ANTINOCICEPTIVE ACTIVITY OF ETHANOLIC EXTRACT AND ISOLATED COMPOUNDS OF URTICA CIRCULARIS

MARRASSINI, CARLA; ACEVEDO, CRISTINA; MIÑO, JORGE; FERRARO, GRACIELA; GORZALCZANY, SUSANA

Hotel 13 de julio, Mar del Plata

Otro; LV Reunión Anual de la Sociedad Argentina de Investigación Clínica , Reunión Sociedad Argentina de Fisiología 2010 y XLII Reunión Sociedad Argentina de Farmacología Experimental (SAFE); 2010

Sociedad Argentina de Farmacología Experimental (SAFE)

It has been widely shown that many plant-derived substances have a relevant place in the process of development of new strategies to treat complains related with pain.  Urtica circularis (Hicken) Sorarú is an Argentinean native herb used in folk medicine as a diuretic, antihipertensive, against hepatic affections and cough and for the relief of pain in inflammatory process. Taking into account that no pharmacological study has been carried out on the possible antinociceptive effect of this plant up to now, we studied this activity of the ethanolic extract of U. circularis and carry out a phytochemical analysis. The effects of the ethanolic extract of U. circularis on three classical nociception models in mice: the acetic acid-induced writhing, the formalin test and the hot plate test were tested. The pretreatment with U. circularis (10-500 mg/kg i.p.) produced a dose-dependent inhibition of the acetic acid-induced writhing response (ED50: 77.1 mg/kg). Besides, 500 mg/kg p.o. produced a significant inhibition of the writhing response (48.4%). To evaluate some of the possible mechanisms involved in the antinociceptive response, yohimbine (1 mg/kg, i.p.), l-arginine (40 mg/kg, i.p.), l-NAME (20 mg/kg i.p.), glibenclamide (2 mg/kg i.p.) and atropine (2 mg/kg i.p.) were used. Only atropine significantly prevented the antinociception caused by U. circularis. In the formalin test, 30 mg/kg i.p or 500 mg/kg p.o. produced a marked reduction of 78.5 and 88.5 % of the licking time in the late phase respectively, showing an ED50: 15.8 mg/kg i.p.. The antinociceptive effect was not reversed by pretreatment with naloxone. Moreover, the extract (250 mg/kg. i.p.) had no effect on thermal pain meanwhile morphine (10mg/kg s.c.) increased the latency time in hot plate test. Chlorogenic acid, caffeic acid, vitexin and apigenine were identified by HPLC method.  In the writing test, chlorogenic acid and vitexin (10 mg/kg i.p.) showed a significant antinociceptive effect meanwhile caffeic acid produced a slight activity at the same dose and apigenin didn´t produce any effect. In conclusion, the results of the present study demostrated that the extract of U. circularis produced dose-related antinociceptive action in chemical models of nociception in mice. The activation of cholinergic systems seems to be one of the possible mechanisms through which the extract exerts its action. Vitexin and chlorogenic acid may be responsible of the effect observed.