Gallic acid

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Gallic acid
Gallic acid.svg
Ácido gálico.png
Names
IUPAC name
3,4,5-Trihydroxybenzoic acid
Other names
Gallic acid
Gallate
3,4,5-Trihydroxybenzoate
Identifiers
149-91-7 YesY
5995-86-8 (monohydrate) N
ChEBI CHEBI:30778 YesY
ChEMBL ChEMBL288114 YesY
ChemSpider 361 YesY
EC Number 205-749-9
5549
Jmol 3D model Interactive image
KEGG C01424 YesY
PubChem 370
RTECS number LW7525000
UNII 632XD903SP YesY
  • InChI=1S/C7H6O5/c8-4-1-3(7(11)12)2-5(9)6(4)10/h1-2,8-10H,(H,11,12) YesY
    Key: LNTHITQWFMADLM-UHFFFAOYSA-N YesY
  • InChI=1/C7H6O5/c8-4-1-3(7(11)12)2-5(9)6(4)10/h1-2,8-10H,(H,11,12)
    Key: LNTHITQWFMADLM-UHFFFAOYAN
  • O=C(O)c1cc(O)c(O)c(O)c1
Properties
C7H6O5
Molar mass 170.12 g/mol
Appearance White, yellowish-white, or
pale fawn-colored crystals.
Density 1.694 g/cm3 (anhydrous)
Melting point 260 °C (500 °F; 533 K)
1.19 g/100 mL, 20°C (anhydrous)
1.5 g/100 mL, 20 °C (monohydrate)
Solubility soluble in alcohol, ether, glycerol, acetone
negligible in benzene, chloroform, petroleum ether
log P 0.70
Acidity (pKa) COOH: 4.5, OH: 10.
Vapor pressure {{{value}}}
Related compounds
Related
 phenols,
carboxylic acids
Related compounds
 Benzoic acid, Phenol, Pyrogallol
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N verify (what is YesYN ?)
Infobox references

Gallic acid is a trihydroxybenzoic acid, a type of phenolic acid, a type of organic acid, also known as 3,4,5-trihydroxybenzoic acid, found in gallnuts, sumac, witch hazel, tea leaves, oak bark, and other plants.[1] The chemical formula is C6H2(OH)3COOH. Gallic acid is found both free and as part of hydrolyzable tannins. The gallic acid groups are usually bonded to form dimers such as ellagic acid. Hydrolysable tannins break down on hydrolysis to give gallic acid and glucose or ellagic acid and glucose, known as gallotannins and ellagitannins respectively.[2]

Gallic acid forms intermolecular esters (depsides) such as digallic and trigallic acid, and cyclic ether-esters (depsidones).[3]

Gallic acid is commonly used in the pharmaceutical industry.[4] It is used as a standard for determining the phenol content of various analytes by the Folin-Ciocalteau assay; results are reported in gallic acid equivalents.[5] Gallic acid can also be used as a starting material in the synthesis of the psychedelic alkaloid mescaline.[6]

The name is derived from oak galls, which were historically used to prepare tannic acid. Despite the name, gallic acid does not contain gallium. Salts and esters of gallic acid are termed "gallates".

Historical context and uses

Gallic acid is an important component of iron gall ink, the standard European writing and drawing ink from the 12th to 19th century with a history extending to the Roman empire and the Dead Sea Scrolls. Pliny the Elder (23-79 AD) describes his experiments with it and writes that it was used to produce dyes. Galls (also known as oak apples) from oak trees were crushed and mixed with water, producing tannic acid. It could then be mixed with green vitriol (ferrous sulfate) — obtained by allowing sulfate-saturated water from a spring or mine drainage to evaporate — and gum arabic from acacia trees; this combination of ingredients produced the ink.[7]

Gallic acid was one of the substances used by Angelo Mai (1782–1854), among other early investigators of palimpsests, to clear the top layer of text off and reveal hidden manuscripts underneath. Mai was the first to employ it, but did so "with a heavy hand", often rendering manuscripts too damaged for subsequent study by other researchers.[citation needed]

Gallic acid was first studied by the Swedish chemist Carl Wilhelm Scheele in 1786.[8] In 1818 the French chemist and pharmacist Henri Braconnot (1780–1855) devised a simpler method of purifying gallic acid from galls;[9] gallic acid was also studied by the French chemist Théophile-Jules Pelouze (1807–1867),[10] among others.

