Hibiscus

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

Medically reviewed by Drugs.com. Last updated on May 22, 2024.

Clinical Overview

Use

The leaves and calyces of hibiscus have been used as food, and the flowers are steeped for tea. Hibiscus has been used in folk medicine as a diuretic and mild laxative, as well as for treating cancer and cardiac and nerve diseases. Hibiscus has been investigated clinically for potential antihypertensive, metabolic/lipid-lowering, and renal effects. However, clinical trial data are lacking to recommend use for any indication.

Dosing

Trials investigating the hypotensive effect of hibiscus have evaluated oral daily dosages of an infusion prepared with 10 g of dry H. sabdariffa calyx in water (standardized to 9.6 mg of anthocyanin content per dose), or an herbal medicinal product prepared from H. sabdariffa dried calyx extract (standardized to 250 mg of total anthocyanins per dose); treatment duration in these studies was 4 weeks. In a 2014 systematic review and meta-analysis investigating blood pressure effects, H. sabdariffa aqueous extract dosages used included 2 "spoonfuls" daily, 100 mg daily, and 3.75 g daily for a duration of 15 days to 6 weeks.

Contraindications

Contraindications have not been identified.

Pregnancy/Lactation

Avoid use. Information regarding safety and efficacy in pregnancy and lactation is lacking.

Interactions

Studies in healthy volunteers have shown altered chloroquine, acetaminophen, and diclofenac pharmacokinetics. The clinical effects of these interactions have not been evaluated. Interactions are also possible with blood pressure–lowering agents, caffeine and caffeine-containing products, diclofenac (systemic), erlotinib, herbs with hypotensive properties, and simvastatin.

Adverse Reactions

Preparations used in clinical trials were well tolerated.

Toxicology

No data.

Scientific Family

• Malvaceae (mallow)

Botany

H. sabdariffa is native to Central and West Africa but grows throughout many tropical areas. It is an annual herb that grows to 1.5 m or more in height and produces elegant red flowers. The flowers (calyx and bract portions) are collected when slightly immature. The major producing countries are Jamaica and Mexico.(Ali 2005, Leung 1980, USDA 2021) A related species, Hibiscus rosa-sinensis (rose of Sharon), is widely cultivated for ornamental planting.

History

Hibiscus has a long history of use in Africa and in 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 widely used in Egypt, Iran, and Thailand, as well as in Western countries. Hibiscus flowers are often used as components of herbal tea mixtures,(Abu-Tarboush 1997, Ali 2005, Haji Faraji 1999, Haruna 1997, Leung 1980) and are a major component of the popular herbal tea blend Red Zinger.

Chemistry

A large variety of compounds have been isolated from the hibiscus plant.(Ali 2005) As expected from their vivid color, hibiscus flowers contain various polyphenols, including anthocyanins, proanthocyanidins, flavonols, and other pigments.(Ali 2005, Du 1973, Sayago-Ayerdi 2007, Wilkinson 1977) Oxalic, malic, citric, stearic, and tartaric acids have been identified; these, 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)(Abu-Tarboush 1997, Ali 2005) and is rich in gamma tocopherol.(Mohamed 2007) Saturated fatty acid (palmitic and stearic) and unsaturated fatty acid (oleic and linoleic) contents have been described.(Abu-Tarboush 1997, Ali 2005) The seeds and flowers contain high amounts of protein, crude oil, ash, and carbohydrate. High amounts of arginine, aspartic acid, and glutamic acid were found in the protein isolated from the seed.(Abu-Tarboush 1997, Sayago-Ayerdi 2007)

Uses and Pharmacology

Alpha-amylase inhibitory activity

In vitro data

Roselle tea extract showed high inhibition against porcine pancreatic alpha-amylase. Potential proposed uses based on this inhibition include for decreased glucose absorption and inhibition of HIV replication.(Hansawasdi 2000)

Antioxidant activity

Animal data

Protective effects of hibiscus plant extracts on induced testicular and hepatic toxicity have been demonstrated in animals; these effects are attributed to antioxidant activity.(Amin 2006, Liu 2006, Wang 2000)

