the three isomeric benzenediols. This colorless compound occurs naturally in trace amoun ...
moiety. There are two
chiral Chirality is a property of asymmetry important in several branches of science. The word ''chirality'' is derived from the Greek (''kheir''), "hand", a familiar chiral object. An object or a system is ''chiral'' if it is distinguishable from i ...
centers on the molecule on carbons 2 and 3. Therefore, it has four
diastereoisomer In stereochemistry, diastereomers (sometimes called diastereoisomers) are a type of stereoisomer. Diastereomers are defined as non-mirror image, non-identical stereoisomers. Hence, they occur when two or more stereoisomers of a compound have dif ...
s. Two of the isomers are in
trans configuration Trans- is a Latin prefix meaning "across", "beyond", or "on the other side of". Used alone, trans may refer to: Arts, entertainment, and media * Trans (festival), a former festival in Belfast, Northern Ireland, United Kingdom * ''Trans'' (fil ...
and are called ''catechin'' and the other two are in
cis configuration Cis or cis- may refer to: Places * Cis, Trentino, in Italy * In Poland: ** Cis, Świętokrzyskie Voivodeship, south-central ** Cis, Warmian-Masurian Voivodeship, north Math, science and biology * cis (mathematics) (cis(''θ'')), a trigonome ...
and are called ''epicatechin''. The most common catechin isomer is (+)-catechin. The other
stereoisomer In stereochemistry, stereoisomerism, or spatial isomerism, is a form of isomerism in which molecules have the same molecular formula and sequence of bonded atoms (constitution), but differ in the three-dimensional orientations of their atoms in ...
is (-)-catechin or ''ent''-catechin. The most common epicatechin isomer is (-)-epicatechin (also known under the names L-epicatechin, epicatechol, (-)-epicatechol, l-acacatechin, l-epicatechol, epi-catechin, 2,3-''cis''-epicatechin or (2''R'',3''R'')-(-)-epicatechin). The different epimers can be separated using chiral column chromatography. Making reference to no particular isomer, the molecule can just be called catechin. Mixtures of the different enantiomers can be called (±)-catechin or DL-catechin and (+/-)-epicatechin or DL-epicatechin. Catechin and epicatechin are the building blocks of the
proanthocyanidin Proanthocyanidins are a class of polyphenols found in many plants, such as cranberry, blueberry, and grape seeds. Chemically, they are oligomeric flavonoids. Many are oligomers of catechin and epicatechin and their gallic acid esters. More compl ...
s, a type of condensed tannin. File:(+)-Catechin.png, (+)-catechin (2''R'',3''S'') File:Catechin.png, (-)-catechin (2''S'',3''R'') File:(–)-Epicatechin.svg, (-)-epicatechin (2''R'',3''R'') File:(+)-epicatechin.svg, (+)-epicatechin (2''S'',3''S'') Moreover, the flexibility of the C-ring allows for two conformation isomers, putting the B-ring either in a pseudoequatorial position (E conformer) or in a pseudoaxial position (A conformer). Studies confirmed that (+)-catechin adopts a mixture of A- and E-conformers in aqueous solution and their conformational equilibrium has been evaluated to be 33:67. As flavonoids, catechins can act as
antioxidants Antioxidants are compounds that inhibit oxidation, a chemical reaction that can produce free radicals. This can lead to polymerization and other chain reactions. They are frequently added to industrial products, such as fuels and lubricants, ...
when in high concentration ''in vitro'', but compared with other flavonoids, their antioxidant potential is low. The ability to quench singlet oxygen seems to be in relation with the chemical structure of catechin, with the presence of the catechol moiety on ring B and the presence of a hydroxyl group activating the double bond on ring C.


