Pakistan Journal of Pharmaceutical Sciences

Abstract: Background: 2-Methoxystypandrone (2-MS), a naphthoquinone from Reynoutria japonica Houtt., has diverse pharmacological activities. However, its antihypertensive and vascular effects remain unexplored. Objectives: This study investigated the antihypertensive and vasorelaxant potential of 2-MS. Methods: In vivo, invasive and in vitro approaches were employed to study the antihypertensive potential of 2-MS in normotensive and high salt-induced hypertensive rats. The responses were recorded and analyzed using the PowerLab Data Acquisition system. In-silico docking predicted potential cardiovascular targets and binding interactions. Results: Intraperitoneal administration of 2-MS (1,3 and 5 mg/kg/day) for 28 days significantly prevented the rise in mean arterial pressure (MAP) and heart rate in hypertensive rats. Intravenous administration in normotensive rats produced a dose-dependent fall in MAP. Pretreatment with L-NAME and atropine attenuated the hypotensive response, suggesting involvement of the endothelial nitric oxide (NO)-linked muscarinic pathway, whereas pretreatment with indomethacin did not alter it. In-vitro, 2-MS relaxed the aortic rings precontracted with phenylephrine. This relaxation to 2-MS was abolished with endothelial removal or L-NAME and atropine pretreatment. 2-MS inhibited both voltage- and receptor-operated Ca²? channels and activated TEA- and 4-minopyridine–sensitive K? channels. Molecular docking revealed strong affinity towards muscarinic M2 receptors, supporting endothelial and smooth muscle actions. Conclusion: These findings demonstrate that the antihypertensive and vasorelaxant effects of 2-MS are mediated by both endothelium-dependent and endothelium-independent pathways.