Garlic bulb contains volatile oil, of which alliin is the major constituent. When the fresh bulb is macerated, alliin is decomposed into allicin by allinase. Allicin is the characteristic odor of the garlic. Allitridi is a highly purified and concentrated garlic essence and is the precursor of allicin. When it is metabolized in the body, it becomes allicin and displays its characteristic odor and pharmacological actions.