Assessment of the vasodilatory activity of an isolate from Moringa oleifera L. (Moringaceae) seeds on thoracic aorta in rats

Moringa oleifera seeds are widely used to manage hypertension in traditional medicine in the northern part of Madagascar. In this work we studied the vasodilatory activity of a molecule isolated from the seeds for the first time 4ʹ-((3,4,5-trihydroxy-6-(1-hydroxyethyl)-tetrahydro-2H-pyran-2-yl)oxy)benzylamino-3ʹ-(2-hydroxyethane) that we coded N-428. It was isolated from ethyl acetate extract. It relaxes rat thoracic aorta contracted with norepinephrine at 10 µM with EC₅₀ equal to 8.92.10^-5 M. Further research revealed that it can dilate endothelium denuded aorta and promotes vasodilation, it provokes a right shift of the concentration-effect curve of norepinephrine without changing the maximal effect, indicating its activity via α1 receptors. Compared to prazosin, a competitive antagonist of norepinephrine its pA2 is  5.78 M, versus 8.249 for prazosin, and Kd of 1.25.10^-6 M, versus 5.63.10^-9 M for prazosin. These results indicate that the isolate exhibits good vasodilatory activity, acting as α1 competitive antagonist of norepinephrine and has the potential to be utilized as a lead vasodilator compound.