Antinociceptive activity of Tibouchina pereirae, an endemic plant from the Brazilian semiarid region.

The anti-nociceptive activity of an extract of Tibouchina pereirae Aubl (AETP) was investigated using two models of chemically induced pain, viz. the acetic acid-induced writhing and the formalin test, respectively, with dipyrone and indomethacin as reference drugs, respectively. In the acetic acid-induced writhing test, AETP application (100 mg/kg) caused a significant reduction of writhing produced by acetic acid. In the formalin test, AETP reduced the formalin effects significantly only in the late phase. These findings thus indicate the involvement of AETP only in peripheral antinociceptive mechanisms. In addition, AETP exhibited good antioxidant activity (EC50 approx. 15 μg/mL) in the DPPH free radical scavenging assay.