Hibiscus (Hibiscus sabdariffa) and Cardiovascular / heart health: evidence and sources

Introduction Hypertension is a common global health problem with significant mortality and morbidity. Hibiscus sabdariffa is a plant known in many countries and is consumed as hot and cold drinks In addition to its use in folk medicine; it has been suggested as treatment for many conditions including hypertension. Objectives The objectives of this review were to examine the evidence of effectiveness and safety of hibiscus in the treatment of hypertension. Methods We searched several medical databases (MEDLINE, EMBASE, CINAHL, Cochrane Central Register of Controlled Trials, and the specialized register of the Cochrane Hypertension Group and the general engine Google) to January 2009. We included randomized controlled trials that had examined Hibiscus's effectiveness and safety in the treatment of primary hypertension in adults. Two authors independently selected the trials for the review, extracted the data, and critically appraised the included studies. Results Four trials, with a total of 390 patients, met our inclusion criteria. Two studies compared Hibiscus sabdariffa to black tea; one study compared it to captopril and one to lisinopril. The studies found that Hibiscus had greater blood pressure reduction than tea but less than the ACE-inhibitors. However, all studies, except one, were short term and of poor quality with a Jadad scoring of Conclusion The four randomized controlled studies identified in this review do not provide reliable evidence to support recommending Hibiscus sabdariffa for the treatment of primary hypertension in adults.

The effectiveness of Hibiscus sabdariffa L. (HS) in the treatment of risk factors associated with cardiovascular disease is assessed in this review by taking a comprehensive approach to interpreting the randomized clinical trial (RCT) results in the context of the available ethnomedical, phytochemical, pharmacological, and safety and toxicity information. HS decoctions and infusions of calyxes, and on occasion leaves, are used in at least 10 countries worldwide in the treatment of hypertension and hyperlipidemia with no reported adverse events or side effects. HS extracts have a low degree of toxicity with a LD50 ranging from 2,000 to over 5,000mg/kg/day. There is no evidence of hepatic or renal toxicity as the result of HS extract consumption, except for possible adverse hepatic effects at high doses. There is evidence that HS acts as a diuretic, however in most cases the extract did not significantly influence electrolyte levels. Animal studies have consistently shown that consumption of HS extract reduces blood pressure in a dose dependent manner. In RCTs, the daily consumption of a tea or extract produced from HS calyxes significantly lowered systolic blood pressure (SBP) and diastolic blood pressure (DBP) in adults with pre to moderate essential hypertension and type 2 diabetes. In addition, HS tea was as effective at lowering blood pressure as the commonly used blood pressure medication Captropril, but less effective than Lisinopril. Total cholesterol, low-density lipoprotein cholesterol (LDL-C), and triglycerides were lowered in the majority of normolipidemic, hyperlipidemic, and diabetic animal models, whereas high-density lipoprotein cholesterol (HDL-C) was generally not affected by the consumption of HS extract. Over half of the RCTs showed that daily consumption of HS tea or extracts had favorable influence on lipid profiles including reduced total cholesterol, LDL-C, triglycerides, as well as increased HDL-C. Anthocyanins found in abundance in HS calyxes are generally considered the phytochemicals responsible for the antihypertensive and hypocholesterolemic effects, however evidence has also been provided for the role of polyphenols and hibiscus acid. A number of potential mechanisms have been proposed to explain the hypotensive and anticholesterol effects, but the most common explanation is the antioxidant effects of the anthocyanins inhibition of LDL-C oxidation, which impedes atherosclerosis, an important cardiovascular risk factor. This comprehensive body of evidence suggests that extracts of HS are promising as a treatment of hypertension and hyperlipidemia, however more high quality animal and human studies informed by actual therapeutic practices are needed to provide recommendations for use that have the potential for widespread public health benefit.

Polyphenols from Hibiscus sabdariffa calices were administered to patients with metabolic syndrome (125 mg/kg/day for 4 wk, n = 31) and spontaneously hypertensive rats (125 or 60 mg/kg in a single dose or daily for 1 wk, n = 8 for each experimental group). The H. sabdariffa extract improved metabolism, displayed potent anti-inflammatory and antioxidant activities, and significantly reduced blood pressure in both humans and rats. Diuresis and inhibition of the angiotensin I-converting enzyme were found to be less important mechanisms than those related to the antioxidant, anti-inflammatory, and endothelium-dependent effects to explain the beneficial actions. Notably, polyphenols induced a favorable endothelial response that should be considered in the management of metabolic cardiovascular risks.

