ANTIOXIDANT MECHANISMS INVOLVED IN GASTROPROTECTIVE EFFECTS OF QUERCETIN

The anti-ulcerogenic and anti-oxidant effects of various flavonoids ha ve been frequently reported. We investigated the cytoprotective proper ties of quercetin. a natural flavone, in gastric mucosal injury induce d by 50% ethanol. since in this experimental model the pathogenesis of the lesions has been related with production of reactive oxygen speci es. The involvement of neutrophil infiltration and the capacity of thi s flavonoid to restrain the oxidative process produced in the gastric tissue after ethanol administration were also investigated. Oral pretr eatment with the highest dose of quercetin (200 mg/kg), 120 min before absolute ethanol was the most effective anti-ulcer treatment. Thiobar bituric acid reactive substances in the gastric mucosa, an index of li pid peroxidation, were increased by ethanol injury, but the increase w as inhibited by the administration of 200 mg/kg of quercetin. This dos e also induced a significant enhancement in the levels of mucosal non- protein SH compounds (important anti-oxidant agents) and in glutathion e peroxidase activity. Exposure of the gastric mucosa to 50% ethanol i nduced a significant increase in myeloperoxidase activity. an index of neutrophil infiltration However, quercetin was not able to modify the increase in enzymatic activity generated by the necrotizing agent. Th e activity of superoxide dismutase enzyme involved in several antioxid ant processes was also not significantly modified after quercetin trea tment. These results suggest that the anti-ulcer activity of quercetin in this experimental model could be partly explained by the inhibitio n of lipid peroxidation, through decrease of reactive oxygen metabolit es. However, the inhibition of neutrophil infiltration or the increase of superoxide dismutase activity does not appear to be involved in ga stroprotective effect of this flavonoid.