Gallic acid

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Gallic acid
Gallic acid.svg
Ácido gálico.png
IUPAC name
3,4,5-Trihydroxybenzoic acid
Other names
Gallic acid
149-91-7 YesY
5995-86-8 (monohydrate)
ChEBI CHEBI:30778 YesY
ChEMBL ChEMBL288114 YesY
ChemSpider 361 YesY
EC number 205-749-9
Jmol-3D images Image
KEGG C01424 YesY
PubChem 370
RTECS number LW7525000
UNII 632XD903SP YesY
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.
MSDS External MSDS
Main hazards Irritant
NFPA 704
Flammability code 0: Will not burn. E.g., water Health code 1: Exposure would cause irritation but only minor residual injury. E.g., turpentine Reactivity (yellow): no hazard code Special hazards (white): no codeNFPA 704 four-colored diamond
5000 mg/kg (rabbit, oral)
Related compounds
carboxylic acids
Related compounds
Benzoic acid, Phenol, Pyrogallol
Except where noted otherwise, data is given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
 YesY verify (what isYesY/N?)
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.

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]

Historical context and uses[edit]

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.[5]

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.[6] In 1818 the French chemist and pharmacist Henri Braconnot (1780–1855) devised a simpler method of purifying gallic acid from galls;[7] gallic acid was also studied by the French chemist Théophile-Jules Pelouze (1807–1867),[8] 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.



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.[9][10]


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.


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[edit]

Gallic acid is found in a number of land plants. It is also found in the aquatic plant Myriophyllum spicatum and shows an allelopathic effect on the growth of the blue-green alga Microcystis aeruginosa.[11]


Gallic acid is easily freed from gallotannins by oxidation.[12] The most expedient method to obtain the acid is to precipitate it from an aqueous solution using concentrated sulfuric acid. A slower but effective means of obtaining the acid is to allow atmospheric oxygen to oxidize the acid passively in water as described by Henry's law. After two or three months a warmed gallic acid solution can be filtered to obtain relatively pure crystals.


List of plants that contain gallic acid[edit]

In food[edit]

Spectral data[edit]

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

d : doublet, dd : doublet of doublets,
m : multiplet, s : singlet

δ :

7.15 (2H, s, H-3 and H-7)

Carbon-13 NMR


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
Masses of
main fragments
ESI-MS [M-H]- m/z : 169.0137 ms/ms (iontrap)@35 CE m/z product 125(100), 81(<1)



Also known as galloylated esters:

Health effects[edit]

It is a weak carbonic anhydrase inhibitor.[19] 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.[20][21][22] 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.[22]

Potential uses[edit]

It can be used to produce polyesters based on phloretic acid and gallic acid.[23]

See also[edit]


