Scientific Name(s): Hibiscus sabdariffa L.
Common Name(s): Hibiscus, Jamaica sorrel, Karkade, Karkadi, Red sorrel, Red tea, Rosa de Jamaica, Rosella, Roselle, Soborodo, Sour tea, Zobo drink
The leaves and calyces have been used as food and the flowers steeped for tea. Hibiscus has been used in folk medicine as a diuretic and mild laxative, as well as in treating cancer and cardiac and nerve diseases. Although information is limited, the potential for hibiscus use in treating hypertension and cancer, as well as for its lipid-lowering and renal effects, are being investigated.
In trials investigating the hypotensive effect of hibiscus, daily dosages of dry calyx 10 g (approximately anthocyanin 9.6 mg) as an infusion in water, and total anthocyanin 250 mg per dose have been used for 4 weeks. Alternatively, doses of H. sabdariffa 3.75 g/day to 2 spoonfuls or 100 mg of aqueous H. sabdariffa for a duration of 15 days to 6 weeks was identified in a 2014 meta-analysis of trials investigating blood pressure effects.
Contraindications have not been identified.
Documented adverse reactions. Avoid use.
Studies in healthy volunteers have shown altered chloroquine, acetaminophen, and diclofenac pharmacokinetics. The clinical effects of these interactions have not been evaluated.
Preparations used in clinical trials were well tolerated.
Data are limited.
- Malvaceae (mallow)
H. sabdariffa is native to Central and West Africa, but grows throughout many tropical areas. This annual herb grows to 1.5 m or higher and produces elegant red flowers. The flowers (calyx and bract portions) are collected when slightly immature. The major producing countries are Jamaica and Mexico.1, 2, 3 A related species, Hibiscus rosa-sinensis (rose of Sharon), is widely cultivated for ornamental planting.
Hibiscus has a long history of use in Africa and neighboring tropical countries for many conditions, including hypertension, liver diseases, cancer, constipation, and fever. The fleshy red calyx is used in the preparation of jams, jellies, drinks, and cold and warm teas. The plant is also widely used in Egypt, Iran, and Thailand, as well as in Western countries. Hibiscus flowers often are found as components of herbal tea mixtures2, 3, 4, 5, 6; it is a major component of the popular herbal blend Red Zinger.
A large variety of compounds have been isolated from the hibiscus plant.2 As expected from their vivid color, hibiscus flowers contain various polyphenols, including anthocyanins, proanthocyanidins, flavonols, and other pigments.2, 7, 8, 9 Oxalic, malic, citric, stearic, and tartaric acids have been identified and are, along with 15% to 28% of hibiscic or hibiscus acid (lactone of hydroxycitric acid), most likely contribute to the tartness of the herb and its teas. Roselle seed oil contains more than 25 volatile compounds, mainly unsaturated hydrocarbons, aldehydes, and alcohols.2, 5 The oil is rich in gamma tocopherol.10 The saturated fatty acids (palmitic and stearic) and unsaturated fatty acids (oleic and linoleic) contents have been described.2, 5 The seeds and flowers contain high amounts of protein and crude oil, ash, and carbohydrate. High amounts of arginine, aspartic acid, and glutamic acid were found in the protein isolated from the seed.5, 9
Uses and Pharmacology
Numerous in vitro experiments have evaluated the effects of hibiscus flower or anthocyanin extracts against various cancer cell lines. Proposed mechanisms of action focus on antioxidant activity and the ability to induce apoptosis.2, 11, 12, 13, 14, 15, 16, 17
Studies in rats have evaluated effects against liver, oral, colon, bladder, and stomach cancers.2
Clinical trials evaluating the use of hibiscus as a chemopreventive or therapeutic agent are lacking. In vitro experiments have shown apoptotic activity against human leukemia (HL-60),2, 12, 13, 14 gastric,15 and cervical17 cell lines.
Studies in hyperlipidemic mice, rats, and rabbits have evaluated the effects of dried calyx extracts on the lipid profile. Although not consistently, the experiments largely demonstrate decreases in serum cholesterol, triglycerides, and LDL, with no effect on high-density lipoprotein (HDL).2, 18, 19, 20, 21, 22, 23, 24
Clinical trials evaluating the hypolipidemic effect of hibiscus are lacking.
