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- Hibiscus (Hibiscus sabdariffa, Malvaceae)
- Blood Pressure
- Hydrochlorothiazide
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Date:
11-30-2015 | HC# 111521-533
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Re: Hibiscus Extract Decreases Blood Pressure to a Greater Extent than Hydrochlorothiazide in Nigerian Patients with Mild to Moderate Hypertension
Nwachukwu
DC, Aneke E, Nwachukwu NZ, Obika L, Nwagha UI, Eze AA. Effect of Hibiscus sabdariffa
on blood pressure and electrolyte profile of mild to moderate hypertensive
Nigerians: a comparative study with hydrochlorothiazide. Niger J Clin Pract. November-December 2015;18(6):762-770.
Hypertension
is one of the risk factors of cardiovascular disease and the main risk factor
for stroke. It affects approximately 20% of the world's population with more
severe sequelae among individuals of African descent. Hypertension is likely
the result of many physiologic changes which include changes in electrolyte
concentrations in the blood. Blood concentrations of sodium and chloride ions
are higher and potassium ions are lower in patients with hypertension than in
individuals with normal blood pressure. One common method of treating
hypertension involves the reduction of blood electrolytes with prescription
medications, such as hydrochlorothiazide (HCTZ). Studies in animal models and
in humans provide evidence that hibiscus (Hibiscus
sabdariffa, Malvaceae) extracts can help lower blood pressure. The goal of
this randomized, controlled study was to compare the effects of a hibiscus
extract and HCTZ on blood pressure and electrolyte balance in Nigerian patients
with mild to moderate hypertension.
Patients were recruited from the Medical Outpatient
Clinic of the Enugu State University Teaching Hospital in Enugu, Nigeria.
Patients were included if they had newly diagnosed mild to moderate
hypertension. Patients were excluded if they were taking prescription
medications for hypertension; had diabetes, nephropathy, hepatic disease,
cardiopathy, or cancer; were pregnant; smoked; or were alcoholics. Patients
were randomly assigned to 1 of 3 groups, which included a placebo group, a
group that drank hibiscus tea, and a group that took HCTZ. Each treatment was
administered once per day before breakfast for 4 weeks. The placebo contained
an extract of black currant (Ribes nigrum,
Grossulariaceae) (GlaxoSmithKline®; London, UK) that was diluted
until the solution matched the color of the hibiscus extract. A preliminary
study found that the black currant dose had no effect on blood pressure. For
each day's supply of hibiscus extract, 20 g of dried calyces, obtained from the
Ogbete Main Market in Enugu, were ground into a powder and then infused with 1
L of boiling water for 30 minutes. The extract was filtered and stored in the
refrigerator. The extract was standardized to a total anthocyanin concentration
of 10.04 mg from 20 g of calyces in 1 L. The HCTZ group took 25 mg of HCTZ
(Esidrex®; Novartis Pharmaceuticals; Basel, Switzerland). Blood
pressure, serum electrolytes, and urine electrolytes were measured at baseline;
at 1, 2, 3, and 4 weeks during the study; and 1 week after the study ended.
Data were analyzed with one-way analysis of variance and Bonferroni tests.
Eighty patients were recruited for the study, of
which 75 completed the study. Both hibiscus and HCTZ decreased systolic blood
pressure (SBP), diastolic blood pressure (DBP), and mean arterial pressure
(MAP) compared to placebo. HCTZ significantly reduced SBP by 12.9 ± 4.31 mmHg and
DBP by 9.50 ± 2.06 mmHg (P < 0.05 and P < 0.001, respectively). There was
an even greater reduction in SBP (17.08 ± 5.12 mmHg) and DBP (11.12 ± 3.12 mmHg)
with the hibiscus treatment than with HCTZ, and these measures also were
significantly lower than the placebo (P < 0.001 for both). MAP also was significantly
lower in the hibiscus and HCTZ groups than in the placebo group at the end of
the study (P < 0.001 and P < 0.01, respectively). Serum sodium and
potassium were significantly lower at the end of the study in both treatment
groups when compared to placebo (P < 0.001). In addition, serum sodium was still
significantly lower in the hibiscus group than in the placebo group 1 week after
the end of the dosing (P < 0.001), though in the HCTZ group it returned to
baseline levels. It should be noted that serum potassium was significantly
lower in the hibiscus group than in the placebo group at baseline (P <
0.001). Serum chloride increased significantly with hibiscus treatment and
decreased significantly with HCTZ treatment (P < 0.001 for both). HCTZ
resulted in a significant increase in urine sodium, potassium, and chloride
concentrations after 4 weeks (P < 0.001, P < 0.001, and P < 0.01,
respectively). The hibiscus treatment resulted in a decrease in the urine
concentration of potassium ions in weeks 2-5 (P < 0.001 for all). Again, it
should be noted that urine concentrations of sodium, potassium, and chloride
ions were lower in the hibiscus group than in the placebo group at baseline (P
< 0.01, P < 0.01, and P < 0.001, respectively).
Hibiscus extract decreased SBP, DBP, and MAP to a
greater extent than HCTZ in Nigerian patients with mild to moderate
hypertension. HCTZ decreased serum concentrations of sodium, potassium, and
chloride ions and increased urine concentrations of these ions. HCTZ is a
diuretic, and these results are in keeping with the function of HCTZ. The
patients in the hibiscus group had significantly lower baseline concentrations
of serum potassium ions and urine sodium, potassium, and chloride ions than did
patients in the placebo group. Because of this bias at baseline, it is
difficult to draw conclusions about the effect of hibiscus on these electrolytes.
Despite these discrepancies, the hibiscus treatment did reduce the serum
concentration of sodium ions and the urinary concentration of potassium ions (a
potassium-sparing effect), even a week after dosing stopped. Hibiscus does not affect
serum and urine concentrations of dissolved ions in the same way as HCTZ. Evidence
has shown that hibiscus may operate via many mechanisms and not only as a
diuretic. Previous studies have shown that hibiscus appears to act as a vasodilator
and diuretic, suppresses uptake of calcium ions, and inhibits angiotensin-converting
enzyme. The study was limited by the small sample size, lack of description of
blinding of the placebo and hibiscus groups, and the inability to blind the
HCTZ group. The authors also recommend quantifying the types and concentrations
of anthocyanins in the hibiscus extract.
—Cheryl McCutchan,
PhD
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