Molecular and CellularBiochemistry 148: 183-189, 1995. 9 1995 Kluwer AcademicPublishers. Printedin the Netherlands. Antioxidant activity of allicin, an active principle in garlic Kailash Prasad, Victor A. Laxdal, Ming Yu and Barbara L. Raney Departments of Physiology and Pathology, College of Medicine, University of Saskatchewan and Royal University Hospi- tal, Saskatoon, Saskatchewan, Canada Received27 January 1995;accepted 18 April 1995 Abstract Garlic has been claimed to be effective against diseases, in the pathophysiology of which oxygen free radicals (OFRs) have been implicated. Effectiveness of garlic could be due to its ability to scavenge OFRs. However, its antioxidant activity is not known. We investigated the ability of allicin (active ingredient of garlic) contained in the commercial preparation Garlicin to scavenge hydroxyl radicals (.OH) using high pressure liquid chromatographic (HPLC) method..OH was generated by pho- tolysis of H202 (1.25-10 lamoles/ml) with ultraviolet light and was trapped with salicylic acid which is hydroxylated to pro- duce -OH adduct products 2,3- and 2,5-dihydroxybenzoic acid (DHBA). H202 produced a concentration-dependent -OH as estimated by .OH adduct products 2,3-DHBA and 2,5-DHBA. Allicin equivalent in Garlicin (1.8, 3.6, 7.2, 14.4, 21.6, 28.8 and 36 lag) produced concentration-dependent decreases in the formation of 2,3-DHBA and 2,5-DHBA. The inhibition of forma- tion of 2,3-DHBA and 2,5-DHBA with 1.8 lag/ml was 32.36% and 43.2% respectively while with 36.0 btg/ml the inhibition was approximately 94.0% and 90.0% respectively. The decrease in .OH adduct products was due to scavenging of.OH and not by scavenging of formed .OH adduct products. Allicin prevented the lipid peroxidation of liver homogenate in a concentra- tion-dependent manner. These results suggest that allicin scavenges .OH and Garlicin has antioxidant activity. (Mol Cell Biochem 148: 183-189, 1995) Key words: allicin, garlicin, hydroxyl radical, 2,3-dihydroxybenzoic acid, 2,5-dihydroxybenzoic acid, antioxidant Introduction Use of garlic is rising in the health conscious population. Reports suggest that it has beneficial effects in diseases such as ischemic-reperfusion arrhythmias and infarction [1,2], ischemic heart disease [3], hypertension [4], hyperlipidemia [5], peripheral arterial occlusive disease [6] and hyper- cholesterolemic atherosclerosis [7-8]. Reactive oxygen metabolites (ROMs) which include superoxide anion (O2-), hydrogen peroxide (H202) and hydroxyl radicals (.OH), have been implicated in the pathophysiology of hyper- cholesterolemic atherosclerosis [9-11], and ischemia- reperfusion cardiac injury [12-15]. Antioxidants are effective against ischemia-reperfusion cardiac injury [12, 14, 15] and hypercholesterolemic atherosclerosis [9-11 ]. The beneficial effects of garlic in the above stated diseases and other undocumented health problems may be due to its antioxidant property. However it is not known if garlic scav- enges O2-, H202 or "OH. "OH is the most toxic of all the ROMs. Allicin (active ingredient of garlic) content of com- mercial preparations of garlic vary tremendously. Garlicin preparations contain 1800 lag ofallicin per tablet (manufac- turer's stated concentration). We therefore investigated, us- ing high pressure liquid chromatography (HPLC), the ability ofallicin an active principle contained in Garlicin tablet to scavenge exogenously generated -OH from ultraviolet (UV) light photolysis of H202. The ability of Garlicin to prevent 9 OH-induced lipid peroxidation in a biological system was also investigated. Address./'oroffprints: K. Prasad, Departmentof Physiology, Collegeof Medicine, University of Saskatchewan, 107 Wiggins Road, Saskatoon, SK S7N 5E5, Canada