Roselle (hibiscus)

About the plant

Roselle is a warm-climate shrub in the mallow family, usually grown as an annual. It has reddish stems, lobed leaves, and pale yellow flowers with dark crimson centers. After flowering, the fleshy red calyx—the protective cup surrounding the developing seed capsule—enlarges and becomes the main medicinal and culinary part.

Generally considered native to tropical Africa, although its precise origins remain debated, roselle is now cultivated throughout tropical and subtropical regions. It thrives in sunshine and well-drained soil, and its dried calyces are sold worldwide for vividly colored, pleasantly sour drinks.

The discovery

Long before clinical trials, communities in Africa used roselle in refreshing drinks, foods, and household remedies. It became familiar as karkade in Egypt and Sudan, bissap in West Africa, and later sorrel drinks in the Caribbean. Traditional use for urinary complaints and elevated blood pressure helped motivate laboratory studies and human trials. These studies investigate possible effects on blood-vessel function and fluid balance, but do not establish a single discoverer or prove every traditional claim.

Traditional uses

• Prepared as a cooling, thirst-quenching drink in hot climates.
• Used traditionally to support blood-pressure control.
• Taken as a mild diuretic to encourage urination.
• Used for mild digestive discomfort.

Research details

How it's used

• Use food-grade dried Hibiscus sabdariffa calyces; ornamental hibiscus plants are not interchangeable.
• A human blood-pressure trial used 1.25 g of dried calyces steeped in about 240 mL of freshly boiled water for six minutes, three times daily for six weeks. This is a studied preparation, not an established treatment dose.
• Choose unsweetened tea when possible. Extracts and capsules vary considerably and cannot be assumed equivalent to tea.
• If using it regularly for blood-pressure support, discuss it with your clinician and monitor your readings; do not change prescribed medication yourself.

Safety

• Food-level tea consumption is generally well tolerated. Stomach upset can occur, and blood-pressure lowering may cause dizziness in susceptible people.
• Avoid medicinal use during pregnancy and breastfeeding because adequate human safety data are lacking.
• Medicinal dosing in children has not been adequately studied; seek pediatric advice.
• Long-term safety of concentrated extracts is uncertain. Clinical studies are generally short, and no evidence-based maximum duration is established.

Drug interactions

• Blood-pressure medicines: additive blood-pressure lowering is possible; monitor for low readings, dizziness, or faintness.
• Diabetes medicines: additional glucose lowering is possible, although clinical interaction evidence is limited.
• Chloroquine: a small human study found reduced chloroquine exposure when taken with a hibiscus beverage; avoid combining them without medical advice.