{{Distinguish|Allysine||halicin}} {{Chembox | Verifiedfields = changed | Watchedfields = changed | verifiedrevid = 477317730 | ImageFile1 = R-allicin-2D-skeletal.svg | ImageName1 = Structural formula of R-allicin | ImageClass1 = skin-invert | ImageFile2 =R-allicin-3D-balls.png | ImageName2 = Ball and stick model of R-allicin | PIN = ''S''-(Prop-2-en-1-yl) prop-2-ene-1-sulfinothioate | OtherNames = 2-Propene-1-sulfinothioic acid S-2-propenyl ester<br />3-[(Prop-2-ene-1-sulfinyl)sulfanyl]prop-1-ene<br />''S''-Allyl prop-2-ene-1-sulfinothioate |Section1={{Chembox Identifiers | CASNo = 539-86-6 | CASNo_Ref = {{cascite|correct|??}} | PubChem = 65036 | ChemSpiderID = 58548 | ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}} | EINECS = 208-727-7 | KEGG_Ref = {{keggcite|correct|kegg}} | KEGG = C07600 | MeSHName = Allicin | ChEBI_Ref = {{ebicite|correct|EBI}} | ChEBI = 28411 | IUPHAR_ligand = 2419 | Beilstein = 1752823 | UNII_Ref = {{fdacite|correct|FDA}} | UNII = 3C39BY17Y6 | SMILES = O=S(SC\C=C)C\C=C | SMILES1 = C=CCSS(=O)CC=C | ChEMBL_Ref = {{ebicite|correct|EBI}} | ChEMBL = 359965 | StdInChI = 1S/C6H10OS2/c1-3-5-8-9(7)6-4-2/h3-4H,1-2,5-6H2 | StdInChI_Ref = {{stdinchicite|correct|chemspider}} | InChI = 1/C6H10OS2/c1-3-5-8-9(7)6-4-2/h3-4H,1-2,5-6H2 | StdInChIKey = JDLKFOPOAOFWQN-UHFFFAOYSA-N | StdInChIKey_Ref = {{stdinchicite|correct|chemspider}} | InChIKey = JDLKFOPOAOFWQN-UHFFFAOYAO}} |Section2={{Chembox Properties | C=6 | H=10 | O=1 | S=2 | Appearance = Colourless liquid | Density = 1.112 g cm<sup>−3</sup> | MeltingPt = < | MeltingPtC= 25 | BoilingPt = decomposes}} }}

'''Allicin''' is an organosulfur compound obtained from garlic and leeks.<ref name="Eric Block 1985 114–119">{{cite journal | vauthors = Block E | title = The Chemistry of Garlic and Onions | journal = Scientific American | volume = 252 | issue = 3 | pages = 114–9 | date = March 1985 | pmid = 3975593 | doi = 10.1038/scientificamerican0385-114 | bibcode = 1985SciAm.252c.114B }}</ref> When fresh garlic is chopped or crushed, the enzyme alliinase converts alliin into allicin, which is responsible for the aroma of fresh garlic.<ref>{{cite journal | vauthors = Kourounakis PN, Rekka EA | title = Effect on active oxygen species of alliin and Allium sativum (garlic) powder | journal = Research Communications in Chemical Pathology and Pharmacology | volume = 74 | issue = 2 | pages = 249–52 | date = November 1991 | pmid = 1667340 }}</ref> Allicin is unstable and quickly changes into a series of other sulfur-containing compounds such as diallyl disulfide.<ref name="ilic">{{cite journal | title = Allicin and related compounds: Biosynthesis, synthesis and pharmacological activity | journal = Facta Universitatis | date = 2011 | volume = 9 | issue = 1 | pages= 9–20 | doi = 10.2298/FUPCT1101009I | url = http://facta.junis.ni.ac.rs/phat/pcat2011/pcat2011-02.pdf| last1 = Ilic | first1 = Dusica | last2 = Nikolic | first2 = Vesna | last3 = Nikolic | first3 = Ljubisa | last4 = Stankovic | first4 = Mihajlo | last5 = Stanojevic | first5 = Ljiljana | last6 = Cakic | first6 = Milorad | name-list-style = vanc }}</ref> Allicin is an antifeedant, i.e. the defense mechanism against attacks by pests on the garlic plant.<ref name="mol">{{cite journal | vauthors = Borlinghaus J, Albrecht F, Gruhlke MC, Nwachukwu ID, Slusarenko AJ | title = Allicin: chemistry and biological properties | journal = Molecules | volume = 19 | issue = 8 | pages = 12591–618 | date = August 2014 | pmid = 25153873 | doi = 10.3390/molecules190812591 | pmc = 6271412 | doi-access = free }}</ref>

