Synthesis, anti-inflammatory and neuroprotective activity of pyrazole and pyrazolo[3,4-d]pyridazine bearing 3,4,5-trimethoxyphenyl

A new series of 3,4,5-trimethoxyphenyl bearing pyrazole (4a-g) and pyrazolo[3,4-d]pyridazine (5a-g) scaffolds were synthesized in good yield. The newly synthesized compounds were characterized on the basis of elemental and spectroscopic analyses. Their inhibitory activity against the pro-inflammatory inducible nitric oxide synthase and cyclooxygenase-2 proteins expression in lipopolysaccharide-stimulated murine RAW 264.7 macrophages were assessed and showed various potencies. All pyrazolo[3,4-d]pyridazine compounds (5a-g) strongly down regulated lipopolysaccharide inducible nitric oxide synthase expression to the range of 20.3 +/- 0.6-51.3 +/- 3.5% relative to the bioactive pyrazole derivatives 4b, 4c, 4e and 4g. With the exception of inactive compounds 4c and 4d, all other synthesized compounds inhibited cyclooxygenase-2 expression below 100% in the lipopolysaccharide-stimulated cells, which being declined maximally to 42.8 +/- 1.4% by one of the pyrazolo[3,4-d]pyridazine compounds (5d). Moreover, the neuroprotective activity of the less cytotoxic compounds 4b, (4e-g) and (5a-g) were evaluated against 6-hydroxydopamine (6-OHDA)-induced neuroblastoma SH-SY5Y cell death and exhibited significant (p < 0.05) cell protection. The pyrazolo[3,4-d]pyridazine compound (5e) exhibited more than 100% of relative neuroprotection (110.7 +/- 4.3%) with an additional advantage of having the highest cell viability index (107.2 +/- 2.9%).