Rheum (U. S. P.)—Rhubarb.
Preparations: Mixture of Rhubarb and Soda - Extract of Rhubarb - Fluid Extract of Rhubarb - Pills of Rhubarb - Compound Pills of Rhubarb - Compound Powder of Rhubarb - Syrup of Rhubarb - Aromatic Syrup of Rhubarb - Compound Syrup of Rhubarb and Potassa - Tincture of Rhubarb - Aromatic Tincture of Rhubarb - Sweet Tincture of Rhubarb - Troches of Rhubarb and Potassa - Wine of Rhubarb
Related entry: Acidum Chrysophanicum.—Chrysophanic Acid - Acidum Oxalicum.—Oxalic Acid
The root of Rheum officinale, Baillon"—(U. S. P.).
COMMON NAMES: Rhubarb root (Rhei radix, Br.).
ILLUSTRATION: Bentley and Trimen, Med. Plants, 213, 214, 215.
Botanical Source and History.—The botanical origin of the species which yielded the best rhubarb, formerly known in commerce as the Russian rhubarb, imported from China via Kiachta, in Siberia, is not known; no competent observer has ever been able to see the growing plant in its native habitat, the mountainous country Tangut, in Chinese Tartary, near the source of the Hoang-ho River. Chinese rhubarb is probably derived from more than one species; the closest approach to it is that described by Baillon, in 1872, as Rheum officinale, the description being taken from a plant successfully grown at Montmorency. This originated from leaves and cuttings forwarded to Dr. Soubeiran, of Paris, in 1867, by the French Consul at Hankow, China, Mr. Dabry de Thiersant, who obtained them from southeastern Thibet through French missionaries. Offsets of the French plant were also forwarded to England, in 1876, and cultivated with success by Rufus Usher, in Bodicote, in Oxfordshire. The common garden rhubarb (from R. rhaponticum and R. undulatum. had been in cultivation in England since 1608. The official rhubarb is that from Rheum officinale, which grows in southeastern Thibet, and probably other localities of the Chinese Empire.
RHEUM OFFICINALE, Baillon, according to Pharmacographia, is a "perennial, noble plant, resembling the common garden rhubarb, but of larger size. It differs from the latter in several particulars. The leaves spring from a distinct crown, rising some inches above the surface of the ground; they have a sub-cylindrical petiole, which, as well as the veins of the under side of the lamina, is covered with a pubescence of short, erect hairs. The lamina, the outline of which is orbicular, cordate at the base, is shortly 5 to 7-lobed, with the lobes coarsely and irregularly dentate. It attains 4 to 4 ½ feet in length, and rather more in breadth. The first leaves in spring display, before expanding, the peculiar, metallic-red hue of copper" (p. 492).
In addition, we quote from Mr. W. Elborne (Pharm. Jour. Trans., Vol. XV, 1884-85, p. 136): "The best distinguishing character of Rheum officinale is the strong development of the sympodium or root-stalk, a large portion of which projects conically above the ground, being provided with a few lateral roots, about the thickness of a finger. Also the first epidermis of the radical portion is remarkable for the bright brownish-red color, the roots of the other species being yellowish-brown."
The microscopical structure of the official root is described by Mr. W. Kirkby (see W. Elborne, loc. cit.) as follows: "The outer layer, immediately beneath the epidermal portion, consists of about 8 rows of the tabular parenchyma, extended tangentially. Within this is a broad zone of loose parenchyma, containing starch, into which the medullary rays entered about half way across. Next comes the dark cambial line, made up of several rows of closely compacted, oblong parenchyma, exhibiting the radial arrangement of the medullary rays. Between the medullary rays are seen groups of large, reticulated vessels, consisting of from 1 to 5 vessels, arranged, for the most part, in a radial manner. They are surrounded by unthickened, elongated parenchyma. The coloring matters are found in the medullary rays. The center of the root shows no definite arrangement of the tissues, being a mass of parenchymatous cells, interspersed irregularly by the medullary rays. The whole root is loaded with starch. The granules are generally compound. The larger single granules have a diameter of about 20 micro-millimeters. The hilum is generally, but only slightly, eccentric, and is seen as a small, black dot. When mounted in Canada balsam, the black cross is distinctly visible with polarized light. Raphides (crystals of calcium oxalate) are fairly numerous, and vary considerably in size. In the loose tissue of the root, just within the zone of radial medullary rays, are found scattered the stars so characteristic of Chinese rhubarb; these exhibit all the anatomical features of the root. R. officinale differs chiefly from Chinese rhubarb in that it contains more starch, and from R. rhaponticum in the vessels and cells of the medullary rays being larger, and the arrangement of the various tissues being less distinct and regular." (Also see microscopical study of several species of Rhubarb, by Prof. L. E. Sayre, Amer. Jour. Pharm., 1898, pp. 129-135.)