Oxidation

Electrochemical experiments show that (+)-catechin oxidation mechanism proceeds in sequential steps, related with the
catechol Catechol ( or ), also known as pyrocatechol or 1,2-dihydroxybenzene, is a toxic organic compound with the molecular formula . It is the ''ortho'' isomer of the three isomeric benzenediols. This colorless compound occurs naturally in trace amoun ...
and
resorcinol Resorcinol (or resorcin) is an organic compound with the formula C6H4(OH)2. It is one of three isomeric benzenediols, the 1,3-isomer (or '' meta''-isomer). Resorcinol crystallizes from benzene as colorless needles that are readily soluble i ...
groups and the oxidation is pH-dependent. The oxidation of the catechol 3',4'-dihydroxyl electron-donating groups occurs first, at very low positive potentials, and is a reversible reaction. The hydroxyl groups of the resorcinol moiety oxidised afterwards were shown to undergo an irreversible oxidation reaction. The
laccase Laccases () are multicopper oxidases found in plants, fungi, and bacteria. Laccases oxidize a variety of phenolic substrates, performing one-electron oxidations, leading to crosslinking. For example, laccases play a role in the formation of l ...
/ ABTS system oxidizes (+)-catechin to oligomeric products of which
proanthocyanidin A2 Procyanidin A2 is an A type proanthocyanidin. It is found in avocado, chestnut, cranberry juice concentrate, lychee fruit pericarp, peanut The peanut (''Arachis hypogaea''), also known as the groundnut, goober (US), pindar (US) or monke ...
is a dimer.


Spectral data


Natural occurrences

(+)-Catechin and (-)-epicatechin as well as their
gallic acid Gallic acid (also known as 3,4,5-trihydroxybenzoic acid) is a trihydroxybenzoic acid with the formula C6 H2( OH)3CO2H. It is classified as a phenolic acid. It is found in gallnuts, sumac, witch hazel, tea leaves, oak bark, and other plants. I ...
conjugates are ubiquitous constituents of
vascular plant Vascular plants (), also called tracheophytes () or collectively Tracheophyta (), form a large group of land plants ( accepted known species) that have lignified tissues (the xylem) for conducting water and minerals throughout the plant. They ...
s, and frequent components of traditional herbal remedies, such as ''
Uncaria rhynchophylla ''Uncaria rhynchophylla'' () or the cat's claw herb is a plant species used in traditional Chinese medicine. (+)-Catechin and (-)-epicatechin are found in the plant as well as the alkaloid rhynchophylline. References External links

* ...
''. The two
isomers In chemistry, isomers are molecules or polyatomic ions with identical molecular formulae – that is, same number of atoms of each element – but distinct arrangements of atoms in space. Isomerism is existence or possibility of isomers. ...
are mostly found as cacao and
tea Tea is an aromatic beverage prepared by pouring hot or boiling water over cured or fresh leaves of ''Camellia sinensis'', an evergreen shrub native to East Asia which probably originated in the borderlands of southwestern China and north ...
constituents, as well as in ''
Vitis vinifera ''Vitis vinifera'', the common grape vine, is a species of flowering plant, native to the Mediterranean region, Central Europe, and southwestern Asia, from Morocco and Portugal north to southern Germany and east to northern Iran. There are curr ...
'' grapes.


