Antinociceptive effects of the essential oil of Croton zehntneri in mice.

Croton zehntneri is an aromatic plant native to Northeastern Brazil, where it is often used in folk medicine. In the present study the antinociceptive effects of the essential oil of Croton zehntneri (EOCz) were evaluated in mice. EOCz administered orally at doses of 100 and 300 mg/kg reduced paw licking time in the second phase of the formalin test from the control value of 41.61 +/- 8.62 to 12.01 +/- 7.97 and 6.57 +/- 3.42 s, respectively. During the first phase of the formalin test only 300 mg/kg induced a significant alteration (from 58.2 +/- 7.02, control, to 28.7 +/- 4.73 s). The number of contortions in response to intraperitoneal injections of acetic acid did not differ significantly between controls (80.6 +/- 9.01) and experimental (300 mg/kg body weight) animals (89.1 +/- 9.53% of the control numbers; P > or =0.05, Student t-test). In the hot-plate test, EOCz at doses > or =100 mg/kg significantly increased the latency time with respect to controls (11.2 +/- 0.80). At 100 and 300 mg/kg this increase persisted for 180 and 240 min, respectively. The data show that EOCz is effective as an antinociceptive agent.