Hibiscus sabdariffa L. (local names: bissap, karkade) and Combretum micranthum (kinkeliba) are widely known in traditional medicines and popular beliefs for their antihypertensive effect. This study assessed the clinical effectiveness of these two plants in the galenic forms of tablet and brew (decoction) in noncomplicated hypertensive patients. In total, 219 hypertensive patients with systolic blood pressure (SBP) between 140 and 180 mmHg and/or diastolic blood pressure (DBP) between 90 and 110 mmHg, without cardiovascular or renal complications, were involved in a multicentric randomized clinical trial in Senegal comparing five treatment regimens: bissap tablets (2 × 375 mg/day), bissap brew (10 g of calyx/day), kinkeliba tablets (2 × 200 mg/day), kinkeliba brew (10 g of leaves/day), and captopril (2 × 50 mg/day) as control. During the 6 months' follow-up, a significant and equivalent decrease of SBP was observed with the herbal drug approach (-19.5 ± 16.1 mmHg, p < 0.001) and control group (-19.7 ± 16.7, p < 0.001). Regarding the galenic forms, the brews tended to be slightly more effective than tablets (reduction of SBP: -20.7 ± 15.1 mmHg vs -18.7 ± 16.7). The rates of clinically significant effectiveness (decrease in SBP ≥ 10 mmHg) were 75%, 67%, and 65% with bissap, kinkeliba, and captopril, respectively. After 6 months, target blood pressure of <140/90 mmHg was attained by 49% of patients with bissap, 51% with kinkeliba and 40% with captopril. Bissap and kinkeliba appeared, at doses utilized, to be as effective as captopril over the 6 months' follow-up. In subsequent studies, brews might be started with a lower dosage.

Ethnopharmacological relevance Prevention of cardiovascular disease by modifying its major risk factors, including serum cholesterol levels, is an important strategy. Hibiscus sabdariffa L. has been promoted for reducing cholesterol levels, but its reported impact on cholesterol levels has been inconsistent. The study aimed to assess systematically the evidence and quality of current research on the effect of Hibiscus sabdariffa L. on blood lipids and its adverse effects. Materials and methods Electronic databases were searched up to June 2013 for relevant randomised controlled trials (RCTs). Journals and conference proceedings were also searched. The quality of the selected trials was assessed using the Cochrane Risk of Bias Assessment Tool. The efficacy results of similar studies were pooled if they used the same comparator. Outcomes examined were levels of total cholesterol, high density lipoprotein cholesterol, low density lipoprotein cholesterol and triglycerides. Results Six studies involving 474 subjects met our inclusion criteria. These studies varied in terms of the types of interventions, comparators used, and duration of trials. Overall, Hibiscus sabdariffa L. did not produce any significant effect on any of the outcomes examined, when compared with placebo, black tea or diet. With short-term use it is well tolerated. Conclusions The available evidence from RCTs does not support the efficacy of Hibiscus sabdariffa L. in lowering serum lipids. Further rigorously designed trials with larger sample sizes are warranted to confirm the effects of HS on serum lipids.

Metabolic syndrome (MS) is an obesity-associated collection of disorders, each of which contributes to cardiovascular risk. For patients with MS, it is difficult to follow a diet/exercise regime that would improve their symptoms. Therefore, the investigation of agents that may deal with its more serious aspects is an important medical field for research. Numerous experimental studies have confirmed the important role of medicinal plants or their active components in the prevention and treatment, and in lowering risk factors of MS. As oxidative stress and inflammation are involved in the association between obesity, insulin resistance (IR) and hypertension, antioxidant and anti-inflammatory plant components like polyphenols might be useful as a treatment for MS. The aqueous extract of Hibiscus Sabdariffa L (HSE), rich in several polyphenols, is commonly and effectively used in native medicines against hypertension, diabetes and liver disorders. HSE has also shown therapeutic promise in the prevention of MS in patients, probably due to its polyphenol content. Curcumins, derived from the spice turmeric, and resveratrol, polyphenols found in grapes and red wine respectively, in addition to their antioxidant and anti-inflammatory properties, inhibit preadipocyte proliferation, de novo lipogenesis and fat accumulation in liver. Thus, due to their efficacy in the regulation of multiple targets, polyphenols have received considerable interest as potential therapeutic agents for the prevention and treatment of MS. This review discusses the therapeutic use of HSE, as well as curcumin and resveratrol, in the context of obesity as an initiator of insulin resistance and hypertension, the two main features of MS, together with the underlying mechanisms of action.