Radix et Rhizoma Rhei
- Name
- Origin
- Where Does It Grow?
- Nature and Flavor
- Identified Active Components / Major Chemical Constituents
- Drug Actions in TCM
- Traditional Uses in TCM
- Pharmacological Actions
- Toxicology
- Administration and Dosage
- Adverse Effect, Side Effects and Cautions
- References
Name
Latin Name: Radix et Rhizoma Rhei
Common Name: Rhubarb
Scientific Name: Rheum palmatum L. / Rheum tanguticum Maxim. Ex Balf. / Rheum officinale Baill.
Chinese Name: 大黃
Pinyin Name: da huang
Origin
The root or tuber of Rheum palmatum L., Rheum tanguticum Maxim. ex Balf. and Rheum officinale Baill., perennial herbal plants of the Polygonaceae family. The medicinal part is used in raw form, alcohol processed or carbonized.1,3
Where Does It Grow?
Rhubarb is cultivated supply nowadays and mainly produced in Gansu, Qinghai, Tibet and Sichuan provinces.2
Nature and Flavor 
Rhubarb is bitter in flavor, cold in nature, and manifests its therapeutic actions in the spleen, stomach, large intestine, liver and heart meridians.3
Identified Active Components / Major Chemical Constituents
Rhubarb mainly contains derivatives of anthoursaquinone in a conjugated form of anthoursaquinone glycoside or diglycoside, and also tannins and their analogues. 6
The anthoursaquinone derivatives such as rhein, emodin, chrysophanol, aloe-emodin, and physcion do not have purgative effect. Those anthoursaquinone glycoside or diglycoside compounds have purgative effect, such as sennoside A-F are most effective but the quantity contained is low; rhein-8-mono-β-D-glucoside, physcion monoglucoside, aloe-emodin-8-monoglucoside, emodin-monoglucoside, chrysophanol monoglucoside have mild purgative effect.
The tannins such as glucogullin, α-catechin, gallic acid, tetrarin, cinnamic acid and rheosmin have anti-purgative effect.
Drug Actions in TCM
Rhubarb can purge intestinal stagnation, clear heat, cool blood, eliminate toxic substance, remove blood stasis and promote blood circulation.5Traditional Uses in TCM
Rhubarb is often used in conditions like constipation, intestinal obstruction, dysentery, bleeding symptoms, red eyes, throat soreness, abdominal abscess, jaundice, carbuncles and furuncles, missed periods, traumatic injuries, and burns and scalds. Processed rhubarb has a reduced purgative effect, and is usually used for treating red eyes, sore throat, gum swelling, carbuncles and furuncles. Carbonized rhubarb is for bleeding symptoms. 3,4,5
•Rhubarb with purgative actions
Rhubarb is especially suitable for constipation with heat. For example, high fever patients that cannot pass stool for days usually suffer from abdominal distention and pain, rhubarb can be prescribed with magnolia bark, immature bitter orange and sodium sulfate to induce bowel movements and relieve the problems. For constipated patients that accompanied with other problems, rhubarb can also work with appropriate ingredients for relief, such as aconite root and dried ginger to treat cold type constipation. In an early stage of bacterial dysentery that develops diarrhea, abdominal pain and tenesmus, physicians prescribe rhubarb with golden thread rhizome and costus root to facilitate the purgation and cleansing process. For digestive problems that caused by food retention, rhubarb is prescribed with green tangerine peel and costus root to promote digestion and induce bowel movements.
•Rhubarb promotes urination to eliminate damp-heat
In TCM, damp-heat is the pathogenic cause of many conditions, and urination plays an important role to eliminate it. For example, jaundice can be due to damp-heat in the liver meridian, rhubarb can work with wormwood herb and gardenia fruit for this; urinary tract infection may be a sign of damp-heat in the bladder, which can be relieved by rhubarb working with akebia stem, talc, Chinese pink herb and gardenia fruit.
