Abstract: The effect of two extracts of Parquetina nigrescens on mucosal antioxidants defense system in ethanol-induced ulcer in rats was studied. Activities of superoxide dismutase (SOD), catalase (CAT) and levels of reduced glutathione (GSH) were determined in the gastric mucosa and liver of normal and experimental groups of rats. The rats were pretreated with 500 and 1000 mg kg-1 of hexane and chloroform extracts of P. nigrescens, respectively dissolved in olive oil for a period of 14 days prior to ethanol induction. It was found that prior to ulcer induction, 14 days pretreatment with hexane and chloroform extract P. nigrescenes significantly reduced ethanol-induced gastric damage. The levels of GSH and activities of the antioxidants enzymes (SOD and CAT) were depressed significantly (p<0.05) in the ulcerated rats when compared with that of normal control. The activity of SOD was lower significantly (p<0.05) in the ulcerated mucosa and liver of the experimental rats when compared to the normal control group. There was a significant increase (p<0.05) in the level of CAT in the groups pretreated with the extracts compared to the ethanol group. A similar result was observed for GSH. Pretreatment with hexane extract caused 75.43 and 74.55% elevations in the activities of SOD in the mucosa and liver homogenate, respectively. Similar elevations were observed in the group pretreated with the chloroform extract. The cimetidine group also caused 69.79 and 69.67% elevation in the SOD activity in the mucosa and liver homogenate, respectively. The pretreatment with P. nigrescens was found to exact a significant gastro protective and antiulcer effect partly by protecting against the ethanol-induced ulcerogenic effects in experimental rats and probably through the induction of antioxidant enzymes.