Antinociceptive effect of the aqueous extract obtained from roots of Physalis angulata L. on mice

In this study, we attempted to identify the possible antinociceptive action of aqueous extract (AE) obtained from roots of Physalis angulata, known in Brazil as "Camapu", used to treat various pain-related physiological conditions. The AE of Physalis angulata (10-30 mg/kg) given by i.p. or p.o. route, 0.5 and 1 h prior, produced significant inhibition of abdominal constrictions caused by acetic acid, with ID50 values of 18.5 (17.4-19.8) and 21.5 (18.9-24.4) mg/kg and inhibitions of 83 +/- 8 and 66 +/- 5%, respectively. The AE (10-60 mg/kg, i.p.) also caused significant inhibition of the late-phase of formal in-induced pain, with an ID50 value of 20.8 (18.4-23.4) mg/kg and inhibition of 100%. Treatment of mice with AE (60 mg/kg, i.p.) or with morphine (10 mg/kg, i.p.) produced a significant increase of the reaction time in the hot-plate test. These results demonstrate, for the first time, that the AE of Physalis angulata produce marked antinociception against the acetic acid-induced visceral pain and inflammatory pain responses induced by formalin in mice. The mechanism by which the AE produces antinociception still remains unclear. However, pharmacological and chemical studies are continuing in order to characterize the mechanism(s) responsible for the antinociceptive action and also to identify the active principles present in Physalis angulata. Moreover, the antinociceptive action demonstrated in the present study supports, at least partly, the ethnomedical uses of this plant. (c) 2005 Elsevier Ireland Ltd. All rights reserved.