Hypertension is one of the most important health challenges facing developed and developing countries and is currently a secondary death cause of cardiopathy, stroke and renal failure caused by vascular accidents. Generally, 18-54% of the global population and 29.7-34.6% of Tehranis suffer from hypertension. Pharmacological control of hypertension prevents debilitation and mortality caused by cardiovascular accidents, cerebral hemorrhage and renal failure Currently, 6 groups of synthetic drugs are used as hypotensive agents, but they all have adverse effects. These groups include anti-adrenergics, vasodilators, Calcium antagonists, angiotensin receptor antagonists and Angiotensin Converting Enzyme Inhibitors (ACEIs). For years and in various countries, aqueous extract of hibiscus has been used to treat gastrointestinal disorders and hypercholesterolemia and as a diuretic, diaphoretic and hypotensive agent. In a study, 500 mg/kg and 1000 mg/kg doses of brewed calyces of roselle flowers significantly reduced systolic and diastolic blood pressures in hypertensive and wistar-kyoto rats (p<0.05). Pharmacological studies have shown that the hypotensive effect of hibiscus is probably induced through a diuretic and angiotensin converting enzyme inhibitory effect.
To compare the anti-hypertensive properties and tolerance of a standard extract of hibiscus with captopril, in a controlled, randomized clinical trial, 30-80 year old patients with diagnosed hypertension were asked not to use any hypotensive drug for one month prior to entering the study. They were administered for 4 weeks a tisane made with 10 g dried calyces of roselle flowers in half a liter of water (containing 9.6 mg anthocyanin) to be taken before breakfast or 25 mg captopril 2 times per day. The outcome variables included tolerance, therapeutic efficacy (a reduction in diastolic pressure of at least 10 mm Hg) and in the case of the group using hibiscus (test group), change in urine electrolytes. 90 patients entered the study. 15 patients were excluded from the study due to non-medical reasons and analysis was carried out on the data of 75 patients. Based on the results of this study, hibiscus managed to reduce systolic pressure from 139.05 to 123.73 mm Hg (p<0.03 ANOVA) and diastolic pressure from 90.81 to 79.52 mm Hg (p<0.25 ANOVA). At the end of the study, there existed no significant difference between measured blood pressure in the two treatment groups (p<0.25 ANOVA). The degree of therapeutic efficacy with hibiscus was 0.7895 and with captopril 0.8438 (p>0.560, x2) and tolerance for both groups was 100%. In the hibiscus group a natriuretic effect was observed. Gathered data showed that standardized hibiscus extract based on 9.6 mg anthocyanin and captopril (50 mg per day) do not manifest significant difference with regard to hypotensive, anti-hypertensive effects and tolerance.
To compare the therapeutic effect, tolerance, effect on serum electrolytes and ACE inhibition of a herbal medicine made from dried calyces of roselle flower with Lisinopril in patients with hypertension, a randomized, controlled, double-blind clinical trial was carried out on 25-61 year old patients of both sexes with stage I and II hypertension. The patients received for 4 weeks, 250 mg total anthocyanin in each dose or 10 mg Lisinopril. The outcome variables included therapeutic efficacy (reduction in diastolic pressure at least 10 mm Hg), safety (absence of pathologic changes in biochemical tests of liver and kidney function), tolerance (absence of serious adverse reactions), effect on serum electrolytes and effect on the activity of ACE. 193 patients entered the study [100 patients in the test group (hibiscus)], but analysis of outcome variables was carried out on 171 patients. Based on the results of this study, in the hibiscus group, blood pressure reduced from 146.48/97.77 to 129.89/85.96 mm Hg and reached an absolute reduction at 17.14/11.97 mm Hg (p<0.05, 11.58/12.21%). In the hibiscus group, therapeutic efficacy was 65.12% and tolerance and safety 100%. Reduction in blood pressure and therapeutic efficacy of hibiscus was less than Lisinopril (p<0.05). In the hibiscus group, serum chlorine increased from 91.71 to 95.13 mmol/l (p=0.0001). The level of sodium decreased (from 139.09 to 137.35, p=0.01) but potassium did not change. The activity of serum ACE was inhibited by hibiscus and decreased from 44.049 to 30.1 units (p=0.0001, us). The researchers came to the conclusion that extract of hibiscus has major anti-hypertensive effects along with considerable tolerance and safety. Also, it significantly reduces the activity of plasma ACE and decreases serum sodium without affecting potassium.