Gallic acid: Difference between revisions

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

{{Chembox

| Verifiedfields = changed

| verifiedrevid = 443831396

| Name = Gallic acid

| ImageFileL1 = Gallic acid.svg

| ImageSizeL1 = 120

| 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

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

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

| UNII1 = 48339473OT

| UNII1_Comment = (monohydrate)

| 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<br />pale fawn-colored crystals.

| Density = 1.694 g/cm³ (anhydrous)

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

| SolubleOther = soluble in [[ethanol|alcohol]], [[diethyl ether|ether]], [[glycerol]], [[acetone]] <br> 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 = [[phenol]]s,<br />[[carboxylic acid]]s

| OtherCompounds = [[Benzoic acid]], [[Phenol]], [[Pyrogallol]]

}}

'''Gallic acid''' (also known as '''3,4,5-trihydroxybenzoic acid''') is a [[trihydroxybenzoic acid]] with the formula [[carbon|C]]₆[[hydrogen|H]]₂([[hydroxide|OH]])₃CO₂H. It is classified as a [[phenolic acid]]. It is found in [[gallnut]]s, [[sumac]], [[Witch-hazel|witch hazel]], [[tea]] leaves, [[oak bark]], and other [[plant]]s.<ref name=Haslam_and_Cai>{{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}}</ref> It is a white solid, although samples are typically brown owing to partial oxidation. [[Salt (chemistry)|Salt]]s and [[ester]]s of gallic acid are termed "gallates".

Its name is derived from [[oak gall]]s, 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|thumb|left|upright|Electrostatic potential map of surface of gallic acid molecule]]

[[File:Ellagic acid.svg|thumb|left|upright=0.9|[[Ellagic acid]] 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|ester links]] ([[lactone]]s) forming two additional 6-piece cycles.]]

Gallic acid is easily freed from [[gallotannin]]s 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 [[gallotannin]]s and [[ellagitannin]]s, respectively.<ref>{{Citation |last=Andrew Pengelly |title=The Constituents of Medicinal Plants |pages=29–30 |year=2004 |edition=2nd |publisher=Allen & Unwin}}</ref>

=== Biosynthesis ===

[[File:3,5-didehydroshikimate.svg|thumb|left|upright=0.7|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 [[aromatization|aromatizes]].<ref>[http://www.metacyc.org/META/NEW-IMAGE?type=PATHWAY&object=PWY-6707 Gallic acid pathway on metacyc.org]</ref><ref>{{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}}</ref>

===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]].<ref name="ull-hcaa" /> Gallic acid forms intermolecular esters ([[depsides]]) such as [[digallic acid|digallic]] and cyclic ether-esters ([[depsidone]]s).<ref name="ull-hcaa">{{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 }}</ref>

====Hydrogenation====

[[Hydrogenation]] of gallic acid gives the cyclohexane derivative hexahydrogallic acid.<ref>{{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}}</ref>

====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 [[verdigris]]<ref>Pliny 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."</ref> 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.<ref>{{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}}</ref>

Gallic acid was one of the substances used by [[Angelo Mai]] (1782–1854), among other early investigators of [[palimpsest]]s, 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.<ref>L.D. Reynolds and N.G. Wilson, "Scribes and Scholars" 3rd Ed. Oxford: 1991, pp 193–4.</ref>

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

== Occurrence ==

Gallic acid is found in a number of [[land plant]]s, such as the [[parasitic plant]] ''[[Cynomorium coccineum]]'',<ref>{{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 }}</ref> the [[aquatic plant]] ''[[Myriophyllum spicatum]]'', and the blue-green [[alga]] ''[[Microcystis aeruginosa]]''.<ref name="Nakai">{{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 }}</ref> Gallic acid is also found in various oak species,<ref>{{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}}</ref> ''[[Caesalpinia mimosoides]],''<ref name="Kilburn">{{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}}</ref> and in the stem bark of ''[[Boswellia dalzielii]],''<ref>{{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.}}</ref> among others. Many foodstuffs contain various amounts of gallic acid, especially fruits (including strawberries, grapes, bananas),<ref name="pmid26251571">{{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 }}</ref><ref>{{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}}</ref> as well as [[tea]]s,<ref name="pmid26251571" /><ref>{{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}}</ref> cloves,<ref name="tdmq">{{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}}</ref> and [[vinegar]]s.<ref>{{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}}</ref>{{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&nbsp;mg per 100&nbsp;g).<ref name="Goulas">{{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 }}</ref>

== Esters ==

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

Gallate esters are [[antioxidant]]s 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 spectroscopy|UV-Vis]]

| <!-- [α]_D (22°C) : -->

! colspan="2" {{Chemical datatable header}} | [[Infrared|IR]]

| ν : 3491, 3377, 1703, 1617, 1539, 1453, 1254&nbsp;cm^&minus;1 (KBr)

! colspan="2" {{Chemical datatable header}} | [[NMR Spectroscopy|NMR]]

| [[Proton NMR]]

! colspan="2" {{Chemical datatable header}} | [[Mass Spectrometry|MS]]

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

<ref name="Kilburn" />

== See also ==

* [[Benzoic acid]]

* [[Catechol]]

* [[Hydrolyzable tannin]]

* [[Pyrogallol]]

* [[Syringol]]

* [[Syringaldehyde]]

* [[Syringic acid]]

* [[Shikimic acid]]

== References ==

{{Authority control}}

[[Category:Antioxidants]]

[[Category:Chelating agents]]

[[Category:Pyrogallols]]

[[Category:Reducing agents]]

[[Category:Trihydroxybenzoic acids]]