Hibiscus tea is a tisane or "herbal tea" consumed both hot and cold by people around the world. The drink is an infusion made from crimson or deep magenta-coloured calyces (sepals) of the Hibiscus sabdariffa flower. It is also referred to as roselle (another common name for the hibiscus flower) or rosella (Australian), flor de Jamaica in Latin America, karkadé in Jordan, Egypt and Sudan, Chai Kujarat in Iraq, Chai Torsh in Iran, gumamela in the Philippines, bissap, tsoborodo or wonjo in West Africa, sorrel in Jamaica and Trinidad and Tobago, red sorrel in the wider Caribbean, and other names in other regions, including the U.S., where it is sometimes known as simply Jamaica. Hibiscus tea has a tart, cranberry-like flavor, and sugar is often added to sweeten the beverage. The tea contains vitamin C and minerals and is used traditionally as a mild medicine. In west Sudan a white hibiscus flower is favored for its bitter taste and is not for sale, but for the use of the owners family and their guests. Hibiscus tea contains 15-30% organic acids, including citric acid, malic acid, and tartaric acid. It also contains acidic polysaccharides and flavonoid glycosides, such as cyanidin and delphinidin, that give it its characteristic deep red colour.
Latin America and the United States 
"Agua de Flor de Jamaica" (pronounced /xaˈmajka/), also called agua de Jamaica and rosa de Jamaica, is popular in Jamaica, Mexico, Central America, and parts of South America and the Caribbean. It is one of several common aguas frescas, which are inexpensive beverages typically made from fresh juices or extracts. Agua de Flor de Jamaica is usually prepared by steeping the calyces, along with ginger (in Jamaica), in boiling water, straining the mixture, pressing the calyces (to squeeze all the juice out), adding sugar, and sometimes a little rum (in Jamaica), and stirring. It is served chilled.
In Panama both the flowers and the drink are called saril (a derivative of the Jamaican word sorrel). It is prepared by picking and boiling the calyces with chopped ginger, sugar, clove, cinnamon, and nutmeg. It is traditionally drunk around Christmas and Chinese New Year, diverging from Mexico and Central America and much more in line with the Caribbean, due to the strong West Indian influence in Panamanian culture specially in Panama City and most of Panama's Atlantic coast.
Dried hibiscus calyces, often labeled Flor de Jamaica, have long been available in health food stores in the United States for making this tea, especially in California and other areas influenced by Mexican customs. Flor de Jamaica has a reputation for being a mild natural diuretic.
Africa and the Caribbean 
Karkadé (pronounced /ˈkɑrkədeɪ/ KAR-kə-day; Egyptian Arabic: كركديه, [kæɾkæˈdeː]) is served hot or chilled with ice. It is very popular in some parts of North Africa, especially in Egypt and Sudan; hibiscus from Upper Egypt and Sudan is highly prized in both countries. In Egypt and Sudan, wedding celebrations are traditionally toasted with a glass of hibiscus tea. On a typical street in downtown Cairo, one can find many vendors and open-air cafés selling the drink.
In Africa, especially the Sahel, hibiscus tea is commonly sold on the street and the dried flowers can be found in every market. Variations on the drink are popular in West Africa and parts of Central Africa. In Senegal, bissop is known as the "national drink of Senegal". Similar beverages include wanjo in The Gambia, dabileni in Mali, and zobo or tsobo in northern Nigeria. Hibiscus tea is especially popular in Sudan where it is often prepared by soaking the calyces in cold water for a few days and then straining the result. Hibiscus tea is often flavored with mint or ginger in West Africa.
In the English-speaking Caribbean, the drink, called sorrel, is made from the fresh fruit, and it is considered an integral part of Christmas celebrations. The Caribbean Development Company, a Trinidad and Tobago brewery, produces a Sorrel Shandy in which the tea is combined with beer.
In Thailand, roselle is drunk as a tea, believed to also reduce cholesterol. It can also be made into a wine, especially if combined with Chinese tea leaves, in the ratio of 4:1 by weight (1/5 Chinese tea). It is also drunk cold and sugared. The beverage is popular in Malaysia and Indonesia as well.
In Italy, the tea, known as carcadè, is usually drunk cold and often sugared with freshly squeezed lemon juice. Introduced while Eritrea was an Italian colony (from 1860 to 1941), once its use was much more widespread. In other European countries, it is often an ingredient in mixed tisanes, (especially with malva flowers or rose hips in the mix, to enhance colouring), and as such, more commonly used than recognized.
Health benefits 
Drinking hibiscus tea can lower blood pressure in people with type 2 diabetes, prehypertension, or mild hypertension. The average systolic blood pressure for diabetics drinking hibiscus tea decreased from 134.8 mmHg (17.97 kPa) at the beginning of one study to 112.7 mmHg (15.03 kPa) at the end of the study, one month later. Drinking 3 cups of hibiscus tea daily for 6 weeks reduced systolic blood pressure by 7 mm Hg in prehypertensive and mildly hypertensive participants. In those with mean systolic blood pressure over 129 mm Hg, the reduction was nearly 14 mm Hg. Hibiscus flowers contain anthocyanins, which are believed to be active antihypertensive compounds, acting as angiotensin-converting enzyme (ACE) inhibitors.
The effects of drinking hibiscus tea are comparable to blood-pressure medication. A study published in 2007 compared Hibiscus sabdariffa L. to the drug lisinopril on people with hypertension. Hibiscus "decreased blood pressure (BP) from 146.48/97.77 to 129.89/85.96 mmHg, reaching an absolute reduction of 17.14/11.97 mmHg (11.58/12.21%, p < 0.05)." Blood pressure "reductions and therapeutic effectiveness were lower than those obtained with lisinopril (p < 0.05)." The authors concluded that hibiscus "exerted important antihypertensive effectiveness with a wide margin of tolerability and safety, while it also significantly reduced plasma ACE activity and demonstrated a tendency to reduce serum sodium (Na) concentrations without modifying potassium (K) levels." They attributed the blood pressure reducing effect of hibiscus to its diuretic effect and its ability to inhibit the angiotensin-converting enzyme through the presence of anthocyanins.
A 2004 study compared the effectiveness of hibiscus to the ACE-inhibiting drug captopril. The authors found that the "obtained data confirm that the H. sabdariffa extract, standardized on 9.6mg of total anthocyanins, and captopril 50 mg/day, did not show significant differences relative to hypotensive effect, antihypertensive effectiveness, and tolerability."
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- Information about Roselle by J. Morton (1987), part of the New Crop Resource Online Program at Purdue University