Mutagenic for mammalian somatic cells, mutagenic for bacteria and yeast
Safety data sheet
sciencelab AppliChem[permanent dead link]
R-phrases (outdated)
R36/37/38
S-phrases (outdated)
S26-S36
Lethal dose or concentration (LD, LC):
LD50 (median dose)
(+)-catechin : 10,000 mg/kg in rat (RTECS) 10,000 mg/kg in mouse 3,890 mg/kg in rat (other source)
Pharmacology
Routes of administration
Oral
Pharmacokinetics:
Excretion
Urines
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Nverify (what is YN ?)
Infobox references
Catechin/ˈkætɪtʃɪn/ is a flavan-3-ol, a type of natural phenol and antioxidant. It is a plant secondary metabolite. It belongs to the group of flavan-3-ols (or simply flavanols), part of the chemical family of flavonoids.
The name of the catechin chemical family derives from catechu, which is the tannic juice or boiled extract of Mimosa catechu (Acacia catechu L.f).[1]
Contents
1Chemistry
1.1Oxidation
1.2Spectral data
2Natural occurrences
2.1In food
3Metabolism
3.1Biosynthesis
3.2Biodegradation
3.3Metabolism in humans
3.3.1Research
3.4Biotransformation
3.5Glycosides
4Bioactivity studies
4.1Vascular function
4.2Possible immune effects
5Botanical effects
6References
7External links
Chemistry
Catechin numbered
Catechin possesses two benzene rings (called the A- and B-rings) and a dihydropyran heterocycle (the C-ring) with a hydroxyl group on carbon 3. The A ring is similar to a resorcinol moiety while the B ring is similar to a catechol moiety. There are two chiral centers on the molecule on carbons 2 and 3. Therefore, it has four diastereoisomers. Two of the isomers are in trans configuration and are called catechin and the other two are in cis configuration and are called epicatechin.
The most common catechin isomer is the (+)-catechin. The other stereoisomer 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 (2R,3R)-(-)-epicatechin).
The different epimers can be distinguished using chiral column chromatography.[2]
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 proanthocyanidins, a type of condensed tannin.
Diastereoisomers gallery
(+)-catechin (2R,3S)
(-)-catechin (2S,3R)
(-)-epicatechin (2R,3R)
(+)-epicatechin (2S,3S)
3D view of "pseudoequatorial" (E) conformation of(+)-catechin
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.[3]
As flavonoids, catechins can act as antioxidants when in high concentration in vitro, but compared with other flavonoids, their antioxidant potential is low.[4] 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.[5]
Oxidation
Electrochemical experiments show that (+)-catechin oxidation mechanism proceeds in sequential steps, related with the catechol and resorcinol 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.[6]
The laccase/ABTS system oxidizes (+)-catechin to oligomeric products[7] of which proanthocyanidin A2 is a dimer.
Spectral data
UV spectrum of catechin.
UV-Vis
Lambda-max:
276 nm
Extinction coefficient (log ε)
4.01
IR
Major absorption bands
1600 cm−1(benzene rings)
NMR
Proton NMR
(500 MHz, CD3OD):
Reference[8] d : doublet, dd : doublet of doublets,
m : multiplet, s : singlet
(+)-Catechin and (-)-epicatechin as well as their gallic acid conjugates are ubiquitous constituents of vascular plants, and frequent components of traditional herbal remedies, such as Uncaria rhynchophylla. The two isomers are mostly found as cacao and tea constituents, as well as in Vitis vinifera grapes.[9][10][11]
In food
Main articles: Phenolic content in tea and Phenolic content in wine
The main dietary sources of catechins in Europe and the United States are tea and pome fruits.[12][13]
Catechins and epicatechins are found in cocoa,[14] which, according to one database, has the highest content (108 mg/100 g) of catechins among foods analyzed, followed by prune juice (25 mg/100 ml) and broad bean pod (16 mg/100 g).[15] Açaí oil, obtained from the fruit of the açaí palm (Euterpe oleracea), contains (+)-catechins (67 mg/kg).[16] (-)-Epicatechin and (+)-catechin are among the main natural phenols in argan oil.[17]
