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:Gallic acid

{{Short description|3,4,5-Trihydroxybenzoic acid}}

{{Chembox

| Verifiedfields = changed

| Watchedfields = changed

| verifiedrevid = 443831396

| Name = Gallic acid

| ImageFileL1 = Gallic acid.svg

| ImageSizeL1 = 120

| ImageClassL1 = skin-invert

| ImageAltL1 = Skeletal formula

| ImageFileR1 = Gallic acid molecule spacefill from xtal.png

| ImageSizeR1 = 120

| ImageAltR1 = Space-filling model of gallic acid

| ImageName = Gallic acid

| PIN = 3,4,5-Trihydroxybenzoic acid

| OtherNames = Gallic acid

|Section1={{Chembox Identifiers

| IUPHAR_ligand = 5549

| ChEBI_Ref = {{ebicite|correct|EBI}}

| ChEBI = 30778

| SMILES = O=C(O)c1cc(O)c(O)c(O)c1

| UNII_Ref = {{fdacite|correct|FDA}}

| UNII = 632XD903SP

| UNII1_Ref = {{fdacite|correct|FDA}}

| UNII1 = 48339473OT

| UNII1_Comment = (monohydrate)

| KEGG_Ref = {{keggcite|correct|kegg}}

| KEGG = C01424

| InChI = 1/C7H6O5/c8-4-1-3(7(11)12)2-5(9)6(4)10/h1-2,8-10H,(H,11,12)

| InChIKey = LNTHITQWFMADLM-UHFFFAOYAN

| ChEMBL_Ref = {{ebicite|correct|EBI}}

| ChEMBL = 288114

| StdInChI_Ref = {{stdinchicite|correct|chemspider}}

| StdInChI = 1S/C7H6O5/c8-4-1-3(7(11)12)2-5(9)6(4)10/h1-2,8-10H,(H,11,12)

| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}

| StdInChIKey = LNTHITQWFMADLM-UHFFFAOYSA-N

| CASNo_Ref = {{cascite|correct|CAS}}

| CASNo = 149-91-7

| CASNo2_Ref = {{cascite|correct|CAS}}

| CASNo2 = 5995-86-8

| CASNo2_Comment = (monohydrate)

| PubChem = 370

| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}

| ChemSpiderID = 361

| EINECS = 205-749-9

| RTECS = LW7525000

}}

|Section2={{Chembox Properties

| Formula = C7H6O5

| MolarMass = 170.12 g/mol

| Appearance = White, yellowish-white, or
pale fawn-colored crystals.

| Density = 1.694 g/cm3 (anhydrous)

| Solubility = 1.19 g/100 mL, 20°C (anhydrous)
1.5 g/100 mL, 20 °C (monohydrate)

| SolubleOther = soluble in alcohol, ether, glycerol, acetone
negligible in benzene, chloroform, petroleum ether

| MeltingPtC = 260

| BoilingPt =

| pKa = COOH: 4.5, OH: 10.

| LogP = 0.70

| MagSus = −90.0·10−6 cm3/mol

}}

|Section3={{Chembox Structure

| CrystalStruct =

| Dipole =

}}

|Section7={{Chembox Hazards

| ExternalSDS = [http://bulkpharm.mallinckrodt.com/_attachments/msds/G0806.htm External MSDS]

| MainHazards = Irritant

| NFPA-H = 1

| NFPA-F = 0

| LD50 = 5000 mg/kg (rabbit, oral)

}}

|Section8={{Chembox Related

| OtherFunction = phenols,
carboxylic acids

| OtherCompounds = Benzoic acid, Phenol, Pyrogallol

}}

}}

Gallic acid (also known as 3,4,5-trihydroxybenzoic acid) is a trihydroxybenzoic acid with the formula C6H2(OH)3CO2H. It is classified as a phenolic acid. It is found in gallnuts, sumac, witch hazel, tea leaves, oak bark, and other plants.{{Cite journal | last1 = Haslam | first1 = E. | last2 = Cai | first2 = Y. | doi = 10.1039/NP9941100041 | title = Plant polyphenols (vegetable tannins): Gallic acid metabolism | journal = Natural Product Reports | volume = 11 | issue = 1 | pages = 41–66 | year = 1994 | pmid = 15206456}} It is a white solid, although samples are typically brown owing to partial oxidation. Salts and esters of gallic acid are termed "gallates".

Its name is derived from oak galls, which were historically used to prepare tannic acid. Despite the name, gallic acid does not contain gallium.

