Comparative hypotensive and respiratory stimulation effects of ripe and unripe fruit mucilage of Cordia myxa and Cordia obliqua in guineapigs and rabbits

The comparative pharmacological activity of Cordia fruit mucilage at different stages of maturity was investigated to determine the stage at which active substances were present in high proportions. The fruit mucilage of ripe and unripe Cordia myxa (RCm and URCm) decreased rabbit arterial blood pressure in a dose dependent manner without affecting the respiratory rate. Mucilage from both ripe and unripe Cordia obliqua (RCo and URCo) decreased rabbit blood pressure and stimulated the respiratory rate. RCm is 12.37-fold more potent as a hypotensive agent than RCo. However the respiratory stimulant effect of RCo is 7-fold more than its own hypotensive effect. Investigation of the mode of action revealed that the hypotensive effect was more likely due to activation of parasympathetic ganglia and dilatation of peripheral blood vessels, whereas the respiratory stimulant effect may partly be due to activation of chemoreceptors in the aortic arch and carotid body. In addition, a subeffective dose of the ripe fruit mucilage specifically antagonized nicotine-induced hypotensive effect on rabbit and nicotine ganglionic stimulant effect on the isolated guineapig ileum.