ABSTRACT
Aims: Origanum majorana (Lamiaceae) is a herbaceous and perennial plant that is used in the Moroccan traditional medicine for treating gastrointestinal disorders. The objectives of this study were to confirm the antispasmodic and the myorelaxant activity of organic fractions of Origanum majorana (OM) in rat and rabbit jejunum. Place and Duration of Study: Laboratory of Physiology, Genetic and Ethnopharmacology, Faculty of Sciences, Mohamed the First University, between September 2013 and July 2014. Methodology: The antispasmodic and the myorelaxant test evaluated in vitro on rat and rabbit intestines mounted inside an isolated organ system with a temperature of 37ºC, pH 7.4 and continuous oxygenation Results: The screening study showed those organic fractions of OM decreased the tone of contraction induced by the Carbachol 10-6 M and the KCl 25 mM in the jejunum. The maximum decrease was obtained by dichloromethane fraction of Origanum majorana (DFOM). DFOM induced dose-dependent and reversible inhibition in intestine contraction of rabbit jejunum with IC50 = 0.162 ± 0.002 mg/ml without any alteration of this effect in the presence of adrenergic inhibitors. Pretreatment of the tissue with this fraction (0.01-0.3 mg/ml) induced a dose-dependent shift of the dose-response curve of Carbachol and CaCl2 to the right. The pharmacological inhibitors such as Atropine, L-NAME, Hexamethonium, Nifedipine and Methylene blue did not alter the relaxing effect of DFOM. Conclusion: The results study confirms the antispasmodic and the myorelaxant effect of OM extract. Also, the results showed that adrenergic receptors, NO, guanylate cyclase or muscarinic receptors pathways did not involve in relaxation induced by DFOM suggesting that it exerts an antispasmodic effect on intestinal smooth muscle like a non-competitive antagonist towards the voltage-dependent calcium channels.