Design, synthesis, and evaluation of antipyrine and nicotinic acid derivatives as anti-inflammatory agents: in vitro and in vivo studies

Abstract

A series of new antipyrine and nicotinic acid-based scaffolds were synthesized and evaluated for their inhibitory activity against cyclooxygenase-1 and cyclooxygenase-2, using indomethacin and celecoxib as reference drugs. Among the synthesized compounds, 4d and 6b demonstrated the most potent COX-2 inhibition, exhibiting IC₅₀ values of 0.940 ± 0.05 μM and 0.614 ± 0.03 μM, respectively, in comparison to celecoxib (IC₅₀ = 0.844 ± 0.04 μM). Compound 4d displayed the highest COX-2 selectivity index (SI = 13.57), surpassing that of celecoxib (SI = 7.92), thereby indicating superior COX-2 selectivity. Consequently, the in vivo anti-inflammatory activity of compound 4d was comparable to that of indomethacin. Compound 4d significantly reduced paw edema, achieving edema inhibition percentages of 14.75 %, 30.77 %, and 45.33 % at the first, second, and third hours, respectively. In contrast, celecoxib exhibited the most pronounced anti-inflammatory effect, achieving edema inhibition percentages of 59.02 %, 69.23 %, and 78.67 % at the corresponding time points. Histopathological examination confirmed the absence of gastric ulceration following oral administration of compound 4d. Furthermore, it effectively lowered serum levels of prostaglandin E2 and interleukin-1β. To elucidate its selectivity and binding affinity, molecular docking of compound 4d into the COX-2 active site was conducted, revealing favorable interactions consistent with its biological activity. Collectively, these findings identify compound 4d, an antipyrine–urea hybrid with para-Cl and meta-CF₃ substitutions, as a useful lead scaffold for effective, safe, and selective COX-2 inhibitors.