Catechins are diverse among foods,[15] from peaches[18] to green tea and vinegar.[15][19] Catechins are found in barley grain where they are the main phenolic compound responsible for dough discoloration.[20] The taste associated with monomeric (+)-catechin or (-)-epicatechin is described as slightly astringent, but not bitter.[21]
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 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-hydroyxylase. 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 by chalcone isomerase which is oxidized to eriodictyol by flavonoid 3'- hydroxylase and further oxidized to taxifolin 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[22][23][24]
Leucocyanidin reductase (LCR) uses 2,3-trans-3,4-cis-leucocyanidin to produce (+)-catechin and is the first enzyme in the proanthocyanidins (PA)-specific pathway. Its activity has been measured in leaves, flowers, and seeds of the legumes Medicago sativa, Lotus japonicus, Lotus uliginosus, Hedysarum sulfurescens, and Robinia pseudoacacia.[25] The enzyme is also present in Vitis vinifera (grape).[26]
Biodegradation
Catechin oxygenase, a key enzyme in the degradation of catechin, is present in fungi and bacteria.[27]
Among bacteria, degradation of (+)-catechin can be achieved by Acinetobacter calcoaceticus. Catechin is metabolized to protocatechuic acid (PCA) and phloroglucinol carboxylic acid (PGCA).[28] It is also degraded by Bradyrhizobium japonicum. Phloroglucinol carboxylic acid is further decarboxylated to phloroglucinol, which is dehydroxylated to resorcinol. Resorcinol is hydroxylated to hydroxyquinol. 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.[29]
Among fungi, degradation of catechin can be achieved by Chaetomium cupreum.[30]
Metabolism in humans
Human metabolites of epicatechin (excluding colonic metabolites)[31]
Schematic representation of (−)-epicatechin metabolism in humans as a function of time post-oral intake. SREM: structurally related (−)-epicatechin metabolites. 5C-RFM: 5-carbon ring fission metabolites. 3/1C-RFM: 3- and 1-carbon-side chain ring fission metabolites. The structures of the most abundant (−)-epicatechin metabolites present in the systemic circulation and in urine are depicted.[31]
Catechins are metabolised upon uptake from the gastrointestinal tract, in particular the jejunum,[32] and in the liver, resulting in so-called structurally-related epicatechin metabolites (SREM).[33] The main metabolic pathways for SREMs are glucuronidation, sulphation and methylation of the catechol group by catechol-O-methyl transferase, with only small amounts detected in plasma.[34][31] The majority of dietary catechins are however metabolised by the colonic microbiome to gamma-valerolactones and hippuric acids which undergo further biotransformation, glucuronidation, sulphation and methylation in the liver.[34]
The stereochemical configuration of catechins has a strong impact on their uptake and metabolism as uptake is highest for (-)-epicatechin and lowest for (-)-catechin.[35]
Research
Inter-species differences in (-)-epicatechin metabolism.[31]
Nanoparticle methods are under preliminary research as potential delivery systems of catechins.[36] Cocoa catechins are under preliminary research for their potential to affect the risk of cardiovascular diseases.[37] 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.[38]
Biotransformation
Biotransformation of (+)-catechin into taxifolin by a two-step oxidation can be achieved by Burkholderia sp.[39]
(+)-Catechin and (-)-epicatechin are transformed by the endophytic filamentous fungus Diaporthe 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.[40]
Leucoanthocyanidin reductase (LAR) uses (2R,3S)-catechin, NADP+ and H2O to produce 2,3-trans-3,4-cis-leucocyanidin, NADPH, and H+. Its gene expression has been studied in developing grape berries and grapevine leaves.[41]
Glycosides
(2R,3S)-Catechin-7-O-β-D-glucopyranoside can be isolated from barley (Hordeum vulgare L.) and malt.[42]
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.[43]
Bioactivity studies
Vascular function
Association between flavan-3-ol intake and incidence of cardiovascular disease in different cohort studies.[44] Data compare the bottom and top quintiles of intake.
