Anti-nociceptive effect of stigmasterol in mouse models of acute and chronic pain
ETHNOPHARMACOLOGICAL RELEVANCE The infusion or decoction of Mirabilis jalapa leaves is used in traditional medicine in Brazil to treat inflammatory and painful diseases. AIM OF THE STUDY The present study examined the antinociceptive effect of Mirabilis jalapa extracts from leaves and stems in models of pain in mice. MATERIALS, METHODS AND RESULTS The crude hydroethanolic extract from leaves (CrdL) was more potent than the crude extract from stems (CrdS) to inhibit abdominal constrictions induced by acetic acid, with ID(50) values of 5.5 (2.3-13.1) and 18.0 (11.3-28.5) mg/kg, respectively. Among the fractions tested, the Eta fraction from leaves (Eta) was more effective (maximal inhibition of 83+/-8%) and potent (ID(50) of 1.1 (0.6-2.1) mg/kg) to induce antinociception. Eta and CrdL also possessed an antinociceptive effect in the tail-flick test. Pre-treatment with naloxone did not modify the antinociceptive effect of Eta, but co-administration with atropine completely prevented it. This suggests that the antinociceptive effect might depend on the cholinergic system. Instead, Eta was not able to alter the acetylcholinesterase activity in blood or spinal cord. Concerning side effects, Eta did not alter locomotor activity, body temperature, gastrointestinal transit and did not produce gastric lesions. CONCLUSION Our results demonstrate that Mirabilis jalapa presents antinociceptive activity in mice, which supports its folkloric use as an analgesic.