Isoeugenol, a component of clover oil, possesses potent anti-inflammatory and antioxidant activity. In the present study, we investigated the effect on experimentally induced adjuvant arthritis in rats. Induction of arthritis in adjuvant exposed rats was confirmed by appearance of several physical symptoms such as redness, swelling and stiffness of paws, radiographic analysis revealing joint damage, soft tissue swelling of the footpad, histopathologic changes and expression of proinflammatory enzymes and mediators in the joint tissue. Treatment of rats with isoeugenol, however, conferred a significant protection against almost all the investigated parameters. Isoeugenol significantly and dose dependently attenuated arthritic index, paw circumference, joint stiffness and the levels of proinflammatory mediators. Exposure to isoeugenol inhibited the release of nitric oxide and proinflammatory cytokines the including PGE(2) and TNFα from lipopolysaccharide primed macrophages. Isoeugenol also showed a significant analgesic activity in acetic acid-induced writhing model. Further, unlike most antiarthritic drugs, isoeugenol had no damaging effect on gastric mucosa, which makes it a favorable antiarthritic drug. Thus, the results obtained in the present study indicate isoeugenol to possess a promising antiarthritic activity and further advocate the efficacy of natural products as antiarthritic therapeutics.
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