Alliin

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. 

Scheme 10 The formation of allicin from alliin by alliinase action...

Garlic supplements - powder tablets or capsules, steam-distilled oil, vegetable oil macerate extract, or extract aged in dilute alcohol - are widely available and are taken by millions. Since the active principle, allicin, is not present in garlic bulb, the supplements rely on the presence of precursor alliin and enzyme alliinase. In tests on 24 commercial brands of enteric-coated tablets, all except one gave low dissolution allicin release 83% of the brands released less than 15% of their potential allicin.78,79 Relevant factors were impaired enzyme activity caused by excipients and slow tablet disintegration. Caveat emptor ... 

Constituents that have some known pharmacological activity that contributes to some extent to the efficacy of the product have been identified. These are known as active markers. An example of this category is alliin, which is converted to allicin in presence of allinase enzyme, and is present in garlic. These active markers may or may not have clinically proven efficacy in their own right. A minimum content or range for active markers is usually specified in pharmacopeial articles. A quantitative determination of active marker(s) during... 

This enzyme [EC 4.4.1.6] catalyzes the pyridoxal-phos-phate-dependent hydrolysis of an 5-alkyl-L-cysteine to generate an alkyl thiol, ammonia, and pyruvate. The reaction is an a,/3-elimination. In yeast, the enzyme may be identical to cystathionine /3-lyase. See also Alliin Lyase... 

ALANINE RACEMASE S-ALKYLCYSTEINE LYASE ALLIIN LYASE... 

The recommended dose is about 4g of fresh garlic daily, which is equivalent to approximately 8 mg garlic oil or 600 to 900 mg garlic powder preparations standardized to 1.3% alliin content. Adverse effects of garlic are usually mild and transient they include breath and body odor, allergic reactions, nausea, heartburn, and flatulence. 

In rats, alliin and allicin were administered orally at doses of 8mg/kg... 

Lachmann G, Lorenz D, Radeck W, Steiper M. The pharmacokinetics of the S35 labeled garlic constituents alliin, allicin and vinyldithiine. Arzneimittel-forschung 1994 44 734-743. 

Dried, powdered garlic products should be standardized to contain 1.3% alliin (the allicin precursor) or have an allicin -generating potential of 0.6%. Enteric-coated formulations are recommended to minimize degradation of the active substances. A daily dose of 600-900 mg/d of powdered garlic is most common. This is equivalent to one clove of raw garlic (2-4 g) per day. 

N.A. Alliin, iodine, diallyl trisulfide, 2-vinyl-4h-l,3-dithin, ajoene, linoleic acid, diallyl disulfide, scordinins, selenium.98 99 107 511 Reduce serum cholesterol, lower blood pressure, and platelet aggregation. It is anticancer, antimicrobial, antithrombotic. 

Onions contain an amino acid that is a positional isomer of alliin. When acted upon by alliinase it produces 2-propene sulfenic acid, which isomerizes to the lachrima-tory factor that brings tears to the eyes of onion cutters.c This, too, decomposes to form many other compounds.3... 

When garlic is cut and the parenchyma is destroyed, alliin is the major cysteine sulfoxide liberated. Alliin is acted upon by the enzyme allinase (alliin lyase) to produce allicin. Allicin [S-(2-... 

Garlic also contains S-propylcysteine-sulfoxide (PCSO) and S-methylcysteine-sulfoxide (MCSO). PCSO can generate over 50 compounds depending on temperature and water content. The action of allinase on the mixture of alliin, PCSO, and MCSO can produce many other molecules, including allyl methane thiosulfinate, methyl methanethiosulfinate, and other mixed or symmetrical thiosulfinates (R-S-S-R ), where R and R are methyl, propyl, and allyl groups. 

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. 

---