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Family: N.O Polygonaceeae
Rhubarb occurs in commerce under various names: Russian, Turkey, East Indian and Chinese; but the geographical source of all species is the same, the commercial names of the drug indicating only the route by which it formerly reached the European market. Previous to 1842, Canton being the only port of the Chinese Empire holding direct communication with Europe, Rhubarb mostly came by overland routes: the Russian Rhubarb used to be brought by the Chinese to the Russian frontier town of Kiachta; the Turkey Rhubarb received its name because it came to us by way of Asiatic Turkey, through the Levant; East Indian came by way of Singapore and other East Indian ports, and Chinese Rhubarb was shipped from Canton. At the present day practically all is conveyed to Europe via Shanghai.
According to Lindley's Treasury of Botany, the technical name of the genus is said to be derived from Rha, the ancient name of the Volga, on whose banks the plants grow; other authorities derive the name from the Greek rheo ('to flow'), in allusion to the purgative properties of the root.
Botanical: Rheum palmatum, Rheum rhaponticum
---Description---The leaves of the Turkey Rhubarb are palmate and somewhat rough. The root is thick, of an oval shape, sending off long, tapering branches; externally it is brown, internally a deep yellow colour.
The stem is erect, round, hollow, jointed, branched towards the top, from 6 to 10 feet high.
This species is distinguished from our familiar garden Rhubarb by its much larger size, the shape of its leaves, with their oblong, sharpish segments, and the graceful looseness of its little panicles of greenish-white flowers. The first buds which appear in spring are yellow, not red.
It was not until the year 1732 that botanists knew any species of Rheum from which the true Rhubarb seemed likely to be obtained. Then Boerhaave, the celebrated Dutch physician, procured from a Tartarian Rhubarb merchant the seeds of the plant which produced the roots he annually sold, and which were admitted at St. Petersburg to be the real Rhubarb. These seeds on being sown produced two distinct species: Rheum Rhaponticum, our Garden Rhubarb, and Rheum and R. palmatum, Turkey Rhubarb.
The Turkey Rhubarb grows remarkably quickly - a six-year-old plant was found to grow between April, when the stalk first emerged from the ground, to the middle of July, when it was at its greatest height, to 11 feet 4 inches. In one day it was observed to grow 3 inches and over 4 inches in one night. Many of its leaves were 5 feet long. The root, taken up in October, weighed 36 lb. when cleaned, washed and deprived of its small fibres.
'J. D. B. (31/10). - The rhubarb rhizome official in the British Pharmacopoeia, 1914, must be collected in China and Thibet. English-grown rhubarb is inferior to the official rhubarb in medicinal qualities.'
We still depend upon Northern China and Thibet for Rhubarb; that grown in the English climate, near Banbury, does not command a high price in the market, although its medicinal properties are the same as those of the Chinese roots. If English growers would endeavour to produce a more marketable root by experimenting with different soils and methods of cultivation, the results might meet with success. It is possible that English roots are harvested when too young, and that not so much attention is paid to trimming the roots for market as is done by the Chinese. It is never collected from plants that are less than six years old.
It is said that the odour of the best samples is so delicate that the assistants in the wholesale drug-houses are not permitted to touch it without gloves.
---Part Used---The root, scraped or rasped, halved longitudinally when very large, and then cut into transverse pieces and strung on cords to dry in the sun, the drying afterwards being completed by stove heat. It is dug in October.
Chinese or Turkey Rhubarb occurs in commerce in brownish-yellow pieces of various size, usually perforated, the holes often containing a portion of the cord used to hang the sections of the root on during drying. The outer surface is generally powdery (the bark having been removed) and shows a network of white lines.
The taste is astringent and nauseous, and there is a characteristic odour.
The preparations used in medicine are: the powdered root, a fluid extract, a tincture, syrup, infusion and solution. It is also employed as a principal ingredient in compound powder (Gregory's Powder) and in compound pills.