George Washington used gallic acid to communicate with spies[clarification needed] during the American Revolutionary War, according to the miniseries America: The Story of Us.[citation needed]

Gallic acid is a component of some pyrotechnic whistle mixtures.

Metabolism

Biosynthesis

Chemical structure of 3,5-didehydroshikimate

Gallic acid is formed from 3-dehydroshikimate by the action of the enzyme shikimate dehydrogenase to produce 3,5-didehydroshikimate. This latter compound tautomerizes to form the redox equivalent gallic acid, where the equilibrium lies essentially entirely toward gallic acid because of the coincidentally occurring aromatization.[11][12]

Degradation

Gallate dioxygenase is an enzyme found in Pseudomonas putida that catalyses the reaction

gallate + O2 → (1E)-4-oxobut-1-ene-1,2,4-tricarboxylate.

Gallate decarboxylase is another enzyme in the degradation of gallic acid.

Conjugation

Gallate 1-beta-glucosyltransferase is an enzyme that uses UDP-glucose and gallate, whereas its two products are UDP and 1-galloyl-beta-D-glucose.

Natural occurrences

Gallic acid is found in a number of land plants, such as the parasitic plant, Cynomorium coccineum,[13] the aquatic plant, Myriophyllum spicatum, and the blue-green alga, Microcystis aeruginosa.[14]

Production

Gallic acid is easily freed from gallotannins by acidic or alkaline hydrolysis. When gallic acid is heated with concentrated sulfuric acid, rufigallol is produced by condensation. Oxidation with arsenic acid, permanganate, persulfate, or iodine yields ellagic acid, as does reaction of methyl gallate with iron(III) chloride.[3]

Sources

List of plants that contain gallic acid

In food

Spectral data

UV-Vis
Lambda-max: 220, 271 nm (ethanol)
Spectrum of gallic acid
Extinction coefficient (log ε)
IR
Major absorption bands ν : 3491, 3377, 1703, 1617, 1539, 1453, 1254 cm−1 (KBr)
NMR
Proton NMR


(acetone-d6):
d : doublet, dd : doublet of doublets,
m : multiplet, s : singlet

 δ :

7.15 (2H, s, H-3 and H-7)
Carbon-13 NMR


(acetone-d6):

 δ :

167.39 (C-1),
144.94 (C-4 and C-6),
137.77 (C-5),
120.81 (C-2),
109.14 (C-3 and C-7)
Other NMR data
MS
Masses of
main fragments		 ESI-MS [M-H]- m/z : 169.0137 ms/ms (iontrap)@35 CE m/z product 125(100), 81(<1)

Reference[16]

Esters

Also known as galloylated esters:

Health effects

It is a weak carbonic anhydrase inhibitor.[23] In basic research, gallic acid extracted from grape seeds has been shown to inhibit the formation of amyloid fibrils, one of the potential causes of Alzheimer's disease and Parkinson's disease.[24][25][26] One study indicated that gallic acid has this effect on amyloid protein formation by modifying the properties of alpha-synuclein, a protein associated with the onset of neurodegenerative diseases.[26]

Gallic acid is classified as mutagen and teratogen.[3]

Potential uses

It can be used to produce polyesters based on phloretic acid and gallic acid.[27]

See also

References

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External links

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  1. ↑ LD Reynolds and NG Wilson, "Scribes and Scholars" 3rd Ed. Oxford: 1991. pp193–4.
  2. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  3. ↑ 3.0 3.1 3.2 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. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  7. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  8. ↑ Carl Wilhelm Scheele (1786) "Om Sal essentiale Gallarum eller Gallåple-salt" (On the essential salt of galls or gall-salt), Kongliga Vetenskaps Academiens nya Handlingar (Proceedings of the Royal [Swedish] Academy of Science), vol 7, pages 30-34.
  9. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  10. ↑ J. Pelouze (1833) "Mémoire sur le tannin et les acides gallique, pyrogallique, ellagique et métagallique," Annales de chimie et de physique, vol. 54, pages 337-365 [presented February 17, 1834].
  11. ↑ Gallic acid pathway on metacyc.org
  12. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  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. ↑ 16.0 16.1 Lua error in package.lua at line 80: module 'strict' not found.
  17. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  18. ↑ 18.0 18.1 Lua error in package.lua at line 80: module 'strict' not found.
  19. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  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. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  26. ↑ 26.0 26.1 Lua error in package.lua at line 80: module 'strict' not found.
  27. ↑ Lua error in package.lua at line 80: module 'strict' not found.
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