Allicin

Allicin is an organosulfur compound obtained from garlic. It is also obtainable from onions, and other species in the family Alliaceæ.

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Définitions :

  • Allicin is an organic compound obtained from garlic. It is also obtainable from onions, and other species in the family Alliaceæ.... (source : en.wikipedia)
  • The allicin in garlic dœs not exist unless you make it. In other words, there isn't any allicin in garlic to begin with.... (source : findhealer)
Allicin
Allicin
S-allicin
IUPAC name
Identifiers
CAS number 539-86-6
PubChem 65036
SMILES
Properties
Molecular formula C6H10OS2
Molar mass 162.28 g/mol
Density 1.112 g/cm3
Melting point

<25 °C

Boiling point

dec.

Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Allicin is an organosulfur compound obtained from garlic. It is also obtainable from onions, and other species in the family Alliaceæ. [1] It was first isolated and studied in the laboratory by Chester J. Cavallito in 1944. [2] This colourless liquid has a différentively pungent smell. This compound exhibits antibacterial and anti-fungal properties. [3] Allicin is garlic's defence 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 and occurs naturally as only a single enantiomer. The racemic form can be generated by oxidation of diallyldisulfide :[5]

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

Alliinase is irreversibly deactivated below a pH of 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 23C. [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. [17]

In 2009, Vaidya, Ingold, and Pratt have clarified exactly how allicin works to produce its medicinal effects, such as trapping damaging radicals. According to them, it is the sulfenic acids, which are produced by the decomposition of allicin, that extremely rapidly react with free radicals, and bind with them. "We suggest that the peroxyl-radical-trapping activity of garlic is primarily due to 2-propenesulfenic acid formed by the decomposition of allicin. "[18]

The antibacterial activity

The antibacterial activity of allicin was reviewed by Ankri and Mirelman in 1999. [19] Due to the increasing prevalence of methicillin-resistant Staphylococcus aureus (MRSA) in hospitals and the community, there has been an urgent need for new agents that could be used to deal with these bacteria. In this connection, in 2004, Cutler and Wilson have studied the effect of allicin on these bacteria. [20] They used a new stable, aqueous extract of allicin, and have achieved very promising results.

Cutler and Wilson note that the use of a water-based extract of allicin stabilises the allicin molecule. [20] They note further that this may be due to the hydrogen bonding of water to the reactive oxygen atom in allicin; also, there may be water-soluble components in crushed garlic that destabilise the molecule. [21] (Presumably, the dilution of these components in water helps to preserve the allicin molecule. )

Cutler and Wilson tested allicin on 30 clinical isolates of MRSA that show a range of susceptibilities to mupirocin. Strains were tested using agar diffusion tests. Of the strains tested, 88% had minimum inhibitory concentrations for allicin liquids of 16 µg/mL, and all strains were inhibited at 32 µg/mL. Furthermore, 88% of clinical isolates had minimum bactericidal concentrations of 128 µg/mL, and all were killed at 256 µg/mL. Of these strains, 82% showed intermediate or full resistance to mupirocin.

Also, Cutler and Wilson found that an aqueous cream of allicin was somewhat less effective than allicin liquid. At 500 µg/mL, however, the cream was still active against all the organisms tested—which compares well with the 20, 000 µg/mL mupirocin currently used for topical application. [22]

See also

References

  1. ˆ a b c Eric Block (1985). "The chemistry of garlic and onions". Scientific American 252 (March)  : 114–119.  
  2. ˆ Chester J. Cavallito, John Hays Bailey, "Allicin, the Antibacterial Principle of Allium sativum. I. Isolation, Physical Properties and Antibacterial Action", Journal of the American Chemical Society, 1944, volume 66, pp 1950 - 1951. doi :10.1021/ja01239a048
  3. ˆ Chester J. Cavallito, John Hays Bailey "Allicin, the Antibacterial Principle of Allium sativum. I. Isolation, Physical Properties and Antibacterial Action" Journal of the American Chemical Society, 1944, volume 66, pp 1950 - 1951. doi :10.1021/ja01239a048
  4. ˆ http ://www. phytochemicals. info/phytochemicals/allicin. php
  5. ˆ R. J. Cremlyn “An Introduction to Organosulfur Chemistry” John Wiley and Sons : Chichester (1996). ISBN 0 471 95512 4.
  6. ˆ Brodnitz, M. H. Pascale, J. V., and Derslice, L. V. Flavor components of garlic extract. J. Agr. Food. Chem. 19 (2)  :273-275, 1971
  7. ˆ Yu. T-H, and Wu, C-M. Stability of allicin in garlic juice. J. Food Sci. 54 (4)  : 977-981, 1989
  8. ˆ Hahn, G; in Koch HP, Lawson LD, eds. (1996). Garlic : the science and therapeutic application of Allium sativum L and related species (2nd edn) . Baltimore : Williams and Wilkins. pp.  1–24.  
  9. ˆ S. Eilat, Y. Œstraicher, 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 forment of garlic". Coron. Artery Dis. 6 : 985–990.  
  10. ˆ 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 : 515–519. doi :10.1097/00019501-199910000-00012.  
  11. ˆ Silagy CA, Neil HA (1994). "A meta-analysis of the effect of garlic on blood pressure". J Hypertens 12 (4)  : 463–468.  
  12. ˆ 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 : 1053–1056. doi :10.1016/j. amjhyper. 2003.07.011.  
  13. ˆ 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.  
  14. ˆ 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 : 391–399. doi :10.1111/j. 0019-2805.2004.01841. x.  
  15. ˆ Lindsey J. Macpherson, Bernhard H. Geierstanger, Veena Viswanath, Michæl 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 (May 24)  : 929–934.  
  16. ˆ 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. PMID 16103371.  
  17. ˆ Lawson, L. D., Ransom, D. K. and Hughes, B. G. Inhibition of whole blood platelet-aggregation by compounds in garlic clove extracts and commercial garlic products. Throm. Res. 65 : 141-156, 1992.
  18. ˆ Vaidya, Vipraja; Keith U. Ingold, Derek A. Pratt (2009). "Garlic : Source of the Ultimate Antioxidants - Sulfenic Acids". Angewandte Chemie 121 (1)  : 163-166. doi :10.1002/ange. 200804560. http ://www3. interscience. wiley. com/cgi-bin/fulltext/121541722/HTMLSTART. Retrieved 21 Feb 2009.  
  19. ˆ Ankri, S; Mirelman D (1999). "Antimicrobial properties of allicin from garlic". Microbes Infect 2 : 125–9.  
  20. ˆ a b Cutler, RR; P Wilson (2004). "Antibacterial activity of a new, stable, aqueous extract of allicin against methicillan-resistant Staphylococcus aureus (PDF file) ". British Journal of Biomedical Science 61 (2)  : 71-4. http ://www. allimax. us/Cutler. pdf. Retrieved 20 Feb 2009.  
  21. ˆ Lawson, LD; Koch HP, Lawson LD, eds. (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 edn) . Baltimore : Williams and Wilkins. pp.  37–107.  
  22. ˆ Cutler, RR; P Wilson (2004). "Antibacterial activity of a new, stable, aqueous extract of allicin against methicillan-resistant Staphylococcus aureus (PDF file) ". British Journal of Biomedical Science 61 (2)  : 71-4. http ://www. allimax. us/Cutler. pdf. Retrieved 20 Feb 2009.  

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Ce texte est issu de l'encyclopédie Wikipedia. Vous pouvez consulter sa version originale dans cette encyclopédie à l'adresse http://en.wikipedia.org/wiki/allicin.
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