Biol. Pharm. Bull. 29(11) 2206—2213 (2006)

lated to play an important role in the pathogenesis of acute gastric mucosal injury induced by ischemia-reperfusion, stress, ethanol and anti-inflammatory drugs in rats. Furthermore, it has been suggested that free radicals generated by neutrophils may be important factors in delaying the healing of acetic acid-induced chronic gastric ulcers in these animals. It has been reported that polaprezinc, an antiulcer agent, probucol, a lipid-lowering agent, quercetin, a flavonoid, a-tocopherol, an antioxidant vitamin, nifedipine, Ca -channel blocker, and tetracycline, an antibiotic, possess antioxidant actions and are effective on experimental acute and chronic gastric ulcers in rats. Catechins are a main constituent of green tea and belong to polyphenols chemically. Green tea catechins consist primarily of four components: ( )-epicatechin (EC), ( )-epicatechin gallate (ECg), ( )-epigallocatechin (EGC) and ( )epigallocatechin gallate (EGCg). These catechins possess potent antioxidant activity. Therefore, catechins as well as the antioxidants mentioned above are expected to have the antiulcer action. The present study was designed to clarify the effects of tea catechin (EGCg 50%, ECg 13%, 92% as polyphenols) in comparison with omeprazole or sucralfate on ethanolor restraint plus water-immersion stress-induced acute gastric mucosal injury and acetic acid-induced chronic gastric ulcers in rats. In a second study, in order to clarify whether or not it exerts an anti-ulcer action by means of its antioxidant activity, we examined the superoxide anion (O2 )-scavenging activity of tea catechin in vitro. We also examined the effect of this component on the content of thiobarbituric acid-reactive substances, an index of lipid peroxidation, in the injured or ulcerated mucosa in acute (ethanol) and chronic (acetic acid)-induced experimental models. As another mechanism for the anti-ulcer action of tea catechin, we examined the effects of this component on basal gastric acid secretion in normal rats and on the content of gastric mucosal hexosamine, an index of gastric mucus, after intragastric ethanol instillation in rats.