Calyx, flower, fruit, leaf, seed. Hibiscus (roselle) tea is commonly sold as "flowers", but actually contains the calyx (flower casing).
This section is a list of chemical entities identified in this dietary supplement to possess pharmacological activity. This list does not imply that other, yet unidentified, constituents do not influence the pharmacological activity of this dietary supplement nor does it imply that any one constituent possesses greater influence on the overall pharmacological effect of this dietary supplement.
Up to 30% plant acids, including hibiscic, citric, malic, protocatechuic and tartaric acids; flavonoids gossypetine, hibiscin, hibiscetine and sabdaretine (the calyx contains a reported 1.5% anthocyanins);(
1) pectin; minerals such as calcium, phosphorus, iron and malic acid; phytosterol oils (in seeds), including sitosterol, campesterol, stigmasterol, 5-avenasterol, and cholesterol;(
2) polysaccharides, including arabinans and arabinogalactan.
Hibiscus sabdariffa L., or commonly known as roselle or hibiscus, is a member of the Malvaceae family. It is an annual, grows to 5-7 feet in height, and has narrow, lobed leaves that are reddish green in color. Roselle grows native from India to Malaysia, but is now found in many parts of the world. There are more than 300 species of hibiscus, growing in both tropical and subtropical regions. African slaves reportedly brought the seeds of hibiscus to the New World.
Today, the red calyces are available commercially from many countries, including Thailand, Sudan, China, Mexico, and various other smaller producing nations including Egypt, Senegal, Tanzania, Mali, and Jamaica. Most varieties of hibiscus are used as ornamental plants, but the swollen red calyces of hibiscus are dried and exported to Europe, Australia and the United States, where they are used as teas, food coloring agents and other culinary uses.(3) In parts of Africa, the dried flowers are commonly sold and the calyces used to make a sweetened tea that is commonly sold on the streets. In the Caribbean, a popular drink is made from the fresh fruit, especially at Christmas time. In China the seeds are often used for the oils (sitosterol and others).
Many cultures around the world enjoy hibiscus in traditional foods, such as stews, jams and jellies, iced drinks, ice-cream, tarts, pies, teas, syrups, relishes and sauces. Hibiscus also contains high quantities of pectin (up to 3.19%), so it is not necessary to add pectin to make jelly from this plant.(4) Some countries are even looking into using hibiscus as a source of pectin in the fruit preserving industry. The young, tender leaves and stalks are eaten as salad and as a seasoning in curries. The seeds have also been used as an aphrodisiac and coffee substitute.
Hibiscus is also a source of the red beverage known as “karkade”, a tart, bright-red beverage that can be served hot or chilled with ice. It is very popular in some parts of the Middle East and Northern Africa. This drink was reported to have been consumed in ancient Egypt and was a preferred drink of pharaohs. In Egypt and the Sudan, wedding celebrations are traditionally toasted with a glass of karkade.
Interactions and Depletions
As a tea by infusion, use ½ to 1 teaspoonful of the dried calyx in a cup of boiling water. Some dried calyces may need boiling (a decoction) instead of steeping.
As a tea by infusion, use ½ to 1 teaspoonful of the dried calyx in a cup of boiling water. Some dried calyces may need boiling (a decoction) instead of steeping.
*Standardization represents the complete body of information and controls that serve to enhance the batch to batch consistency of a botanical product, including but not limited to the presence of a marker compound at a defined level or within a defined range.
There are no standardized dosages of hibiscus at this time.
Frequently Reported Uses
Other Reported Uses
- Antibacterial/antifungal
- Antispasmodic
- Appetite suppressant
- Cholesterol-lowering
- Colds
- Diuretic
- Immune modulation
- Mucolytic
- Pain/fever
- Radio-contrast agent
Extracts of hibiscus have not been reported to be toxic in recommended dosages.(
5) Some individuals may experience GI upset, such as nausea and vomiting. In a laboratory animal study, the LD50 of H. sabdariffa calyx extract in rats was found to be above 5000 mg/kg, indicating low toxicity.(
6)
If pregnant or nursing, consult a physician before use.
