Rhubarb

Information
Application
Notes
References

Photo: Sertürner Bildarchiv

Botanical name

Rheum palmatum L. - Medicinal rhubarb
Rheum officinale Baill. - Chinese rhubarb

Family

Polygonaceae

Common name

Pie plant, Siberian rhubarb, Tibetan rhubarb, Ornamental rhubarb, Turkey rhubarb

Information about the plant

Medicinal rhubarb is native to the mountains of northeastern Tibet and northwestern China, while Chinese rhubarb originates from southeastern Tibet, southwestern China, and Myanmar. Both species were introduced to Europe via India in the 12th century. They are now cultivated as ornamental perennials and medicinal plants.

During its spread to the west, it carried the Persian name "rêwend" (= rhubarb species), which became "rhêon" in Greek and rheum" in Latin. "Rhâ" is the ancient name of the river Volga. It is believed that the plant was either cultivated there or exported via the Volga. From the medieval Latin "ra-", connected with the Latin "barbarus" (= foreign, strange), the name "rhubarb" developed. The species epithet palmatum refers to the palm-shaped leaves of the plant, while officinalis suggests that this is an old medicinal plant, as the "officina" is the sales room of a pharmacy and “officinalis” means commonly used in the pharmacy.

Medicinal rhubarb is quite similar to garden rhubarb, whose stems are often eaten cooked as a compote. Its large leaves are palmately lobed, with a rough upper surface, and the petioles are almost round. The leafy scapes rise up to 1.50m above the foliage and bear numerous small pink flowers arranged in dense panicles. Chinese rhubarb has rounded to kidney-shaped leaves, and the flowers are greenish. The flowering period is from May to June.

Medicinally used parts of plants (herbal drug)

The dried underground parts are used (Rhei radix). The drug consists of the turnip-shaped root, often split and sold with the outer bark and lateral roots removed.

The commercially available drug comes from China and India.

Constituents of the herbal drug

Rhubarb root contains anthranoids (hydroxyanthracene derivatives, “anthraquinones”), mainly glycosides of rhein, rheum-emodin, aloe-emodin, and chrysophanol. It also contains tannins.

Quality of the drug

The quality of the following drugs and drug preparations is specified in the European Pharmacopoeia (Ph. Eur.):

Rhubarb root (Rhei radix)
Standardized dry rhubarb extract (Rhei extractum siccum normatum)

Medical applications

Recognised medical use

The HMPC has accepted the internal use of rhubarb root for the short-term treatment of occasional constipation as a “well-established use.”

ESCOP: For short-term treatment of occasional constipation.

Clinical data have also confirmed the following application for alcoholic extracts of rhubarb root (approval): External use for inflammation of the gums and oral mucosa, as a brushing solution.

Traditional use

No listing as a traditional herbal medicinal product (Article 16a of Directive 2001/83/EC).

Herbal drug preparations in finished dosage forms

Cut or coarsely powdered rhubarb root for tea preparation
Rhubarb root dry extracts standardized to anthranoids (rhein), dissolved in liquid medicinal forms for external use (brushing the gums)

Dosage

Finished medicinal products: See patient information leaflet.

Tea: 20 to 30 mg of anthranoids are sufficient for a laxative effect. This corresponds to a tea prepared from 1 to 2g of coarsely powdered rhubarb root. The tea should be taken in the evening before bedtime. It is advisable to combine it with other herbal drugs such as senna leaves (also has a laxative effect) or caraway (for flatulence).

Preparation of a tea

Pour 150ml of boiling water over 1 to 2g coarsely powdered rhubarb root and strain after 5 minutes.

Notes

Rhubarb root may not be taken longer than 2 weeks (gut-irritating laxative); long-term use may increase constipation. It is recommended to take rhubarb root only 2 to 3 times per week, in the evening.

Rhubarb root should not be used in cases of intestinal obstruction, appendicitis, inflammatory bowel disorders (e.g. Crohn's disease, ulcerative colitis), abdominal pain of unknown origin, or severe dehydration. A slight discoloration of the urine may occur during the ingestion of rhubarb roots.

Although there are currently no reports of adverse or harmful effects in pregnant women and the fetus, the use of rhubarb root during pregnancy is not recommended due to the potential genotoxicity of various anthranoids. Transfer of anthranoids into breast milk cannot be excluded; therefore, use during lactation is not recommended. Similarly, use in children under 12 years of age is not recommended.

Side effects

Rarely, gastrointestinal cramp complaints (reduce dosage!). Prolonged ingestion of rhubarb root (laxative abuse) can lead to disturbances in water and electrolyte balance, especially potassium loss. Protein and blood may appear in the urine (proteinuria, hematuria). Chronic use may lead to (reversible) pigmentation of the intestinal mucosa.

Interactions

Chronic use of rhubarb root (laxative abuse) can increase the effects of digitalis drugs (drugs with cardiac glycosides) due to potassium depletion. The effect of antiarrhythmic drugs may also be affected. Potassium loss may be further exacerbated by concomitant use of thiazide diuretics, adrenal corticosteroids, and licorice root.