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Hibiscus (Karkadé) for the Treatment of Hypertension

Contributed by M. Mohsen Ibrahim, MD
Saturday, 21 January 2017

President's Message

Hibiscus (Karkadé) for the Treatment of Hypertension


In Egypt, there is a common belief among the public whether of low or upper class that drinking Hibiscus infusion, known as Karkadé, is useful for high blood pressure. The idea is that Karkadé  can replace antihypertensive drugs for treating hypertension. Besides, being cheap, readily available- common source is Aswan area, it is without side effects. It was my personal feeling that this is mere nonsense and I never believed in herbal or folkloric medicine. I always criticized my patients if they talked about Karkadé as a treatment for their high blood pressure.

However, few days ago, I was approached by a drug company specialized in natural and herbal medicines. They asked me to study the effect of their product which is a hibiscus derivative for treating patients with mild hypertension. I immediately rejected the idea and stated this type of medication is a sort of quacks and folkloric medicine that is popular among lay people common in developing and poor countries. I said frankly that this type of research will not be approved if submitted to our medical research ethics committee, which I chair at Cairo University.

In an effort to convince me with the idea, the company representatives provided me with a number of publications, some in critically reviewed journals that address the value of hibiscus in lowering high blood pressure. I began reading for the first time about the scientific basis and clinical trials discussing hibiscus in hypertension. Also, I searched the internet for more information.

Hibiscus is a bushy annual plant, parts of the flower are used to make the popular drink Karkadé in Egypt. There are more than 300 species of hibiscus around the world. One of them is Hibiscus Sabdariffa (HS). The main constituents of HS are organic acids, anthocyanins, polysaccharides, flavonoid and other glucosides. Anthocyanins found in abundance in HS calyxes generally considered the phytochemicals responsible for the antihypertensive effects.

HS decoction and infusion of calyxes and on occasion leaves are used in at least 10 countries worldwide in the treatment of hypertension with no reported adverse events or side effects except for possible adverse hepatic effects at high doses. In a recent meta-analysis (2015) five randomized controlled trials were selected, 390 participants were randomized, 225 were allocated to HS supplementation and 165 to the control group. Studies were published between 1999 and 2013 and were conducted in the USA, Mexico and Iran. HS extract powder was compared vs black tea, diet and drugs (captopril and lisinopril). In many trials, collected material for HS flowers was dried and then ground to obtain products of < 2 mm, packed in paper envelopes, which are added to water to produce sour tea. This meta-analysis showed a significant effect of HS in lowering both systolic and diastolic blood pressure. The effect of HS was greater than black tea but less than ACE inhibitors. Comparing HS extract (250 mg of anthocyanin dose) with lisinopril (10 mg) in patients stage 1 or 2 hypertension. HS reduced blood pressure by 17.1/11.9 mmHg compared with lisinopril 23.3/15.3 mmHg. However, analyses of results from various clinical studies suggest that there is not enough evidence to draw strong conclusions about the effects of HS in reducing high blood pressure. The effectiveness rating for HS based on scientific evidence is possible effective for high blood pressure. Current trials of HS effects in reducing high blood pressure were poor except for one which compared HS to ACE inhibitors and not to placebo.

The limitations of reported trials include the small number of participants, short duration of follow-up, optimal dose is not identified, lack of standardization of the amount and the conditions for preparation of HS (infusion, decoction, and extractions), and lack of attention to adverse effects of HS. Furthermore, the control groups were different in studies, e.g. black tea, green tea, placebo and drugs. Blood pressure lowering was different in various populations.

The exact mechanisms of hypotensive action of HS are not known. Analyzing all flavonoids in HS extracts, quercetin has been shown the most powerful antihypertensive agent through vasodilatation. Another components of HS are inhibitors of ACE activity. HS is rich in polyphenolic antioxidants which improve endothelial function and decrease blood pressure through regulating NO bioavailability. Anthocyanins found in abundance in HS calyxes are generally considered the phytochemicals responsible for the antihypertensive effects.

Different studies have reported HS activity on the cardiovascular system, both an ACE inhibitory effect and angioprotective activity. A relaxing activity on the aortic rings and a hypotensive dose dependent effect on anaesthetized cats and rats were observed. In addition HS has a diuretic effect, which might be responsible for the blood pressure lowering action.


Conclusion

According to available scientific evidence Hibiscus is possibly effective for high blood pressure. Majority of current trails carried to test Hibiscus effectiveness are poor. Further well-designed trials are necessary before recommending Karkadé for high blood pressure. Dose finding studies and controlled randomized trials comparing Hibiscus extracts with placebo and established antihypertensive drugs are needed to be carried on a larger number of patients and for a relatively long periods.

President of the Egyptian Hypertension Society

M. Mohsen Ibrahim, MD

Prof. of Cardiology- Cairo University



References

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