Synthesis and antinociceptive activities of some pyrazoline derivatives.

In the present study, some pyrazoline derivatives were synthesized to investigate their potential antinociceptive activities. 1-[(Benzoxazole/benzimidazole-2-yl)thioacetyl]pyrazoline derivatives were obtained by reacting 3,5-diaryl-1-(2-chloroacetyl)pyrazolines with 2-marcaptobenzoxazole/benzimidazole. The chemical structures of the compounds were elucidated by IR, (1)H NMR and FAB(+)-MS spectral data and Elemental Analyses. All of the compounds (100 mg/kg) exhibited significant antinociceptive activities in both hot plate and acetic acid-induced writhing tests. Naloxone (5 mg/kg) pre-treatment reversed the antinociceptive activities suggesting the involvement of opioid system in the analgesic actions. None of the compounds impaired motor coordination of animals when assessed in the Rota-Rod model. These results support the previous papers reporting the opioid sensitive antinociceptive activities of various benzoxazole/benzimidazole-pyrazoline derivative compounds.