Gallic acid

Gallic acid
IUPAC name

3,4,5-trihydroxybenzoic acid
Other names

Gallic acid
Gallate
3,4,5-trihydroxybenzoate
Identifiers
CAS number 149-91-7 Y, [5995-86-8] (Monohydrate)
PubChem 370
ChemSpider 361 Y
UNII 632XD903SP Y
KEGG C01424 Y
ChEBI CHEBI:30778 Y
ChEMBL CHEMBL288114 Y
Jmol-3D images Image 1
Properties
Molecular formula C7H6O5
Molar mass 170.12 g/mol
Exact mass 170.021523 u
Appearance White, yellowish-white, or
pale fawn-colored crystals.
Density 1.7 g/cm3 (anhydrous)
Melting point

250 °C, 523 K, 482 °F
Solubility in water 1.1 g/100 ml water @ 20°C (anhydrous)
1.5 g/100 ml water @ 20 °C (monohydrate)
Acidity (pKa) COOH: 4.5, OH: 10.
Hazards
MSDS External MSDS
Main hazards Irritant
Related compounds
Related compounds Benzoic acid, Phenol, Pyrogallol
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Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
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 tannins. Salts and esters of gallic acid are termed 'gallates'. Despite its name, it does not contain gallium.

Gallic acid is commonly used in the pharmaceutical industry.[2] 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.[3] Gallic acid can also be used as a starting material in the synthesis of the psychedelic alkaloid mescaline.[4]

Gallic acid seems to have anti-fungal and anti-viral properties. Gallic acid acts as an antioxidant and helps to protect human cells against oxidative damage. Gallic acid was found to show cytotoxicity against cancer cells, without harming healthy cells. Gallic acid is used as a remote astringent in cases of internal haemorrhage. Gallic acid is also used to treat albuminuria and diabetes. Some ointments to treat psoriasis and external haemorrhoids contain gallic acid.[5]

Contents

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 gallic acid (hence the name). It could then be mixed with green vitriol (ferrous sulfate), obtained by allowing sulfate saturated spring or mine drainage water to evaporate, and gum arabic from acacia trees to produce the ink[6] .

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 damaging manuscripts for future study.

It has been discovered by French chemist and pharmacist Henri Braconnot (1780–1855) in 1818 and studied by French chemist Théophile-Jules Pelouze (1807–1867).

Early photographers also used it, Joseph Bancroft Reade (1801–1870) for instance and William Fox Talbot (1800–1877) for developing latent images in calotypes. It has also been used as a coating agent in zincography.

It was also used by George Washington to communicate with spies during the United States war of Independence (American Revolution) according to the miniseries America: The Story of Us.

Gallic acid is a component of some whistle mixtures.

List of plants or foods that contain the chemical

Spectral data

UV-Vis
Retention time
Lambda-max: 220, 271 nm (ethanol)
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

Reference[7]

Esters

Also known as galloylated esters:

Metabolism

Gallate 1-beta-glucosyltransferase (EC 2.4.1.136) is an enzyme that uses UDP-glucose and gallate, whereas its two products are UDP and 1-galloyl-beta-D-glucose.

Gallate decarboxylase (EC 4.1.1.59)is another enzyme.

See also

References

  1. ^ LD Reynolds and NG Wilson, “Scribes and Scholars” 3rd Ed. Oxford: 1991. pp193–4.
  2. ^ S. M. Fiuza. "Phenolic acid derivatives with potential anticancer properties––a structure–activity relationship study. Part 1: Methyl, propyl and octyl esters of caffeic and gallic acids". Elsevier. doi:10.1016/j.bmc.2004.04.026. 
  3. ^ Andrew Waterhouse. "Folin-Ciocalteau Micro Method for Total Phenol in Wine". UC Davis. http://waterhouse.ucdavis.edu/phenol/folinmicro.htm. 
  4. ^ Tsao, Makepeasce (July 1951). "A New Synthesis Of Mescaline". Journal of the American Chemical Society 73 (11): 5495–5496. doi:10.1021/ja01155a562. ISSN 0002-7863. 
  5. ^ phytochemicals.info
  6. ^ Fruen, Lois. "Iron Gall Ink". http://www.realscience.breckschool.org/upper/fruen/files/Enrichmentarticles/files/IronGallInk/IronGallInk.html. 
  7. ^ a b Antimicrobial gallic acid from Caesalpinia mimosoides Lamk. Anchana Chanwitheesuk, Aphiwat Teerawutgulrag, Jeremy D. Kilburn and Nuansri Rakariyatham, Food Chemistry, Volume 100, Issue 3, 2007, pp. 1044-1048, doi:10.1016/j.foodchem.2005.11.008
  8. ^ Pathak, S. B. et al.; Niranjan, K.; Padh, H.; Rajani, M. (2004). "TLC Densitometric Method for the Quantification of Eugenol and Gallic Acid in Clove". Chromatographia 60 (3 - 4): 241–244. doi:10.1365/s10337-004-0373-y. 

External links
Types of gallotannins
Aglycones
Examples
Burkinabin A | B | C | Galloyl glucose | Digalloyl glucose | Trigalloyl glucose: 1,2,6-Trigalloyl glucose / 1,3,6,-Trigalloyl glucose (Corilagin) | Tetragalloyl glucose: 1,2,3,6-tetragalloylglucose | Pentagalloyl glucose: 1,2,3,4,6-pentagalloyl-glucose and 6-digalloyl-1,2,3-trigalloyl-glucose | Hexagalloyl glucose | Heptagalloyl glucose | Octagalloyl glucose | Nonagalloyl glucose | Decagalloyl glucose | 1,3,4-Tri-O-galloylquinic acid | 3,4,5-Tri-O-galloylquinic acid | 3,5-di-O-galloyl-shikimic acid | 3,4,5-tri-O-galloylshikimic acid | 1,2,6-trigalloyl alloside | 1,3,6-trigalloyl alloside | 1,2,3,6-tetragalloyl alloside
Monohydroxybenzoic acids
Dihydroxybenzoic acids
Trihydroxybenzoic acids