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Background: Benzimidazoles are a group of hetrocyclic compounds containing fused benzene ring with an imidazole ring. It has been shown benzimidazoles retain important biological activity including antioxidant, analgesic and anti-inflammatory activity. In order to find analogues with improved activity, 13 benzimidazole derivatives which previously synthesized by our group were biologically investigated. Materials and Methods: This study is a pilot attempt to explore the antioxidant, analgesic and antiinflammatory activity of the 13 compounds. The in vitro antioxidant potential was investigated using DPPH free radical scavenging assay. Two models of pain assessment ie thermally induced pain by hot plate and chemically induced pain by acetic acid were used to evaluate the analgesic activity of the compounds under test. However, formalin induced pain and inflammation in mouse paw was employed as a model to assess the antiinflammatory activity.

Results: Mice treated at dose of 50 mg/kg of compounds 6, 10 and 1a produced a significant reduction in the percentage of writhings response to acetic acid injection to 45%, 18.7% and 48% of control respectively. Comparatively the same dose of Aspirin (50 mg/kg) reduced the responses to 8% from the control. Benzimidazole derivatives 1, 3, 6, 7, 9, 10, 11, 12 and 1a produced a significant increase in the response time of animals to heat upon putting on hot plate surface. Compounds 1, 6, 12 and the main compound (1a) in a dose of 50 mg/kg produced similar effect or higher than that produced by morphine at a dose of 25 kg/mg, ie almost half potency of morphine. Compounds 1a and 6 were …