Analgesic and anti-inflammatory activities of Polygonum stagninum.

The n-hexane, ethyl acetate (EtOAc), and methanol extracts of the aerial parts of Polygonum stagninum Buch.-Ham. ex Meissn. (Polygonaceae), a Bangladeshi medicinal plant, were assessed for analgesic and anti-inflammatory properties in experimental mice and/or rat models. In the acetic-acid-induced writhing test in mice, all extracts displayed a dose dependent analgesic effect. The most potent analgesic activity was observed with the EtOAc extract at the dose of 400 mg/kg body weight, with an inhibition of writhing response of 50.3% compared to 62.2% for the positive control aminopyrine. Among the extracts, n-hexane extract at the doses of 200 and 400 mg/kg body weight showed the highest levels of anti-inflammatory activity after 2 h, with the inhibition of paw edema of 60.1% and 64.1%, respectively, and this effect was much better than that of the conventional anti-inflammatory agent phenylbutazone (maximum inhibition of 38.3% after 4 h).