Novel ketoprofen–antioxidants mutual codrugs as safer nonsteroidal anti‐inflammatory drugs: Synthesis,kinetic and pharmacological evaluation

Ketoprofen belongs to one of the most common nonsteroidal anti‐inflammatory drugs (NSAIDs) but its clinical usefulness has been restricted due to the high incidence of gastrointestinal complications. The release of reactive oxygen species (ROS) in NSAIDs therapy plays a major role in causing gastric complications. Antioxidants not only prevent gastric ulceration and lipid peroxidation but also preserve glutathione‐type peroxidase (GPO) activity. Therefore, the present study investigates the utility of combining anti‐inflammatory and antioxidant properties of two different compounds in a single molecule to form a series of 16 ketoprofen–antioxidant mutual codrugs. The free carboxylic group, which is believed to be one of the reasons for gastric toxicity of ketoprofen, was masked temporarily by simple and double esterification with alcoholic/phenolic–OH of natural antioxidants. In simple esterification, ketoprofen is directly linked to natural antioxidants ( IIa–h ) in the hope to obtain drugs free of gastric side effects. In an attempt to improve the in vivo lability, as well as gastric side effects, the double ester codrugs, that is, ketoprofen–antioxidant through the glycolic acid spacer (–CH₂COO; IIIa–h ), have also been designed and synthesized. The synthesized codrugs were characterized by IR, ¹H NMR, ¹³C NMR, mass spectroscopy and elemental analysis. The in vitro hydrolysis studies showed the lowest hydrolysis (highest stability) in acidic pH 1.2, whereas moderate hydrolysis was seen at pH 7.4 and significant hydrolysis in 80% human blood plasma, as indicated by their t_1/2. The pharmacological evaluation results indicate that these ketoprofen–antioxidant mutual codrugs showed the retention of anti‐inflammatory and analgesic activity with a significant reduction in the ulcer index.