In food

The main dietary sources of catechins in Europe and the United States are
tea Tea is an aromatic beverage prepared by pouring hot or boiling water over cured or fresh leaves of ''Camellia sinensis'', an evergreen shrub native to East Asia which probably originated in the borderlands of southwestern China and north ...
and pome fruits. Catechins and epicatechins are found in cocoa, which, according to one database, has the highest content (108 mg/100 g) of catechins among foods analyzed, followed by
prune juice Prune juice is a fruit juice derived from prunes (dried plums) that have been rehydrated. It is a mass-produced product that is often produced using a hot extraction method, and juice concentrate is typically produced using a low-temperature ext ...
(25 mg/100 ml) and
broad bean ''Vicia faba'', commonly known as the broad bean, fava bean, or faba bean, is a species of vetch, a flowering plant in the pea and bean family Fabaceae. It is widely cultivated as a crop for human consumption, and also as a cover crop. Varieti ...
pod (16 mg/100 g).
Açaí oil Açaí oil is obtained from the fruit of ''Euterpe oleracea'' (açaí palm), which grows in the Amazon rainforest. The oil is rich in phenolic compounds similar in profile to the pulp itself, such as vanillic acid, syringic acid, p-hydroxybenzoi ...
, obtained from the fruit of the açaí palm (''Euterpe oleracea''), contains (+)-catechins (67 mg/kg). Catechins are diverse among foods, from
peach The peach (''Prunus persica'') is a deciduous tree first domesticated and cultivated in Zhejiang province of Eastern China. It bears edible juicy fruits with various characteristics, most called peaches and others (the glossy-skinned, non-f ...
es to green tea and
vinegar Vinegar is an aqueous solution of acetic acid and trace compounds that may include flavorings. Vinegar typically contains 5–8% acetic acid by volume. Usually, the acetic acid is produced by a double fermentation, converting simple sugars to eth ...
. Catechins are found in
barley Barley (''Hordeum vulgare''), a member of the grass family, is a major cereal grain grown in temperate climates globally. It was one of the first cultivated grains, particularly in Eurasia as early as 10,000 years ago. Globally 70% of barley p ...
grain where they are the main phenolic compound responsible for
dough Dough is a thick, malleable, sometimes elastic paste made from grains or from leguminous or chestnut crops. Dough is typically made by mixing flour with a small amount of water or other liquid and sometimes includes yeast or other leavenin ...
discoloration. The taste associated with monomeric (+)-catechin or (-)-epicatechin is described as slightly
astringent An astringent (sometimes called adstringent) is a chemical that shrinks or constricts body tissues. The word derives from the Latin ''adstringere'', which means "to bind fast". Calamine lotion, witch hazel, and yerba mansa, a Californian pla ...
, but not bitter.


