Antinociceptive and anti-inflammatory effects of a Geissospermum vellosii stem bark fraction

Geissospermum vellosii (Pao pereira) is a Brazilian tree whose stem barks are rich in indole alkaloids that present intense anticholinesterase activity. The present study evaluated the effects of a stem bark fraction (PPAC fraction) and ethanolic extract (EE) of Pao pereira in classic murine models of inflammation and pain. The EE and PPAC fraction, both at a dose of 30 mg/kg, significantly reduced mice abdominal constriction induced by acetic acid by 34.8% and 47.5%, respectively. In the formalin test, EE (30 mg/kg) and PPAC fraction (30 and 60 mg/kg) inhibited only the second phase, by 82.8%, 84.9% and 100%, respectively. Compared with indomethacin, similar doses of EE or PPAC fraction were approximately twice as effective in causing antinociception. PPAC fraction was not effective in the hot plate test but reduced the inflammatory response at the second (50.6%) and third (57.8%) hours of rat paw edema induced by carrageenan. Antihyperalgesic activity was observed within 30 min with a peak at 2 h (60.1%). These results demonstrate that compounds in PPAC fraction have anti-inflammatory and antinociceptive activity by a mechanism apparently unrelated to the opioid system. Regardless of similar responses to indomethacin, the effects of PPAC fraction are mainly attributed to acetylcholine actions.