Isolation and derivatives

File:Gallic acid ESP.png

File:Ellagic acid.svg molecule structure resembles that of two gallic acid molecules assembled in head to tail position and linked together by a C–C bond (as in biphenyl) and two cyclic ester links (lactones) forming two additional 6-piece cycles.]]

Gallic acid is easily freed from gallotannins by acidic or alkaline hydrolysis. When heated with concentrated sulfuric acid, gallic acid converts to rufigallol. Hydrolyzable tannins break down on hydrolysis to give gallic acid and glucose or ellagic acid and glucose, known as gallotannins and ellagitannins, respectively.{{Citation |last=Andrew Pengelly |title=The Constituents of Medicinal Plants |pages=29–30 |year=2004 |edition=2nd |publisher=Allen & Unwin}}

= Biosynthesis =

File:3,5-didehydroshikimate.svg

Gallic acid is formed from 3-dehydroshikimate by the action of the enzyme shikimate dehydrogenase to produce 3,5-didehydroshikimate. This latter compound aromatizes.[http://www.metacyc.org/META/NEW-IMAGE?type=PATHWAY&object=PWY-6707 Gallic acid pathway on metacyc.org]{{Cite journal|pmc=1184696|year=1969|last1=Dewick|first1=PM|last2=Haslam|first2=E|title=Phenol Biosynthesis in Higher Plants. Gallic Acid|volume=113|issue=3|pages=537–542|journal=Biochemical Journal|pmid=5807212|doi=10.1042/bj1130537}}

=Reactions=

==Oxidation and oxidative coupling==

Alkaline solutions of gallic acid are readily oxidized by air. The oxidation is catalyzed by the enzyme gallate dioxygenase, an enzyme found in Pseudomonas putida.

Oxidative coupling of gallic acid with arsenic acid, permanganate, persulfate, or iodine yields ellagic acid, as does reaction of methyl gallate with iron(III) chloride. Gallic acid forms intermolecular esters (depsides) such as digallic and cyclic ether-esters (depsidones).{{citation | author=Edwin Ritzer | author2=Rudolf Sundermann | contribution=Hydroxycarboxylic Acids, Aromatic | title=Ullmann's Encyclopedia of Industrial Chemistry | edition=7th | publisher=Wiley | year=2007 | page=6| title-link=Ullmann's Encyclopedia of Industrial Chemistry }}

==Hydrogenation==

Hydrogenation of gallic acid gives the cyclohexane derivative hexahydrogallic acid.{{cite journal |doi=10.15227/orgsyn.042.0062|title=Hexahydrogallic Acid and Hexahydrogallic Acid Triacetate|journal=Organic Syntheses|year=1962|volume=42|page=62|author=Albert W. Burgstahler and Zoe J. Bithos}}

==Decarboxylation==

Heating gallic acid gives pyrogallol (1,2,3-trihydroxybenzene). This conversion is catalyzed by gallate decarboxylase.

==Esterification==

Many esters of gallic acid are known, both synthetic and natural. Gallate 1-beta-glucosyltransferase catalyzes the glycosylation (attachment of glucose) of 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 centuries, with a history extending to the Roman empire and the Dead Sea Scrolls. Pliny the Elder (23–79 AD) describes the use of gallic acid as a means of detecting an adulteration of verdigrisPliny the Elder with John Bostock and H.T. Riley, trans., The Natural History of Pliny (London, England: Henry G. Bohn, 1857), vol. 6, [https://books.google.com/books?id=IEoMAAAAIAAJ&pg=PA196 p. 196.] In Book 34, Chapter 26 of his Natural History, Pliny states that verdigris (a form of copper acetate (Cu(CH3COO)2·2Cu(OH)2), which was used to process leather, was sometimes adulterated with copperas (a form of iron(II) sulfate (FeSO4·7H2O)). He presented a simple test for determining the purity of verdigris. From p. 196: "The adulteration [of verdigris], however, which is most difficult to detect, is made with copperas; ... The fraud may also be detected by using a leaf of papyrus, which has been steeped in an infusion of nut-galls; for it becomes black immediately upon the genuine verdigris being applied." 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{{citation needed|date=October 2021}}—and gum arabic from acacia trees; this combination of ingredients produced the ink.{{cite web|last=Fruen|first=Lois|title=Iron Gall Ink|url=http://www.realscience.breckschool.org/upper/fruen/files/Enrichmentarticles/files/IronGallInk/IronGallInk.html|url-status=dead|archive-url=https://web.archive.org/web/20111002191808/http://www.realscience.breckschool.org/upper/fruen/files/Enrichmentarticles/files/IronGallInk/IronGallInk.html|archive-date=2011-10-02}}

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.L.D. Reynolds and N.G. Wilson, "Scribes and Scholars" 3rd Ed. Oxford: 1991, pp 193–4.

