Determination of the mitigating effect of colon-specific bioreversible codrugs of mycophenolic acid and aminosugars in an experimental colitis model in Wistar rats

AIM To design colon-targeted codrugs of mycophenolic acid(MPA) and aminosugars as a safer option to mycophenolate mofetil(MMF) in the management of inflammatory bowel disease. METHODS Codrugs were synthesized by coupling MPA with aminosugars(D-glucosamine and D-galactosamine) using EDCI coupling. The structures were confirmed by infrared radiation, nuclear magnetic resonance, mass spectroscopy and elemental analysis. The release profile of codrugs was extensively studied in aqueous buffers, upper gastrointestinal homogenates, faecal matter and caecal homogenates(in vitro) and rat blood(in vitro). Anti-colitic activity was assessed in 2,4,6-trinitrobezenesulfonic acid-induced colitis in Wistar rats by the estimation of various demarcating parameters. Statistical evaluation was performed by applying one-way and two-way ANOVA when compared with the disease control.RESULTS The prodrugs resisted activation in HCl buffer(pH 1.2) and stomach homogenates of rats with negligible hydrolysis in phosphate buffer(p H 7.4) and intestinal homogenates. Incubation with colon homogenates(in vitro) produced 76% to 89% release of MPA emphasizing colon-specific activation of codrugs and the release of MPA and aminosugars at the site of action. In the in vitro studies, the prodrug of MPA with D-glucosamine(MGLS) was selected which resulted in 68% release of MPA in blood. in vitro studies on MGLS revealed its colon-specific activation after a lag time of 8 h which could be ascribed to the hydrolytic action of N-acyl amidases found in the colon. The synthesized codrugs markedly diminished disease activity score and revived the disrupted architecture of the colon that was comparable to MMF but superior to MPA. CONCLUSION The significant attenuating effect of prodrugs and individual aminosugars on colonic inflammation proved that the rationale of the codrug approach is valid.