---Constituents---The chemical constituents of Rhubarb root are not yet completely known. Recent investigations indicate that the most important constituents are a number of substances which may be divided into two groups, viz. tannoid constituents and purgative constituents, several of which have been isolated in a free state: the former are astringent and the latter laxative.
Three crystalline tannoids have been extracted. The purgative constituents apparently exist in the form of an unstable crystalline substance: Rheopurgarin. This splits up into four glucosides: two of these yield Chrysophanic acid (so named from its forming yellow crystals) and Rheochrysidin respectively. The other two glucosides have not yet been isolated, but they appear to yield Emodin and Rhein.
There are also several resinous matters, one of which, Phaoretin, is purgative, and mineral compounds are also present, especially Oxalate of Calcium. The astringency of Rhubarb is due to a peculiar tannic acid (Rheo-tannic), which is soluble in water and alcohol.
---Medicinal Action and Uses---Astringent, tonic, stomachic, aperient. In large doses, Rhubarb powder acts as a simple and safe purgative, being regarded as one of the most valuable remedies we possess, effecting a brisk, healthy purge, without clogging the bowels and producing constipation, too often consequent upon the use of the more active purgatives.
It is especially useful in cases of diarrhoea, caused by an irritating body in the intestines: the cause of irritation is removed and the after-astringent action checks the diarrhoea.
The tincture is chiefly used, but the powder is equally effective and reliable.
Rhubarb when chewed increases the flow of saliva.
---Preparations and Dosages---Powdered root, 3 to 30 grains. Comp. powder, B.P. (Gregory's), 20 to 60 grains. Comp. pill, B.P., 4 to 8 grains. Solid extract, U.S.P., 4 grains. Solid extract, B.P., 2 to 8 grains. Tincture comp., B.P., 1/2 to 4 drachms. Tincture, U.S.P., 1 drachm. Tincture aromat., U.S.P., 1/2 drachm. Fluid extract, 10 to 30 drops. Syrup, B.P., 1/2 to 2 drachms. Infusion, B.P., 1/2 to 1 OZ. Syrup, B.P. and U.S.P., 1/2 to 2 drachms. Arom. syrup, U.S.P., 2 drachms. Rheum, 1 to 4 grains.
Botanical: Rheum rhaponticum (WILLD.)
---Parts Used---Root, stems.
English Rhubarb is similar in action to Turkey or Chinese Rhubarb, though milder. It is derived from Rheum rhaponticum, the ordinary Garden Rhubarb, and from R. officinale.
It has blunt, smooth leaves; large, thick roots, running deep into the ground, reddishbrown outside and yellow within, and stems 2 to 3 feet high, jointed and purplish. The flowers are white.
About 1777, Hayward, an apothecary, of Banbury, in Oxfordshire, commenced the cultivation of Rhubarb with plants of R. Rhaponticum, raised from seeds sent from Russia in 1762, and produced a drug of excellent quality, which used to be sold as the genuine Rhubarb, by men dressed up as Turks. The Society for the encouragement of Arts, Manufactures and Commerce exerted itself for many years in promoting the cultivation of Rhubarb, granting medals not only to this original pioneer, but also, some years later, to growers of Rhubarb in Somersetshire, Yorkshire and Middlesex, some of whom, it appears, attempted also to cultivate R. palmatum. When Hayward died, he left his Rhubarb plantations to the ancestor of the present cultivators of the Rhubarb fields at Banbury, where R. officinale is also now cultivated, from specimens first introduced into this country in 1873. Both R. Rhaponticum and R. officinale are at the present time grown, not only in Oxfordshire but also in Bedfordshire. Although specimens of R. palmatum were raised from seed as early as 1764, in the Botanical Gardens in Edinburgh, it is not grown now in this country for medicinal purposes, experiments having shown that it is the least easily cultivated of the rhubarbs, the main root in this climate being liable to rot. R. officinale and R. Emodi have to some extent been grown also as an ornamental plant, being also quite hardy and readily propagated.
