Allicin

Structural formula
Structural formula without stereochemistry - stereocenter on the sulfur atom of the S = O group
General
Surname	Allicin
other names	Prop-2-en-1-thiosulfinic acid S -allyl ester
Molecular formula	C 6 H 10 OS 2
External identifiers / databases
CAS number 539-86-6 EC number 208-727-7 ECHA InfoCard 100.007.935 PubChem 65036 DrugBank DB11780 Wikidata Q409641
properties
Molar mass	162.28 g mol −1
Physical state	liquid
density	1.11 g cm −3 (20 ° C)
solubility	moderately in water, miscible with diethyl ether and ethanol
Refractive index	1.561 (20 ° C)
safety instructions
GHS labeling of hazardous substances Caution H and P phrases H: 315-319-335 P: ?
Toxicological data	60 mg kg −1 ( LD 50 ,  mouse ,  iv )
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions . Refractive index: Na-D line , 20 ° C

Allicin is the conversion product of the non-proteinogenic amino acid alliin found in garlic . Since allicin is not stable, it is sometimes spontaneously converted into di- and trisulphides, and in oil also into vinyldithiines and ajoene . Only these compounds are responsible for the typical garlic smell.

Occurrence

Allicin is formed by changing the cell structure of e.g. B. Garlic is destroyed. Alliin comes into contact with an alliinase, so that ultimately allicin is formed:

Alliin ( 1 ) is transformed into allylsulfenic acid ( 2 ) and dehydroalanine ( 3 ) by alliinase . The latter component reacts with water to form ammonia and pyruvic acid .

Two molecules of allylsulfenic acid then condense to form allicin.

chemistry

Allicin is chiral , but occurs naturally as a racemate . Racemic allicin can be produced synthetically by oxidizing diallyl disulfide with a percarboxylic acid:

(SCH ₂ CH = CH ₂ ) ₂ + RCO ₃ H → CH ₂ = CHCH ₂ S (O) SCH ₂ CH = CH ₂ + RCO ₂ H

Allicin can spontaneously convert to allyl sulfides or diallyl sulfides in an aqueous medium . In an oil phase (e.g. with garlic oil macerates ) vinyldithiins (70%), sulphides (18%) and ajoene (12%) are formed.

Allicin itself is unstable and converts to disulfides (diallyl disulfide 1 ) or higher sulfides (e.g. diallyl trisulfide 2 ) in an aqueous medium . In the oil phase, vinyl dithiines (2-vinyl-4 H -1,3-dithiin 3a or 3-vinyl-4 H -1,2-dithiin 3b ) and ajoenes ( E- ajoene 4a or Z- ajoene 4b ) educated.

Allicin itself is odorless, but causes v. a. Diallylsulfide and vinyldithiine give the garlic-typical odor.

Biological importance

Allicin can be easily absorbed. In the blood it is broken down into allyl mercaptan (allyl thiol ). In the lungs, it is finally converted to allyl methyl sulfide, which requires SAM .

It is assumed that the majority of the allyl mercaptan is oxidized to allyl sulfonic acids - analogous to the oxidation of cysteine to taurine .

If allicin gets into the blood, it is broken down into allyl mercaptan (allyl thiol ). Methylation using SAM causes it to be excreted in the lungs as allyl methyl sulfide ( S -methyl allyl mercaptan).

The tear-irritating allicin is antibacterial in the stomach: even when diluted 100,000 times, it kills both gram-positive and gram-negative bacteria . Due to its lipid- lowering effect (in vitro and in animal experiments), allicin - and thus garlic - is said to have a positive therapeutic effect on arteriosclerosis . A reduction in LDL cholesterol could not be demonstrated in a double-blind study with fresh garlic, garlic powder, garlic extract and placebos in 192 patients with slightly elevated cholesterol levels. Too high LDL cholesterol levels are linked to the development of arteriosclerosis.

pharmacology

Allicin has cytotoxic (cell-killing) properties, but these do not have any effect when consumed, as it is further broken down very quickly into non-toxic substances (see above). The basis of the action of allicin is that it is able to react with thiols , which occur in proteins in residues of the amino acid cysteine . There are two theories that explain the effect of allicin: On the one hand, it is conceivable that allicin reacts directly with cysteine ​​residues of enzymes and thereby oxidizes them to mixed disulfides; on the other hand, the oxidation on cysteine ​​can also lead to the formation of non-native disulfide bridges .

Allicin is being studied for the prevention and treatment of tumors , including breast cancer and stomach cancer .

