Diallyl thiosulfinate

Several other spices have even better antibacterial properties than chilli. Garlic, clove, and cinnamon have chemicals that destroy the deadly bacteria Escherichia coli 0157 117. The chemicals responsible for the activity of these spices are cinnamic aldehyde in cinnamon, eugenol in clove, and diallyl thiosulfinate in garlic. The spices with the... 

When garlic is mechanically disrupted, alliinase or alliin lyase (EC 4.4.1.4.) catalyzes the conversion of the cysteine sulfoxides to the biologically active diallyl thiosulfinates via sulfenic acid intermediates (Block, 1992). Alliinase is localized to a few vascular bundle sheath cells around the veins or phloem, whereas alliin and other cysteine sulfoxides are found in the clove mesophyll storage cells. This enzyme is approximately 10 times more abundant in the cloves than in the leaves and accounts for at least 10% of the total protein in the cloves (Ellmore and Feldberg, 1994). Alliinase is temperature and pH dependent optimal activity is between pH 5.0-10.0, but allinase can be irreversibly deactivated at pH 1.5-3.0 (Krest and Keusgen, 1999). 

Bocchini, P., Andalo, C., Pozzi, R., Galletti, G.C. and Antonelli, A. (2001) Determination of diallyl thiosulfinate (allicin) in garlic (Allium sativum L.) by high performance liquid chromatography with a post-column photochemical reactor, Anal. Chim. Acta, 441(1), 37-43. 

Attempts by Brodnitz et al. in 1971 to determine allicin by gas chromatography-mass spectrometry (GC-MS) provided evidence for an unusual mode of decomposition (70). They indicated that GC caused diallyl thiosulfinate to dehydrate according to the reaction C6HiqS20 -> C gS2 + H2O, affording a 2.4 1 mixture of two compounds, claimed (incorrectly as we shall see below) to be 3-vinyl-4H-l,2-dithiin (10, equation 1) and 3-vinyl-6H-l,2-dithiin (10a, equation 1) (70). Analytical methods for allicin quantitation that rely on GC detection of compounds 10 and 10a are still used (77), even though serious problems exist with this method and more accurate high-performance liquid chromatographic (HPLC) methods have been developed (see below). 

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. 

The characteristic aroma of fresh garlic Allium sativum, Amaryl-Hdaceae) is almost exclusively represented by diallyl thiosulfinate (aUicin) and to a lesser extent by allyhnethyl thiosulfinate. The aroma of heat-treated garhc is associated with degradation products of thiosulhnates, especially diallyl sulfide, diallyl disulfide, diallyl... 

The volatile oil contains allicin (diallyldi-sulfide-5-oxide diallyl thiosulfinate), allyl-propyl disulfide, diallyl disulfide, and diallyl trisulfide as the major components, with lesser amounts of dimethyl sulfide, dimethyl disulfide dimethyl trisulfide, allylmethyl sulfide, 2,3,4-trithiapentane, bis-2-propenyl... 

At room temperature the thiosulfinates (e.g., allicin) convert to variorrs diallyl and allyl sulfides, etc., which may be accelerated by heating. Pnre allicin itself is an unstable oily liquid, lasting less than 20 hours at room temperature (equivalent to say a half-life of a few hours, as has been reported). The decomposition products include various organic sulfides, and it is also been observed that allicin is very reactive with the amino acid cysteine. 

As for the inhibiting action of garhc oil, onion oil, and diallyl sullide on skin cancers, thrae is evidently a beneficial action on epidermis cells. As for stomach and colon cancer, it is advanced that the antimicrobial effect of the thiosulfinates in garlic inhibits some of the less desirable gut flora. Otho- findings are repeated as follows ... 

The transformation products of allicin and odier thiosulfinates present in crushed garlic is greatly accelerated and expanded upon heating such as during steam distillation or cooking. As many as 20 different sulfides have been identified in the steam distillate and include diallyl mono to hexasulfides, allyl methyl mono to hexasulfides dimethyl mono to hexasulfides, and allyl 1-propenyl di and trisulfides [38]. 

The main products of alliin transformation in polar media are sulfides. At room temperature or on heating, allicin is converted by water into diaUyl disulfide, diaUyl trisulfide and diallyl polysulfides, which are the principal components of garlic essential oil and aged garlic (Figure 8.62). Other reaction products are allyl alcohol, sulfur dioxide and propene. Disproportionation of thiosulfinates in aqueous (polar) solutions also leads to disulfides and thiosuhonates of general formula R-SO2-S-R. For example. 

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