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

Field: Pharmacology, Toxicology and Pharmaceutics (Life Sciences)

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<0.05) in stomach and liver tissue of aspirin
plus pylorus ligated rats and were increased by pretreatment with
gallic acid and its combinations proving the ulcer protective action of
gallic acid.
Antiulcerogenic potential of gallic acid and its combination was
further evidenced by the histopathological study of stomach tissue. No
ulceration was observed in higher dose combinations like GA 200 +
FM 20, GA 200 + FM 10, GA 200 + FM 10 and mild inflammation of
submucosa or congesion of submucosa was observed in other
treatment groups, suggesting the antiulcer activity of gallic acid and its
combinations.
In conclusion, all these result suggest that gallic acid has a
gastroprotective effect on gastric lesion induced by aspirin plus pyrolus ligation. Ulcer healing effect of gallic acid may be due to its
increased mucosal defensive and decreased offensive factors. Gallic
acid also effectively quenches the free radicals and LPO and positively
modulates antioxidant status. The antioxidant property of the test drug
might contribute to its antiulcerogenic activity. Combination of both
gallic acid and famotidine showed good antiulcer activity, suggesting
the interaction of both agents in protection of ulcer.