Alliin The chemical in garlic By: Eric Coleman, 3rd yr Chemist, Bristol University, Molecule of the Month, July 2002

Garlic produces a number of small bulbs called cloves rather than one large bulb like onions. Each garlic bulb contains several cloves enclosed in a white or purplish parchment-like sheath or skin.

The cloves themselves consist of cells containing contain both a cysteine-based sulfur rich amino acid, called alliin (diallyl disulphide oxide) and a protein-based enzyme called allinase, which acts as a catalyst. These compounds are kept apart by the cell walls.

The clove had little or no discernible smell until the clove is sliced and the two compounds are mixed. These two compounds form a third compound, diallyl thiosulphinate, commonly called allicin.