Garlic has been used as a food ingredient and for medicinal purposes for centuries, and it is among the oldest of all cultivated plants. In garlic cells, alliin [(+)-S=allyl-L-cysteine sulfoxide], which is a major sulphur-containing compound in raw garlic, is physically separated from the alliinase enzyme: the enzyme resides in micro-compartments separated from alliin by thin membranes. When the raw garlic clove is damaged, the compartmentalization is broken down, bringing alliin and alliinase into contact, leading to the almost instantaneous formation of allicin (2-propene-1-sulfinothioic acid S-2-propenyl) from the condensation of two molecules of two allylsulfenic acids (Figure 1) (Block, 2010).

Allicin was found by Chester J. Cavallito in the year 1944 in New York. Cavallito et al. identified the compound as an antibacterial substance and since then, allicin is a well-known active thiosulfinate that has shown myriad of properties, such as, antibacterial, antifungal, anticancer, anti-inflammatory and so on. However, allicin is unstable. Allicin as a labile compound transforms readily into a wide range of lipid soluble organosulfur compounds.

At room temperature, and upon heating, allicin forms ajoene (Figure 1), vinyl dithiins, diallyl disulfide, diallyl trisulfides, and other higher polysulfides (Block, 2010).