Centuries ago, catechin-containing extracts were thought to be useful for treating heart diseases,[45][46] and an effect on the permeability of capillaries was shown in 1936.[47] Limited evidence from dietary studies indicates that catechins may have an effect on endothelium-dependent vasodilation which could contribute to normal blood flow regulation in humans.[48][49] Green tea catechins may improve blood pressure, especially when systolic blood pressure is above 130 mmHg.[50] 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.[34][51]
The European Food Safety Authority established that cocoa flavanols have an effect on vascular function in healthy adults by concluding: "cocoa flavanols help maintain endothelium-dependent vasodilation, which contributes to normal blood flow".[52] Data from observational cohort studies have not shown a consistent association between flavan-3-ol intake and risk of cardiovascuar diseases.[44]
A meta-analysis also indicated that green tea catechins may favorably affect cholesterol.[50]
Possible immune effects
Depending on dose consumed, catechins and their metabolites can bind to red blood cells and possibly induce release of autoantibodies, resulting in haemolytic anaemia and renal failure.[53] This resulted in the withdrawal of the catechin-containing drug Catergen, used to treat viral hepatitis, from the European market in 1985.[54][55]
Botanical effects
Catechins released into the ground by some plants may hinder the growth of their neighbors, a form of allelopathy.[56]Centaurea maculosa, the spotted knapweed often studied for this behavior, releases catechin 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 wave through the target plant's root to kill root cells by apoptosis.[57] 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 is an invasive, uncontrolled weed.[56]
Catechin acts as an infection-inhibiting factor in strawberry leaves.[58] Epicatechin and catechin may prevent coffee berry disease by inhibiting appressorial melanization of Colletotrichum kahawae.[59]
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External links
Look up Catechin or catechine in Wiktionary, the free dictionary.
Media related to (+)-Catechin at Wikimedia Commons
Delivery of green tea catechin and epigallocatechin gallate in liposomes incorporated into low-fat hard cheese.
Rashidinejad A1, Birch EJ2, Sun-Waterhouse D3, Everett DW4.Author information 1Department of Food Science, University of Otago, PO Box 56, Dunedin 9054, New Zealand; Riddet Institute, Private Bag 11 222, Palmerston North 4442, New Zealand. Electronic address: ali.rashidinejad@otago.ac.nz.2Department of Food Science, University of Otago, PO Box 56, Dunedin 9054, New Zealand.3Plant and Food Research, Auckland Mail Centre, Private Bag 92169, Auckland 1142, New Zealand.4Department of Food Science, University of Otago, PO Box 56, Dunedin 9054, New Zealand; Riddet Institute, Private Bag 11 222, Palmerston North 4442, New Zealand.AbstractThe encapsulation of green tea catechin and epigallocatechin gallate (EGCG) in soy lecithin liposomes was examined at four concentrations (0%, 0.125%, 0.25% and 0.5% w/v), and inclusion in cheese at 0% and 0.25% w/v. The empty capsules had a mean diameter of 133nm and significantly (p<0.05) increased with the addition of catechin or EGCG. Electron microscopy revealed the lamellae and central core of the liposomes. Addition of antioxidants gave a significant (p<0.05) increase in the size of liposomes. Liposomes had surface potentials of -42.4 to -46.1mV with no significant difference between treatments, suggesting stable liposome systems. High efficiency (>70%) and yield (∼80%) were achieved from the incorporation of catechin or EGCG inside the liposome structure. Addition of either antioxidant increased the liposome phase transition temperature (>50°C). Nanocapsules containing these antioxidants were effectively retained within a low-fat hard cheese, presenting a simple and effective delivery vesicle for antioxidants.
Food chemistry.Food Chem.2014 Aug 1;156:176-83. doi: 10.1016/j.foodchem.2014.01.115. Epub 2014 Feb 6.
The encapsulation of green tea catechin and epigallocatechin gallate (EGCG) in soy lecithin liposomes was examined at four concentrations (0%, 0.125%, 0.25% and 0.5% w/v), and inclusion in cheese at 0% and 0.25% w/v. The empty capsules had a mean diameter of 133nm and significantly (p<0.05) incre
Effects of season and plantation on phenolic content of unfermented and fermented Sri Lankan tea.