Do not use in children under 2 years of age unless recommended by a physician.
The pharmacological actions of the hibiscus calyx extracts include powerful in vitro and in vivo antioxidant activity.(7) In rats and rabbits, the extract showed anti-hypercholesterolaemic, antihypertensive, antinociceptive and antipyretic activity, but not anti-inflammatory activity.(8) In laboratory and human studies, antihypertensive action has been demonstrated.(9) The effects of the calyx extracts on smooth muscles in vitro are variable, but they mostly inhibit the tone of the isolated muscles. Oil extracted from the plant's seeds has been reported to have an inhibitory effect on certain bacteria and fungi in vitro.
Hibiscus does contain some phytochemicals with reported benefits in humans, although they have not been studied as isolated from Hibiscus sabdariff. Phytosterols, such as those found in hibiscus, have been reported to have immune modulating function, cholesterol lowering activity and aid in general health during cancer.(10),
Another phytochemical, arabinogalactan, is a polysaccharide found in many plants including hibiscus. Arabinogalactan has been reported to have immune modulating activity and is used as a supplement in cancer treatments and other conditions needing immune support.(11),(12)
Antibacterial Effects
An in vitro study reported the inhibitory effect of hibiscus calyx and protocatechuic acid, a compound derived from hibiscus calyx, on the growth of methicillin-resistant Staphylococcus aureus, Klebsiella pneumoniae, Pseudomonas aeruginosa and Acinetobacter baumannii.(13) The growth of all test bacterial pathogens were effectively inhibited by both The data from inhibition zone and minimum inhibitory concentration (MIC) values showed that both hibiscus calyx extract and the protocatechuic acid inhibited effectively the growth of all test bacterial pathogens, with heat treatment and without. The antibacterial activity of the isolated protocatechuic acid was statistically significantly greater than the hibiscus calyx, and was concentration dependent in both broth testing and human plasma. However, protocatechuic acid was less inhibitory in human plasma than in broth. The authors concluded that hibiscus calyx and isolated protocatechuic acid may be useful as clinical antibacterial agents based on their lower MIC values, heat tolerance and concentration dependent antibacterial activity.
Antihypertensive Effects
A controlled, randomized clinical trial investigated the antihypertensive effectiveness and tolerability of a standardized extract from Hibiscus sabdariffa with the commonly prescribed ACE-inhibitor, captopril.(14) Patients diagnosed with and without hypertension (39 with and 36 without, aged 30 to 80 years) were included in the 4-week study. Patients were administered an oral infusion of H. sabdariffa (10 gm dried calyx, standardized to 9.6 mg anthocyanins) daily before breakfast, or captopril 25 mg twice a day, for 4 weeks. Results reported that the extract of hibiscus decreased the systolic blood pressure (BP) from 139.05 to 123.73mm Hg and the diastolic BP from 90.81 to 79.52mm Hg. When the study concluded, there were no significant differences between the BP of both groups, and tolerability (side effects) was similar (100%). Excretion of sodium and fluid occurred in all patients receiving the hibiscus extract and the captopril (natriuresis). The authors concluded that the data supported that the H. sabdariffa extract, standardized on 9.6mg of total anthocyanins, and captopril 50 mg/day, did not report significant differences in hypotensive effects and tolerability of the two agents.