Metabolism


Biosynthesis

The biosynthesis of catechin begins with ma 4-hydroxycinnamoyl CoA starter unit which undergoes chain extension by the addition of three malonyl-CoAs through a PKSIII pathway. 4-hydroxycinnamoyl CoA is biosynthesized from
L-phenylalanine Phenylalanine (symbol Phe or F) is an essential α-amino acid with the formula . It can be viewed as a benzyl group substituted for the methyl group of alanine, or a phenyl group in place of a terminal hydrogen of alanine. This essential amin ...
through the Shikimate pathway. L-phenylalanine is first deaminated by phenylalanine ammonia lyase (PAL) forming cinnamic acid which is then oxidized to 4-hydroxycinnamic acid by cinnamate 4-hydroxylase. Chalcone synthase then catalyzes the condensation of 4-hydroxycinnamoyl CoA and three molecules of malonyl-CoA to form chalcone. Chalcone is then isomerized to
naringenin Naringenin is a flavorless, colorless flavanone, a type of flavonoid. It is the predominant flavanone in grapefruit, and is found in a variety of fruits and herbs. Structure Naringenin has the skeleton structure of a flavanone with three hydro ...
by chalcone isomerase which is oxidized to
eriodictyol Eriodictyol is a bitter-masking flavanone, a flavonoid extracted from yerba santa (''Eriodictyon californicum''), a plant native to North America. Eriodictyol is one of the four flavanones identified in this plant as having taste-modifying pro ...
by flavonoid 3'- hydroxylase and further oxidized to
taxifolin Taxifolin (5,7,3',4'-flavan-on-ol), also known as dihydroquercetin, belongs to the subclass flavanonols in the flavonoids, which in turn is a class of polyphenols. Stereocenters Taxifolin has two stereocenters on the C-ring, as opposed to quer ...
by flavanone 3-hydroxylase. Taxifolin is then reduced by dihydroflavanol 4-reductase and leucoanthocyanidin reductase to yield catechin. The biosynthesis of catechin is shown below
Leucocyanidin reductase In enzymology, a leucoanthocyanidin reductase () (LAR, aka leucocyanidin reductase or LCR) is an enzyme that catalyzes the chemical reaction :(2R,3S)-catechin + NADP+ + H2O \rightleftharpoons 2,3-trans-3,4-cis-leucocyanidin + NADPH + H+ The 3 s ...
(LCR) uses 2,3-trans-3,4-cis-
leucocyanidin Leucocyanidin is a colorless chemical compound that is a member of the class of natural products known as leucoanthocyanidins. Chemistry (+)-Leucocyanidin can be synthesized from (+)-dihydroquercetin by reduction with sodium borohydride. Mola ...
to produce (+)-catechin and is the first enzyme in the
proanthocyanidins Proanthocyanidins are a class of polyphenols found in many plants, such as cranberry, blueberry, and grape seeds. Chemically, they are oligomeric flavonoids. Many are oligomers of catechin and epicatechin and their gallic acid esters. More co ...
(PA)-specific pathway. Its activity has been measured in leaves, flowers, and seeds of the legumes ''
Medicago sativa Alfalfa () (''Medicago sativa''), also called lucerne, is a perennial flowering plant in the legume family Fabaceae. It is cultivated as an important forage crop in many countries around the world. It is used for grazing, hay, and silage, as w ...
'', '' Lotus japonicus'', ''
Lotus uliginosus ''Lotus pedunculatus'' (formerly ''Lotus uliginosus''), the big trefoil, greater bird's-foot-trefoil or marsh bird's-foot trefoil, is a member of the pea family (Fabaceae). It is a herbaceous perennial growing throughout Europe in damp, open loc ...
'', ''
Hedysarum sulfurescens ''Hedysarum sulphurescens'', the yellow sweetvetch or white sweetvetch, is a perennial herb species. Leucocyanidin reductase (LCR) uses 2,3-trans-3,4-cis-leucocyanidin to produce (+)-catechin and is the first enzyme in the proanthocyanidins P ...
'', and ''
Robinia pseudoacacia ''Robinia pseudoacacia'', commonly known in its native territory as black locust, is a medium-sized hardwood deciduous tree, belonging to the tribe Robinieae of the legume family Fabaceae. It is endemic to a few small areas of the United States, ...
''. The enzyme is also present in ''
Vitis vinifera ''Vitis vinifera'', the common grape vine, is a species of flowering plant, native to the Mediterranean region, Central Europe, and southwestern Asia, from Morocco and Portugal north to southern Germany and east to northern Iran. There are curr ...
'' (grape).


Biodegradation

Catechin oxygenase, a key enzyme in the degradation of catechin, is present in fungi and bacteria. Among bacteria, degradation of (+)-catechin can be achieved by ''
Acinetobacter calcoaceticus ''Acinetobacter calcoaceticus'' is a bacterial species of the genus ''Acinetobacter''. It is a nonmotile, Gram-negative coccobacillus. It grows under aerobic conditions, is catalase positive and oxidase negative. ''A. calcoaceticus'' is a part ...
''. Catechin is metabolized to
protocatechuic acid Protocatechuic acid (PCA) is a dihydroxybenzoic acid, a type of phenolic acid. It is a major metabolite of antioxidant polyphenols found in green tea. It has mixed effects on normal and cancer cells in ''in vitro'' and ''in vivo'' studies. Biolo ...
(PCA) and phloroglucinol carboxylic acid (PGCA). It is also degraded by ''
Bradyrhizobium japonicum ''Bradyrhizobium japonicum'' is a species of legume- root nodulating, microsymbiotic nitrogen-fixing bacteria. The species is one of many Gram-negative, rod-shaped bacteria commonly referred to as rhizobia. Within that broad classification, w ...
''. Phloroglucinol carboxylic acid is further decarboxylated to
phloroglucinol Phloroglucinol is an organic compound with the formula C6H3(OH)3. It is a colorless solid. It is used in the synthesis of pharmaceuticals and explosives. Phloroglucinol is one of three isomeric benzenetriols. The other two isomers are hydroxyqu ...
, which is dehydroxylated to
resorcinol Resorcinol (or resorcin) is an organic compound with the formula C6H4(OH)2. It is one of three isomeric benzenediols, the 1,3-isomer (or '' meta''-isomer). Resorcinol crystallizes from benzene as colorless needles that are readily soluble i ...
. Resorcinol is hydroxylated to
hydroxyquinol Hydroxyquinol is an organic compound with the formula C6H3(OH)3. It is one of three isomeric benzenetriols. The compound is a colorless solid that is soluble in water. It reacts with air to give a black insoluble solid. Production It is prepar ...
. Protocatechuic acid and hydroxyquinol undergo intradiol cleavage through protocatechuate 3,4-dioxygenase and hydroxyquinol 1,2-dioxygenase to form β-carboxy cis, cis-muconic acid and
maleyl acetate Maleylacetic acid is a chemical compound produced in the biodegradation of catechin by ''Bradyrhizobium japonicum''. The enzyme maleylacetate reductase uses 3-oxoadipate, NAD+, and NADP+ to produce 2-maleylacetate, NADH Nicotinamide ad ...
. Among fungi, degradation of catechin can be achieved by '' Chaetomium cupreum''.