Cultivation and Collection.—Little is known about the cultivation and collection of Chinese rhubarb, the best of which seems to be obtained from wild varieties (Flückiger, Pharmacognosie des Pflanzenreichs, 3d ed., 1891, p. 399). According to Pereira, "the method of curing or preparing Asiatic rhubarb for the market varies somewhat in different localities. In China it is as follows: The roots are dug up, cleansed, cut in pieces, and dried on stone tables, heated beneath by fire. During the process, the roots are frequently turned. They are afterward pierced, strung upon cords, and further dried in the sun. In Tartary the roots are cut in small pieces, in order that they may dry the more readily, and a hole is made in the middle of every piece, through which a cord is drawn, in order to suspend them in any convenient place. They hang them, for the most part, about their tents, and sometimes on the horns of their sheep. Sievers, however, states that the roots are cut in pieces, strung upon threads, and dried under sheds, so as to protect them from the rays of the sun. He also tells us that sometimes a year elapses from the time of their collection until they are ready for exportation." The best grade is that known as Shensi rhubarb.
As regards cultivation in Europe, Mr. Elborne remarks (loc. cit.) that, as a general principle, forced cultivation produces a plant inferior in medicinal value, because it is chiefly inert tissue which is benefited by such cultivation. Propagation is effected from offsets or lateral shoots of 4-year-old plants, set at distances of 6 to 8 feet apart, and left to grow from 5 to 7 years, then the roots are ready for collection. They are dug up in dry weather, between July and September, peeled, sliced into pieces, known in trade as" flats" and" rounds." The rootlets furnish "small rounds," or "sticks." They are then exposed to a current of dry air in an open bedding for several days, and the drying is completed by exposure to artificial heat of 90° F., or, preferably, 80° F. for Rheum officinale.
Description and Commercial History.—As described by the U. S. P., rhubarb occurs "in cylindrical, conical, or flattish segments, deprived of the dark-brown, corky layer, smoothish or somewhat wrinkled, externally covered with a bright, yellowish-brown powder, marked with white, elongated meshes, containing a white, rather spongy tissue, and a number of short, reddish-brown or brownish-yellow striae; compact, hard; fracture uneven; internally white, with numerous red, irregularly curved and interrupted medullary rays, which are radially parallel only near the cambium line; odor somewhat peculiar, aromatic; taste bitter, somewhat astringent. When chewed, rhubarb feels gritty between the teeth, and imparts a yellow color to the saliva. Rhubarb which is very porous, or has a prominently mucilaginous taste, or is of a dark-brown color internally, should be rejected"—(U. S. P.). The grittiness observed when rhubarb is chewed is due to the oxalate of calcium present. Commercial rhubarbs, according to their geographical and botanical origin, may be classed as follows (Elborne, loc. cit.):
ASIATIC RHUBARBS.—Chinese (Russian, Muscovy or Turkey; Canton or East Indian; Batavian or Dutch-trimmed), yielded by R. palmaticum var. tanguticum and R. officinale(?). Siberian, from R. rhaponticum. Himalayan (large), from R. Emodi; small, from R. Webbianum. Bucharian, from R. undulatum.
EUROPEAN RHUBARBS.—English, from R. rhaponticum and R. officinale. French, from R. rhaponticum, R. compactum, and R. undulatum. Austrian (Moravian), from R. rhaponticum.
