Antioxidant activity and vasorelaxant effect of Marrubium multibracteatum via receptor-activated calcium channels and nitric oxide pathways in rats

According to several studies, antihypertensive drugs have side effects on human health. Therefore, natural products are also being investigated as alternatives to these drugs. For this reason, the present study aimed to examine the vasorelaxant properties of Marrubium multibracteatum aqueous extract (MMAE) on isolated rat aortic rings. The antioxidant potential of MMAE was also evaluated. The vasorelaxant activity of MMAE was assessed on aortic rings precontracted with epinephrine (EP, 10 μM) and potassium chloride (KCl, 80 mM). The antioxidant potential of MMAE was determined using the DPPH (2,2-diphenyl-1-picrylhydrazyl) radical scavenging assay. In addition, the extract underwent phytochemical screening. The results showed that cumulative concentrations of MMAE (0.75 – 1.50 mg/mL) induced a vasorelaxant effect on epinephrine-precontracted aortic rings via the nitric oxide (NO) pathway and inhibited extracellular Ca2+ entry through receptor-operated calcium channels (ROCCs). However, the same concentrations of MMAE exhibited only minimal vasorelaxant effects on KCl (80 mM)-precontracted aortic rings. In contrast, MMAE demonstrated significant antioxidant activity. These findings suggest that MMAE exhibits both potent vasorelaxant and antioxidant properties, likely due to its phytochemical composition, particularly the presence of polyphenols, flavonoids and tannins. Therefore, this extract may represent a promising natural alternative to certain synthetic antihypertensive drugs.