RHUBARB, POLYGONACEAE, are native to Asia, species are numerous and as they are plants that hybridize, horticulturists have created various hybrid varieties interesting for their medicinal, culinary or decorative properties.
RHEUM OFFICINALE and RHEUM PALMATUM and their hybrids are traditionally medicinal species.
RHABARBARUM RHEUM and its hybrids with other non-medicinal species are rather culinary and decorative.
Rhubarb has been used for a very long time in continental Asia (China and Korea) as both a medicinal plant (Ma huang in Chinese) and edible plants.
They were introduced quite late in the West via Turkey and Russia.
Edible rhubarb is cultivated and has become very common in all temperate western countries including North America.
Rhubarb are perennial plants with a very developed rhizomatous root, they have large, very green leaves with a fleshy and often colored petiole (in red or green).
The rhizomatous roots of Rheum officinale, Rheum palmatum and their hybrids are the medicinal parts.
The fleshy petioles of Rheum rhabarbarum and its hybrids may be with Rheum rhaponticum are the edible parts; the roots of the latter species have an interest in herbal medicine but are less used.
RHUBARB ROOT OF RHUBARB LAXATIVE RHEUM OFFICINALE RHEUM PALMATUM RHEUM RHABARBARUM DIETARY
CHEMICAL COMPOSITION AND PROPERTIES
RHUBARB ROOT
Rhubarb roots ensure perenniality of the plant and its spread anually becomming large (several kg on a rhubarb 4 to 5 years old).
Among the many components present in rhubarb root we distinguish mainly:
- anthraquinone glycosides (60 to 80%) and sennosides (10 to 20%): compounds also present in other medicinal plants (aloe, senna, for example),
- gallic tannins (5 to 10%),
- flavonoids ,
- stilbenes,
- oxalic acid and oxalates.
Anthraquinone glycosides and sennosides are potent laxatives that act on the colon (large intestine) after being transformed by the intestinal microbial flora, so it takes about 6 to 12 hours after drug absorption to get a laxative effect.
These substances released by colonic bacteria cause both an increase in contractions of the large intestine and a « fluidification » of fecal matter that facilitates defecation but also facilitates the leakage of some important electrolytes including potassium.
Gallic tannins have an opposite effect, they « dry » the digestive mucosa (anti-diarrhea) and have an antimicrobial effect.
Stilbenes are known for their estrogenic power (female hormone).
RHUBARB LEAVES
Rhubarb « officinale » leaves are not used in western medicine.
In the leaves of « edible » rhubarb, the petiole is consumed, ie the stem, and the chlorophyllian green part is discarded.
This green part of the leaves contains a significant percentage of oxalic acid and oxalate which are toxic above a certain dose by a mechanical effect (the oxalate crystals irritate the mucous membranes) or by a metabolic effect.
Oxalic acid absorbed by the digestive tract can cause disorders of blood coagulation, digestive, respiratory and renal disorders.
The petiole of edible rhubarb is fleshy, often colored in purplish red or green, it contains soluble and insoluble fibers, organic acids (including oxalic acid), some vitamin C.
USES
RHUBARB ROOT, laxative but use with caution
In Western medicine, rhubarb root is mainly used for its laxative power, to fight obstinate constipation.
This way of fighting constipation is not « natural » because it relies on the irritating nature of anthraquinone derivatives and their important modification of the regulation of water reabsorption in the colon )
Therefore:
- Limit in time use of rhubarb or its extracts: a maximum of 2 weeks of treatment.
- Do not use in children under 12 years, and avoid in pregnant or breastfeeding women.
- Do not use rhubarb or its extracts if there are signs of intestinal inflammation, bowel obstruction, digestive disorders such as pain or vomiting.
- As the prolonged use for several days causes a potassium leak, there is a risk of hypokalemia which can lead to cardiac disorders especially with cardiac arrythmia, and when patients take drugs based on digitalis or diuretics.
Examples of dosage
- Pharmaceutical Specialties:
It is estimated that not more than 20 to 30 mg of anthraquinone derivatives per day should be taken, at the beginning of the night, 2 to 3 times a week.
Since pharmaceutical preparations containing rhubarb root extracts have different dosages of active substance, follow laboratory’s instructions (dosage).
- Rhubarb root powder: decoction of a coffee cup of powder in 1/3 of a liter of water for 10 minutes, absorb half of the preparation at bedtime, double the dose if necessary.
- Tincture of rheum officinale (1/10) : 25 to 100 drops at bedtime
OTHER USES OF RHUBARBE ROOT
- Rhubarb root by its tannin content is astringent and constipating, it is paradoxical for a laxative: a small amount can constipate.
Approximately 1/4 of the laxative dose can be used to reduce diarrhea.
The content of tannin is also interesting in case of mouth ulcers: mouthwash or application of the decoction on canker sores.
- Traditional Chinese medicine uses rhubarb root extensively in combination with other plants.
Chinese or Korean studies have recently shown, for example, that rhubarb extracts can be combined into preparations to reduce weight, reduce the effects of type 2 diabetes, reduce the risk of antibiotic resistance, reduce the risk of delay the course of renal failure or as an antiviral.
- For many years, a specialty based on Rheum rhaponticum (probably native to eastern Europe) root extract has been proposed in Germany to reduce the effects of menopause. EDIBLE RHUBARB LEAVES Rheum rhahbarbarum and hybrids
As we have seen above, only the fleshy petiole of the rhubarb leaf is edible.
It is used in many ways, raw or cooked, its tangy taste is pleasant and enhances many dishes, pies, compotes or jams.
The content of soluble and insoluble fiber makes it a natural laxative and rather « soft » which must in addition attenuate the absorption and reabsorption of cholesterol at the intestinal level.
It is therefore an interesting fruit vegetable at the diet level.
People who are likely to have kidney stones (especially oxalate) should be wary of rhubarb which contains a lot of oxalic acid.
EDIBLE RHUBARB CULTIVATION
The edible rhubarb is present in many gardens, it is an easy plant to cultivate, very resistant to cold but which requires a deep soil, rich and fresh.
Propagation can be done by seeds or more quickly vegetatively by segmenting the root provided with some buds primer of stem which makes it possible to preserve the cultural variety.
It is a perennial plant that can live for many years and have abundant and spreading foliage.
ABSTRACT
RHUBARBS LAXATIVE AND DIETETIC MEDICINAL PLANTS
There are rhubarb officinalis whose roots contain laxative substances and edible rhubarbs (often hybrids) grown in many countries for their fleshy and edible petiole, dietary and slightly laxative.
The rule is to limit taking rhubarb root to less than 2 weeks because it strongly irritates the large intestine and increases the risk of heart problems by hypokalemia.
Copyright 2023 : Dr Jean-Michel Hurtel
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