Pyrazole-hydrazone derivatives as anti-inflammatory agents: Design, synthesis, biological evaluation, COX-1,2/5-LOX...

A new series of pyrazole-hydrazone derivatives 4a-i were designed and synthesized, their chemical structures were confirmed by IR, ¹H NMR, ¹³C NMR, MS spectral data and elemental analysis. IC₅₀ values for all prepared compounds to inhibit COX-1, COX-2 and 5-LOX enzymes were determined in vitro. Compounds 4a (IC₅₀=0.67μM) and 4b (IC₅₀=0.58μM) showed better COX-2 inhibitory activity than celecoxib (IC₅₀=0.87μM) with selectivity index (SI=8.41, 10.55 in sequent) relative to celecoxib (SI=8.85). Also, compound 4a and 4b exhibited superior inhibitory activity against 5-LOX (IC₅₀=1.92, 2.31μM) higher than zileuton (IC₅₀=2.43μM). All target pyrazoles were screened for their ability to reduce nitric oxide production in LPS stimulated peritoneal macrophages. Compounds 4a, 4b, 4f and 4i displayed concentration dependent reduction and were screened for in vivo anti-inflammatory activity using carrageenan-induced rat paw edema assay. Compound 4f showed the highest anti-inflammatory activity (% edema inhibition=15-20%) at all doses when compared to reference drug celecoxib (% edema inhibition=15.7-17.5%). Docking studies were carried out to investigate the interaction of target compounds with COX-2 enzyme active site.