Antinociceptive properties of conocarpan and orientin obtained from Piper solmsianum C. DC. var. solmsianum (Piperaceae).

The antinociceptive properties of some fractions and two pure compounds, conocarpan and orientin, obtained from P. solmsianum leaves were investigated in several models of pain in mice. The results indicated that this plant exhibits a promising antinociceptive profile, as it produces active principles which are several times more active than some reference drugs used for comparison. The main compound tested, orientin, caused potent and dose-dependent effects against acetic acid-induced writhing and capsaicin- and glutamate-induced nociception, being more effective against the first one, with an ID(50) value of 6.5 mg/kg (14.5 micromol/kg). Orientin was about 20-fold more potent than acetylsalicylic acid and 3.5-fold more active than indomethacin. The antinociceptive effects of this plant may be attributed, at least partially, to the presence of conocarpan and, in particular, to the flavonoid orientin.