Attenuation of visceral nociception by alpha- and beta-amyrin, a triterpenoid mixture isolated from the resin of Protium heptaphyllum, in mice.

In the search for novel natural compounds effective against visceral nociception, the triterpenoid mixture alpha- and beta-amyrin, isolated from Protium heptaphyllum resin, was assessed in two established mouse models of visceral nociception. Mice were pretreated orally with alpha- and beta-amyrin (3, 10, 30, and 100 mg/kg) or vehicle, and the pain-related behavioral responses to intraperitoneal cyclophosphamide or to intracolonic mustard oil were analyzed. The triterpenoid mixture showed a dose-related significant antinociception against the cyclophosphamide-induced bladder pain, and at 100 mg/kg, the nociceptive behavioral expression was almost completely suppressed.