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Allicin

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Allicin
Structural formula of R-allicin
Structural formula of R-allicin
Ball and stick model of R-allicin
Ball and stick model of R-allicin
Names
Preferred IUPAC name
2-Propene-1-sulfinothioic acid S-2-propenyl ester
Systematic IUPAC name
3-[(Prop-2-ene-1-sulfinyl)sulfanyl]prop-1-ene
Identifiers
3D model (JSmol)
1752823
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard 100.007.935 Edit this at Wikidata
EC Number
  • 208-727-7
KEGG
MeSH Allicin
UNII
  • InChI=1S/C6H10OS2/c1-3-5-8-9(7)6-4-2/h3-4H,1-2,5-6H2 checkY
    Key: JDLKFOPOAOFWQN-UHFFFAOYSA-N checkY
  • InChI=1/C6H10OS2/c1-3-5-8-9(7)6-4-2/h3-4H,1-2,5-6H2
    Key: JDLKFOPOAOFWQN-UHFFFAOYAO
  • O=S(SC\C=C)C\C=C
  • C=CCSS(=O)CC=C
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).
checkY verify (what is checkY☒N ?)

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] This colorless liquid has a distinctively pungent smell. This compound exhibits antibacterial and anti-fungal properties.[2] Allicin is garlic's defense mechanism against attacks by pests.[4]

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,[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:[5]

(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.[6][7] Furthermore, allicin can be unstable, breaking down within 16 h at 23 °C.[8]

Potential health benefits

Several animal studies published between 1995 and 2005 indicate that allicin may: reduce atherosclerosis and fat deposition,[9][10] normalize the lipoprotein balance, decrease blood pressure,[11][12] have anti-thrombotic[13] and anti-inflammatory activities, and function as an antioxidant to some extent.[14][15][16] Other studies have shown a strong oxidative effect in the gut that can damage intestinal cells, although these results were in laboratory animals, not humans. Furthermore, many of these results were obtained by excessive amounts of allicin, which has been clearly shown to have some toxicity at high amounts, or by physically injecting the lumen itself with allicin, which may not be indicative of what would happen via oral ingestion of allicin or garlic supplements.[17] [18] A randomized clinical trial funded by the National Institutes of Health (NIH) in the United States and published in the Archives of Internal Medicine in 2007 found that the consumption of garlic in any form did not reduce blood cholesterol levels in patients with moderately high baseline cholesterol levels.[19] The fresh garlic used in this study contained substantial levels of allicin so this study casts doubt on the ability of allicin when taken orally to reduce blood cholesterol levels in human subjects.

In 2009, Vaidya, Ingold and Pratt clarified the mechanism of the antioxidant activity of garlic, such as trapping damaging free radicals. When allicin decomposes, it forms 2-propenesulfenic acid, and this compound is what binds to the free-radicals.[20] The 2-propenesulfenic formed when garlic is cut or crushed has a lifetime of less than one second.[21]

Antibacterial activity

Allicin has been found to have numerous antimicrobial properties, and has been studied in relation to both its effects and its biochemical interactions.[22] One potential application is in the treatment of methicillin-resistant Staphylococcus aureus (MRSA), an increasingly prevalent concern in hospitals. A screening of allicin against 30 strains of MRSA found high level of antimicrobial activitity, including against strains that are resistant to other chemical agents.[23] Of the strains tested, 88% had minimum inhibitory concentrations for allicin liquids of 16 mg/L, and all strains were inhibited at 32 mg/L. Furthermore, 88% of clinical isolates had minimum bactericidal concentrations of 128 mg/L, and all were killed at 256 mg/L. Of these strains, 82% showed intermediate or full resistance to mupirocin. This same study examined use of an aqueous cream of allicin, and found it somewhat less effective than allicin liquid. At 500 mg/L, however, the cream was still active against all the organisms tested—which compares well with the 20 g/L mupirocin currently used for topical application.[23]

A water-based formulation of purified allicin was found to be more chemically stable than other preparations of garlic extracts.[23] They proposed that the stability may be due to the hydrogen bonding of water to the reactive oxygen atom in allicin and also to the absence of other components in crushed garlic that destabilize the molecule.[24] (Presumably, the dilution of these components in water helps to preserve the allicin molecule.)

See also

Wikimedia Commons has media related to allicin.

