Antinociceptive effects of Peganum harmala L. alkaloid extract on mouse formalin test.

Abstract

PURPOSE: To evaluate the effect of Peganum harmala (Syrian rue) a wild-growing flowering plant belonging to the family Zygophylaceae and found abundantly in Iran on formalin-induced pain response in mice. METHODS: Total alkaloid extract was prepared from dry seeds of Peganum harmala. All doses of extract were dissolved in normal saline and administered intraperitoneally 30 minutes before formalin injection to the mouse paw. Nociception was recorded 0-5 (early phase, A) and 15-40 (late phase, B) minutes after formalin injection. The alkaloid extract was subjected to silica gel column chromatography using a linear gradient with a CHCl3-MeOH system and different fractions collected. The effective fraction in formalin test were further purified and isolated by preparative thin layer chromatography (TLC) and identified on the basis of nuclear magnetic resonance (NMR) and mass spectrometry (MS) analysis. RESULTS: Alkaloid extract in doses (mg/kg) used induced significant reduction in pain response when compared to control as follow: 16 (28.63%), 20 (59.15%), 24 (80.75%), 28 (90.14%) and 30 (100%) in the early phase and 20 (24.67%), 24 (59.93%), 28 (78.52%) and 30 (100%) in late phase. Observed responses in both phases of A and B were dose-dependent with r2 of 0.93 and 0.99 respectively. ED50 for phases of A and B were 27.87 and 24.63 mg/kg respectively (p<0.001 for all groups). CONCLUSION: Harmaline, the last step of extraction is the main effective antinociceptive agent of the Peganum harmala alkaloid extract.