Antihypertensive effect of roselle (Hibiscus sabdariffa) calyx infusion inspontaneously hypertensive rats and a comparison of its toxicity with thatin Wistar rats

The LD50 of roselle calyx extract and its effect on blood pressure were det ermined. The LD50 was found to be above 5000 mg kg(-1). Roselle calyx infus ion was found to lower significantly (p < 0.05) both systolic and diastolic pressure in spontaneously hypertensive and normotensive Wistar-Kyoto rats at tested doses of 500 and 1000 mg kg(-1) body weight. The reduction in blo od pressure in both groups was positively correlated with weight. Continuou s consumption of the infusion at 1000 mg kg(-1) was discovered to lead to s udden death in spontaneously hypertensive rats but not in Wistar-Kyoto rats . Water intake was not significantly different (p > 0.05) in the control gr oups of the two strains of rats used, neither was there a significant diffe rence in their urine output. The water intake in the treated spontaneously hypertensive and normotensive rats was not different from the corresponding control groups. However the urine output of the treated spontaneously hype rtensive rats was significantly higher. A significant decrease in serum cre atinine, cholesterol, and glucose in the treated rats compared with the con trol as well as a significant increase in serum uric acid was observed. The serum proteins (albumin and total protein) in the treated rats when compar ed with the control groups was not changed significantly. Copyright (C) 199 9 John Wiley & Sons, Ltd.