O2-Acetoxymethyl-protected diazeniumdiolate-based NSAIDs (NONO–NSAIDs): Synthesis, nitric oxide release, and biological evaluation studies Original Research Article

A novel group of O2-acetoxymethyl-protected diazeniumdiolate-based non-steroidal anti-inflammatory prodrugs (NONO–NSAIDs) were synthesized by esterifying the carboxylate group of aspirin, ibuprofen, or indomethacin with O2-acetoxymethyl 1-[N-(2-hydroxyethyl)-N-methylamino]diazeniumdiolate. The resulting nitric oxide (radical dotNO)-releasing prodrugs (7–9) did not exhibit in vitro cyclooxygenase (COX) inhibitory activity against the COX-1 and COX-2 isozymes (IC50s > 100 μM). In contrast, prodrugs 7 and 8 significantly decreased carrageenan-induced rat paw edema showing enhanced in vivo anti-inflammatory activities (ID50’s = 552 and 174 μmol/kg, respectively) relative to those of the parent NSAIDs aspirin (ID50 = 714 μmol/kg) and ibuprofen (ID50 = 326 μmol/kg). The rate of porcine liver esterase-mediated radical dotNO release from prodrugs 7–9 (2 mol of radical dotNO/mol of test compound in 0.6–6.5 min) was substantially higher compared to that observed without enzymatic catalysis (about 1 mol of radical dotNO/mol of test compound in 40–48 h). These incubation studies suggest that both radical dotNO and the parent NSAID would be released upon in vivo activation (hydrolysis) by esterases. Data acquired in an in vivo ulcer index (UI) assay showed that NONO–aspirin (UI = 0.8), NONO–indomethacin (UI = 1.3), and particularly NONO–ibuprofen (UI = 0) were significantly less ulcerogenic compared to the parent drugs aspirin (UI = 57), ibuprofen (UI = 46) or indomethacin (UI = 34) at equimolar doses. The release of aspirin and radical dotNO from the NONO–aspirin (7) prodrug constitutes a potentially beneficial property for the prophylactic prevention of thrombus formation and adverse cardiovascular events such as stroke and myocardial infarction.