Comparative Inhibitory Efficacy on the iNOS/NO System of Curcuminand Tetrahydrocurcumin-Self-Microemulsifying Liquid Formulation in Chronic Gastric Ulcer Model

Background: Curcumin was found to accelerate gastric ulcer healing by the main mechanism, i.e., the suppression of iNOS mediated inflammation. Although Tetrahydrocurcumin (THC) is claimed to be an active antioxidant element of curcumin, its antiulcer activity has not been systematically examined. The utility of Self-Microemulsifying Drug Delivery Systems (SMEDDSs) for curcumin and THC formulations in the liquid form was also found to increase the rate and extent of release of curcumin- and THC-SMEDDS. Nevertheless, the beneficial antiulcer effect of these nanoproducts has not yet been evaluated. Objective: This study aimed to evaluate and compare the antiulcer efficacy of curcumin- and THCSMEDDS through the inhibition of the iNOS/NO system in the rat model. Methods: Antiulcer efficacy was compared in terms of the ability to accelerate healing of gastric ulcer including the efficient inhibitory action on inflammatory NO production in activated macrophages and iNOS mRNA expression at the ulcerated area. Results: THC was found to have less ulcer healing capacity than curcumin with a lack of significant inhibitory effect on the iNOS/NO system. The SMEDDS used in the study significantly increased the inhibitory efficacy of THC on iNOS/NO production and iNOS mRNA expression compared to the inhibitory potency of curcumin. An oral administration of curcumin- or THC-SMEDDS once a day was appropriate for exerting a comparable curative efficacy to a twice-daily oral administration of curcumin or THC. Conclusion: The SMEDDS used in the study was observed to enhance the inhibitory efficacy of the antiulcer drug on the iNOS/NO system, leading to a reduction of daily dosing and dosing frequency.