Antinociceptive action of extracts and fractions from Rubus imperialis (Rosaceae).

Rubus imperialis is a Brasilian medicinal plant which previously exhibited therapeutical perspectives. This work describes the antinociceptive action of methanolic extracts obtained from different parts of the plant (roots and branches) as well as hexane, chloroform and ethyl acetate fractions obtained from branches. Such extracts or fractions caused significative inhibition in the writhing test in mice at 10 mg/kg, given intraperitoneally. They were more active than two reference drugs, aspirin and paracetamol. The fractions also exhibited antinociceptive activity in the writhing test when administered orally at 200 mg/kg. When analyzed in the formalin test, the chloroform fraction was the most active, causing considerable inhibition against both neurogenic and inflammatory phases of pain.