A study of the smooth muscle relaxant actions of harman alkaloids isolated from the seeds of peganum harmala

Introduction: The plant Peganum harmala is a shrub native to the arid parts of the world including India. It’s therapeutic value is attributed to the presence of alkaloids harmala and harmine in the dried ripe seeds. In traditional medicine these seeds are considered to have anti-spasmodic, hypnotic, anodyne, emetic, emmenogogue, stimulant, aphrodisiac, lactogogue and antihelminthic actions. Objectives: The present study was undertaken to find out the effects of the active principle extracted from the seeds of Peganum harmala on isolated smooth muscle and skeletal muscle preparations and the probable mechanism of action Materials & Methods: The harman alkaloid isolated from Peganum harmala seeds was used for experiments on isolated preparations of rat uterus, guinea pig ileum, rabbit jejunum and frog rectus abdominis muscles and the responses were recorded on a rotating smoked drum on a kymograph. Results: The active principle in Peganum harmala seeds was shown to inhibit spontaneous movements of isolated rat uterus, guinea pig ileum and rabbit jejunum. Also shown to inhibit contractions of oestranised rat uterus induced by oxytocin, contractions of guinea pig ileum induced by histamine and acetyl choline. Have not shown any effect on contractions of frog rectus abdominus muscle. Conclusion: Harman alkaloids have anti-spasmodic, tocolytic, anti-cholinergic and anti-histaminic activities, it is unlikely that these alkaloids have a specific receptor antagonistic activity. Also these have found to inhibit the smooth muscle contractions but not the skeletal muscle contractions. The smooth muscle relaxant action may be due to calcium channel blockad