Antiulcerogenic and Ulcer Healing Effects of Gallic Acid Alone and in Combination with H2 Blocker Famotidine

The present study antiulcer effect of the phytoconstituent gallic acid alone and in combination with known antiulcer drug famotidine was investigated in aspirin plus pylorus ligation induced ulcer in rats. NSAIDs like aspirin interfere prostaglandin synthesis through cyclooxygenase pathways and produce neutrophil and oxygen radical dependent microvascular injury leading to mucosal damage (Jafri et al., 2001; Maity et al., 1995; Pal and Chaudhuri, 1991). Aspirin acts directly by increasing the H+ ion transport while on the mucosal epithelial cells, it decreases mucin, surface-active phospholipids, bicarbonate secretion (Sairam et al., 2003). In pylorus ligated rats accumulation of gastric acid and pepsin secretion are important factors for generation of ulceration. When aspirin was administered to pylorus ligated rats, it further aggravated the acidity and the resistance of the gastric mucosa was decreased thereby imposing extensive damage to the glandular region of the stomach (Sanmugapriya and Venkataraman., 2007; Dharmani et al., 2004). The protective effect of gallic acid as evidenced by percentage inhibition of ulcer against aspirin induced gastric lesions could be due to its cytoprotective effect. Treatment with gallic acid and its combinations decreased the ulcer index compared to ulcer control group, which is the direct indication of its antiulcer activity. Gallic acid and combination treatment also decreased volume of acid secretion, peptic activity, total and free acidity and increased pH of the gastric juice compared to ulcer control group proving the antiulcer activity of gallic acid. Mucus act as defensive factor by preventing physical damage to mucosa leading to lesser degree of ulceration (Sairam et al., 2002). The individual carbohydrates such as hexoses, fucose and hexosamine concentrations are the index of mucin content in gastric juice (Annop and Jegadeesan, 2003). Aspirin plus pylorus ligated rat group showed a decrease in the concentration of hexoses, hexosamine and fucose which was reversed by gallic acid and its combinations. Administration of gallic acid resulted in a significant increase in glycoprotein content in gastric mucosa and a net increase in synthesis of mucus contributing to its ulcer protective role. Increase in protein content of gastric juice resulted in a decrease in total carbohydrate and protein ratio in aspirin plus pylorus ligated rat leading to the damage of gastric mucosa (Jainu et al., 2006). Pretreatment with gallic acid, famotidine and their combinations decreased the plasma protein leakage from gastric mucosa by strengthening the mucosal barrier. The decrease in protein contents of gastric juice by the drugs lead to an increase of total carbohydrate/protein ratio proving the efficacy of combination treatment. The strengthening of mucosal defense is further exemplified by decrease in cell exfoliation as seen from the reduction in DNA content of the gastric juice (Mukhopadhyaya et al., 1987). The reduced level of DNA in all the drug treated groups further suggests the increase in mucosal defense capacity of the gallic acid. Free radicals are detrimental to the integrity of biological tissue and mediate their injury (Demir et al., 2003). It is now generally agreed that among various mechanisms, oxidative damage of the gastric mucosal cell membrane by ROS is the major causative factor for gastric ulceration. This decreases the membrane permeability, activities of enzyme and receptors and activation of cells. Drugs that scavenge or inhibit the generation of ROS may be effective in the prevention of gastric damage (Halici et al., 2005; Huh et al., 2003). Antioxidants constitute the foremost defense system that limit the toxicity associated with free radicals. Gallic acid possess potent antioxidant property (Yen et al., 2002), therefore in the present study the antioxidant levels in stomach and liver tissue was investigated to know the protective role of gallic acid in gastric ulcers. SOD catalyses the reduction of superoxide anion (O2 ● -) to H2O2 and O2 while CAT converts H2O2 to water and molecular oxygen preventing the oxidative damage (Machado-Vieira et al., 2007; Sairam et al., 2003). GPx calalyses the oxidation of GSH to oxidized glutathione (GSSG) at the expense of H2O2 and convert it to water. GSSG can be reduced to GSH by GR in presence of NADPH (Liu et al., 2007; Ali et al., 1996). The decrease in antioxidant enzymes levels lead to accumulation of ROS by increasing lipid peroxidation. Depletion in SOD, CAT, GR, GPx were observed in the pylorus ligated stomach and liver tissue homogenates. Gallic acid and its combination with famotidine significantly increased the level of these antioxidant enzymes proving the gastroprotective action by its antioxidant defense mechanism. GSH present in the stomach plays an important role in maintaining the gastric mucosal cell integrity. GSH depletion is associated with generation of gastric lesion in the rats. GSH is a non enzymatic component and has a central role in antioxidant network (Anandan et al., 1999; Altinkaynak et al., 2003). In pylorus ligated stomach, decreased GSH level was observed while in drug treated groups an elevated level was noticed substantiating its antioxidant property. A similar increase was also observed in liver tissue homogenate. Infiltration of neutrophils into gastric mucosal tissue is a critical process in the pathogenesis of gastric ulcer and can be checked by MPx activity. MPx mediates lipid peroxidation in the presence of H2O2 and Cl−. Increase in MPx show an increase in level of neutrophil infiltration into gastric damage tissue (Ohata et al., 1999; Odabasoglu et al., 2006). An increase in level of MPx was observed in the pylorus ligated stomach tissue and upon administration of gallic acid and its combinations, decreased MPx levels thereby protecting the rats from gastric damage. Increased lipid peroxidation is one of the major indications of ROS generation in gastric mucosa accompanied by increase of TBARS and HP (Jainu and Devi, 2006; Bafna and Balaraman, 2005). Our data also shows ameliorative increase of lipid peroxides in pylorus ligated aspirin induced ulcers in rats liver and stomach homogenate. Treatment with gallic acid and its combination resulted in suppression in the levels of TBARS and HP. Polyhydroxy phenolic substances like gallic acid having potent antioxidant properties are anticipated to exert protective effects on ulceration. G6PD is a cytoplasmic enzyme and acts as a supporter of the primary antioxidant enzymes. It provides coenzymes and substrate to the primary antioxidant enzymes thus playing a protective role against ROS induced oxidative stress. G6PD can slow down the production of cytosolic NADPH by controlling the step from glucose-6-phosphate to 6-phospho-gluconate in pentose phosphate pathway (Ramesh and Pugalendi, 2006; Agarwal and Rami, 2003). G6PD enzyme level significantly decreased (P