---Cultivation---Rhubarb may be raised from seed, but it is better and more usual to obtain established roots. Seeds may be sown, however, in drills a foot or more apart, in the open, from March to April, and the young plants thinned out to 10 inches, transplanting them in the autumn, allowing about 4 feet every way to each plant.
Rhubarb roots may be planted at any time of the year, although mild weather in autumn or early spring is best; it should be planted on a clear, open spot, on good soil, which should be well trenched 3 feet deep, and before planting, a good substance of rotten manure should be worked into the soil.
When the plants are to be increased, it is merely necessary to take up large roots and divide them with a spade: every piece that has a crown to it will grow. Fresh plantations are generally made in February or March, but Rhubarb may still be divided early in May.
To ensure fine rhubarb for table use, a large dressing of well-rotted manure should be dug in about the roots as soon as the last of the leaves have been pulled. It is not right to wait until the winter, before the plants are dressed.
Old roots ought to be divided and replanted every fourth or fifth year, when the plants are grown for the use of the stems.
If Rhubarb be forced on the ground where it grows, nothing more is required than to cover with large pots, half casks, or boxes, round and over which should be placed plenty of stable manure. Roots forced in greenhouse or in frames do not need to have the light excluded from them. Such roots, however, require dividing and replanting in the spring out of doors.
---Part Used Medicinally and Preparation---The roots of English Rhubarb are generally taken from plants from four years old and upwards. They are dug up in October, washed thoroughly and the fibres taken away. The bark of English Rhubarb is not usually removed.
The roots of both R. Officinale and R. Rhaponticum are much smaller than those of the Chinese Rhubarb and are easily distinguished by their distinctly radiate structure. They are also more shrunken, more or less distinctly pink in colour, and have a diffuse circle of isolated star-spots on the transverse section. The roots of R. officinale cultivated in England resemble Chinese Rhubarb, but are more spongy, and shrink and wrinkle as they dry, and are softer to cut. They have a less rich colour than the Chinese, and have no network of white lines on the outer surface, the dark red and white lines usually running parallel to each other and the star-spots being less developed, fewer and more scattered.
The English Rhubarb from R. Rhaponticum shows red veins, that of R. officinale is usually in larger pieces and has blackish veins.
The root is used as a drug in powdered form.
---Constituents---Root. The constituents of R. officinale are similar to those of Chinese Rhubarb.
Rhapontic or Garden Rhubarb contains no emodine, rhein or rhabarberine, but has in it a crystalline body, rhaponticin.
Stem and Leaves of R. Rhaponticum. Potassium oxalate is present in quantity in Rhubarb leaf-stems, and certain persons who are constitutionally susceptible to salts of oxalic acid, show symptoms of irritant poisoning after eating rhubarb stewed in the ordinary manner. Many people of a gouty tendency do well to avoid it, and those subject to urinary irritation should take it very sparingly or not at all.
Rhubarb stems did not come into general use as a substitute for fruit till about 100 years ago. We hear of a pioneer grower, Joseph Myatt, of Deptford, sending, in 1810, five bunches of Rhubarb to the Borough Market and only being able to dispose of three. But he persevered in his efforts to make a market for Rhubarb, raised improved varieties, and a few years after, Rhubarb had become established in public favour as a culinary plant.
It was, however, soon realized that the use of Rhubarb as food was sometimes attended with some risk to health. Lindley, in his Vegetable Kingdom, 1846, remarks that oxalic acid exists in both Docks and Rhubarb, and that the latter contains also an abundance of nitric and malic acid, and goes on to say that whilst these give an agreeable taste to the Rhubarb when cooked, he considers them illsuited to the digestion of some persons. The Penny Cyclopaedia, 1841, warned persons subject to calculous complaints against eating Rhubarb stalks, owing to the presence of oxalic acid, stating that 'the formation of oxalate of lime, or mulberry calculus, may be the consequence of indulgence.'
