Caffeic acid

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Caffeic acid
2D diagram of caffeic acid
3D ball-and-stick model of caffeic acid
3D space filling model of caffeic acid
Names
IUPAC names
3-(3,4-Dihydroxyphenyl)-2-propenoic acid
3,4-Dihydroxy-cinnamic acid
trans-Caffeate
3,4-Dihydroxy-trans-cinnamate)
(E)-3-(3,4-dihydroxyphenyl)-2-propenoic acid
3,4-Dihydroxybenzeneacrylicacid
3-(3,4-Dihydroxyphenyl)-2-propenoic acid
Identifiers
331-39-5 YesY
ChEBI CHEBI:16433 YesY
ChEMBL ChEMBL145 YesY
ChemSpider 600426 YesY
DrugBank DB01880 YesY
5155
Jmol 3D model Interactive image
KEGG C01481 YesY
PubChem 689043
UNII U2S3A33KVM YesY
  • InChI=1S/C9H8O4/c10-7-3-1-6(5-8(7)11)2-4-9(12)13/h1-5,10-11H,(H,12,13)/b4-2+ YesY
    Key: QAIPRVGONGVQAS-DUXPYHPUSA-N YesY
  • InChI=1/C9H8O4/c10-7-3-1-6(5-8(7)11)2-4-9(12)13/h1-5,10-11H,(H,12,13)/b4-2+
    Key: QAIPRVGONGVQAS-DUXPYHPUBE
  • O=C(O)\C=C\c1cc(O)c(O)cc1
Properties
C9H8O4
Molar mass 180.16 g/mol
Density 1.478 g/cm3
Melting point 223 to 225 °C (433 to 437 °F; 496 to 498 K)
UV-vis (λmax) 327 nm and a shoulder at c. 295 nm in acidified methanol[1]
Vapor pressure {{{value}}}
Related compounds
Related compounds
 Chlorogenic acid
Cichoric acid
Coumaric acid
Quinic acid
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
YesY verify (what is YesYN ?)
Infobox references

Caffeic acid is an organic compound that is classified as hydroxycinnamic acid. This yellow solid consists of both phenolic and acrylic functional groups. It is found in all plants because it is a key intermediate in the biosynthesis of lignin, one of the principal components of plant biomass and its residues.[2]

Natural occurrences

Caffeic acid can be found in the bark of Eucalyptus globulus.[3] It can also be found in the freshwater fern Salvinia molesta[4] or in the mushroom Phellinus linteus.[5]

Occurrences in food

Caffeic acid is found at a very modest level in coffee, at 0.03 mg per 100 ml.[6] It is one of the main natural phenols in argan oil.[7]

It is found at high level in some herbs, especially thyme, sage and spearmint (at about 20 mg per 100 grams), at high levels in spices, especially Ceylon cinnamon and star anise (at about 22 mg per 100 grams), found at fairly high level in sunflower seeds (8 mg per 100 grams), and at modest levels in red wine (1.88 mg per 100 ml) and in applesauce, apricot and plum prunes (at about 1 mg per 100 grams). It is at super high level in black chokecherry (141 mg per 100 grams) and in fairly high level in ligonberry (6 mg per 100 grams).[6]

It is also found in barley grain.[8] and in rye grain.[6]

Metabolism

Biosynthesis

Caffeic acid, which is unrelated to caffeine, is biosynthesized by hydroxylation of coumaroyl ester of quinic acid (esterified through a side chain alcohol). This hydroxylation produces the caffeic acid ester of shikimic acid, which converts to chlorogenic acid. It is the precursor to ferulic acid, coniferyl alcohol, and sinapyl alcohol, all of which are significant building blocks in lignin.[2] The transformation to ferulic acid is catalyzed by the enzyme caffeic acid-O-methyltransferase.

Caffeic acid and its derivative caffeic acid phenethyl ester (CAPE) are produced in many kinds of plants.[9][10][11]

In plants, caffeic acid (middle) is formed from 4-hydroxycinnamic acid (left) and is transformed to ferulic acid.

Dihydroxyphenylalanine ammonia-lyase was presumed to use 3,4-dihydroxy-L-phenylalanine (L-DOPA) to produce trans-caffeate and NH3. However, the EC number for this purported enzyme was deleted in 2007, as no evidence has emerged for its existence [12]

Biotransformation

Caffeate O-methyltransferase is an enzyme responsible for the transformation of caffeic acid into ferulic acid.

