Antinociceptive activity of the ethanolic extract from barks and leaves of Cnidoscolus quercifolius (Euphorbiaceae) in mice

Cnidoscolus quercifolius is a species native to the Brazilian Caatinga (semi-arid vegetation) popularly known as "favela" and "faveleira" and used in folk medicine to treat pain. The objective of this work was to evaluate the antinociceptive effect of the ethanolic extract from barks (Cqb-EtOH) and leaves (Cql-EtOH) of C. quercifolius in mice using experimental models of nociception. The antinociceptive activity was evaluated by writhing, hot plate and formalin tests. In addition, the rota-rod test was used to evaluate motor coordination. In the acetic acid-induced writhing test, the Cqb-EtOH (100, 200 and 400 mg/kg, i.p.) reduced the number of writhing by 83.70, 81.40 and 88.10%, respectively, while Cql-EtOH reduced by 71.30, 79.40, and 98.70%, respectively. In the formalin test, the extracts reduced the paw licking time in the first and second phases, but the best results were observed in the second phase (inflammatory pain), reducing by 66.08, 78.26 and 73.97%, as well as 60.11, 75.58, and 79.46% for Cqb-EtOH and Cql-EtOH, respectively. In the hot plate test, the extracts increased the reaction time when compared to control only at dose of 400 mg/kg. Using the rota-rod test, mice treated did not demonstrate any significant motor performance changes. It can be concluded that Cqb-EtOH and Cql-EtOH of C. quercifolius have antinociceptive activity, which supports the popular use of this plant to treat pain.