Vasorelaxation effect of Syzygium polyanthum (wight) walp. Leaves extract on isolated thoracic aorta rings of normal and hypertensive rats

Introduction: Syzygium polyanthum (Wight) Walp. leaves are traditionally consumed by the Malays as an alternative treatment for hypertension. Until now, effect of S. polyanthum leaves extract on blood vessel is not yet disclosed. Methods: This study investigated the effect of S. polyanthum leaves aqueous extract (AESP) (0.01, 0.1, 1 & 10 mg/ml) on isolated thoracic aorta rings of normotensive Wistar-Kyoto rats (WKY) and Spontaneously Hypertensive rats (SHR). Both rings were pre-contracted using phenylephrine (1 μM). Distilled water that dissolved AESP served as negative control. Results: As compared to negative control, AESP at 0.1, 1, and 10 mg/ml significantly relaxed aorta rings of WKY by 39.81 ± 2.99 % (P<0.001), 59.55 ± 7.60 % (P<0.001), and 72.58 ± 5.57 % (P<0.001), respectively. In SHR, AESP at 1 and 10 mg/ml significantly relaxed the aorta rings of SHR by 40.53 ± 3.66 % (P<0.001) and 65.73 ± 8.24 % (P<0.001), respectively. There was a significant difference between AESP-induced vasorelaxation in WKY and in SHR at a concentration of 0.1 mg/ml (P