Pharmacological Study of the Effect of Cold and Hot Aqueous Extracts of Hibiscus sabdariffa on Vascular Activity of Diabetic Albino Rats

The oxidative stress has been indicated to play an important role in the development and progression of diabetic complications such as decreased vascular reactivity, hypertension….etc. Previous studies show that Hibiscus sabdariffa possesses a hypoglycemic effect and useful in some diseases including hypertension. Our study aimed to evaluate the possible protective effect of Hibiscus sabdariffa aqueous extract on diabetic vascular complications and blood pressure and compare between cold and hot aqueous extracts by studying their effects on the reactivity of the isolated rat aorta to norepinephrine and acetylcholine in the diabetic albino rats. The results show that the rats systolic blood pressure and, the contractile response of the isolated rat aortae to norepinephrine are increased significantly and the relaxant response of the rat aortae to acetylcholine is decreased significantly as compared with those obtained from the nondiabetic rats. Treatment with both cold and hot hibiscus as well as glibenclamide decreased significantly the systolic blood pressure and the contractile response of the isolated aortae to norepinephrine as well as increased significantly the relaxant response of the isolated aortae to acetylcholine. In conclusion, Hibiscus sabdariffa aqueous extracts, either cold or hot can protect against the diabetes mellitus- induced vascular complications by decreasing the elevated blood pressure and the increased norepinephrine- induced contractile effect as well as by improving the decreased relaxant responses to acetylcholine in the Streptozotocin- induced diabetic male albino rats.