Antihypertensive and vasorelaxant effects of Salvia tingitana in rats

Salvia tingitana (S. tingitana) is a medicinal and aromatic plant that belongs to the Lamiaceae family with several medicinal properties. Secondary metabolites, including flavonoids, polyphenols and tannins, were identified through phytochemical analysis of the aerial parts of S. tingitana. In addition, pharmacological investigation revealed this plants’ antihyperglycemic and antihyperlipidemic activities. This study aimed to investigate the antihypertensive and vasorelaxant activities of the aqueous extract of S. tingitana (AEST) in normal and L-NAME-induced hypertensive rats by assessing its effects on heart rate (HR), systolic blood pressure (SBP), mean blood pressure (MBP) and diastolic blood pressure (DBP). The study further investigated the vasorelaxant effect of AEST on isolated rat thoracic aorta and elucidated the underlying mechanisms. As a result, AEST significantly lowered SBP after single and repeated oral administration in normal rats without affecting MBP, DBP and heart rate. Interestingly, after repeated oral AEST administration, arterial blood pressure parameters (SABP, DBP and MBP) significantly decreased in hypertensive rats. The vasorelaxation effect induced by AEST in aortic rings was mediated through numerous pathways involving calcium channels, nitric oxide synthase, muscarinic receptors and inward-rectifying potassium channels. In contrast, the pretreatment with methylene blue, glibenclamide, indomethacin and propranolol did not significantly alter AEST-induced vasorelaxation. The study showed that AEST exhibits a significant antihypertensive effect in L-NAME-rats and exhibits vasorelaxant properties in rat aortic rings via mechanisms involving calcium channels, nitric oxide synthase, muscarinic receptors and inward-rectifying K+ Channels. Interestingly, many further studies on the structure-activity relationship of S. tingitana are needed to explain the mechanisms of action that have been revealed.