Catechin

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(Redirected from
Epicatechin
)
Catechin
Chemical structure of (+)-Catechin
Names
IUPAC name
(2R,3S)-2-(3,4-Dihydroxyphenyl)-3,4-dihydro-2H-chromene-3,5,7-triol
Other names
Cianidanol
Cyanidanol
(+)-catechin
D-Catechin
Catechinic acid
Catechuic acid
Cianidol
Dexcyanidanol
(2R,3S)-Catechin
2,3-trans-Catechin
(2R,3S)-Flavan-3,3′,4′,5,7-pentol
Identifiers
3D model (
JSmol
)
3DMet
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard
 100.005.297 Edit this at Wikidata
EC Number
  • 205-825-1
KEGG
UNII
  • InChI=1S/C15H14O6/c16-8-4-11(18)9-6-13(20)15(21-14(9)5-8)7-1-2-10(17)12(19)3-7/h1-5,13,15-20H,6H2/t13-,15+/m0/s1 checkY
    Key: PFTAWBLQPZVEMU-DZGCQCFKSA-N checkY
  • InChI=1/C15H14O6/c16-8-4-11(18)9-6-13(20)15(21-14(9)5-8)7-1-2-10(17)12(19)3-7/h1-5,13,15-20H,6H2/t13-,15+/m0/s1
    Key: PFTAWBLQPZVEMU-DZGCQCFKBX
  • Oc1ccc(cc1O)[C@H]3Oc2cc(O)cc(O)c2C[C@@H]3O
Properties
C15H14O6
Molar mass 290.271 g·mol−1
Appearance Colorless solid
Melting point 175 to 177 °C (347 to 351 °F; 448 to 450 K)
UV-vis (λmax) 276 nm
+14.0°
Hazards
Occupational safety and health (OHS/OSH):
Main hazards
 Mutagenic for mammalian somatic cells, mutagenic for bacteria and yeast
GHS labelling:
GHS07: Exclamation mark
Warning
H315, H319, H335
P261, P264, P271, P280, P302+P352, P304+P340, P305+P351+P338, P312, P321, P332+P313, P337+P313, P362, P403+P233, P405, P501
Lethal dose or concentration (LD, LC):
(+)-catechin : 10,000 mg/kg in rat (RTECS)
10,000 mg/kg in mouse
3,890 mg/kg in rat (other source)
Safety data sheet (SDS) sciencelab AppliChem[permanent dead link]
Pharmacology
Oral
Pharmacokinetics:
Urines
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
☒N verify (what is checkY☒N ?)

Catechin

flavonoids
.

The name of the catechin chemical family derives from

Acacia catechu L.f).[1]

Chemistry

Catechin numbered

Catechin possesses two

cis configuration
and are called epicatechin.

The most common catechin isomer is (+)-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, epicatechin, 2,3-cis-epicatechin or (2R,3R)-(−)-epicatechin).

The different epimers can be separated 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 (2R,3S)
  • (−)-catechin (2S,3R)
    (−)-catechin (2S,3R)
  • (−)-epicatechin (2R,3R)
    (−)-epicatechin (2R,3R)
  • (+)-epicatechin (2S,3S)
    (+)-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

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

δ :

2.49 (1H, dd, J = 16.0, 8.6 Hz, H-4a),
2.82 (1H, dd, J = 16.0, 1.6 Hz, H-4b),
3.97 (1H, m, H-3),
4.56 (1H, d, J = 7.8 Hz, H-2),
5.86 (1H, d, J = 2.1 Hz, H-6),
5.92 (1H, d, J = 2.1 Hz, H-8),
6.70 (1H, dd, J = 8.1, 1.8 Hz, H-6'),
6.75 (1H, d, J = 8.1 Hz, H-5'),
6.83 (1H, d, J = 1.8 Hz, H-2')

Carbon-13 NMR
Other NMR data
MS
Masses of
main fragments 		ESI-MS [M+H]+ m/z : 291.0


273 water loss
139 retro Diels–Alder
123
165
147

Natural occurrences

(+)-Catechin and (−)-epicatechin as well as their

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

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]

Catechins are diverse among foods,[15] from peaches[17] to green tea and vinegar.[15][18] Catechins are found in barley grain where they are the main phenolic compound responsible for dough discoloration.[19] The taste associated with monomeric (+)-catechin or (−)-epicatechin is described as slightly astringent, but not bitter.[20]

Metabolism

Biosynthesis

The biosynthesis of catechin begins with ma

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 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[21][22][23]

Hedysarum sulfurescens, and Robinia pseudoacacia.[24] The enzyme is also present in Vitis vinifera (grape).[25]

Biodegradation

Catechin oxygenase, a key enzyme in the degradation of catechin, is present in fungi and bacteria.[26]

Among bacteria, degradation of (+)-catechin can be achieved by

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.[28]

Among fungi, degradation of catechin can be achieved by Chaetomium cupreum.[29]

Metabolism in humans

Human metabolites of epicatechin (excluding colonic metabolites)[30]
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.[30]

Catechins are metabolised upon uptake from the

gamma-valerolactones and hippuric acids which undergo further biotransformation, glucuronidation, sulfation and methylation in the liver.[33]

The stereochemical configuration of catechins has a strong impact on their uptake and metabolism as uptake is highest for (−)-epicatechin and lowest for (−)-catechin.[34]

Biotransformation

Biotransformation of (+)-catechin into taxifolin by a two-step oxidation can be achieved by Burkholderia sp.[35]

(+)-Catechin and (−)-epicatechin are transformed by the endophytic filamentous fungus

(+)-(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.[36]

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.[37]

Glycosides

Research

Interspecies differences in (−)-epicatechin metabolism.[30]

Vascular function

Only limited evidence from dietary studies indicates that catechins may affect

blood flow regulation in humans.[40][41] Green tea catechins may improve blood pressure, especially when systolic blood pressure is above 130 mmHg.[42][43]

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.[33][44]

Adverse events

Catechin and its metabolites can bind tightly to red blood cells and thereby induce the development of

renal failure.[45] This resulted in the withdrawal of the catechin-containing drug Catergen, used to treat viral hepatitis,[46] from market in 1985.[47]

Catechins from green tea can be hepatotoxic[48] and the European Food Safety Authority has recommended not to exceed 800 mg per day.[49]

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.[50] Nanoparticle methods are under preliminary research as potential delivery systems of catechins.[51]

Botanical effects

Catechins released into the ground by some plants may hinder the growth of their neighbors, a form of

Centaurea maculosa is an invasive, uncontrolled weed.[52]

Catechin acts as an infection-inhibiting factor in strawberry leaves.[54] Epicatechin and catechin may prevent coffee berry disease by inhibiting appressorial melanization of Colletotrichum kahawae.[55]

References

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  26. ^ Arunachalam, M.; Mohan Raj, M.; Mohan, N.; Mahadevan, A. (2003). "Biodegradation of Catechin" (PDF). Proceedings of the Indian National Science Academy. B69 (4): 353–370. Archived from the original (PDF) on 2012-03-16.
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  48. ^ Health Canada (2017-11-15). "Summary Safety Review - Green tea extract-containing natural health products - Assessing the potential risk of liver injury (hepatotoxicity)". www.canada.ca. Retrieved 2022-05-06.
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External links

Look up Catechin or catechine in Wiktionary, the free dictionary.
Retrieved from "https://en.wikipedia.org/w/index.php?title=Catechin&oldid=1182668486"