Cancer

Animal and in vitro data

Numerous in vitro experiments have evaluated the effects of hibiscus flower or anthocyanin extracts on various cancer cell lines. Proposed mechanisms of action include antioxidant activity and the ability to induce apoptosis.(Chang 2005, Hou 2005, Lin 2007, Lo 2007, Olvera-García 2008, Tseng 1998, Tseng 2000)

In vitro experiments have shown apoptotic activity against human leukemia (HL-60),(Ali 2005, Chang 2005, Hou 2005, Tseng 2000) gastric,(Lin 2007), and cervical(Olvera-García 2008) cell lines.

Studies in rats have evaluated effects against liver, oral, colon, bladder, and stomach cancers.(Ali 2005)

Hypertension

Animal data

Experiments in animals show that aqueous and methanol extracts of hibiscus calyces have antihypertensive actions.(Ajay 2007, Ali 2005, Mojiminiyi 2007, Odigie 2003) Suggested mechanisms of action include inhibition of angiotensin I–converting enzyme,(Ali 2005) partial cholinergic and/or histaminic mechanisms,(Ali 2005) vasodilation,(Ajay 2007) and natriuretic effects.(Mojiminiyi 2007)

Clinical data

A number of small clinical trials evaluated the effect of aqueous calyx extracts on blood pressure.(Ali 2005) Methods of randomization and blinding were not clearly described; in addition, differences in baseline parameters among study groups and lack of intention-to-treat analyses limit confidence in the findings.(Haji Faraji 1999, Herrera-Arellano 2004, Herrera-Arellano 2007) In 2 studies by the same group of investigators, aqueous preparations of the hibiscus calyx (ie, an infusion prepared with 10 g of dry H. sabdariffa calyx in water [standardized to 9.6 mg of anthocyanin content per dose] or an herbal medicinal product prepared from H. sabdariffa dried calyx extract [standardized to 250 mg of total anthocyanins per dose] for 4 weeks) demonstrated dose-dependent decreases in systolic and diastolic blood pressure comparable with that of captopril and lisinopril. A natriuretic effect was also observed in these studies.(Herrera-Arellano 2004, Herrera-Arellano 2007) In an earlier trial, patients with essential but untreated hypertension experienced a decrease in blood pressure with sour tea therapy, with a return to their hypertensive state upon cessation of therapy.(Haji Faraji 1999) A systematic review and meta-analysis of 5 randomized placebo-controlled parallel or crossover trials (N=390) published through June 2014 evaluated the effect of H. sabdariffa (sour tea) on blood pressure; drug-comparator trials were excluded. Dosages included 2 "spoonfuls" daily, 100 mg daily, and 3.75 g daily of aqueous H. sabdariffa for a duration of 15 days to 6 weeks; one trial included healthy volunteers as well as patients with metabolic syndrome. Pooled estimates revealed a significant effect of sour tea on systolic blood pressure and diastolic blood pressure, and fixed-effect meta-regression found a significant inverse relationship between baseline blood pressure and effect (P=0.0005 for systolic blood pressure and P=0.002 for diastolic blood pressure). No adverse effects were observed.(Serban 2015)

The acute impact of H. sabdariffa calyces (HSC) extract on blood pressure, vascular function, and other cardiometabolic risk markers was assessed in a randomized, controlled, single-blind, 2-meal crossover study. Men with cardiovascular disease risk (N=25) were randomized to consume either 250 mL of an aqueous extract of HSC or water with breakfast. Acute consumption of the aqueous extract of HSC caused a significant increase in flow-mediated dilatation (P<0.001) and a nonsignificant decrease in systolic blood pressure and diastolic blood pressure. The investigators concluded that the extract of HSC improved postprandial vascular function and that it may be a useful dietary strategy to reduce endothelial dysfunction and cardiovascular disease risk; however, these findings require confirmation.(Abubakar 2019)

