Antinociceptive effect of Encholirium spectabile: A Bromeliaceae from the Brazilian caatinga biome

Background: Encholirium spectabile is a species found in outcrops rocky throughout the Brazilian Caatinga. Objective: This study was carried out to evaluate the antinociceptive effects of ethanolic extract of the leaves from E. spectabile (Es-EtOH) in mice using chemical and thermal models of nociception. Material and Methods: HPLC was used to determine the fingerprint chromatogram. The Es-EtOH was examined for its antinociceptive activity at the doses of 100, 200 and 400 mg/kg intraperitoneal (i.p.). The evaluation of antinociceptive activity was carried out by the acetic acid-induced writhing, formalin and hot plate tests in mice. Rota-rod test was used for the evaluation of motor coordination. Results: In the acetic acid-induced writhing test, the Es-EtOH (100, 200 and 400 mg/kg, i.p.) reduced the number of writhings by 68.59, 79.33 and 65.28%, respectively. Additionally, Es-EtOH (100, 200 and 400 mg/kg, i.p.) decreased by 34.14, 52.61 and 60.97% the paw licking time in the first phase, as well as 89.56, 79.90 and 96.71% in the second phase of the formalin test, respectively. Es-EtOH also showed effect in the hot plate test, since increased the latency time at dose of 100 mg/kg after 60 minutes. In addition, Es-EtOH did not impair motor coordination. The presence of phenolic compounds in the extract was confirmed using HPLC. These results indicate that Es-EtOH has antinociceptive activity, probably of peripheral origin. The mechanism involved is not completely understood but, at least in part there is the participation of opioid receptors.