The objective of this study was to evaluate the anti-inflammatory and analgesic activities of the hydro-alcoholic extract of the pods of Astragalus hamosus (HAAH), a plant used in Iranian traditional medicine, and antinociceptive effects of different fractions in animal models. The anti-inflammatory effect was evaluated by the rat paw edema induced by formalin. Also the analgesic effect was examined by the acetic-acid-induced writhing response and hot plate test. The analgesic effects of chloroform, hexane, ethyl acetate and aqueous fractions were evaluated by the hot-plate method. The hydroalcoholic extract of Astragalus hamosus could reduce the edema in a dose-dependent manner (P<0.05). In the acute phase, the result of 1000 mg/Kg and in the chronic phase, the result of 100 and 300 mg/Kg of the extract were more significant and comparable with the effect of sodium salicylate. Also application of different doses of HAAH had significant anti-nociceptive effects on both animal models. The findings showed that HAAH at doses of 700 and 1000 mg/Kg produced analgesic effects comparable to sodium salicylate. The hexane and ethyl acetate (but not the other fractions) showed significant analgesic activity in hot plate test, when compared to morphine. The results of this study demonstrated the anti-inflammatory and analgesic effects of HAAH extract and hexane and ethyl acetate fractions of the extract in animal models and justify traditional use of this plant in the treatment of pain and inflammatory conditions. More studies to clarify the active components are necessary.
Keywords: Analgesic; Anti-inflammatory; Astragalus hamosus; Traditional Iranian Medicine.