Metabolic syndrome/Cardiovascular disease

Clinical data

A systematic review and meta-analysis of 9 randomized controlled trials (N=503) assessed the efficacy of H. sabdariffa (various dosages) in regulating blood lipids in patients with metabolic syndrome and related disorders. Compared with the control group, H. sabdariffa supplementation reduced total cholesterol (weighted mean difference [WMD]=−14.66 [95% CI, −18.22 to −11.1]; P=0; I²=46.9%) and low-density lipoprotein (LDL) cholesterol (WMD=−9.46 [95% CI, −14.93 to −3.99]; P=0.001; I²=50.1%) but did not effectively reduce triglycerides (WMD=−0.77 [95% CI, −7.87 to 6.33]; P=0.832; I²=0%). While results suggest that H. sabdariffa supplementation in patients with metabolic diseases is associated with beneficial cholesterol-lowering effects, more high-quality clinical trials are needed to confirm these results.(Zhang 2020)

Another systematic review and meta-analysis of randomized clinical trials evaluated the antidiabetic activity of various dosages of H. sabdariffa. Five outcome measures were assessed, including fasting plasma glucose (FPG), total cholesterol, high-density lipoprotein (HDL), LDL, and triglycerides. Overall pooled results showed a significant reduction in FPG (WMD=−3.964 mg/dL [95% CI, −6.227 to −1.702]; P=0.001) and LDL (WMD=−7.843 mg/dL [95% CI, −14.337 to −1.35]; P=0.018) with hibiscus compared to placebo. However, the pooled estimate showed no statistically significant change in total cholesterol (WMD=−30.382 mg/dL [95% CI, −66.752 to 5.989]; P=0.102), HDL (WMD=0.074 mg/dL [95% CI, −1.986 to 2.135]; P=0.944), or triglycerides (WMD=−9.05 mg/dL [95% CI, −30.819 to 12.719]; P=0.102) compared with placebo. While results suggest that H. sabdariffa has antidiabetic activity, these findings, as well as clarity regarding lipid-lowering effects of H. sabdariffa require further study in larger randomized controlled trials.(Bule 2020)

A systematic review and meta‐analysis of 7 randomized controlled clinical trials (N=362) examined the effects of various dosages of sour tea on cardiovascular disease risk factors, including lipid profiles, FPG, and blood pressure. Pooled effect size demonstrated that sour tea consumption significantly reduces FPG (mean difference vs control, −3.67 mg/dL [95% CI, −7.07 to −0.27]; P=0.03; I²=37%), systolic blood pressure (−4.71 mm Hg [95% CI, −7.87 to −1.55]; P=0.003; I²=53%), and diastolic blood pressure (−4.08 mm Hg [95% CI, −6.48 to −1.67]; P=0.0009; I²=14%). No significant effects on triacylglycerol, total cholesterol, or HDL cholesterol were observed following sour tea consumption; however, a trend toward a significant reduction was found in LDL cholesterol serum concentrations (P=0.08). Results suggest that sour tea consumption could have beneficial effects in controlling glycemic status and blood pressure in adults.(Najafpour Boushehri 2020)

Reports have also shown that H. sabdariffa–derived bioactive compounds may be potent in the treatment of obesity, with an evident reduction in body weight, inhibition of lipid accumulation, and suppression of adipogenesis.(Ojulari 2019)

Renal system

Animal data

Studies in rats suggest a uricosuric effect of the calyx extract.(Ali 2005)

Clinical data

Clinical data are conflicting regarding the effect of hibiscus extracts on the excretion of uric acid.(Ali 2005, Kirdpon 1994, Prasongwatana 2008) 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.(Ali 2005, Herrera-Arellano 2004, Herrera-Arellano 2007)

Smooth muscle effects

Animal and in vitro data

Aqueous hibiscus extracts have shown inhibitory effects on the contractility of various muscle tissues, including uterine,(Ali 2005, Fouda 2007) as well as stimulatory effects in frog abdominal/rectal tissues.(Ali 2005) In other experiments, H. sabdariffa extracts have demonstrated a mild cathartic activity (ie, increase in number of wet feces) in rats in the absence of increased peristalsis, possibly due to the extract's saponin-like compounds.(Haruna 1997)

