Alliin

Alliin is a sulfoxide that is a natural constituent of fresh garlic. It is a derivative of the amino acid cysteine. When fresh garlic is chopped or crushed, the enzyme alliinase converts alliin into allicin, which is responsible for the aroma of fresh garlic.

Allicin and other thiosulfinates in garlic are unstable and form a number of other compounds, such as diallyl sulfide (DAS), diallyl disulfide (DADS) and diallyl trisulfide (DAT), dithiins and ajoene.

Garlic powder is not a source of alliin, nor is fresh garlic upon maceration, since the enzymatic conversion to allicin takes place in the order of seconds.

Source: https://en.wikipedia.org/wiki/Alliin