Allicin is an oily, slightly yellow liquid that gives garlic its distinctive odor. It is a thioester of a sulfinic acid. It is also known as allyl thiosulfinate.<ref name="PMID 14964414">{{cite journal | vauthors = Nikolic V, Stankovic M, Nikolic L, Cvetkovic D | title = Mechanism and kinetics of synthesis of allicin | journal = Die Pharmazie | volume = 59 | issue = 1 | pages = 10–4 | date = January 2004 | pmid = 14964414 }}</ref> Its biological activity can be attributed to both its antioxidant activity and its reaction with thiol-containing proteins.<ref name="PMID 9528659">{{cite journal | vauthors = Rabinkov A, Miron T, Konstantinovski L, Wilchek M, Mirelman D, Weiner L | title = The mode of action of allicin: trapping of radicals and interaction with thiol containing proteins | journal = Biochimica et Biophysica Acta (BBA) - General Subjects | volume = 1379 | issue = 2 | pages = 233–44 | date = February 1998 | pmid = 9528659 | doi = 10.1016/s0304-4165(97)00104-9 }}</ref>

==Structure and occurrence== Allicin features the thiosulfinate functional group, R-S(O)-S-R. The compound is not present in garlic unless tissue damage occurs,<ref name="Eric Block 1985 114–119"/> and is formed by the action of the enzyme alliinase on alliin.<ref name="Eric Block 1985 114–119"/> Allicin is chiral but occurs naturally only as a racemate.<ref name="eric">{{Cite book |last=Block |first=Eric |title=Garlic and Other Alliums: The Lore and the Science |date=2010 |publisher=Royal Society of Chemistry |isbn=978-0-85404-190-9 |location=Cambridge |name-list-style=vanc}}</ref> The racemic form can also be generated by oxidation of diallyl disulfide:<ref>{{cite book | vauthors = Cremlyn RJ |title=An introduction to organosulfur chemistry |publisher=Wiley |year=1996 |isbn=0-471-95512-4 }}</ref><ref name=Mol>{{cite journal | vauthors = Borlinghaus J, Albrecht F, Gruhlke MC, Nwachukwu ID, Slusarenko AJ | title = Allicin: chemistry and biological properties | journal = Molecules | volume = 19 | issue = 8 | pages = 12591–12618 | date = August 2014 | pmid = 25153873 | pmc = 6271412 | doi = 10.3390/molecules190812591 | doi-access = free }}</ref>

{{block indent|1='''(SCH<sub>2</sub>CH=CH<sub>2</sub>)<sub>2</sub> + 2 RCO<sub>3</sub>H + H<sub>2</sub>O → 2 CH<sub>2</sub>=CHCH<sub>2</sub>SOH + 2 RCO<sub>2</sub>H'''}} {{block indent|1='''2 CH<sub>2</sub>=CHCH<sub>2</sub>SOH → CH<sub>2</sub>=CHCH<sub>2</sub>S(O)SCH<sub>2</sub>CH=CH<sub>2</sub> + H<sub>2</sub>O'''}}

Alliinase is irreversibly deactivated below pH 3; as such, allicin is generally not produced in the body from the consumption of fresh or powdered garlic.<ref>{{cite journal | vauthors = Brodnitz MH, Pascale JV, Derslice LV |title=Flavor components of garlic extract |journal=Journal of Agricultural and Food Chemistry |volume=19 |issue=2 |pages=273–275 |year=1971 |doi= 10.1021/jf60174a007 |bibcode=1971JAFC...19..273B }}</ref><ref>{{cite journal|doi=10.1111/j.1365-2621.1989.tb07926.x|title=Stability of Allicin in Garlic Juice|year=1989|last1=Yu|first1=Tung-Hsi|last2=Wu|first2=Chung-May | name-list-style = vanc |journal=Journal of Food Science|volume=54|page=977|issue=4}}</ref> Furthermore, allicin can be unstable, breaking down within 16 hours at 23&nbsp;°C.<ref>{{cite book |title= Garlic: the science and therapeutic application of ''Allium sativum'' L and related species |edition=2nd | vauthors = Hahn G | veditors = Koch HP, Lawson LD |year= 1996 |publisher= Williams and Wilkins |location= Baltimore |isbn=978-0-683-18147-0 |pages= 1–24}}</ref>

