HS was a more effective antihypertensive agent than HCTZ in mild to moderate hypertensive Nigerians and did not cause electrolyte imbalance. HS showed longer duration of action compared to HCTZ and reduction in serum Na+ may be another antihypertensive mechanism of action of HS.

Objectives:The present study investigated the effects of aqueous extract of Hibiscus sabdariffa (HS) on the three basic components of renin-angiotensin-aldosterone system: Plasma renin, serum angiotensin-converting enzyme (ACE), and plasma aldosterone (PA) in mild to moderate essential hypertensive Nigerians and compared with that of lisinopril, an ACE inhibitor.Materials and Methods:A double-blind controlled randomized clinical study was used. Seventy-eight newly diagnosed but untreated mild to moderate hypertensive subjects attending Medical Outpatients Clinic of Enugu State University Teaching Hospital, Enugu were recruited for the study. Those in Group A received placebo (150 mg/kg/day), Group B were given lisinopril (10 mg once daily) while those in Group C received aqueous extract of HS (150 mg/kg/day). After 4 weeks of treatment, the levels of plasma renin, serum ACE, and PA were determined.Results:HS and lisinopril significantly (P < 0.001) reduced PA compared to placebo by 32.06% and 30.01%, respectively. Their effects on serum ACE and plasma renin activity (PRA) were not significant compared to placebo; they reduced ACE by 6.63% and 5.67% but increased plasma PRA by 2.77% and 5.36%, respectively.Conclusion:HS reduced serum ACE and PA in mild to moderate hypertensive Nigerians with equal efficacy as lisinopril. These actions are possibly due to the presence of anthocyanins in the extract.

Hibiscus sabdariffa (HS) has been traditionally used as a herbal medicine in Nigeria mainly because of its antihypertensive action. In view of the recent increase in the prevalence of renal failure, we have investigated the effect of HS consumption on renal function in Nigerians with mild to moderate hypertension. A total of 78 newly diagnosed but untreated subjects with mild to moderate hypertension attending the medical outpatients unit of Enugu State University Teaching Hospital (Enugu, Nigeria) were recruited for the study. These subjects were randomly divided into three equally sized groups that received HS or lisinopril (treatment groups) or placebo (control group), once daily for 4 weeks. Indices of renal function (urine volume and creatinine clearance) were measured at baseline and weekly throughout the study period. HS and lisinopril significantly increased (P < 0.001) urine volume compared to placebo, and HS significantly (P < 0.001) increased urine volume more than lisinopril. HS significantly increased (P < 0.001) creatinine clearance compared to placebo whereas lisinopril did not. These results indicate that HS consumption improved indices of renal function in our study population of Nigerians with mild to moderate hypertension.

SUMMARY1. The effect of intra-arterial prostaglandin E1 (PGE1) infusion on urinary kallikrein, sodium, potassium and water excretion was studied in normal anaesthetized dogs.2. Infusion of PGE1 caused a dose-related increase in urinary excretion of kallikrein, sodium, potassium and water as well as an increase in renal blood flow (R.B.F.) and a fall in urinary osmolality and renal vascular resistance.3. The changes occurred in the absence of appreciable changes in inulin clearance (CIN), arterial blood pressure, haematocrit, and plasma sodium and potassium concentrations.4. The increased urinary kallikrein excretion correlated positively with the natriuresis, diuresis and kaliuresis and the increase in renal blood flow, but negatively with the urinary osmolality and renal vascular resistance.5. It is concluded that renal kallikrein is involved in the renal response to arterial infusion of PGE1.

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