5-Allyl cysteine sulfoxide

Naturally occurring alliin, the major precursor to the garlic aroma, is (RcSs)-( I )-,S -allyl-[.-cysteine sulfoxide 26 (Scheme 10) with both a chiral carbon and chiral sulfur - probably the first such compound (note that sulforaphene - see earlier - was isolated more or less simultaneously with alliin). Hence there are four possible stereoisomers. The alliin level in garlic is significant 5-14 mg g 1 fresh weight. 

Garlic oil and S-allyl-cysteine sulfoxide (Alliin), a garlic compound, exhibited similar antioxidant properties. Aged garlic extract prevents ischemia and reperfusion injuries to the heart and brain. 

Allylcatechol methylene ether 12. Ip Allyl cysteine sulfoxide 14.6o... 

Known active constituents of garlic (there are at least 35 other constituents whose actions are unknown) ajoene, allicin, aliin, allixin, allyl mercaptan, allyl methyl thiosulfmate, allyl methyl trisulfide, allyl propyl disulfide, diallyl disulfide, diallyl hepta sulfide, diallyl hexa sulfide, diallyl penta sulfide, diallyl sulfide, diallyl tetra sulfide, diallyl tri sulfide, dimethyl disulfide, dimethyl trisulfide, dirpopyl disulfide, methyl ajoene, methyl allyl thiosulfmate, propyline sulfide, 2-vinyl-4H-l, 3-tithiin, 3-vinyl-4H-1, 2dithiin, S-allyl cysteine sulfoxide, S-allyl mercapto, cysteine. 

Alliin Allyl cysteine sulfoxide Allicin Allyl disulfide Diallyl disulfide Cysteine Allium sativa... 

FIGURE 18.1. Postulated pathways for biosynthesis of allyl cysteine sulfoxide. 

S-allyl cysteine sulfoxide ( S-2-Drooenvl cvsteine sulfoxide)... 

FIGURE 18.4. Formation of flavor compounds from S-allyl cysteine sulfoxide. 

Nishimura and coworkers57-59 studied the y-radiolysis of aqueous solutions of sulfoxide amino acids. Sulfoxide amino acids are the precursors of the flavors of onions (S-propyl-L-cysteine sulfoxide, S-methyl-L-cysteine sulfoxide and S-(l-propenyl)-L-cysteine sulfoxide) and garlic (S-allyl-L-cysteine sulfoxide). In studies on sprout inhibition of onion by /-irradiation it was found that the characteristic flavor of onions became milder. In the y-radiolysis of an aqueous solution of S-propyl-L-cysteine sulfoxide (PCSO)57,58 they identified as the main products alanine, cysteic acid, dipropyl disulfide and dipropyl sulfide. In the radiolysis of S-allyl-L-cysteine sulfoxide (ACSO) they found that the main products are S-allyl-L-cysteine, cysteic acid, cystine, allyl alcohol, propyl allyl sulfide and diallyl sulfide. The mechanisms of formation of the products were partly elucidated by the study of the radiolysis in the presence of N20 and Br- as eaq - and OH radicals scavengers, respectively. 

Alline S-Propenyl-cysteine sulfoxide 7-L-Glutamyl-S-allyl-cysteine... 

Members of the allium family (onions, garlic, and leeks) contain cysteine sulfoxide derivatives (allyl sulfur compounds), such as allicin and alliin (see Figure 14.9). When the plant cells are damaged, the enzyme alliinase is released from vacuoles and catalyzes the formation of thiosulfinates and thiols, including the lachrymator thiopropanal S-oxide. Their function in the plant is presumably to provide protection against attack by pests. 

Garlic is also a medicinal used by the Kallawaya herbalists, and it is mentioned that crushed garlic contains the powerful bactericidal agent allyl allylthiosulfinate (allicin), which is formed by the interaction of the enzyme allinase with the substrate 5-ethyl L-cystein sulfoxide (Bastien, 1987, p. 102, n. 6). Bastien in turn supplies the results of an experiment on mice. Thus, in miee infected with sarcoma, injection either of the enzyme allinase or the substrate 5-ethyl L-cystein sulfoxide (alliin) alone had no effect, all animals dying within 16 days. However, in infected mice treated with both the enzyme and the substrate, the animals were still alive after 6 months. Allicin is therefore the active anticancer ingredient, as will be emphasized especially in Chapter 5. 

SCHWiMMER, S. S-Allyl-L-cysteine sulfoxide lyase [Allium cepa (Onion)]. Methods Enzymol. 17 B, 475 (1971). 

Cycloalliin Cysteine -S-allylcysteine -S-allyl-mercapto cysteine Cysteine sulfoxides 5-glutamyl cysteines Cystine... 

Raw garlic per se 5-glutamyl-5-allyl-L-cysteines, 5-allyl-L-cysteine sulfoxides, allicin, adenosine Intact clove with the white or pink skin by simple pull off Precursor of allicin, methiin, (-t-j-S-ftrani-l-propenyO-L-cysteine sulfoxide, and cycloalliin... 

The flavor precursors, 5 -alk(en)yl-L-cysteine sulfoxides, themselves do not have any specific flavor. However, when garlic or onion cells are damaged by cutting or crushing and the 5 -alk(en)yl-L-cysteine sulfoxides meet the C-S lyase (alliinase), they are converted into various volatile sulfuric compounds. Stoll and Seebeck (1951) first proposed the production of diallyl thiosulfinate (allicin) from the 5 -allyl-L-cysteine sulfoxide (alliin) by the C-S lyase. Through the reaction catalyzed by the C-S lyase, 5 -alk(en)yl-L-cysteine sulfoxides yield alk(en)yl sulfenic acid and aminoacrylic acid, the latter being spontaneously degraded... 

Similar to the S-allyl-L-cysteine sulfoxide in garlic, the C-S lyase can also catalyze the flavor formation from the 5 -methyl-L-cysteine sulfoxide. Therefore, when garlic is cut or crushed, methyl sulfenic acid and allyl sulfenic acid can be produced from 5 -methyl-L-cysteine sulfoxide and S-allyl-L-cysteine sulfoxide, respectively (Figure 18.5). As sulfenic acids are quite reactive, methyl sulfenic acid and allyl sulfenic acid will quickly form the metiiyl 2-propenethiosulfinate and allyl methaneth-iosulfinate. With the similar reaction to that from diallyl thiosulfinate, these thiosulfinates produce allyl methyl disulfide and allyl methyl trisulfide. 

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