Metabolism in humans

Catechins are metabolised upon uptake from the gastrointestinal tract, in particular the
jejunum The jejunum is the second part of the small intestine in humans and most higher vertebrates, including mammals, reptiles, and birds. Its lining is specialised for the absorption by enterocytes of small nutrient molecules which have been previou ...
, and in the
liver The liver is a major organ only found in vertebrates which performs many essential biological functions such as detoxification of the organism, and the synthesis of proteins and biochemicals necessary for digestion and growth. In humans, it ...
, resulting in so-called structurally-related epicatechin metabolites (SREM). The main metabolic pathways for SREMs are
glucuronidation Glucuronidation is often involved in drug metabolism of substances such as drugs, pollutants, bilirubin, androgens, estrogens, mineralocorticoids, glucocorticoids, fatty acid derivatives, retinoids, and bile acids. These linkages involve gl ...
,
sulfation Sulfation is the chemical reaction that entails the addition of SO3 group. In principle, many sulfations would involve reactions of sulfur trioxide (SO3). In practice, most sulfations are effected less directly. Regardless of the mechanism, the ...
and methylation of the
catechol Catechol ( or ), also known as pyrocatechol or 1,2-dihydroxybenzene, is a toxic organic compound with the molecular formula . It is the ''ortho'' isomer of the three isomeric benzenediols. This colorless compound occurs naturally in trace amoun ...
group by
catechol-O-methyl transferase Catechol-''O''-methyltransferase (COMT; ) is one of several enzymes that degrade catecholamines (neurotransmitters such as dopamine, epinephrine, and norepinephrine), catecholestrogens, and various drugs and substances having a catechol struct ...
, with only small amounts detected in plasma. The majority of dietary catechins are however metabolised by the colonic microbiome to gamma-valerolactones and
hippuric acid Hippuric acid ( Gr. ''hippos'', horse, ''ouron'', urine) is a carboxylic acid and organic compound. It is found in urine and is formed from the combination of benzoic acid and glycine. Levels of hippuric acid rise with the consumption of phenol ...
s which undergo further
biotransformation Biotransformation is the biochemical modification of one chemical compound or a mixture of chemical compounds. Biotransformations can be conducted with whole cells, their lysates, or purified enzymes. Increasingly, biotransformations are effected w ...
,
glucuronidation Glucuronidation is often involved in drug metabolism of substances such as drugs, pollutants, bilirubin, androgens, estrogens, mineralocorticoids, glucocorticoids, fatty acid derivatives, retinoids, and bile acids. These linkages involve gl ...
,
sulfation Sulfation is the chemical reaction that entails the addition of SO3 group. In principle, many sulfations would involve reactions of sulfur trioxide (SO3). In practice, most sulfations are effected less directly. Regardless of the mechanism, the ...
and methylation in the
liver The liver is a major organ only found in vertebrates which performs many essential biological functions such as detoxification of the organism, and the synthesis of proteins and biochemicals necessary for digestion and growth. In humans, it ...
. The stereochemical configuration of catechins has a strong impact on their uptake and metabolism as uptake is highest for (-)-epicatechin and lowest for (-)-catechin.