The chemical constituents of Rhubarb leaves were till recently not fully ascertained, but the analysis has lately been undertaken under orders from the Home Office, in consequence of fatal and injurious effects having resulted from eating the leaves cooked as spinach. The report of the official analyist states that the leaves contain some 0.3 per cent oxalates of potassium and calcium oxalates. It is possible that the recent cases of poisoning occurred in subjects specially susceptible to oxalic poisoning, as there are also many cases reported of no harm ensuing from a use of Rhubarb leaves as a vegetable.
Further reference to the Gardeners' Chronicle, of 1847, shows records of the varying results of eating the young inflorescence, producing no ill-effects in some cases and serious illness in others, and a case is recorded of severe sickness attacking a whole family after partaking of the leaves boiled as a vegetable. In 1853 we find the question again raised. In 1872 we hear of deaths from eating the leaves in America, and in 1899 we find a revival of interest in Rhubarb leaves as a vegetable, quite opposite opinions being expressed in a correspondence in the gardening papers. In 1901 we hear of a man dying after eating stewed Rhubarb leaves, the verdict at the inquest being: 'Accidental death, caused by eating rhubarb-leaves.' It was stated then that the leaves were used as a vegetable in parts of Hampshire. The British Medical Journal in December, 1910, mentions several cases of rhubarb poisoning.
The leaves are sometimes made use of in the fabrication of fictitious cigars and tobacco. The shape of the hairs, however, as seen under a microscope, can enable the observer to detect the presence or absence of tobacco, but it is not so easy to determine the source of the fraudulent admixtures.
It is possible that the chemical composition of Rhubarb varies to some extent according to the variety and the soil on which it is grown. It has been stated that the amount of water present is less when the plants are grown on poor soil, while the acid principle is more abundant.
As regards the method of cooking, the British Medical Journal points out that hard water would precipitate the oxalate, while a soft water might leave it in the form of soluble oxalate, more readily assimilated into the systems of those susceptible to this kind of poisoning. In a recent case that terminated fatally, the leaves were well washed, drained, cut up and put into boiling water, in an iron saucepan, for 20 minutes. A little salt and kitchen soda were added, but nothing else. Being acid, the leaves should, of course, not be cooked in a copper vessel.
---Medicinal Action and Uses---Though the English Rhubarb root is milder as a purgative, it is more astringent, and has been considered a better stomachic than the foreign.
It is specially useful in infantile stomach troubles and looseness of the bowels.
In fairly large doses it acts as a laxative.
Dose of powdered root, 5 to 60 grains. The dose is entirely individual, 12 grains acting on some persons, as much as 20 on others of the same age. It has been held that 20 grains of the seed are equal to 30 of the root, as regards purgative power. The properties of the seeds are similar to those of the root.
A decoction of the seeds is supposed not only to ease pains in the stomach, but to strengthen it by increasing the appetite.
A strong decoction of the root has been employed as a good w ash for scrofulous sores.
If a portion of the root be infused in water, and when strained a few grains of salt of tartar be added, a very beautiful red tincture results, which might prove valuable for the purposes of a dye.
Botanical: Rumex alpinus (LINN.)---Synonym---Garden Patience.
Monk's Rhubarb is, as Culpepper tells us, 'a Dock bearing the name of Rhubarb for some purging quality within.'
The root was formerly used medicinally, and the leaves as a pot-herb.
It is found on roadsides near cottages in the North of England and in Scotland, but is rare and naturalized.
The root-stock is very stout, of a yellow colour; the stem 2 to 4 feet high, bearing pale green leaves, broad and very long, the edges waved, but not cut into. The tops of the stems are divided into many small branches, bearing reddish or purple flowers, succeeded by angular seeds, as in other docks.
The medicinal virtues of the root, when dried, are similar to the Garden or Bastard Rhubarb, but are not so strong.
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