Web links

• Wissenschaft.de: Antibodies with a stink effect - garlic ingredient allicin turns defense proteins into effective weapons against cancer cells
• Wissenschaft.de: Why garlic burns on the tongue - allicin activates heat-sensitive receptors

Individual evidence

1. ↑ ^{a b c d} Entry on allicin. In: Römpp Online . Georg Thieme Verlag, accessed on November 10, 2014.
2. ↑ David R. Lide (Ed.): CRC Handbook of Chemistry and Physics . 90th edition. (Internet version: 2010), CRC Press / Taylor and Francis, Boca Raton, FL, Physical Constants of Organic Compounds, pp. 3-10.
3. ↑ There is not yet a harmonized classification for this substance . A labeling of S-allyl acrylo-1-sulphinothioate in the Classification and Labeling Inventory of the European Chemicals Agency (ECHA), retrieved on December 3, 2017, is reproduced from a self-classification by the distributor .
4. ↑ Eric Block: Garlic and Other Alliums: The Lore and the Science. Royal Society of Chemistry, Cambridge 2010.
5. ↑ RJW Cremlyn: An introduction to organosulfur chemistry . Wiley, 1996, ISBN 0-471-95512-4 .
6. ^ ^{A b} Eric Block: Garlic and Other Alliums: The Lore and the Science . Royal Society of Chemistry, Cambridge 2010, ISBN 978-0-85404-190-9 ( limited preview in Google book search).
7. ↑ Eric Block: The organosulfur chemistry of the genus Allium and its importance for the organic chemistry of sulfur. In: Angewandte Chemie . 104, 1992, pp. 1158-1203, doi: 10.1002 / anie.19921040906 .
8. ↑ ^{a b} Theodor Dingermann, Rudolf Hänsel, Ilse Zündorf (eds.): Pharmaceutical Biology: Molecular Basics and Clinical Applications. 1st edition. Springer Verlag, Berlin 2002, ISBN 3-540-42844-5 , pp. 62-63.
9. ↑ Christoph Gardener et al .: Effect of Raw Garlic vs Commercial Garlic Supplements on Plasma Lipid Concentrations in Adults With Moderate Hypercholesterolemia: A Randomized Clinical Trial. In: Archives of Internal Medicine . 167, 2007, pp. 346-353. PMID 17325296 .
10. ^ J. Borlinghaus, F. Albrecht, MC Gruhlke, ID Nwachukwu, AJ Slusarenko: Allicin: chemistry and biological properties. In: Molecules . Volume 19, number 8, August 2014, pp. 12591-12618, doi : 10.3390 / molecules190812591 , PMID 25153873 .
11. ↑ ED Wills: Enzyme Inhibition by Allicin, the Active Principle of Garlic. In: Biochem. J. 63, 1956, pp. 514-520. PMC 1216205 (free full text).
12. ↑ G. Schäfer, CH Kaschula: The immunomodulation and anti-inflammatory effects of garlic organosulfur compounds in cancer chemoprevention. In: Anti-Cancer Agents in Medicinal Chemistry . Volume 14, Number 2, February 2014, pp. 233-240, PMID 24237225 , PMC 3915757 (free full text).
13. ^ S. Rajput, M. Mandal: Antitumor promoting potential of selected phytochemicals derived from spices: a review. In: European Journal of Cancer Prevention  : the official journal of the European Cancer Prevention Organization. Volume 21, Number 2, March 2012, pp. 205-215, doi : 10.1097 / CEJ.0b013e32834a7f0c , PMID 21876437 .
14. ↑ SC Gupta, JH Kim, S. Prasad, BB Aggarwal: Regulation of survival, proliferation, invasion, angiogenesis, and metastasis of tumor cells through modulation of inflammatory pathways by nutraceuticals. In: Cancer Metastasis Reviews . Volume 29, number 3, September 2010, pp. 405-434, doi : 10.1007 / s10555-010-9235-2 , PMID 20737283 , PMC 2996866 (free full text).
15. ↑ A. Tsubura, YC Lai, M. Kuwata, N. Uehara, K. Yoshizawa: Anticancer effects of garlic and garlic-derived compounds for breast cancer control. In: Anti-Cancer Agents in Medicinal Chemistry . Volume 11, Number 3, March 2011, pp. 249-253, PMID 21269259 .
16. ↑ A. Haghi, H. Azimi, R. Rahimi: A Comprehensive Review on Pharmacotherapeutics of Three Phytochemicals, Curcumin, Quercetin, and Allicin, in the Treatment of Gastric Cancer. In: Journal of Gastrointestinal Cancer . Volume 48, Number 4, December 2017, pp. 314-320, doi : 10.1007 / s12029-017-9997-7 , PMID 28828709 .

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