Experiments in animals have shown aqueous and methanol extracts of the plant calyces have hypertensive actions.2, 25, 26, 27 Suggested mechanisms of action include inhibition of angiotensin I converting enzyme,2 partial cholinergic and/or histaminic mechanisms,2 vasodilation,26 and natriuric effects.27
A number of small clinical trials evaluated the effect of aqueous calyx extracts on blood pressure.2 Methods of randomization and blinding are not clearly described in the studies. In addition, differences in baseline parameters among study groups and lack of intention-to-treat analyses limit confidence in the findings.6, 28, 29
A dose-dependent decrease in systolic and diastolic blood pressure has been demonstrated for aqueous preparations of the hibiscus calyx comparable in effect to that of captopril and lisinopril. A natriuric effect was also observed in these studies.28, 29 In an earlier trial, patients with essential, but untreated, hypertension demonstrated a decrease in blood pressure with sour tea therapy. Their hypertensive state returned on cessation of therapy.6 A systematic review and meta-analysis of randomized placebo-controlled parallel or crossover trials published through June 2014 that evaluated the effect of H. sabdariffa (sour tea) on blood pressure identified 5 trials (N = 390) that met inclusion criteria; drug-comparator trials were excluded. Doses ranged from 3.75 g/day to 2 spoonfuls or 100 mg of aqueous H. sabdariffa for a duration of 15 days to 6 weeks; 1 trial included healthy volunteers as well as patients with metabolic syndrome. Pooled estimates revealed a significant effect of sour tea on systolic blood pressure (SBP) and diastolic blood pressure (DPB), and fixed-effect meta-regression found a significant inverse relationship between baseline blood pressure and effect (P = 0.0005 for SBP and P = 0.002 for DBP). No adverse effects were observed.43
Studies in rats suggest a uricosuric effect of the calyx extract.2
Conflicting clinical data exist regarding the effect of hibiscus extracts on the excretion of uric acid.2, 30, 31 The study parameters vary with respect to dose, preparation used, and study population, making conclusions difficult. Increased urinary sodium excretion has been demonstrated in trials evaluating hypotensive effects of hibiscus extracts.2, 28, 29
Aqueous hibiscus extracts have shown inhibitory effects on the contractility of various muscle tissues, including uterine.2, 32 In other experiments, extracts have demonstrated a mild cathartic activity in rats4 in the absence of increased peristalsis, as well as stimulatory effects in frogs' abdominal/rectal tissues.2
Roselle tea extract exhibited high inhibition against porcine pancreatic alpha-amylase. Proposed uses for this inhibition include decreased glucose absorption and inhibition of HIV replication.33
In trials investigating the hypotensive effect of hibiscus, daily dosages of dry calyx 10 g (equivalent to anthocyanin 9.6 mg) as an infusion in water28 and total anthocyanin 250 mg per dose29 have been used for 4 weeks. The kinetics and urinary excretion of the anthocyanin glycosides have been studied in healthy volunteers. An estimated half-life of 2.6 hours and a maximum excretion at 1.5 to 2 hours was noted.37 Alternatively, doses of H. sabdariffa of 3.75 g/day to 2 spoonfuls or 100 mg of aqueous H. sabdariffa for a duration of 15 days to 6 weeks was identified in a 2014 meta-analysis of trials investigating blood pressure effects.43
Pregnancy / Lactation
Studies in healthy volunteers have shown altered chloroquine,39 acetaminophen,2 and diclofenac40 pharmacokinetics with concomitant consumption of hibiscus preparations. The clinical effects of these interactions have not been evaluated.
Digoxin lab assay
Hibiscus, rose hip, and hibiscus-rose hip tea has been shown to interfere with the electrochemiluminescent immunoassay method for measuring serum digoxin levels resulting in false positives. Crossreactivity was not found using the Abbott Digoxin II (MEIA) or Immulite Digoxin assays.42
Data are limited. The median lethal dose of the calyx extract in rats is estimated to be higher than 5 g/kg.2
An experiment in rats using dosages of up to 5 g/kg daily over 12 weeks found a reduction in epididymal sperm count, evidence of histological damage, and disintegration of sperm cells.2 Conversely, a study evaluating the effects of hibiscus 1 g/kg/day on cisplatin-induced reproductive toxicity found a protective effect as measured by sperm motility. The effect was attributed to an antioxidant effect.41
- Hibiscus rosa-sinensis
- rose of Sharon
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