Garlic disulfides

Carbon Sulfotelluride. Carbon sulfoteUuride [10340-06-4] CSTe, exists as a yeUow-red Hquid having a garlic-like odor. It is decomposed by light, even at —50°C, to carbon disulfide, carbon, and teUurium. 

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. 

Self-Test 4.11B The Codex Ebers, an Egyptian medical papyrus, describes the use of garlic as an antiseptic. Chemists today have verified that the oxide of diallyl disulfide... 

Ajoene (Spanish, ajo, garlic), 4,5,9-trithiadodeca-l,6,ll-triene-9-oxide 35 (Scheme 12), an antithrombotic compound with other well-defined physiological properties, is formed from allicin.84 Like allicin, ajoene is a sulfoxide but has two further sulfur atoms in a disulfide linkage. E and Z isomeric forms are possible involving the C=C bond at positions 6 and 7. Ajoene is somewhat more stable than allicin. The formation of ajoene probably involves condensation of 2 molecules of allicin forming a sulfonium salt 33, with elimination of propenesulfenic acid. Elimination of a second molecule of propenesulfenic acid... 

Note that we have something new here a sulfur-sulfur bond. Allicin is a disulfide. Finally, allicin is converted to a molecule largely responsible for garlic breath — dipropenyl disulhde ... 

Note that we encountered disulfide bonds in chapter 4 when we described certain compounds that are formed in cut cloves of garlic. 

Five known natural product HDAC inhibitors can be consumed in the human diet butyrate, diallyl disulfide (DADS), flavones, pomiferin, and sulforaphane (SFN). These compounds are found in fiber, garlic, broccoli, and various fruits. The first clinical use of HDAC inhibitors come from the butyrate class. 

A number of volatile aliphatic compounds that contain nitrogen or sulfur atoms are important aroma constituents. Alkyl thiols, dialkyl sulfides and disulfides, and alkyl thiocyanates belong to this group. They occur widely in foods and spices and determine the odor of, for example, onions, garlic, and mustard. Because of their potent smell, they are used in high dilution and are often produced only in small quantities. The same is true for the following ... 

Diallyl disulfide [2179-57-9] is an essential odor component of garlic oil [233]. 

Recently, Germain et al. (90) studied the in vivo metabolism of diallyl disulfide (DADS), a garlic compound claimed to have anticarcinogenic effects. After oral administration of a single dose of 200mg/kg, metabolites were measured in the stomach, liver, plasma, and urine by GC coupled with MS over 15 days. DADS was detected in almost all analyzed tissues within the first hours. In addition, the metabolites allylmercaptan (AM) and allyl methyl sulfide (AMS) were detected. The Cmav of the metabolites were higher than that of DADS (1.46 pg/mL). The %ax for DADS was estimated to be less than one hour, whereas this time increased to 24 hours for AM and AMS (90). 

Allium victorialis L. var. platyphyllum (Hult.) Makino Ge Cong (Serpent garlic) (whole plant) Methyl allyl disulfide, dially disulfide, methyl allyltrisulfide, 1-propenyl sulfonic acid, methyl-1-propenyl disulfide, allyl-l-propenyl disulfide.48-50 A diuretic, vermifuge, treat cold. 

Ajoene, Fig. (10), an unsaturated sulfoxide disulfide, is the principal chemical responsible for garlic s anticoagulant properties. It has been also investigated for its acaricidal activity on T. urticae [275]. Complete mortality (100%) by ajoene was observed at 0.075% after 14 h of treatment, a dose comparable with other synthetic acaricides used in the experiment. At lower concentrations (0.05%), it affected female fecundity... 

Another German investigator (Semmler, 1892) also produced garlic oil via steam distillation. The oil yielded diallvl disulfide, CH2=CHCH2SSCH2 CH = CH2, with minor amounts of diallyl trisulfide and diallyl tetrasulfide present. The oil yielded by similar experimentation with onions was different, containing essentially propionaldehyde, C2H5CHO, plus a number of sulfur compounds, of which dipropyl disulfide, C5H12S2, was one. 

Self-Test 4.10B The Codex Ebers, an Egyptian medical papyrus, describes the use of garlic to treat many ailments, including the cleansing of wounds. Chemists today have discovered that the oxide of diallyl disulfide (the volatile compound responsible for garlic odor) is a powerful antibacterial agent more potent against typhoid than penicillin. At 177°C and 200 Torr, a sample of diallyl disulfide vapor has a density of 1.04 g-L 1. What is the molar mass of diallyl disulfide ... 

Among well-known spice allergens are diallyl disulfide and Allicin (garlic allergens, Allium sativum), eugol (nutmeg, cloves, and Jamaica pepper), cinnamic aldehyde (cinnamon), dipentene (caraway, cardamom, and spearmint), and linalool (basilica, coriander) (Kanerva 2002). 

