Allicin

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Allicin
Structural formula of R-allicin
Ball and stick model of R-allicin
Names
Preferred IUPAC name
S-Prop-2-en-1-yl prop-2-ene-1-sulfinothioate
Other names
2-Propene-1-sulfinothioic acid S-2-propenyl ester
3-[(Prop-2-ene-1-sulfinyl)sulfanyl]prop-1-ene
S-Allyl prop-2-ene-1-sulfinothioate
Identifiers
539-86-6 N
1752823
ChEBI CHEBI:28411 YesY
ChEMBL ChEMBL359965 YesY
ChemSpider 58548 YesY
EC Number 208-727-7
2419
Jmol 3D model Interactive image
Interactive image
KEGG C07600 YesY
MeSH Allicin
PubChem 65036
UNII 3C39BY17Y6 YesY
Properties
C6H10OS2
Molar mass 162.26 g·mol−1
Appearance Colourless liquid
Density 1.112 g cm−3
Melting point <25 °C
Boiling point decomposes
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N verify (what is YesYN ?)
Infobox references

Allicin is an organosulfur compound obtained from garlic, a species in the family Alliaceae.[1] It was first isolated and studied in the laboratory by Chester J. Cavallito and John Hays Bailey in 1944.[2][3] When fresh garlic is chopped or crushed, the enzyme alliinase converts alliin into allicin, which is responsible for the aroma of fresh garlic.[4] The allicin generated is unstable and quickly changes into a series of other sulfur-containing compounds such as diallyl disulfide.[5] Allicin is part of a defense mechanism against attacks by pests on the garlic plant.[6]

Structure and occurrence[edit]

Allicin features the thiosulfinate functional group, R-S(O)-S-R. The compound is not present in garlic unless tissue damage occurs,[1] and is formed by the action of the enzyme alliinase on alliin.[1] Allicin is chiral but occurs naturally only as a racemate.[3] The racemic form can also be generated by oxidation of diallyl disulfide:[7]

(SCH2CH=CH2)2 + RCO3H → CH2=CHCH2S(O)SCH2CH=CH2 + RCO2H

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.[8][9] Furthermore, allicin can be unstable, breaking down within 16 hours at 23 °C.[10]

Biosynthesis[edit]

Allicin is an oily, slightly yellow liquid that gives garlic its unique odor. It is a thioester of sulfenic acid and is also known as allyl thiosulfinate.[11] Its biological activity can be attributed to both its antioxidant activity and its reaction with thiol containing proteins.[12]

In the biosynthesis of allicin (thio-2-propene-1-sulfinic acid S-allyl ester), cysteine is first converted into alliin (+ S-allyl-L-cysteine sulfoxide). The enzyme alliinase, which contains pyridoxal phosphate (PLP), cleaves alliin, generating allysulfenic acid, pyruvate, and ammonium.[12] At room temperature allysulfenic acid is unstable and highly reactive, which cause two molecules of it to spontaneously combine in a dehydration reaction to form allicin.[11]

Produced in garlic cells, allicin is released upon disruption, producing a potent characteristic scent when garlic is cut or cooked.[5][6]

Biosynthesis of Allicin

Research[edit]

Garlic has been assessed for its potential to fight the common cold. A Cochrane review found there is insufficient clinical trial evidence to indicate that garlic is useful in preventing or treating the common cold, stating that claims of effectiveness rely on poor-quality evidence and folk medicine.[13]

A randomized clinical trial found that the consumption of garlic in any form did not reduce blood cholesterol levels in patients with moderately high baseline cholesterol levels.[14]

See also[edit]

References[edit]

  1. ^ a b c Eric Block (1985). "The chemistry of garlic and onions". Scientific American. 252 (March): 114–9. doi:10.1038/scientificamerican0385-114. PMID 3975593. 
  2. ^ Cavallito, Chester J.; Bailey, John Hays (1944). "Allicin, the Antibacterial Principle of Allium sativum. I. Isolation, Physical Properties and Antibacterial Action". Journal of the American Chemical Society. 66 (11): 1950. doi:10.1021/ja01239a048. 
  3. ^ a b Eric Block (2010). Garlic and Other Alliums: The Lore and the Science. Cambridge: Royal Society of Chemistry. 
  4. ^ Kourounakis, PN; Rekka, EA (November 1991). "Effect on active oxygen species of alliin and Allium sativum (garlic) powder". Res Commun Chem Pathol Pharmacol. 74 (2): 249–252. PMID 1667340. 
  5. ^ a b Ilic, Dusica; Nikolic, Vesna; Nikolic, Ljubisa; Stankovic, Mihajlo; Stanojevic, Ljiljana; Cakic, Milorad (2011). "Allicin and related compounds: Biosynthesis, synthesis and pharmacological activity" (PDF). Facta Universitatis. 9 (1): 9–20. doi:10.2298/FUPCT1101009I. 
  6. ^ a b Borlinghaus, J; Albrecht, F; Gruhlke, M. C.; Nwachukwu, I. D.; Slusarenko, A. J. (2014). "Allicin: Chemistry and biological properties". Molecules. 19 (8): 12591–618. doi:10.3390/molecules190812591. PMID 25153873. 
  7. ^ Cremlyn, R. J. W. (1996). An introduction to organosulfur chemistry. Wiley. ISBN 0-471-95512-4. 
  8. ^ Brodnitz, M.H.; Pascale, J.V.; Derslice, L.V. (1971). "Flavor components of garlic extract". Journal of Agricultural and Food Chemistry. 19 (2): 273–5. doi:10.1021/jf60174a007. 
  9. ^ Yu, Tung-HSI; Wu, Chung-MAY (1989). "Stability of Allicin in Garlic Juice". Journal of Food Science. 54 (4): 977. doi:10.1111/j.1365-2621.1989.tb07926.x. 
  10. ^ Hahn, G (1996). Koch, HP; Lawson, LD, eds. Garlic: the science and therapeutic application of Allium sativum L and related species (2nd ed.). Baltimore: Williams and Wilkins. pp. 1–24. ISBN 0-683-18147-5. 
  11. ^ a b Nikolic, V; Stankovic, M; Nikolic, Lj; Cvetkovic, D (Jan 2004). "Mechanism and kinetics of synthesis of allicin". Pharmazie. 59 (1): 10–4. PMID 14964414. 
  12. ^ a b Rabinkov, A; Miron, T; Konstantinovski, L; Wilchek, M; Mirelman, D; Weiner, L (Feb 1998). "The mode of action of allicin: trapping of radicals and interaction with thiol containing proteins". Biochim Biophys Acta. 1379 (2): 233–44. doi:10.1016/s0304-4165(97)00104-9. PMID 9528659. 
  13. ^ Lissiman, E; Bhasale, A. L.; Cohen, M (2014). "Garlic for the common cold". The Cochrane Database of Systematic Reviews (11): CD006206. doi:10.1002/14651858.CD006206.pub4. PMID 25386977. 
  14. ^ Gardner CD, Lawson LD, Block E, et al. (2007). "Effect of raw garlic vs commercial garlic supplements on plasma lipid concentrations in adults with moderate hypercholesterolemia: a randomized clinical trial". Arch. Intern. Med. 167 (4): 346–53. doi:10.1001/archinte.167.4.346. PMID 17325296. 

External links[edit]