Antihypertensive and Vasorelaxant Effects of Hibiscus rosa-sinensis through Angiotensin-Converting Enzyme-2 (ACE-2), and Ca²⁺ Channels Pathways

Aims: The aim of the study was to assess the antihypertensive activity of Hibiscus rosasinensis. Background: Hibiscus rosa-sinensis is used traditionally to treat hypertension. Objective: The goal of the study was to investigate the effect of the aqueous extract of Hibiscus rosa- sinensis flowers (AEHRS) on resting blood pressure in rats. Methods: In the present study, AEHRS was prepared, and its antihypertensive activity was evaluated using in vivo and in vitro studies. In the in vivo study, hypertensive and normotensive rats were treated by AEHRS (100 mg/kg) orally for 6 hours in the acute treatment and for 7 days in the subchronic treatment. Systolic, diastolic, and mean arterial blood pressure values and heart rate were then recorded using a tail-cuff and a computer-assisted monitoring device. To assess the vasorelaxant activity of AEHRS, isolated thoracic aortic rings were suspended in a tissue bath, and changes in tension were recorded using a data acquisition system. Potential pathways involved in the vasorelaxant activity were evaluated using several standard pharmacological agents. Results: The results indicated that repeated oral administration of AEHRS during 7 days lowered systolic, diastolic, and mean arterial blood pressure in hypertensive rats without affecting normotensive rats. Furthermore, the data revealed that AEHRS exerts vasorelaxant properties via an endothelium- independent pathway. More interestingly, the study demonstrates that the vasorelaxant capacity of AEHRS seems to be exerted through the stimulation of angiotensin-converting enzyme-2 (ACE-2) and the inhibition of Ca²⁺ channels pathway. Conclusion: The present study revealed that aqueous extract of Hibiscus rosa-sinensis has a significant antihypertensive activity and that its vasorelaxant effect may be mediated through stimulation of ACE-2, and inhibition of the Ca²⁺ channels.