Caffeic acid and related o-diphenols are rapidly oxidized by o-diphenol oxidases in tissue extracts.[13]

Biodegradation

Caffeate 3,4-dioxygenase is an enzyme that uses caffeic acid and oxygen to produce 3-(2-carboxyethenyl)-cis,cis-muconate.

Glysosides

3-O-caffeoylshikimic acid (dactylifric acid) and its isomers, are enzymic browning substrates found in dates (Phoenix dactylifera fruits).[14]

Pharmacology

Caffeic acid has a variety of potential pharmacological effects in in vitro studies and in animal models, and inhibitory effect of caffeic acid on cancer cell proliferation by oxidative mechanism in human HT-1080 fibrosarcoma cell line has recently been established.[15]

Caffeic acid is an antioxidant in vitro and also in vivo.[11] Caffeic acid also shows immunomodulatory and anti-inflammatory activity. Caffeic acid outperformed the other antioxidants, reducing aflatoxin production by more than 95 percent. The studies are the first to show that oxidative stress that would otherwise trigger or enhance Aspergillus flavus aflatoxin production can be stymied by caffeic acid. This opens the door to using natural fungicide methods by supplementing trees with antioxidants.[16]

Studies of the carcinogenicity of caffeic acid have mixed results. Some studies have shown that it inhibits carcinogenesis, and other experiments show carcinogenic effects.[17] Oral administration of high doses of caffeic acid in rats has caused stomach papillomas.[17] In the same study, high doses of combined antioxidants, including caffeic acid, showed a significant decrease in growth of colon tumors in those same rats. No significant effect was noted otherwise. Caffeic acid is listed under some Hazard Data sheets as a potential carcinogen,[18] as has been listed by the International Agency for Research on Cancer as a Group 2B carcinogen ("possibly carcinogenic to humans").[19] More recent data show that bacteria in the rats' guts may alter the formation of metabolites of caffeic acid.[20][21] Other than caffeic acid being a thiamine antagonist (anti-thiamine factor), there have been no known ill-effects of caffeic acid in humans.

Chemistry

Caffeic acid is susceptible to autoxidation. Glutathione and thiol compounds (cysteine, thioglycolic acid or thiocresol) or ascorbic acid have a protective effect on browning and disappearance of caffeic acid.[22] This browning is due to the conversion of o-diphenols into reactive o-quinones. Chemical oxidation of caffeic acid in acidic conditions using sodium periodate leads to the formation of dimers with a furan structure (isomers of 2,5-(3′,4′-dihydroxyphenyl)tetrahydrofuran 3,4-dicarboxylic acid).[23] Caffeic acid can also be polymerized using the horseradish peroxidase/H2O2 oxidizing system.[24]

Other uses

Caffeic acid may be the active ingredient in caffenol, a do-it-yourself black-and-white photographic developer made from instant coffee.[25] The developing chemistry is similar to that of catechol or pyrogallol.[26]

It is also used as a matrix in MALDI mass spectrometry analyses.[27]

Isomers

Isomers with the same molecular formula and in the hydroxycinammic acids family are:

References

  1. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  2. ↑ 2.0 2.1 Lua error in package.lua at line 80: module 'strict' not found..
  3. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  4. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  5. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  6. ↑ 6.0 6.1 6.2 http://phenol-explorer.eu/contents/polyphenol/457
  7. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  8. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  9. ↑ Red Clover Flowers Herbal Information
  10. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  11. ↑ 11.0 11.1 Lua error in package.lua at line 80: module 'strict' not found.
  12. ↑ [1]
  13. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  14. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  15. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  16. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  17. ↑ 17.0 17.1 Lua error in package.lua at line 80: module 'strict' not found.
  18. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  19. ↑ Agents Classified by the IARC Monographs, International Agency for Research on Cancer
  20. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  21. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  22. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  23. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  24. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  25. ↑ Caffenol blog "Caffenol-C-M, recipe"
  26. ↑ Williams, Scott "A Use for that Last Cup of Coffee: Film and Paper Development", Technical Photographic Chemistry 1995 Class, Imaging and Photographic Technology Department, School of Photographic Arts and Sciences Rochester Institute of Technology
  27. ↑ Lua error in package.lua at line 80: module 'strict' not found.

External links

  • Lua error in package.lua at line 80: module 'strict' not found.
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