Gallic acid was first studied by the Swedish chemist Carl Wilhelm Scheele in 1786.Carl Wilhelm Scheele (1786) [https://books.google.com/books?id=6eE4AAAAMAAJ&pg=PA30 "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), 7: 30–34. In 1818, French chemist and pharmacist Henri Braconnot (1780–1855) devised a simpler method of purifying gallic acid from galls;{{cite journal | author = Braconnot Henri | year = 1818 | url = https://books.google.com/books?id=OwXcSjJbARAC&pg=PA181 |title=Observations sur la préparation et la purification de l'acide gallique, et sur l'existence d'un acide nouveau dans la noix de galle |trans-title=Observations on the preparation and purification of gallic acid, and on the existence of a new acid in galls | journal = Annales de Chimie et de Physique | volume = 9 | pages = 181–184 }} gallic acid was also studied by the French chemist Théophile-Jules Pelouze (1807–1867),J. Pelouze (1833) [https://books.google.com/books?id=ISpCAAAAcAAJ&pg=PA337 "Mémoire sur le tannin et les acides gallique, pyrogallique, ellagique et métagallique,"] Annales de chimie et de physique, 54: 337–365 [presented February 17, 1834]. among others.

When mixed with acetic acid, gallic acid had uses in early types of photography, like the calotype to make the silver more sensitive to light; it was also used in developing photographs.{{Cite book |last1=Taylor |first1=Roger |url=https://books.google.com/books?id=DnfBcmW-OkYC&pg=PA65 |title=Impressed by Light: British Photographs from Paper Negatives, 1840-1860 |last2=Schaaf |first2=Larry John |date=2007 |publisher=Metropolitan Museum of Art |isbn=978-1-58839-225-1 |language=en}}