Wound healing

Animal data

In an excision wound model in rats, a petroleum ether extract of hibiscus and hibiscus mucilage formulated into wound-dressing sponges demonstrated increased healing and decreased TNF-alpha.(Bakr 2021)

Dosing

Trials investigating the hypotensive effect of hibiscus have evaluated oral daily dosages of an infusion prepared with 10 g of dry H. sabdariffa calyx in water (standardized to 9.6 mg of anthocyanin content per dose),(Herrera-Arellano 2004) or an herbal medicinal product prepared from H. sabdariffa dried calyx extract (standardized to 250 mg of total anthocyanins per dose)(Herrera-Arellano 2007); treatment duration in these studies was 4 weeks. In a 2014 systematic review and meta-analysis investigating blood pressure effects, H. sabdariffa aqueous extract dosages used included 2 "spoonfuls" daily, 100 mg daily, and 3.75 g daily for a duration of 15 days to 6 weeks.(Serban 2015)

Systematic reviews and meta-analyses of randomized controlled trials have examined various hibiscus formulations and dosages for effects on metabolic syndrome/cardiovascular disease risk factors.(Bule 2020, Najafpour Boushehri 2020, Zhang 2020)

Various dosages of H. sabdariffa extract for various conditions have been summarized in a phytochemistry and therapeutic uses review.(Riaz 2018)

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 were noted.(Frank 2005)

Pregnancy / Lactation

Avoid use. Information regarding safety and efficacy in pregnancy and lactation is lacking.(Ali 2005, Ernst 2002, Fouda 2007)

Interactions

Studies in healthy volunteers have shown altered chloroquine,(Mahmoud 1994) acetaminophen,(Ali 2005) and diclofenac(Fakeye 2007) pharmacokinetics with concomitant consumption of hibiscus preparations. The clinical effects of these interactions have not been evaluated.

Hibiscus tea, rose hip tea, and hibiscus/rose hip tea have been shown to interfere with the electrochemiluminescent immunoassay method for measuring serum digoxin levels, resulting in false positives. Cross-reactivity was not found using the Abbott Digoxin II (MEIA) or Immulite Digoxin assays.(Fresz 2014)

Blood pressure–lowering agents: Herbs with hypotensive properties may enhance the hypotensive effect of blood pressure–lowering agents. Monitor therapy.(Ernst 2003, Richard 2005)

Caffeine and caffeine-containing products: Hibiscus may increase the serum concentration of caffeine and caffeine-containing products. No action needed.(Johnson 2013, Showande 2019)

Chloroquine: Hibiscus may decrease the serum concentration of chloroquine. Monitor therapy.(Mahmoud 1994)

Diclofenac (systemic): Hibiscus may increase the serum concentration of diclofenac (systemic). No action needed.(Fakeye 2007, Johnson 2013)

Erlotinib: Hibiscus may enhance the adverse/toxic effect of erlotinib. Monitor therapy.(Jacquin-Porretaz 2017, Johnson 2013, Showande 2017)

Herbs (hypotensive properties): Herbs with hypotensive properties may enhance the adverse/toxic effect of other herbs with hypotensive properties. Excessive blood pressure lowering may manifest. Monitor therapy.(Ernst 2003, Richard 2005)

Simvastatin: Hibiscus may decrease the serum concentration of simvastatin. No action needed.(Showande 2017)

Adverse Reactions

Research reveals little information regarding adverse reactions with the use of hibiscus. Preparations used in clinical trials were well tolerated.(Ali 2005, Herrera-Arellano 2004, Zhang 2020)

Toxicology

Data are limited. The median lethal dose of hibiscus calyx extract in rats is estimated to be higher than 5 g/kg.(Ali 2005)

A rat experiment using H. sabdariffa calyx extract dosages of up to 4.6 g/kg daily over 12 weeks found a reduction in epididymal sperm count, evidence of histological damage, and disintegration of sperm cells.(Ali 2005) 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. This effect was attributed to antioxidant activity.(Amin 2005)

Index Terms

• Hibiscus rosa-sinensis
• Rose of Sharon

References

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