Alliin

Alliin /ˈæli.ɪn/ is a sulfoxide that is a natural constituent of fresh garlic.^[1] It is a derivative of the amino acid cysteine. When fresh garlic is chopped or crushed, the enzyme alliinase converts alliin into allicin, which is responsible for the aroma of fresh garlic. Allicin and other thiosulfinates in garlic are unstable and form a number of other compounds, such as diallyl sulfide (DAS), diallyl disulfide (DADS) and diallyl trisulfide (DAT), dithiins and ajoene.^[2] Garlic powder is not a source of alliin, nor is fresh garlic upon maceration, since the enzymatic conversion to allicin takes place in the order of seconds.

Alliin

Alliin skeletal view
Alliin ball view
Names
Systematic IUPAC name (2R)-2-Amino-3-[(S)-(prop-2-ene-1-sulfinyl)]propanoic acid
Other names 3-(2-Propenylsulfinyl)alanine (S)-3-(2-Propenylsulfinyl)-L-alanine 3-[(S)-Allylsulfinyl]-L-alanine S-Allyl-L-cysteine sulfoxide
Identifiers
CAS Number	556-27-4 N
3D model (JSmol)	Interactive image Interactive image
ChEBI	CHEBI:2596 N
ChEMBL	ChEMBL464166 N
ChemSpider	7850537 Y
ECHA InfoCard	100.008.291
EC Number	209-118-9
KEGG	C08265
PubChem CID	9576089
UNII	7I4L2D0E9G
CompTox Dashboard (EPA)	DTXSID801020639
InChI InChI=1S/C6H11NO3S/c1-2-3-11(10)4-5(7)6(8)9/h2,5H,1,3-4,7H2,(H,8,9)/t5-,11-/m0/s1 Y Key: XUHLIQGRKRUKPH-DYEAUMGKSA-N Y
SMILES C=CCS(=O)CC(C(=O)O)N N[C@H](C(=O)O)C[S@@](=O)CC=C
Properties
Chemical formula	C6H11NO3S
Molar mass	177.22 g·mol−1
Appearance	White to off white crystalline powder
Melting point	163–165 °C (325–329 °F)
Solubility in water	Soluble
Hazards
GHS labelling:
Pictograms
Signal word	Warning
Hazard statements	H315, H319, H335
Precautionary statements	P261, P264, P271, P280, P302+P352, P304+P340, P305+P351+P338, P312, P321, P332+P313, P337+P313, P362, P403+P233, P405, P501
NFPA 704 (fire diamond)	1 1 0
Safety data sheet (SDS)	External MSDS
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). N verify (what is YN ?) Infobox references

Alliin was the first natural product found to have both carbon- and sulfur-centered stereochemistry.^[3]

Chemical synthesis

The first reported synthesis, by Stoll and Seebeck in 1951,^[4] begins the alkylation of L-cysteine with allyl bromide to form deoxyalliin. Oxidation of this sulfide with hydrogen peroxide gives both diastereomers of L-alliin, differing in the orientation of the oxygen atom on the sulfur stereocenter.

A newer route, reported by Koch and Keusgen in 1998,^[5] allows stereospecific oxidation using conditions similar to the Sharpless asymmetric epoxidation. The chiral catalyst is produced from diethyl tartrate and titanium isopropoxide.

Medical exploration

Garlic has been used since antiquity for conditions now associated with oxidative stress (production and accumulation of reactive oxygen species (ROS)).^{[citation needed]} In an in vitro test, garlic powder showed antioxidant properties, and alliin showed good hydroxyl radical-scavenging effect.^[6] Alliin has also been found to affect immune responses in blood cells in vitro.^[7]