Design and Synthesis of Novel Ibuprofen Derivatives as Selective COX-2 Inhibitors and Potential Anti-Inflammatory Agents: Evaluation of PGE2, TNF-α, IL-6 and Histopathological Study.

Background: The reported binding mode of ibuprofen in the COX-2 binding site indicated that the carboxylic group binds with Arg-120 and Tyr-355 at the entrance of the cyclooxygenase channel and does not extend into the pocket. This accounted for the non-selectivity of ibuprofen. Based on this fact, we assumed that extending the length of the carboxylic acid moiety in ibuprofen and adding more bulky rigid groups as well as bulky groups carrying H-bonding functions might increase the selectivity and reduce the side effects of ibuprofen while maintaining its analgesic and anti-inflammatory activities.

Objective: In this work, four series of ibuprofen derivatives were designed and prepared. The compounds were designed by increasing the length of the carboxylate group along with the incorporation of large hydrophobic groups.

Methods: Four series of ibuprofen derivatives were synthesized starting from ibuprofen. Their chemical structure was confirmed by spectral data. All the compounds were tested for their COX inhibitory activity.

Results: The best COX-2 activity and selectivity were obtained with compounds 5c and 5d, which were subjected to further in vivo testing (carrageenan-induced paw edema, rat serum PGE2, TNF- α and IL-6, hot plate latency test) to investigate their anti-inflammatory and analgesic activities as well as their effects on the gastric mucosa. The anti-inflammatory activity of both compounds was comparable to that of ibuprofen, diclofenac, and indomethacin. Both compounds suppressed the production of PGE2 as well as the rat serum concentrations of both TNF-α and IL-6. This potent antiinflammatory and analgesic behavior was not accompanied by any effect on the gastric mucosa. Docking simulation studies of the two compounds explained the higher selectivity for the COX-2 enzyme.

Conclusion: Potent and selective ibuprofen derivatives can be successively obtained by extending the length of the carboxylic acid moiety in ibuprofen and adding more bulky rigid groups as well as bulky groups with H-bonding functions.