  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. 
  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. ^ Fruen, Lois. "Iron Gall Ink". 
  6. ^ 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.
  7. ^ Braconnot Henri (1818). "Observations sur la préparation et la purification de l'acide gallique, et sur l'existence d'un acide nouveau dans la noix de galle" [Observations on the preparation and purification of gallic acid, and on the existence of a new acid in galls]. Annales de chimie et de physique 9: 181–184. 
  8. ^ 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].
  9. ^ Gallic acid pathway on
  10. ^ Dewick, PM; Haslam, E (1969). "Phenol biosynthesis in higher plants. Gallic acid". Biochemical Journal 113 (3): 537–542. PMC 1184696. PMID 5807212. 
  11. ^ Nakai, S (2000). "Myriophyllum spicatum-released allelopathic polyphenols inhibiting growth of blue-green algae Microcystis aeruginosa". Water Research 34 (11): 3026. doi:10.1016/S0043-1354(00)00039-7. 
  12. ^ Watt, Alexander (1906). Leather Manufacture: A Practical Handbook of Tanning, Currying, and Chrome Leather Dressing 5th Ed. New York: D. Van Nostrand Company. pp. 58–61. 
  13. ^ Mämmelä, Pirjo; Savolainen, Heikki; Lindroos, Lasse; Kangas, Juhani; Vartiainen, Terttu (2000). "Analysis of oak tannins by liquid chromatography-electrospray ionisation mass spectrometry". Journal of Chromatography A 891 (1): 75–83. doi:10.1016/S0021-9673(00)00624-5. PMID 10999626. 
  14. ^ a b Chanwitheesuk, Anchana; Teerawutgulrag, Aphiwat; Kilburn, Jeremy D.; Rakariyatham, Nuansri (2007). "Antimicrobial gallic acid from Caesalpinia mimosoides Lamk". Food Chemistry 100 (3): 1044. doi:10.1016/j.foodchem.2005.11.008. 
  15. ^ Antibacterial phenolics from Boswellia dalzielii. Alemika Taiwo E, Onawunmi Grace O and Olugbade, Tiwalade O, Nigerian Journal of Natural Products and Medicines, 2006 (abstract)
  16. ^ Pathak, S. B.; Niranjan, K.; Padh, H.; Rajani, M. et al. (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. 
  17. ^ Gálvez, Miguel Carrero; Barroso, Carmelo García; Pérez-Bustamante, Juan Antonio (1994). "Analysis of polyphenolic compounds of different vinegar samples". Zeitschrift für Lebensmittel-Untersuchung und -Forschung 199: 29. doi:10.1007/BF01192948. 
  18. ^ Koyama, K; Goto-Yamamoto, N; Hashizume, K (2007). "Influence of maceration temperature in red wine vinification on extraction of phenolics from berry skins and seeds of grape (Vitis vinifera)". Bioscience, biotechnology, and biochemistry 71 (4): 958–65. PMID 17420579.  edit
  19. ^ Satomi, H; Umemura, K; Ueno, A; Hatano, T; Okuda, T; Noro, T (1993). "Carbonic anhydrase inhibitors from the pericarps of Punica granatum L". Biological & Pharmaceutical Bulletin 16 (8): 787–90. doi:10.1248/bpb.16.787. PMID 8220326. 
  20. ^ Liu, Y; Pukala, T. L.; Musgrave, I. F.; Williams, D. M.; Dehle, F. C.; Carver, J. A. (2013). "Gallic acid is the major component of grape seed extract that inhibits amyloid fibril formation". Bioorganic & Medicinal Chemistry Letters 23 (23): 6336–40. doi:10.1016/j.bmcl.2013.09.071. PMID 24157371.  edit
  21. ^ Wang, Y. J.; Thomas, P; Zhong, J. H.; Bi, F. F.; Kosaraju, S; Pollard, A; Fenech, M; Zhou, X. F. (2009). "Consumption of grape seed extract prevents amyloid-beta deposition and attenuates inflammation in brain of an Alzheimer's disease mouse". Neurotoxicity Research 15 (1): 3–14. doi:10.1007/s12640-009-9000-x. PMID 19384583.  edit
  22. ^ a b Liu, Y; Carver, J. A.; Calabrese, A. N.; Pukala, T. L. (2014). "Gallic acid interacts with α-synuclein to prevent the structural collapse necessary for its aggregation". Biochimica et Biophysica Acta (BBA) - Proteins and Proteomics 1844 (9): 1481–1485. doi:10.1016/j.bbapap.2014.04.013. PMID 24769497.  edit
  23. ^ New polymer syntheses, 101. Liquid-crystalline hyperbranched and potentially biodegradable polyesters based on phloretic acid and gallic acid. Antonio Reina, Andreas Gerken, Uwe Zemann and Hans R. Kricheldorf, Macromolecular Chemistry and Physics, July 1999, Volume 200, Issue 7, pages 1784–1791, doi:10.1002/(SICI)1521-3935(19990701)200:7<1784::AID-MACP1784>3.0.CO;2-B

External links[edit]