Another randomized, placebo-controlled human trial investigated the antihypertensive effects of hibiscus tea (sour tea).(15) 31 patients with essential hypertension received hibiscus tea and 23 clinically similar patients received placebo. Both systolic and diastolic blood pressures (BPs) were monitored for 15 days during the trial. Results after 12 days of treatment reported a statistically significant lowering of BPs in the group receiving hibiscus tea (11.2% systolic lowering and 10.7% diastolic lowering). Of interest is that three days after stopping the therapy with hibiscus tea, systolic blood pressure was elevated by 7.9%, and diastolic pressure was elevated by 5.6% in the experimental and control groups. Results from another study once again revealed that hibiscus was effective in reducing blood pressure in pre to mildly hypertensive adults.(16)
Antioxidant Effects
Hibiscus contains anthocyanins (Greek. anthos = Flower, kyáneos = purple). The anthocyanins themselves are subdivided into the anthocyanidine aglycones and the anthocyanin glycosides. Anthocyanins, along with anthocyanidins and proanthocyanidins, are the water-soluble flavonoid pigments (blue, purple, violet and red colors) found in fruits and vegetables, such as grapes, cherries, blueberries, blackberries, strawberries, pomegranates, red bell peppers, and purple cauliflower and eggplant. In flowers, anthocyanins help attract pollinators, and in fruits, the colorful skins help to attract animals, which eat the fruits and disperse the seeds.
In photosynthetic tissues, such as leaves, anthocyanins have been reported to have "sunscreen" activity, protecting cells from photo-damage by absorbing UV and blue-green light during periods of high light stress, such as high light along with cold or drought. Anthocyanins act as powerful antioxidants, helping to protect the plant during stress.
The human consumption of diets rich in these "bio-flavanoids", such as anthocyanins, has been reported to have positive physiological effects on the human body, including cardiovascular health, chronic inflammation, bone/joint health, ocular health, cancer prevention and therapy, hypercholesterolemia prevention and therapy, gastrointestinal health and liver diseases.(17),(18),(19),(20),(21),(22),(23)
A laboratory animal study found that hibiscus had hypolipidemic and antioxidant effects when tested against LDL oxidation.(24) Water extracts of the dried calyx of hibiscus were administered at doses of 500 and 1,000 mg/kg together with continuous cholesterol feeding to hypercholesterolemic rats for 6 weeks. With the two dosages, results were a significant decrease in serum cholesterol levels by 22% and 26%, respectively, serum triglycerides levels were lowered by 33% and 28%, respectively, serum LDL levels were also lowered by 22% and 32%, respectively, without affecting serum HDL levels. Another laboratory animal study reported similar benefits on hypercholesterolemic rabbits.(25) Animals fed hibiscus extracts along with various diets to induce hypercholesterolemia had lower incidence of atherosclerosis and hyperlipidemia than animals fed the diets alone, suggesting anti-aterosclerotic activity of hibiscus tea.
A laboratory animal study was conducted to evaluate the protective effects of hibiscus against cisplatin-induced reproductive toxicity in rats.(26) An ethanol extract of hibiscus (1g/kg/day) was given orally to rats for 26 days (beginning 21 days before a single intraperitoneal cisplatin injection). The extract of hibiscus reduced the extent of cisplatin-induced sperm abnormality and enhanced sperm motility. The hibiscus extract increased the activities of testicular antioxidant enzymes and restored sperm motility of cisplatin-treated rats. The authors concluded that extracts of H. sabdariffa (roselle/ hibiscus) had potent antioxidant activity, helping decrease the negative side effects of a cisplatin dose.
Radio-contrast Agent
A human study evaluated the efficacy of hibiscus flower tea (RFT) as an oral negative contrast agent for magnetic resonance cholangiopancreatography (MRCP).(27) An infusion of 4,000 gm of dried hibiscus tea was prepared in 480 ml of hot water. RFT was administered orally and then a qualitative analysis was made by evaluation of the visibility of the biliary system. Quantitative comparison was performed by comparing the contrast-to-noise ratio between each part of the biliary system with the stomach and duodenum. RFT effectively reduced signal intensity of the stomach and duodenum, with a statistically significant improvement in the visibility of the common bile duct, the ampulla, and the main pancreatic duct, with contrast-to-noise ratios all statistically significantly improved. The authors concluded that hibiscus flower tea might be a very efficient oral negative contrast agent that is natural, safe, inexpensive and palatable for oral administration.