In this study, we investigated the anti-ulcerogenic action of semipurified fibers - orange pulp (OP), guar gum (GG), and a mixture of guar gum and orange pulp (OPG) - on ethanol, indomethacin, and pylorus ligature-induced gastric lesions in the rat. Gastric wall mucus, prostaglandin synthesis, and gastrin level were determined in the gastric mucosal from Wistar rats. Acute administration of GG and OPG inhibited the ulcerative lesion index by 50% and increased the adhered mucus, pH levels, and prostaglandin E-2 production. Moreover, these fibers decreased the gastric secretion, total acid content, and gastrin levels; OP did not prevent mucosal lesions. Results indicated that the protection of GG and OPG could be due to a synergism of several effects: mechanical action, reduction in H+ ion concentration and gastrin levels, and increase in prostaglandin E-2 and mucus production. (c) 2007 Elsevier Inc. All rights reserved.272109112