The aim of this study was to investigate the antihypertensive effects of methanol extract of H. sabdariffa leaves (MEHS) in rats. Hypertension was induced in the rats by adding 8% NaCl in their diet (salt-loading) for 6 weeks. The rats were randomly divided into five groups of 5 rats each. Group 1 was the normotensive control group and was fed with normal rat chow and water ad libitum; groups 2 and 3 were the hypertensive and positive control groups respectively while groups 4 and 5 were the experimental groups. Group 2 was given normal rat chow and water while group 3 was treated with 30 mg/kg captopril. Groups 4 and 5 were treated (p.o) with 200 and 400 mg/kg b. wt. of MEHS respectively per day for 4 weeks. The LD50 of MEHS was greater than 2000 mg/kg. Qualitative phytochemical studies revealed the presence of saponins, tannins, flavonoids, phenols, steroids, triterpenoids, and fixed oils. The MEHS significantly reduced (p<0.05) blood pressure and heart rate in hypertensive rats in a dose-dependent manner. The blood pressure reduction was associated with a reduction in serum lipid peroxidation product, as well as with an increase in serum antioxidant enzyme activities in hypertensive rats. The effects of MEHS on blood pressure and oxidative stress markers were similar to those of captopril. The results suggest that the MEHS possesses significant antihypertensive effect against salt-induced hypertension in rats. The antihypertensive effect appears to be mediated by a reduction in serum oxidative stress.