Jayasekera S1, Kaur L2, Molan AL3, Garg ML4, Moughan PJ5.Author information 1Riddet Institute, Massey University, Palmerston North 4442, New Zealand.2Riddet Institute, Massey University, Palmerston North 4442, New Zealand. Electronic address: L.Kaur@massey.ac.nz.3Institute of Food, Nutrition and Human Health, College of Health, Massey University, Palmerston North, New Zealand.4Riddet Institute, Massey University, Palmerston North 4442, New Zealand; Nutraceuticals Research Group, School of Biomedical Sciences & Pharmacy, University of Newcastle, Australia.5Riddet Institute, Massey University, Palmerston North 4442, New Zealand. Electronic address: P.J.Moughan@massey.ac.nz.AbstractThe effects of season and plantation on the polyphenol content of Camellia sinensis (tea) leaves were determined. Aqueous and organic extracts of freeze-dried fresh (unfermented) and black (fully-fermented) tea leaves were prepared for a structured set of samples (fermented and unfermented teas from six high-, mid- and low-grown plantations; fermented and unfermented teas from two harvesting seasons from four highland plantations), collected from the main tea-growing regions in Sri Lanka. Total catechin content and amounts of individual catechins, flavonols and theaflavins were determined by HPLC. Mean values for the phenolic constituents were generally significantly higher (p<0.05) with solvent extraction. The mean values for total catechins, total flavonols and caffeine in the aqueous extracts from unfermented teas were 10.6%, 1.5% and 2.9%, respectively. For both unfermented and fermented tea leaves, a significant (p<0.05) interaction between plantation and season was observed for phenolic constituents. Ferric reducing antioxidant power was positively (p<0.05) correlated with (-)-epicatechin gallate and total phenolic contents.
Food chemistry.Food Chem.2014 Jun 1;152:546-51. doi: 10.1016/j.foodchem.2013.12.005. Epub 2013 Dec 8.
The effects of season and plantation on the polyphenol content of Camellia sinensis (tea) leaves were determined. Aqueous and organic extracts of freeze-dried fresh (unfermented) and black (fully-fermented) tea leaves were prepared for a structured set of samples (fermented and unfermented teas from
Wheat bran particle size influence on phytochemical extractability and antioxidant properties.
Brewer LR1, Kubola J2, Siriamornpun S2, Herald TJ3, Shi YC4.Author information 1Department of Grain Science and Industry, Kansas State University, Manhattan, KS 66506, USA.2Department of Food Technology and Nutrition, Mahasarakham University, Mahasarakham 44000, Thailand.3USDA-ARS, Center for Grain and Animal Health Research, 1515 College Avenue, Manhattan, KS 66502, USA.4Department of Grain Science and Industry, Kansas State University, Manhattan, KS 66506, USA. Electronic address: ycshi@ksu.edu.AbstractIt is unknown if particle size plays a role in extracting health promoting compounds in wheat bran because the extraction of antioxidant and phenolic compounds with particle size reduction has not been well documented. In this study, unmilled whole bran (coarse treatment) was compared to whole bran milled to medium and fine treatments from the same wheat bran. Antioxidant properties (capacity, ability, power), carotenoids and phenolic compounds (phenolic acids, flavonoids, anthocyanins) were measured and compared. The ability of whole bran fractions of differing particle size distributions to inhibit free radicals was assessed using four in vitro models, namely, diphenylpicrylhydrazyl radical-scavenging activity, ferric reducing/antioxidant power (FRAP) assay, oxygen radical absorbance capacity (ORAC), and total antioxidant capacity. Significant differences in phytochemical concentrations and antioxidant properties were observed between whole bran fractions of reduced particle size distribution for some assays. The coarse treatment exhibited significantly higher antioxidant properties compared to the fine treatment; except for the ORAC value, in which coarse was significantly lower. For soluble and bound extractions, the coarse treatment was comparatively higher in total antioxidant capacity (426.72 mg ascorbic acid eq./g) and FRAP value (53.04 μmol FeSO4/g) than bran milled to the finer treatment (314.55 ascorbic acid eq./g and 40.84 μmol FeSO4/g, respectively). Likewise, the fine treatment was higher in phenolic acid (7.36 mg FAE/g), flavonoid (206.74 μg catechin/g), anthocyanin (63.0 μg/g), and carotenoid contents (beta carotene, 14.25 μg/100 g; zeaxanthin, 35.21 μg/100 g; lutein 174.59 μg/100 g) as compared to the coarse treatment. An increase of surface area to mass increased the ORAC value by over 80%. With reduction in particle size, there was a significant increase in extracted anthocyanins, carotenoids and ORAC value. Particle size does effect the extraction of phytochemicals.
Food chemistry.Food Chem.2014 Jun 1;152:483-90. doi: 10.1016/j.foodchem.2013.11.128. Epub 2013 Dec 8.
It is unknown if particle size plays a role in extracting health promoting compounds in wheat bran because the extraction of antioxidant and phenolic compounds with particle size reduction has not been well documented. In this study, unmilled whole bran (coarse treatment) was compared to whole bran
Green tea catechins are four molecules, high amounts of which are present in green tea and other sources. The most potent one is EGCG. It is effective in respect to most claims and potent in a few. Any fat burning ...