===Biosynthesis=== The biosynthesis of allicin commences with the conversion of cysteine into ''S''-allyl-<small>L</small>-cysteine. Oxidation of this thioether gives the sulfoxide (alliin). The enzyme alliinase, which contains pyridoxal phosphate (PLP), cleaves alliin, generating allylsulfenic acid (CH<sub>2</sub>=CHCH<sub>2</sub>SOH), pyruvate, and ammonium ions.<ref name="PMID 9528659"/> At room temperature, two molecules of allylsulfenic acid condense to form allicin.<ref name="PMID 14964414"/><ref name=Mol/>

==Research== Allicin has been studied for its potential to treat various kinds of multiple drug resistance bacterial infections, as well as viral and fungal infections in vitro, but as of 2016, the safety and efficacy of allicin to treat infections in people was unclear.<ref>{{cite journal|doi=10.1016/j.tifs.2016.03.010 |title= Antifungal and antibacterial activities of allicin: A review |journal=Trends in Food Science and Technology |volume=52 |pages=49–56 |year=2016 |last1=Marchese |first1=Anna |last2=Barbieri |first2=Ramona |last3=Sanches-Silva |first3=Ana |last4=Daglia |first4=Maria |last5=Nabavi |first5=Seyed Fazel |last6=Jafari |first6=Nematollah Jonaidi |last7=Izadi |first7=Morteza |last8=Ajami |first8=Marjan |last9=Nabavi |first9=Seyed Mohammad | name-list-style = vanc }}</ref>

A Cochrane review found there to be insufficient clinical evidence regarding the effects of allicin in preventing or treating common cold.<ref>{{cite journal | vauthors = Lissiman E, Bhasale AL, Cohen M | title = Garlic for the common cold | journal = The Cochrane Database of Systematic Reviews | issue = 11 | article-number = CD006206 | date = November 2014 | volume = 2020 | pmid = 25386977 | doi = 10.1002/14651858.CD006206.pub4 | pmc = 6465033 }}</ref>

==History== It was first isolated and studied in the laboratory by Chester J. Cavallito and John Hays Bailey in 1944.<ref name=j1>{{cite journal|doi=10.1021/ja01239a048|year=1944|last1=Cavallito|first1=Chester J.|last2=Bailey|first2=John Hays | name-list-style = vanc |journal=Journal of the American Chemical Society|volume=66|page=1950|issue=11|title=Allicin, the Antibacterial Principle of Allium sativum. I. Isolation, Physical Properties and Antibacterial Action|bibcode=1944JAChS..66.1950C }}</ref><ref name=eric/> Allicin was discovered as part of efforts to create thiamine derivatives in the 1940s, mainly in Japan. Allicin became a model for medicinal chemistry efforts to create other thiamine disulfides. The results included sulbutiamine, fursultiamine (thiamine tetrahydrofurfuryl disulfide) and benfothiamine. These compounds are hydrophobic, easily pass from the intestines to the bloodstream, and are reduced to thiamine by cysteine or glutathione.<ref name=BettendorfHandbook>{{cite book |last1=Bettendorff |first1=Lucien |editor1-last=Zempleni |editor1-first=Janos |editor2-last=Suttie |editor2-first=John W. |editor3-last=Gregory |editor3-first=Jesse F. |editor4-last=Stover |editor4-first=Patrick J. | name-list-style = vanc |title=Handbook of vitamins |date=2014 |publisher=CRC Press |location=Hoboken |isbn=978-1-4665-1557-4 |pages=267–324 |edition=Fifth |chapter=Chapter 7 - Thiamine }}</ref>{{rp|302}}

== See also == {{commons category}} * Allyl isothiocyanate, the active piquant chemical in mustard, radishes, horseradish and wasabi * ''syn''-Propanethial-''S''-oxide, the lachrymatory chemical found in onions * List of phytochemicals in food

== References == {{Reflist|2}}

{{Allium}} {{Transient receptor potential channel modulators}} {{Authority control}}

Category:Thiosulfinates Category:Anti-inflammatory agents Category:Antibiotics Category:Dietary antioxidants Category:Pungent flavors Category:Allium Category:Garlic Category:Antifungals Category:Allyl compounds Category:Transient receptor potential channel modulators