Thiocarbonyl oxides are a subject of active investigation. The natural occurrence of sulfines and related compounds in plants of the genus Allium (onion, garlic, etc.) is included in a superb and extensive review by Block [91]. Two detailed papers [92, 93] report the isolation of zwiebelanes from onions and their chemical synthesis involving intermediate sulfines produced by oxidation of di-l-propenyl disulfide, subsequent sulfoxide accelerated [3.3] sigmatropic shift and the [2+2] cycloaddition of the C=S and C=S=0 moieties. A further article [94] provides a great deal of information on the mechanism of formation of (Z)-propanethial S-oxide, the lachrymatory factor of the onion, as well as its chemical synthesis and reactions. Techniques of analysis of the volatiles of onions have been further improved [95]. 

Sulfur-containing compounds. These are not derived from the terpenes. They have very pungent smells, e.g. diallyl disulfide found in garlic. 

Garlic Allium sativum dimethyl trisulfide Allicin (151), di(2-propenyl) disulfide (152), dimethyl 131,171... 

Garlic, Allium sativum L., is a species in the onion family, Alliaceae. Onion, shallot, and leek are close relatives. Garlic has been used throughout history for both culinary and medicinal purposes. It has a pungent hot sensation that mellows and sweetens considerably with cooking. A large number of sulfur compounds contribute to the smell and taste of members of the onion family. Diallyl disulfide and diallyl sulfide are... 

The pungent constituents of onion are somewhat different from those of garlic and this accounts for their different odors and pungency. It has been reported that the major pungent constituents of onion are di- -propyl disulfide and methyl- -propyl disulfide201... 

Alkyl sulfides and thiols. Some alkyl thiols and sulfides, notably those from commonly ingested Allium sativum (garlic) and Allium cepa (onion) (Alliaceae), are variously bioactive as odorants and antimicrobials. Propanethial S-oxide (CH3-CH2-CH=S=0) is a lachrymatory irritant principle of onion. Allicin (S-oxodiallydisulfide CH2=CH—CH2-SO-S-CH2— CH=CH2), diallyldisulfide (CH2=CH-CH2-S-S-CH2-CH=CH2) and diallylsulfide (CH2=CH—CH2—S—CH2-CH=CH2) are major odorants of garlic that are reactive and irritant because of the allyl groups. Dimethyl disulfide (CH3—S—S-CH3), dipropyl disulfide (CH3-CH2-CH2-S-S-CH2-CH2-CH3), methyl allyl disulfide (CH3-S-S-CH2-CH=CH2) and propane-1-thiol (CH3-CH2—CH2—SH) are further Allium odorants. Methane thiol (methyl mercaptan CH3—SH) is a widespread plant volatile and notably derives from anaerobic bacterial degradation of cysteine as in human flatus and bad mouth odour. The aliphatic disulfides allicin and ajoene inhibit proinflammatory expression of iNOS. 

Diallyl disulfide Allium sativum (bulb, garlic oil) (Liliaceae) OD-R (garlic)... 

Diallyl disulfide (alkene sulfide) Allium cepa (onion), A. sativum (garlic) (Liliaceae) [bulb] SLOX (competitive)... 

All possible combinations of methyl, propyl, allyl, and 1-propenyl disulfides (primarily), monosulfides, and trisulfides have been found among the volatile flavor components of onion (28,29, 30,31), garlic (32), caucas Allium victorialis) (33), and other Allium species 28) although proportions vary with species. These compounds are presumably derived from the corresponding thiolsulfinates. This is accomplished either by direct decomposition by an unknown mechanism with evolution of SO2 (32) or by interaction with cysteine to produce a mixed disulfide (15),... 

Several questions arise—why is the first compound observed as a product of the enzymatic reaction a dimer, except in onion 21), although a monomeric product is expected Why are the 1-propenyl disulfides found only in small quantities although S-l-propenylcysteine sulfoxide is the principal precursor present Why do onions make the eyes water when garlic does not Why is a monomeric product found only in onions although the enzyme from all sources acts similarly on all types of substrate ... 

Disulfides (73) are oxidised by hydrogen peroxide to the corresponding sulfenic acids (45) dialkyl disulfides may also be converted to thiol sulfinates by treatment with perbenzoic acid thus, diallyl disulfide (71) yields allicin (72), an essential component of garlic (Scheme 55). The latter reaction involves a nucleophilic attack of the sulfur atom on the oxygen of the peroxide group, and therefore the more electron-rich sulfur atom is preferentially oxidised. For instance, methyl phenyl disulfide (85) yields the sulfoxide (86) (Scheme 56). 

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