|CAS number||, [5995-86-8] (monohydrate)|
|Jmol-3D images||Image 1|
|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)|
|Solubility in water||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
|Acidity (pKa)||COOH: 4.5, OH: 10.|
|LD50||5000 mg/kg (rabbit, oral)|
|Related compounds||Benzoic acid, Phenol, Pyrogallol|
|Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)|
|(what is: / ?)|
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. The chemical formula is C6H2(OH)3COOH. Gallic acid is found both free and as part of hydrolyzable tannins.
Gallic acid is commonly used in the pharmaceutical industry. 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. Gallic acid can also be used as a starting material in the synthesis of the psychedelic alkaloid mescaline.
||This article contains too many or too-lengthy quotations for an encyclopedic entry. (March 2013)|
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.
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.
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.
Gallic acid was first studied by the Swedish chemist Carl Wilhelm Scheele in 1786. In 1818 the French chemist and pharmacist Henri Braconnot (1780–1855) devised a simpler method of purifying gallic acid from galls; gallic acid was also studied by the French chemist Théophile-Jules Pelouze (1807–1867), among others.
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.
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.
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.
Gallic acid is easily freed from gallotannins by oxidation. 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 the chemical
- Gallic acid is found in oaks species like the North American white oak (Quercus alba) and European red oak (Quercus robur).
- Caesalpinia mimosoides
- stem bark of Boswellia dalzielii
- Drosera (sundew)
- Rhodiola rosea (Golden root)
- Triphala (Ayurvedic herbal rasayana formula)
- Toona sinensis
- Urtica dioica (Stinging Nettle)
- Areca nut
- Bearberry (Arctostaphylos sp)
- Bergenia sp
- Hot chocolate
- Juglans regia (Common walnut)
- Mango in peels and leaves
- Phyllanthus emblica (Indian gooseberry) in fruits
- Syzygium aromaticum (clove)
- Witch hazel (Hamamelis virginiana)
- White tea
|Lambda-max:||220, 271 nm (ethanol)
|Extinction coefficient (log ε)|
|Major absorption bands||ν : 3491, 3377, 1703, 1617, 1539, 1453, 1254 cm−1 (KBr)|
7.15 (2H, s, H-3 and H-7)
|Other NMR data|
|ESI-MS [M-H]- m/z : 169.0137|
Also known as galloylated esters:
- Methyl gallate
- Ethyl gallate, a food additive with E number E313
- Propyl gallate, or propyl 3,4,5-trihydroxybenzoate, an ester formed by the condensation of gallic acid and propanol
- Octyl gallate, the ester of octanol and gallic acid
- Dodecyl gallate, or lauryl gallate, the ester of dodecanol and gallic acid
- Epicatechin gallate, a flavan-3-ol, a type of flavonoid, present in green tea
- Epigallocatechin gallate (EGCG), also known as epigallocatechin 3-gallate, the ester of epigallocatechin and gallic acid, and a type of catechin
- Gallocatechin gallate (GCG), the ester of gallocatechin and gallic acid and a type of flavan-3ol
- Theaflavin-3-gallate, a theaflavin derivative
- LD Reynolds and NG Wilson, "Scribes and Scholars" 3rd Ed. Oxford: 1991. pp193–4.
- 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.
- Andrew Waterhouse. "Folin-Ciocalteau Micro Method for Total Phenol in Wine". UC Davis.
- 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.
- Fruen, Lois. "Iron Gall Ink".
- 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.
- 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.
- 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].
- Gallic acid pathway on metacyc.org
- Dewick, PM; Haslam, E (1969). "Phenol biosynthesis in higher plants. Gallic acid". Biochemical Journal 113 (3): 537–542. PMC 1184696.
- 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.
- 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.
- 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.
- 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.
- Antibacterial phenolics from Boswellia dalzielii. Alemika Taiwo E, Onawunmi Grace O and Olugbade, Tiwalade O, Nigerian Journal of Natural Products and Medicines, 2006 (abstract)
- 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.
- 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.
- 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.
- 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