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-Dihydroxycinnamic 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
Preferred IUPAC name
(2E)-3-(3,4-Dihydroxyphenyl)prop-2-enoic acid
Identifiers
3D model (
JSmol
)
1954563
ChEBI
ChEMBL
ChemSpider
DrugBank
ECHA InfoCard
100.005.784 Edit this at Wikidata
EC Number
  • 206-361-2
IUPHAR/BPS
KEGG
UNII
  • 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+ checkY
    Key: QAIPRVGONGVQAS-DUXPYHPUSA-N checkY
  • 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-vismax) 327 nm and a shoulder at c. 295 nm in acidified methanol[1]
Hazards
GHS labelling:
GHS07: Exclamation markGHS08: Health hazard
Warning
H315, H319, H335, H351, H361
P201, P202, P261, P264, P271, P280, P281, P302+P352, P304+P340, P305+P351+P338, P308+P313, P312, P321, P332+P313, P337+P313, P362, P403+P233, P405, P501
NFPA 704 (fire diamond)
NFPA 704 four-colored diamondHealth 1: Exposure would cause irritation but only minor residual injury. E.g. turpentineFlammability 1: Must be pre-heated before ignition can occur. Flash point over 93 °C (200 °F). E.g. canola oilInstability 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
1
1
0
Related compounds
Related compounds
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
checkY verify (what is checkY☒N ?)

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

Natural occurrences

Caffeic acid can be found in the bark of

Phellinus linteus.[6]

Occurrences in food

Free caffeic acid can be found in a variety of beverages, including brewed coffee at 0.13 mg per 100 ml[7] and red wine at 2 mg per 100 ml.[8] It is found at relatively high levels in herbs of the mint family, especially thyme, sage and spearmint (at about 20 mg per 100 g), and in spices, such as Ceylon cinnamon and star anise (at about 22 mg per 100 g). Caffeic acid occurs at moderate levels in sunflower seeds (8 mg per 100 g), apple sauce, apricots and prunes (at about 1 mg per 100 g).[9] It occurs at remarkably high levels in black chokeberry (141 mg per 100 g).[10] It is also quite high in the South American herb yerba mate (150 mg per 100 g based on thin-layer chromatography densitometry[11] and HPLC [12]). It is also found at lower levels in barley and rye.[13]

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 caffeate O-methyltransferase.

Caffeic acid and its derivative caffeic acid phenethyl ester (CAPE) are produced in many kinds of plants.[14][15][16]

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.[17]

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.[18]

Biodegradation

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

Glycosides

Phoenix dactylifera fruits).[19]

Pharmacology

Caffeic acid has a variety of potential pharmacological effects in in vitro studies and in animal models, and the inhibitory effect of caffeic acid on cancer cell proliferation by an oxidative mechanism in the human HT-1080 fibrosarcoma cell line has recently been established.[20]

Caffeic acid is an antioxidant in vitro and also in vivo.[16] 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 use as a natural fungicide by supplementing trees with antioxidants.[21]

Studies of the

Group 2B carcinogen ("possibly carcinogenic to humans").[24] More recent data show that bacteria in the rats' guts may alter the formation of metabolites of caffeic acid.[25][26] Other than caffeic acid being a thiamine
antagonist (antithiamine factor), there have been no known ill effects of caffeic acid in humans. Also, caffeic acid treatment attenuated lipopolysaccharide (LPS)-induced sickness behaviour in experimental animals by decreasing both peripheral and central cytokine levels along with oxidative stress inflicted by LPS.[27]

Chemistry

Caffeic acid is susceptible to

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).[29] Caffeic acid can also be polymerized using the horseradish peroxidase/H2O2 oxidizing system.[30]

Other uses

Caffeic acid may be the active ingredient in caffenol, a do-it-yourself black-and-white photographic developer made from instant coffee.[31] The developing chemistry is similar to that of catechol or pyrogallol.[32]

It is also used as a matrix in MALDI mass spectrometry analyses.[33]

Isomers

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

References

  1. PMID 10948238
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  2. ^ .
  3. .
  4. .
  5. .
  6. .
  7. .
  8. ^ "Showing all foods in which the polyphenol Caffeic acid is found - Phenol-Explorer".
  9. PMID 8411618
    .
  10. .
  11. .
  12. .
  13. .
  14. ^ "Red Clover Benefits & Information". indigo-herbs.co.uk. Retrieved 4 April 2018.
  15. ^ "Dr. Duke's Phytochemical and Ethnobotanical Databases". Archived from the original on 2000-12-05.
  16. ^
    PMID 11208940
    .
  17. ^ "EC 4.3.1.11". www.chem.qmul.ac.uk. Archived from the original on 3 March 2016. Retrieved 4 April 2018.
  18. PMID 4980678
    .
  19. .
  20. .
  21. ^ "Nuts' New Aflatoxin Fighter: Caffeic Acid?".
  22. ^
    PMID 9472713
    .
  23. ^ "Caffeic Acid". IARC Summary & Evaluation. 1993.
  24. ^ "Agents Classified by the IARC Monographs" (PDF). iarc.fr. International Agency for Research on Cancer. Archived from the original (PDF) on 25 October 2011. Retrieved 4 April 2018.
  25. PMID 4504351
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  26. .
  27. .
  28. .
  29. .
  30. .
  31. ^ "Caffenol-C-M, recipe". Caffenol blog. 2 March 2010.
  32. ^ 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.
  33. PMID 2520223
    .

External links