References

  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. ^ a b Cavallito, Chester J.; Bailey, John Hays (1944). Journal of the American Chemical Society. 66 (11): 1950. doi:10.1021/ja01239a048. {{cite journal}}: Missing or empty |title= (help)
  3. ^ a b Eric Block, "Garlic and Other Alliums: The Lore and the Science" (Cambridge: Royal Society of Chemistry, 2010)
  4. ^ What is Allicin?
  5. ^ Cremlyn, R. J. W. (1996). An introduction to organosulfur chemistry. Wiley. ISBN 0-471-95512-4.
  6. ^ Brodnitz, M.H., Pascale, J.V., Derslice, L.V. (1971). "Flavor components of garlic extract". J. Agr. Food. Chem. 19 (2): 273–5. doi:10.1021/jf60174a007.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  7. ^ 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.
  8. ^ Hahn, G (1996). 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. {{cite book}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  9. ^ S. Eilat, Y. Oestraicher, A. Rabinkov, D. Ohad, D. Mirelman, A. Battler, M. Eldar and Z. Vered (1995). "Alteration of lipid profile in hyperlipidemic rabbits by allicin, an active constituent of garlic". Coron. Artery Dis. 6 (12): 985–990. PMID 8723021.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  10. ^ D. Abramovitz, S. Gavri, D. Harats, H. Levkovitz, D. Mirelman, T. Miron, S. Eilat-Adar, A. Rabinkov, M. Wilchek, M. Eldar and Z. Vered, (1999). "Allicin-induced decrease in formation of fatty streaks (atherosclerosis) in mice fed a cholesterol-rich diet". Coron. Artery Dis. 10 (7): 515–9. doi:10.1097/00019501-199910000-00012. PMID 10562920.{{cite journal}}: CS1 maint: extra punctuation (link) CS1 maint: multiple names: authors list (link)
  11. ^ Silagy CA, Neil HA (1994). "A meta-analysis of the effect of garlic on blood pressure". J Hypertens. 12 (4): 463–8. PMID 8064171.
  12. ^ A. Elkayam, D. Mirelman, E. Peleg, M. Wilchek, T. Miron, A. Rabinkov, M. Oron-Herman and T. Rosenthal (2003). "The effects of allicin on weight in fructose-induced hyperinsulinemic, hyperlipidemic, hypertensive rats". Am. J. Hypertens. 16 (12): 1053–6. doi:10.1016/j.amjhyper.2003.07.011. PMID 14643581.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  13. ^ Srivastava KC (1986). "Evidence for the mechanism by which garlic inhibits platelet aggregation". Prostaglandins Leukot Med. 22 (3): 313–321. doi:10.1016/0262-1746(86)90142-3. PMID 3088604.
  14. ^ U. Sela, S. Ganor, I. Hecht, A. Brill, T. Miron, A. Rabinkov, M. Wilchek, D. Mirelman, O. Lider and R. Hershkoviz (2004). "Allicin inhibits SDF-1alpha-induced T cell interactions with fibronectin and endothelial cells by down-regulating cytoskeleton rearrangement, Pyk-2 phosphorylation and VLA-4 expression". Immunology. 111 (4): 391–399. doi:10.1111/j.0019-2805.2004.01841.x. PMC 1782446. PMID 15056375.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  15. ^ Lindsey J. Macpherson, Bernhard H. Geierstanger, Veena Viswanath, Michael Bandell, Samer R. Eid, SunWook Hwang, and Ardem Patapoutian (2005). "The pungency of garlic: Activation of TRPA1 and TRPV1 in response to allicin]". Current Biology. 15 (10): 929–934. doi:10.1016/j.cub.2005.04.018. PMID 15916949.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  16. ^ Bautista DM, Movahed P, Hinman A, Axelsson HE, Sterner O, Hogestatt ED, Julius D, Jordt SE and Zygmunt PM (2005). "Pungent products from garlic activate the sensory ion channel TRPA1". Proc Natl Acad Sci USA. 102 (34): 12248–52. doi:10.1073/pnas.0505356102. PMC 1189336. PMID 16103371.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  17. ^ Banerjee, SK; Mukherjee, PK; Maulik, SK (2001). "Garlic as an Antioxidant: The Good, The Bad and The Ugly". Phytotherapy Research. 17 (2): 97–106. doi:10.1002/ptr.1281. PMID 12601669.
  18. ^ Amagase, H; Petesch, BL; Matsuura, H; Kasuga, S; Itakura, Y (2003). "Intake of garlic and its bioactive components". J Nutr. 131 (3s): 955S–62S. PMID 11238796.
  19. ^ 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. {{cite journal}}: Explicit use of et al. in: |author= (help)CS1 maint: multiple names: authors list (link)
  20. ^ Vaidya, Vipraja (2009). "Garlic: Source of the Ultimate Antioxidants – Sulfenic Acids". Angewandte Chemie. 121 (1): 163–6. doi:10.1002/ange.200804560. PMID 19040240. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  21. ^ Block E, Dane AJ, Thomas S, Cody RB (2010). "Applications of Direct Analysis in Real Time–Mass Spectrometry (DART-MS) in Allium Chemistry. 2-Propenesulfenic and 2-Propenesulfinic Acids, Diallyl Trisulfane S-Oxide and Other Reactive Sulfur Compounds from Crushed Garlic and Other Alliums". Journal of Agricultural and Food Chemistry. 58 (8): 4617–25. doi:10.1021/jf1000106. PMID 20225897.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  22. ^ Ankri, S (1999). "Antimicrobial properties of allicin from garlic". Microbes Infect. 2 (2): 125–9. doi:10.1016/S1286-4579(99)80003-3. PMID 10594976. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  23. ^ a b c Cutler, RR (2004). "Antibacterial activity of a new, stable, aqueous extract of allicin against methicillan-resistant Staphylococcus aureus" (PDF). British Journal of Biomedical Science. 61 (2): 71–4. PMID 15250668. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  24. ^ Lawson, LD; Koch HP, ed. (1996). The composition and chemistry of garlic cloves and processed garlic; in Garlic: the science and therapeutic application of Allium sativum L and related species (2nd ed.). Baltimore: Williams and Wilkins. pp. 37–107. ISBN 0-683-18147-5.{{cite book}}: CS1 maint: multiple names: editors list (link)

External links

  • Johnston, Nicole (2002). "News in Brief: Garlic: A natural antibiotic". Mdd modern drug discovery. 5 (4). Allicin, the major component of garlic, is one such agent, and it was recently shown to be potent against VRE and MRSA in two studies presented at the 41st Interscience Conference on Antimicrobial Agents and Chemotherapy in Chicago in December.
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