Allicin

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Allicin
Identifiers
CAS number539-86-6 N
PubChem65036
ChemSpider58548 YesY
UNII3C39BY17Y6 YesY
EC number208-727-7
KEGGC07600 YesY
MeSHAllicin
ChEBICHEBI:28411 YesY
ChEMBLCHEMBL359965 YesY
IUPHAR ligand2419
Beilstein Reference1752823
Jmol-3D imagesImage 1
Image 2
Properties
Molecular formulaC6H10OS2
Molar mass162.27 g mol−1
AppearanceColourless liquid
Density1.112 g cm−3
Melting point<25 °C
Boiling pointdecomposes
 N (verify) (what is: YesY/N?)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
Infobox references
 
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Allicin
Identifiers
CAS number539-86-6 N
PubChem65036
ChemSpider58548 YesY
UNII3C39BY17Y6 YesY
EC number208-727-7
KEGGC07600 YesY
MeSHAllicin
ChEBICHEBI:28411 YesY
ChEMBLCHEMBL359965 YesY
IUPHAR ligand2419
Beilstein Reference1752823
Jmol-3D imagesImage 1
Image 2
Properties
Molecular formulaC6H10OS2
Molar mass162.27 g mol−1
AppearanceColourless liquid
Density1.112 g cm−3
Melting point<25 °C
Boiling pointdecomposes
 N (verify) (what is: YesY/N?)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
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] 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[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:[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[edit]

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 animal studies have shown a strong oxidative effect in the gut that can damage intestinal cells, though 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 the 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[edit]

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 activity, 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]

Antiviral activity[edit]

Although there are preliminary studies indicating some potential benefit of garlic in treating the common cold,[25] [26][27][28] a 2012 report in the Cochrane Database of Systematic Reviews concluded that "there is insufficient clinical trial evidence regarding the effects of garlic in preventing or treating the common cold. A single trial - The trial that relied on self reported episodes of the common cold but was of reasonable quality in terms of randomisation and allocation concealment, suggested that garlic may prevent occurrences of the common cold but more studies are needed to validate this finding. Claims of effectiveness appear to rely largely on poor-quality evidence."[29] Similar conclusions are voiced in a 2013 report, which states "Garlic as a preventative or treatment option for the common cold ... could not be recommended, as only one relatively small trial evaluated the effects separately. Garlic might be effective in some areas of clinical practice, but the evidence levels were low, so further researches should be well designed using rigorous method to avoid potential biases"[30]

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. ^ a b Cavallito, Chester J.; Bailey, John Hays (1944). Journal of the American Chemical Society 66 (11): 1950. doi:10.1021/ja01239a048. 
  3. ^ a b Eric Block, "Garlic and Other Alliums: The Lore and the Science" (Cambridge: Royal Society of Chemistry, 2010)
  4. ^ What is Allicin?. Phytochemicals.info. Retrieved on 2012-12-26.
  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". Journal of Agricultural and Food Chemistry 19 (2): 273–5. doi:10.1021/jf60174a007. 
  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; in Koch HP, Lawson LD, eds. (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. 
  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. 
  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. 
  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. 
  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. 
  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. 
  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". Proceedings of the National Academy of Sciences of the United States of America 102 (34): 12248–52. doi:10.1073/pnas.0505356102. PMC 1189336. PMID 16103371. 
  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. 
  20. ^ Vaidya, Vipraja; Keith U. Ingold, Derek A. Pratt (2009). "Garlic: Source of the Ultimate Antioxidants – Sulfenic Acids". Angewandte Chemie 121 (1): 163–6. doi:10.1002/ange.200804560. PMID 19040240. 
  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. 
  22. ^ Ankri, S; Mirelman D (1999). "Antimicrobial properties of allicin from garlic". Microbes Infect 2 (2): 125–9. doi:10.1016/S1286-4579(99)80003-3. PMID 10594976. 
  23. ^ a b c Cutler, RR; P Wilson (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. 
  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. 
  25. ^ Nahas, R.; Balla, A. (2011). "Complementary and alternative medicine for prevention and treatment of the common cold". Canadian family physician Medecin de famille canadien 57 (1): 31–36. PMC 3024156. PMID 21322286.  edit
  26. ^ Complementary and alternative medicine for prevention and treatment of the common cold. Cfp.ca. Retrieved on 2012-12-26.
  27. ^ HEALTH | Garlic 'prevents common cold'. BBC News (2001-10-03). Retrieved on 2012-12-26.
  28. ^ Josling, P. (2001). "Preventing the common cold with a garlic supplement: A double-blind, placebo-controlled survey". Advances in therapy 18 (4): 189–193. PMID 11697022.  edit
  29. ^ Lissiman, E.; Bhasale, A.L.; Cohen, M. (March 14, 2012). "Garlic for the common cold". Cochrane Database of Systematic Reviews 3: 3:CD006206. doi:10.1002/14651858.CD006206.pub3. PMID 22419312. 
  30. ^ Li, L.; Sun, T.; Tian, J.; Yang, K.; Yi, K.; Zhang, P. (2013). "Garlic in clinical practice: an evidence-based overview.". Crit Rev Food Sci Nutr. 53: 670–681. doi:10.1080/10408398.2010.537000.pub3. PMID 23638928. 

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