Biotransformation

Biotransformation of (+)-catechin into
taxifolin Taxifolin (5,7,3',4'-flavan-on-ol), also known as dihydroquercetin, belongs to the subclass flavanonols in the flavonoids, which in turn is a class of polyphenols. Stereocenters Taxifolin has two stereocenters on the C-ring, as opposed to quer ...
by a two-step oxidation can be achieved by ''
Burkholderia ''Burkholderia'' is a genus of Pseudomonadota whose pathogenic members include the ''Burkholderia cepacia'' complex, which attacks humans and ''Burkholderia mallei'', responsible for glanders, a disease that occurs mostly in horses and related ...
'' sp. (+)-Catechin and (-)-epicatechin are transformed by the endophytic filamentous fungus ''
Diaporthe ''Diaporthe'' is a genus of endophytic filamentous fungal plant pathogens. ''Diaporthe'' species have been shown to transform the infection-inhibiting factors (+)-catechin and (−)-epicatechin into the 3,4-cis-dihydroxyflavan derivatives. So ...
'' sp. into the 3,4-cis-dihydroxyflavan derivatives, (+)- (2R,3S,4S)-3,4,5,7,3',4'-hexahydroxyflavan (leucocyanidin) and (-)-(2R,3R,4R)-3,4,5,7,3',4'-hexahydroxyflavan, respectively, whereas (-)-catechin and (+)-epicatechin with a 2S-phenyl group resisted the biooxidation. Leucoanthocyanidin reductase (LAR) uses (2''R'',3''S'')-catechin, NADP+ and H2O to produce 2,3-trans-3,4-cis-
leucocyanidin Leucocyanidin is a colorless chemical compound that is a member of the class of natural products known as leucoanthocyanidins. Chemistry (+)-Leucocyanidin can be synthesized from (+)-dihydroquercetin by reduction with sodium borohydride. Mola ...
, NADPH, and H+. Its gene expression has been studied in developing grape berries and grapevine leaves.


Glycosides

* (2R,3S)-Catechin-7-O-β-D-glucopyranoside can be isolated from
barley Barley (''Hordeum vulgare''), a member of the grass family, is a major cereal grain grown in temperate climates globally. It was one of the first cultivated grains, particularly in Eurasia as early as 10,000 years ago. Globally 70% of barley p ...
(''Hordeum vulgare'' L.) and malt. * Epigeoside (Catechin-3-O-alpha-L-rhamnopyranosyl-(1-4)-beta-D-glucopyranosyl-(1–6)-beta-D-glucopyranoside) can be isolated from the rhizomes of '' Epigynum auritum''.


Research


Vascular function

Only limited evidence from dietary studies indicates that catechins may affect
endothelium The endothelium is a single layer of squamous endothelial cells that line the interior surface of blood vessels and lymphatic vessels. The endothelium forms an interface between circulating blood or lymph in the lumen and the rest of the vesse ...
-dependent
vasodilation Vasodilation is the widening of blood vessels. It results from relaxation of smooth muscle cells within the vessel walls, in particular in the large veins, large arteries, and smaller arterioles. The process is the opposite of vasoconstrictio ...
which could contribute to normal
blood flow Hemodynamics or haemodynamics are the dynamics of blood flow. The circulatory system is controlled by homeostatic mechanisms of autoregulation, just as hydraulic circuits are controlled by control systems. The hemodynamic response continuously m ...
regulation in humans. Green tea catechins may improve blood pressure, especially when systolic blood pressure is above 130 mmHg. Due to extensive metabolism during digestion, the fate and activity of catechin metabolites responsible for this effect on blood vessels, as well as the actual mode of action, are unknown.