•Rhubarb is usually used for dragging fire downward
Excessive fire or heat in the upper body usually leads to red eyes, throat soreness and gum swelling, besides applying ingredients like weeping forsythia capsule, baical skullcap root and gardenia fruit to clear heat and eliminate toxic substances, appropriate amount of rhubarb is added in the preparation to enhance the therapeutic efficacy. Sometimes, stomach fire will result in reverse flow of qi that causes nausea and vomiting, rhubarb can be used with liquorice root and golden thread rhizome for relief. When phlegm and fire pathogens irritate the upper body, it may lead to symptoms like cough or convulsion, rhubarb can be used with chlorite stone, baical skullcap root and Chinese eaglewood for treatment.
•Rhubarb can eliminate heat in the blood system
Over-heated blood usually leads to various types of bleeding, rhubarb can be used alone or combined with herbs like baical skullcap root, golden thread rhizome and rehmannia root to cool blood and stop bleeding.
•Rhubarb can activate blood flow and is a usual ingredient for blood stasis conditions
When women develop postpartum abdominal pain, persistent vaginal discharge or missed periods, rhubarb can be used with peach kernel and ground beetles to remove blood stasis and activate blood circulation in the pelvic region. In traumatic injuries, rhubarb can be combined with angelica root, peach kernel, frankincense and myrrh to form internal or external remedies, for clearing blood stasis, relieving swelling and pain.
•Rhubarb can help relieve body fluid retention
In abdominal ascites, rhubarb can be used with fourstamen stephania root, peppertree pricklyash seed and pepperweed seed. For persistent and severer ascites that has involved the chest region, rhubarb can be used with gansui root and sodium sulfate.
•Rhubarb promotes the healing of skin sores or pus-forming infections
In TCM, carbuncles and furuncles are regarded as toxic heat signs of the skin, rhubarb can work with honeysuckle flower, weeping forsythia capsule, Dahurian angelica root and red peony root to promote them healing. For intestinal abscess, rhubarb can work with peony root bark, peach kernel, red peony root and sodium sulfate. Rhubarb powder mixed with honey water can be applied to treat mild skin sores, while rhubarb and processed alum mixture can be applied to treat mouth sores.
•Rhubarb (powdered) mixed with sesame oil or garden burnet root (powdered) can be applied to treat burns and scalds.
In anthelmintic preparations, appropriate amount of rhubarb can help expel the parasites.
Modern TCM also use rhubarb in digestive tract bleeding, acute intestinal obstruction, rosacea, hyperlipidemia, renal failure, uremia and cholelithiasis.
Pharmacological Actions
Researches showed that rhubarb promotes bile secretion, intestinal secretions, bowel movements, and protects digestive lining. In cardiovascular system, rhubarb improves blood capillary circulation, stops bleeding and lowers blood lipid. Others include anti-bacterial and fungal, and inducing urination. 6
Toxicology
Chrysophanol extract 40g (raw herb)/kg, intraperitoneal injected to mice, there were no death and abnormal behavior after 72 hours. Rhubarb solution subcutaneous injected to mice, the LD50 is 4.052g/kg. When anthoursaquinone derivatives of rhubarb were fed to mice, LD50 of physcion is 1.15g/kg, LD50 of emodin is 1.56g/kg and LD50 of chrysophanol is 10g/kg. 6
Administration and Dosage
The usual dose of rhubarb is 5～10g each time for decoction. Raw rhubarb has a strong purgative effect that should not be boiled overtime when using for promoting bowel movements, or just infuse it and drink as tea.3
Adverse Effect, Side Effects and Cautions
Individuals with cold and flu symptoms, a low immunity, poor digestion, or pregnancy or postpartum women should use with caution. 5
References
- Li Jiashi (editor-in-chief), Chinese Medicine Identification, Shanghai Scientific and Technical Publishers, 2000-2.
- Zhao Zhongzhen & Xiao Peigen (editor-in-chief), Contemporary Medicinal Herbal Glossary, Hong Kong Jockey Club Institute of Chinese Medicine, 2006-8.
- Lui Daiquan (editor-in-chief), Chinese Herbal Medicine, Shanghai Scientific and Technical Publishers, 2000-6.
- Tao Yufeng, Clinical Herbal Medicine, People’s Medical Publishing House, 2005-5.
- http://www.zysj.com.cn/zhongyaocai/yaocai_d/daihuang.html#160
- Wang Benxiang (editor-in-chief), Modern Pharmacology of Chinese Medicine, Tianjin Scientific and Technical Publishers, 1990.
