Abstract
This study was aimed to rationalize medicinal use of M. nagi in gut, airways and cardiovascular disorders. The crude extract of M. nagi bark (Mn.Cr), its aqueous (Mn.Aq) and ethyl acetate (Mn.EtAc) fractions were prepared. Antidiarrheal activity of M. nagi was carried out in mice, while its gut modulatory, bronchodilatory and vasodilatory activities were evaluated in isolated tissues of different animals using tissue bath assembly coupled with PowerLab. Orally administered doses (100-500 mg kg(-1)) of Mn.Cr produced protection against castor oil and MgSO4-stimulated diarrhea in mice. In guinea-pig ileum, Mn.Cr and Mn.Aq exhibited atropine-sensitive contractile effect. In rabbit jejunum, Mn.Cr and Mn.Aq exerted atropine-sensitive stimulant effects at 0.01-1 mg mL(-1) followed by relaxation, while Mn.EtAc (0.03-0.1 mg mL(-1)) exhibited only inhibitory effect. Mn.Cr and Mn.EtAc inhibited high K+ (80 mM) induced contractions and shifted Ca++ Concentration Response Curves (CRCs) rightwards in rabbit jejunum. The Mn.Cr inhibited high K+, carbachol (CCh) and phenylephrine (P.E) induced contractions and shifted CRCs of Ca++ rightwards in rabbit trachea and endothelial-intact or denuded aortic tissues of rats. These results indicate the presence of combination of cholinergic and Ca++ antagonist constituents in M. nagi, which may provide scientific basis to its medicinal use in gut, airways and cardiovascular disorders.