Hydrogen sulfide preconditioning by garlic when it starts to smell.

GARLIC (Allium sativum, Liliaceae/Alliaaceae) has long been used for medicinal and culinary purpose. Its first medicinal use was reported 400 years ago, and documented medicinal use can be found in a research finding of Louis Pasteur in the 1800s (8). Originally used as a digestive aid and as an antifungal, antibacterial, or antiviral compound (during the World Wars it achieved the nickname Russian penicillin), garlic was first reported to be a cardioprotective agent in the 1980s (13). Much of its cardioprotective abilities have been attributed toward its ability to function as an antioxidant (4). For example, garlic contains antioxidant vitamins A, C, and E as well as selenium, a key element for the synthesis of the antioxidant enzyme glutathione peroxidase (6). The study by Chuah, Moore, and Zhu (3) appears to be the first report where an alternative mechanism of cardioprotection is proposed. This report is based on the fact that garlic contains an organosulfur-containing compound, S-allylcysteine (12). Raw garlic contains alk(en)yl cysteine sulfoxides and -glutamyl alk(en)yl cysteines, which upon activation, is converted into S-allylcysteine (deoxyallin) because of the deactivation of the enzyme allinase. Allicin is then formed from S-allyl-L-cysteine according to following scheme: