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RHUBARB [大黄, DA HUANG]

Name : Rhubarb

Chinese Name : 大黄

Latin Name : Radix et Rhizoma Rhei

Overview

This herb is the dried root and rhizome of  Rheum palmatum L., R. tanguticun maxim. Ex Balf, or  R. officinale Baill of the family  Polygonaceae. It is mainly grown in the Qinghai, Gansu,  Sichuan, And Yunnan provinces of China. Collected in the late autumn when the stem and leaves begin to wither, it is dried and sliced for use unprepared or stir baked with wine.

Rhubarb is use as a purgative  and detoxicant for treating intestinal  obstruction, food stasis,  and distension, and has been known in China since the time of the Five Rules (circa 2852-2205 B.C.). It is beneficial to the stomach and spleen, invigorates blood circulation, eliminates toxins from the bowels, and prevents senility. It is regarded more as a general eliminant and tonic for the digestive tract.  It was recommended in women’s diseases, especially those attended by congestion of the pelvic organs, such as dysuria and dyspareunia. It was also used in malarial fever and the fevers  of children. The purgative properties  of rhubarb are not as highly regarded by the Chinese as they are in the West . Today, rhubarb is known as a good gastrointestinal detoxicant,  laxative, blood-inactivating,  and Heat-purging drug.

Use of Rhubarb in TCM

Bitter in taste, and cold, it acts on the spleen, large intestine, liver and heart meridians.

Effects, Medicinals, and Combinations

  1. Loosens the bowels and treat bloat: for intestinal food stagnation and constipation, and to relieve pathogenic Heat or toxins in the intestines, rhubarb is an excellent herb. It is often used with mirabilite, immature orange, and magnolia bark, as in Da Cheng Qi Tang (R-73), for abdominal pain, constipation, and a feeling of fullness in the abdomen.
  2. Invigorates blood circulation: for acute postpartum pain, tenderness in the lower abdomen, mass formation, traumatic injuries, and other syndromes due to blood stagnation, rhubarb is combined with peach kernel and ground beetle.
  3. Detoxifies and removes Heat in the blood: for hematemesis, nose bleed, bloodshot eye, sore throat, and swelling of the gums, as well as other pains due to inflammation and excessive Heat in the blood, rhubarb is used with coptis rhizome, scutellaria root, platycodon, licorice root, and cow-bezore (Calculus bovis), as in Niu Huang Jie Du Wan.
  4. For accumulation of Heat, dry stools, constipation, epidemic febrile diseases with high fever, unconsciousness, delirium, madness, headaches, bloodshot eyes, and gum swelling with pain, rhubarb is combined with gardenia, scute, forsythia, and licorice root, as in Liang Ge San.
  5. Removes Damp Heat and has choleretic action to relieve jaundice and strangury: rhubarb is mixed with capillaris and gardenia, as in Yin Chen Hao Tang, to treat jaundice (Zhang, 1988), or with akebia caulis (mu tong), plantago leaves, and gardenia, as in Ba Zheng San, to treat strangury.

Dosage

In a dosage of 3 to 12 g.

Precautions

It is not recommended during pregnancy, menstruation, or breast-feeding.

Side Effects and Toxicity

The therapeutic dose of rhubarb does not generate side effects or toxicity. However, an overdose may cause nausca, vomiting, vertigo, or stomachache. Long-term use resulted in liver damage, and hypertrophy of the thyroid and stomach tissues. Anthraquinones causes diarrhea. The LD50 value of the anthraquinones via oral dose in mice was 0.56 g/kg for emodin, 1.15 g/kg for physcin, and 10 g/kg for chrysophanol.

Chemical Constituents

Rhubard contains about 4.6 percent anthraquinone derivatives, which can be divided into free anthraquinones, anthraquinone glycosides, and bianthrones. More than  thrirty-three ingredients have been isolated. Some of the important ingredients are tannins, organic acids, pectins, minerals, and mucilage.

Pharmacological Findings

  1. Rhubarb is a well-known purgative. Anthraquinone derivatives cause the purgative action.
  2. The hemostatic action has been proven experimentally and clinically for both external and internal hemorrhage.
  3. Rhubarb stimulates constriction of the gallbladder and relaxes Oddi’s sphincter, thus promoting bile secretion. It also increases the contents of bilirubin and bile acid.
  4. Lowers blood density and blood cholesterol levels in rabbits.
  5. Lowers blood pressure, and is diuretic and a stomachic.
  6. Rhubarb contains astringent tannins. Rhubarb taken in a small dose (0.1 to 0.3 g) has an astringent and an antidiarrheal action in mild forms of diarrhea. A high dose (100 to 400 g) produces a mild laxative effect. Since the contents of emodins and tannins are variable, the laxative action is somewhat uncertain. The German pharmacopeia describes a rhubarb root extract that is made with 70 percent ethanol. This extract is adjusted wih lactose as needed to obtain a 4 to 6 percent anthranoid content.
  7. Emodin suppressed the responses of human mononuclear cells to phytohemagglutinin and mixed lymphocyte reaction. It may be a new hope for the development of better immunosuppressive agents for use againts transplantation  rejection and autoimmune diseases.
  8. Antineoplastic and antimutagenic. Intraperitoneal administration of emodin produced an inhibition againts mammary carcinoma in mice. It also inhbited Ehrlich ascites carcinoma.
  9. Other effects : rhubarb was also demonstrated to be diuretic, antispasmodic, antimicrobial, antiparasitic, and anti-inflammatory.