Rhubarb is a vegetable also known as pie-plant which is grown in spring. It has a vibrant pink to crimson-coloured hollow, erect stalk which is sour in taste with thick roots. The colour of the stalk is due to presence of anthocyanins. Rhubarb originates from Asia and was brought to Europe in 1600s. It commonly grows in cool areas of temperate zones. It requires rainfall and an annual cold period of up to 7-9 weeks at 3°C (37°F) to grow well. It has large triangular leaves containing oxalic acid and anthrone glycosides in high content, so the leaves should not be eaten.
There are 23 rhubarb species that have been recorded. The root and underground stem (rhizome) are used to make medicine and the stalk is eaten as vegetable. Anthraquinones are the main characteristic as well as pharmacodynamic ingredients of rhubarb. The proportion of anthraquinones ranges from 3 to 5% in different species. More than 30 anthraquinones have been isolated and identified from rhubarb. Emodin has a wide range of pharmacological effects, including anti-tumour, anti-microbial, antioxidant, anti-inflammatory. It also can bring high blood pressure down, decrease blood lipids, improve microcirculation. Rhubarb is sometimes applied to the skin to treat cold sores.
Rhubarb (Rhei or Dahuang), one of the most ancient and important herbs in traditional Chinese medicine (TCM), belongs to the Rheum L. genus from the Polygonaceae family, and its application can be traced back to 270 BC in “Shen Nong Ben Cao Jing”. Rhubarb has long been used as an antibacterial, anti-inflammatory, anti-fibrotic and anticancer medicine in China. The quality of traditional Chinese medicine (TCM) is closely related to its variety and origin. However, for a variety of reasons, such as origin, variety and processing methods, there are differences in the effective components of rhubarb, which eventually lead to decreased quality and poor efficacy. Traditional methods used to identify rhubarb are mainly based on the characteristics of the flowers, leaves, cross-sections of roots, and crystal characteristics of the powder. Rhubarb has been used as a first-choice herb for constipation in clinic for thousands of years in China. Rhubarb is one of the most popular traditional Chinese herbs used in treating diabetic nephropathy (DN) and chronic renal failure (CRF). Rhubarb could improve the condition of diabetic nephropathy patients by reducing the excretion of urinary protein, lowering blood lipid, improving renal function.
The main chemical compositions of rhubarb include anthraquinones, anthrones, stilbenes, tannins, polysaccharides, etc. These compositions show extensive pharmacological activities including regulating gastrointestinal, anticancer, antimicrobial, hepatoprotective, anti-inflammatory, protecting cardiovascular, cerebrovascular and so on. The main pharmacological activities of rhubarb include antitumor, regulation of gastrointestinal flora, protection of the intestinal mucosal barrier, anti-inflammatory, and inhibition of fibrosis. In addition to emodin and sennoside, which are the main chemical components inhibiting fibrosis and purgation. Most of the pharmacological effects are the result of the joint action of several anthraquinones in rhubarb. Rhubarb has very good antibacterial activities against Staphylococcus aureus, bifidobacteria, Lactobacillus, Helicobacter pylori, Escherichia coli, methicillin-resistant Staphylococcus aureus.
Rhubarb can prevent liver inflammation caused by acute alcohol intake. Oral rhubarb rhizome extract significantly reduced glycosylated hemoglobin, fasting glucose, and body weight in patients with type 2 diabetes. But there are some adverse effects also, like taking rhubarb without prescription may damage the health of the liver. It is recommended to reduce the use of rhubarb in patients with inflammation in the liver due to illness or medication. Rhubarb has significant hepatotoxicity, which may be related to the accumulation of emodin in the liver or its influence on the oxidative phosphorylation pathway. Gender may also be a factor affecting its hepatotoxicity. Patients with kidney disease should also avoid long-term use of rhubarb. Rhubarb poisoning causes abdominal pain, diarrhea, profuse persistent vomiting followed by internal bleeding, convulsions and coma.
The poisoning due to rhubarb leaf show clinical symptoms such as low production of urine (oliguria), excretion of acetone in the urine (acetonuria), and excessive albumin in the urine. Taking rhubarb with a medication that can harm the kidneys and liver might increase the risk of kidney and liver damage. Taking rhubarb along with “water pills” might make potassium levels drop too low. Rhubarb is a stimulant laxative. Stimulant laxatives can decrease potassium levels in the body. Low potassium levels can increase the risk of digoxin side effects. Rhubarb is LIKELY SAFE when the root is consumed as food and is POSSIBLY SAFE for most adults when taken by mouth in medicinal amounts for up to 3 months.
The writers teach at Division of FST, SKUAST-K, Shalimar. [email protected]