Adverse events

Catechin and its metabolites can bind tightly to red blood cells and thereby induce the development of autoantibodies, resulting in
haemolytic anaemia Hemolytic anemia or haemolytic anaemia is a form of anemia due to hemolysis, the abnormal breakdown of red blood cells (RBCs), either in the blood vessels (intravascular hemolysis) or elsewhere in the human body (extravascular). This most commonly ...
and
renal failure Kidney failure, also known as end-stage kidney disease, is a medical condition in which the kidneys can no longer adequately filter waste products from the blood, functioning at less than 15% of normal levels. Kidney failure is classified as eit ...
. This resulted in the withdrawal of the catechin-containing drug Catergen, used to treat
viral hepatitis Viral hepatitis is liver inflammation due to a viral infection. It may present in acute form as a recent infection with relatively rapid onset, or in chronic form. The most common causes of viral hepatitis are the five unrelated hepatotropic vi ...
, from market in 1985. Catechins from green tea can be
hepatotoxic Hepatotoxicity (from ''hepatic toxicity'') implies chemical-driven liver damage. Drug-induced liver injury is a cause of acute and chronic liver disease caused specifically by medications and the most common reason for a drug to be withdrawn fro ...
and the
European Food Safety Authority The European Food Safety Authority (EFSA) is the agency of the European Union (EU) that provides independent scientific advice and communicates on existing and emerging risks associated with the food chain. EFSA was established in February 2002, ...
has recommended not to exceed 800 mg/d.


Other

One limited meta-analysis showed that increasing consumption of green tea and its catechins to seven cups per day provided a small reduction in prostate cancer.
Nanoparticle A nanoparticle or ultrafine particle is usually defined as a particle of matter that is between 1 and 100 nanometres (nm) in diameter. The term is sometimes used for larger particles, up to 500 nm, or fibers and tubes that are less than 10 ...
methods are under preliminary research as potential delivery systems of catechins.


Botanical effects

Catechins released into the ground by some plants may hinder the growth of their neighbors, a form of allelopathy. ''
Centaurea maculosa ''Centaurea stoebe'', the spotted knapweed or panicled knapweed, is a species of ''Centaurea'' native to eastern Europe, although it has spread to North America, where it is considered an invasive species. It forms a tumbleweed, helping to increa ...
'', the spotted knapweed often studied for this behavior, releases catechin
isomers In chemistry, isomers are molecules or polyatomic ions with identical molecular formulae – that is, same number of atoms of each element – but distinct arrangements of atoms in space. Isomerism is existence or possibility of isomers. ...
into the ground through its roots, potentially having effects as an antibiotic or herbicide. One hypothesis is that it causes a
reactive oxygen species In chemistry, reactive oxygen species (ROS) are highly reactive chemicals formed from diatomic oxygen (). Examples of ROS include peroxides, superoxide, hydroxyl radical, singlet oxygen, and alpha-oxygen. The reduction of molecular oxygen () p ...
wave through the target plant's root to kill root cells by apoptosis. Most plants in the European ecosystem have defenses against catechin, but few plants are protected against it in the North American ecosystem where ''
Centaurea maculosa ''Centaurea stoebe'', the spotted knapweed or panicled knapweed, is a species of ''Centaurea'' native to eastern Europe, although it has spread to North America, where it is considered an invasive species. It forms a tumbleweed, helping to increa ...
'' is an invasive, uncontrolled weed. Catechin acts as an infection-inhibiting factor in strawberry leaves. Epicatechin and catechin may prevent coffee berry disease by inhibiting appressorial melanization of '' Colletotrichum kahawae''.


References


External links

* {{Flavanol Flavanols Catechols Nutrition