Occurrence

Gallic acid is found in a number of land plants, such as the parasitic plant Cynomorium coccineum,{{cite journal |last1=Zucca |first1=Paolo |last2=Rosa |first2=Antonella |last3=Tuberoso |first3=Carlo |last4=Piras |first4=Alessandra |last5=Rinaldi |first5=Andrea |last6=Sanjust |first6=Enrico |last7=Dessì |first7=Maria |last8=Rescigno |first8=Antonio |title=Evaluation of Antioxidant Potential of "Maltese Mushroom" (Cynomorium coccineum) by Means of Multiple Chemical and Biological Assays |journal=Nutrients |date=11 January 2013 |volume=5 |issue=1 |pages=149–161 |doi=10.3390/nu5010149 |pmid=23344249 |pmc=3571642|doi-access=free }} the aquatic plant Myriophyllum spicatum, and the blue-green alga Microcystis aeruginosa.{{Cite journal |doi=10.1016/S0043-1354(00)00039-7 |title=Myriophyllum spicatum-released allelopathic polyphenols inhibiting growth of blue-green algae Microcystis aeruginosa |year=2000 |last1=Nakai |first1=S |journal=Water Research |volume=34 |issue=11 |pages=3026–3032|bibcode=2000WatRe..34.3026N }} Gallic acid is also found in various oak species,{{Cite journal|last2=Savolainen|first2=Heikki|last3=Lindroos|first3=Lasse|last4=Kangas|first4=Juhani|last5=Vartiainen|first5=Terttu|year=2000|title=Analysis of oak tannins by liquid chromatography-electrospray ionisation mass spectrometry|journal=Journal of Chromatography A|volume=891|issue=1|pages=75–83|doi=10.1016/S0021-9673(00)00624-5|pmid=10999626|last1=Mämmelä|first1=Pirjo}} Caesalpinia mimosoides,{{Cite journal|last2=Teerawutgulrag|first2=Aphiwat|last3=Kilburn|first3=Jeremy D.|last4=Rakariyatham|first4=Nuansri|year=2007|title=Antimicrobial gallic acid from Caesalpinia mimosoides Lamk|journal=Food Chemistry|volume=100|issue=3|pages=1044–1048|doi=10.1016/j.foodchem.2005.11.008|last1=Chanwitheesuk|first1=Anchana}} and in the stem bark of Boswellia dalzielii,{{cite journal|last2=Onawunmi|first2=Grace O.|last3=Olugbade|first3=Tiwalade A.|year=2007|title=Antibacterial phenolics from Boswellia dalzielii|url=http://www.ajol.info/index.php/njnpm/article/view/11864|journal=Nigerian Journal of Natural Products and Medicine|volume=10|issue=1|pages=108–10|last1=Alemika|first1=Taiwo E.}} among others. Many foodstuffs contain various amounts of gallic acid, especially fruits (including strawberries, grapes, bananas),{{cite journal|year=2015|title=Gallic acid attenuates dextran sulfate sodium-induced experimental colitis in BALB/c mice|journal=Drug Design, Development and Therapy|volume=9|pages=3923–34|doi=10.2147/DDDT.S86345|pmc=4524530|pmid=26251571|vauthors=Pandurangan AK, Mohebali N, Norhaizan ME, Looi CY |doi-access=free }}{{Cite journal|last2=Goto-Yamamoto|first2=N|last3=Hashizume|first3=K|year=2007|title=Influence of maceration temperature in red wine vinification on extraction of phenolics from berry skins and seeds of grape (Vitis vinifera)|journal=Bioscience, Biotechnology, and Biochemistry|volume=71|issue=4|pages=958–65|doi=10.1271/bbb.60628|pmid=17420579|last1=Koyama|first1=K|doi-access=free}} as well as teas,{{cite journal|year=2000|title=Gallic acid metabolites are markers of black tea intake in humans|journal=Journal of Agricultural and Food Chemistry|volume=48|issue=6|pages=2276–80|doi=10.1021/jf000089s|pmid=10888536|vauthors=Hodgson JM, Morton LW, Puddey IB, Beilin LJ, Croft KD|bibcode=2000JAFC...48.2276H }} cloves,{{cite journal|last1=Pathak|first1=S. B.|last2=Niranjan|first2=K.|last3=Padh|first3=H.|last4=Rajani|first4=M.|year=2004|title=TLC Densitometric Method for the Quantification of Eugenol and Gallic Acid in Clove|journal=Chromatographia|volume=60|issue=3–4|pages=241–244|doi=10.1365/s10337-004-0373-y|s2cid=95396304|display-authors=etal}} and vinegars.{{Cite journal|last2=Barroso|first2=Carmelo García|last3=Pérez-Bustamante|first3=Juan Antonio|year=1994|title=Analysis of polyphenolic compounds of different vinegar samples|journal=Zeitschrift für Lebensmittel-Untersuchung und -Forschung|volume=199|pages=29–31|doi=10.1007/BF01192948|last1=Gálvez|first1=Miguel Carrero|s2cid=91784893}}{{Clarify|date=November 2016|reason=Type(s) of vinegar unstated, as well as quantity of gallic acid present.}} Carob fruit is a rich source of gallic acid (24–165 mg per 100 g).{{cite journal | last1=Goulas | first1=Vlasios | last2=Stylos | first2=Evgenios | last3=Chatziathanasiadou | first3=Maria | last4=Mavromoustakos | first4=Thomas | last5=Tzakos | first5=Andreas | title=Functional Components of Carob Fruit: Linking the Chemical and Biological Space | journal=International Journal of Molecular Sciences | volume=17 | issue=11 | date=10 November 2016 | issn=1422-0067 | doi=10.3390/ijms17111875 | page=1875|pmid=27834921|pmc=5133875| doi-access=free }}

Esters

Also known as galloylated esters:

Gallate esters are antioxidants useful in food preservation, with propyl gallate being the most commonly used. Their use in human health is scantly supported by evidence.

Spectral data

style="margin: 0 0 0 0.5em; background: #FFFFFF; border-collapse: collapse; border-color: #C0C090;" border="1" cellspacing="0" cellpadding="3"

! colspan="2" {{Chemical datatable header}} | UV-Vis

Lambda-max:

| 220, 271 nm (ethanol)
File:Gallic acid spectrum.PNG

Extinction coefficient (log ε)

|

colspan="2" {{Chemical datatable header}} | IR
Major absorption bands

| ν : 3491, 3377, 1703, 1617, 1539, 1453, 1254 cm−1 (KBr)

colspan="2" {{Chemical datatable header}} | 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
colspan="2" {{Chemical datatable header}} | 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)

See also

References

{{Reflist}}

{{Gallotannin}}

{{Phenolic acid}}

{{Authority control}}

{{DEFAULTSORT:Gallic Acid}}

Category:Antioxidants

Category:Astringent flavors

Category:Chelating agents

Category:Gallotannins

Category:Pyrogallols

Category:Reducing agents

Category:Trihydroxybenzoic acids