Efficacy of a chitosan-curcumin mixture in treating indomethacin-induced acute gastric ulcer in rats

BACKGROUND

Curcumin is claimed as a potent protectant against gastric ulcer (GU) induced by strong necrotizing agents including NSAIDs through its antioxidant, anti-inflammatory and gastroprotective activities. However, it was found to exert opposite effects to either delay ulcer healing or exacerbate ulcer inflammation through some curative mechanisms differently modified by curcumin dosage. Its ability in inhibiting the expression of COX-2 may also delay the healing of NSAIDs-induced GU. Recently, a topical chitosan-curcumin solution has been found to be a safe and potential alternative agent in treating oral ulcer. Therefore, an oral chitosan-curcumin mixture was developed and determined for its efficacy in treating NSAIDs-induced GU in rat.

METHODS

A chitosan (150 mg)-curcumin (20 mg) mixture with optimal gastric pH was developed. Indomethacin (30 mg/kg) was given orally to the rat and test preparations were administered orally at 5 h later and then every 24 h for two consecutive days. The sum of all gastric ulcerated areas (mm2) for each stomach was used as ulcer index. Gastric pro-inflammatory mediators and cytoprotective factors were determined.

RESULTS

An oral administration of a chitosan-curcumin mixture exerted a superior efficacy than curcumin, chitosan or lansoprazole (a standard antiulcer agent) in healing indomethacin-induced GU. It was revealed that the mixture exhibited the highest anti-oxidant, anti-inflammatory and gastric mucus producing activities including the high potency in down-regulating pro-inflammatory COX-2 and iNOS expression but up-regulating cytoprotective COX-1, nNOS and eNOS expression.

CONCLUSION

The present findings indicated the benefit of a chitosan-curcumin mixture as a potential alternative agent in treating NSAIDs-induced gastric ulcer.

Effects of Morinda citrifolia aqueous fruit extract and its biomarker scopoletin on reflux esophagitis and gastric ulcer in rats

AIMS OF THE STUDY

The present study was carried out to evaluate the effect of dried mature unripe Morinda citrifolia L. (Rubiaceae) fruit, commonly known as "Noni", in an aqueous extract preparation (AFE) as used in Thai traditional medicine and its biomarker scopoletin on gastro-esophageal inflammatory models that are related to the claimed pharmacological properties of AFE and/or resembled the human esophagitis or gastric ulcer.

MATERIALS AND METHODS

The powder of dried mature unripe Noni fruit was boiled in water until it became a sticky paste and was then dried into a powder by lyophilization. The pharmacological activity of AFE and pure scopoletin at the same equivalent dose present in AFE was investigated in rat on gastro-esophageal inflammatory models (acid reflux esophagitis, acute gastritis induced by ethanol and serotonin, and chronic gastric ulcer induced by acetic acid); gastric biochemical parameters and gastrointestinal motility.

RESULTS

AFE (0.63-2.50 g/kg) significantly prevented the formation of acid reflux esophagitis, reduced the formation of ethanol-induced acute gastric lesions, suppressed the development of gastric lesions in response to serotonin, and accelerated the healing of acetic acid-induced chronic gastric ulcer in rats with equal potency to those obtained by standard antisecretory agents (ranitidine and lansoprazole). AFE also significantly inhibited gastric acid secretion and pepsin activity in pylorus ligated rats. Additionally, AFE strongly increased the gastrointestinal transit of charcoal meal with a higher potency than cisapride. Pure scopoletin, when compared at the same equivalent dose containing in AFE, possessed similar antiulcer and antisecretory properties to that of AFE although it exerted a less prokinetic activity than AFE.

CONCLUSION

The findings indicated that AFE as well as its biomarker: scopoletin may be beneficial as a potential preventive and therapeutic agent for gastro-esophageal inflammatory diseases, mainly through its antisecretory and prokinetic activities including an inhibitory activity on serotonin, free radicals, and cytokine-mediated inflammation. Additionally, scopoletin might be one of the biomarker constituents to use for the quality assessment of Noni fruit products used for treating gastro-esophageal inflammatory diseases.

Comparative antiulcer effect of bisdemethoxycurcumin and curcumin in a gastric ulcer model system

The antiulcer effect of bisdemethoxycurcumin, a yellow pigment found mainly in rhizomes of Curcuma longa, was compared with curcumin in gastric ulcer model systems to validate its clinical application as a remedy for peptic ulcer. Western blot analysis of mouse macrophage cell line RAW 264.7 activated with lipopolysaccharide showed that bisdemethoxycurcumin inhibited inducible nitric oxide synthase (iNOS) production significantly but had no effect on tumor necrosis factor-alpha (TNF-alpha) production, whereas curcumin showed stronger suppression of iNOS protein production and inhibited TNF-alpha protein production significantly. However, bisdemethoxycurcumin and curcumin possessed similar potency in scavenging nitric oxide generated from mouse macrophage cell line RAW 264.7. Reverse-transcriptase polymerase chain reaction (RT-PCR) analysis showed that both curcuminoids inhibited the induction of iNOS dose-dependently at the transcriptional level and curcumin also appeared to inhibit the induction of TNF-alpha at post-transcriptional level. In an animal model, intraduodenal administration of bisdemethoxycurcumin (5-80 mg/kg body wt.) showed a strong inhibitory effect on gastric acid secretion in pylorus-ligated rats whereas curcumin (5-20 mg/kg body wt.) showed a less inhibitory effect, with maximum potency at a dose of 20mg/kg body wt. Moreover, oral administration of bisdemethoxycurcumin at doses of 20-80 mg/kg body wt. twice daily for 10 days showed a significant curative efficacy in accelerating the healing of acetic acid-induced chronic gastric ulcer and promotion of mucosal regeneration in the ulcerated portion in a dose-related manner with potency equal to curcumin. In contrast, the curative potency of curcumin tended to decrease at doses over 160 mg/kg body wt./day. Western blot analysis in ulcerated gastric mucosa showed that bisdemethoxycurcumin dose-dependently reduced the increased protein expression level of iNOS but not TNF-alpha. These results indicated that bisdemethoxycurcumin directly accelerates gastric ulcer healing with potency equal to curcumin. Its antiulcer effect might be due to its properties of decreasing gastric acid secretion and enhancing the mucosal defensive mechanism through suppression of iNOS-mediated inflammation.