EVALUATION OF HYDROXYL RADICAL-SCAVENGING PROPERTY OF GARLIC

Garlic has been reported to provide protection against hypercholestero lemic atherosclerosis and ischemia-reperfusion-induced arrhythmias and infarction. Oxygen free radicals (OFRs) have been implicated as causa tive factors in these diseases and antioxidants have been shown to be effective against these conditions. The effectiveness of garlic in the se disease states could be due to its ability to scavenge OFRs. Howeve r, the OFR-scavenging activity of garlic is not known. Also it is not known if its activity is affected by cooking. We therefore investigate d, using high pressure liquid chromatography, the ability of garlic ex tract (heated or unheated) to scavenge exogenously generated hydroxyl radical (. OH). . OH was generated by photolysis of H2O2 (1.2-10 mu mo les/ml) with ultraviolet (UV) light and was trapped with salicylic aci d (500 mu moles/ml). H2O2 produced OH in a concentration-dependent man ner as estimated by . OH adduct products 2,3-dihydroxybenzoic acid (DH BA) and 2,5-DHBA. Garlic extract (5-100 mu l/ml) produced an inhibitio n (30-100%) of 2,3-DHBA and 2,5-DHBA generated by photolysis of H2O2, (5.00 pmoles/ml) in a concentration-dependent manner. Its activity is reduced by 10% approximately when heated to 100 degrees C for 20, 40 o r 60 min. The extent of reduction in activity was similar for the thre e heating periods. Garlic extract prevented the . OH-induced formation of malondialdehyde in the rabbit liver homogenate in a concentration- dependent manner. It alone did not affect the MDA levels in the absenc e of . OH. These results indicate that garlic extract is a powerful sc avenger of . OH and that heating reduces its activity slightly.