The former trade in Russian rhubarb was a government monopoly and the article, called crown rhubarb, has disappeared from commerce. It was collected in Chinese Tartary and sold to the Russian government, at the frontier town of Kiachta, where it was sorted by especially appointed apothecaries, and only the best grade accepted, the inferior grade being destroyed. It came to Europe by way of Asia Minor, and for this reason the term, Turkey rhubarb, established itself. Since the opening of the Chinese ports to European commerce in the '60s, the trade via Kiachta rapidly declined. (For interesting details regarding Russian rhubarb and its trade, see A. Fero, Amer. Jour. Pharm., 1867, p. 212; also Druggists' Circular, 1897, p. 278.) Chinese or East-Indian rhubarb is that now mostly in use. It is the official kind of rhubarb. It was formerly brought from Canton, but is now collected in Hankow and exported from Tien-Tsin (see Amer. Jour. Pharm., 1866, p. 153, for details regarding this grade). The European rhubarb (see English Rhubarb above) is produced in quite considerable quantity. Mr. Elborne (1884) reports that 12,000 pounds of English rhubarb were being gathered annually.
In selecting rhubarb, roots only should be taken which are sound and hard, of a bright-yellow color, of a strong rhubarb-aromatic smell, of a bitterish, slightly astringent taste, without viscidity, which feel gritty under the teeth, and which communicate a bright-yellow color to the saliva; they should present, when fractured, a marbled appearance of red and whitish veins, and be easily reduced to a bright-yellow powder, sometimes tawny-tinged (Ed.—T.). Inferior rhubarb is sometimes colored with turmeric, which may be detected by placing the rhubarb in powder on filtering paper, and moistening with chloroform, drop by drop. The turmeric color is thus transferred to the paper; dry the latter, moisten with solution of borax, then with hydrochloric acid. A brown-red tinge is formed if turmeric is present (see E. L. Howie, Amer. Jour. Pharm., 1874, p. 16).
Rhubarb, if boiled in water till it becomes soft, then crushed and agitated in the water, deposits pale-gray sandy crystals of oxalate of calcium. Continued boiling injures its virtues. Proof-spirit is a more ready solvent of the active ingredients of rhubarb than water. Solution of caustic potash is colored blood-red by rhubarb. Lime-water causes at first a pale cherry-red haze, which slowly gives place to a red precipitate. Ferric chloride produces a green precipitate, and solution of isinglass a yellow, curdy deposit, owing to the presence of tannin.
Chemical Composition.—G. Dragendorff (Jahresb. der Pharm., 1878, p. 74) analyzed 5 species of rhubarb, partly historical specimens, and found them to contain moisture (8.7 to 11.3 per cent), ash (3.2 to 24 per cent), mucilaginous matters (11 to 17 per cent), starch (6.2 to 16.5 per cent), sugar (3.7 to 5.5 per cent), cellulose, pectose, lignin, etc. (21 to 30 per cent), cathartic acid (2.03 to 5.25 per cent), oxalic acid (occurring as calcium oxalate, 1.12 to 4.6 per cent), malic acid (a trace to 1.24 per cent), free chrysophanic acid soluble in petroleum ether, absent or traces—in one instance 1.01 per cent—chrysophan and tannin (4.8 to 17.1 per cent), emodin, and resins soluble in alcohol, e. g., erythroretin, phaeoretin, etc. (1.15 to 6.29 per cent), white crystalline resin soluble in ether, insoluble in alcohol (0.15 to 2.32 per cent), fatty matter (traces, to 0.32 per cent), albuminous bodies (3.17 to 4.39 per cent). The results of an analysis of the species Rheum officinale, R. rhaponticum (both being English rhubarbs) and East-Indian and Russian rhubarbs, by Mr. William Elborne (Pharm. Jour. Trans., Vol. XV, 1884, p. 137) practically agree with those of Dragendorff. The latter considers cathartic acid, a glucosidal, nitrogenous substance, to be the purgative principle of rhubarb, greatly resembling that occurring in the leaves of senna and the bark of frangula. Quite recently, A. B. Stevens (Proc. Amer. Pharm. Assoc., 1898, p. 339) again laid stress upon cathartic acid, and gave a method for its preparation. The tonic action of rhubarb, Dragendorff considers due to the tannin present (rheo-tannic acid [C26H26O14] of Kubli), and the unmistakable antiseptic action, in cases of catarrhal affections of the intestines, due to the coloring matters chrysophanic acid, emodin and allied substances. Tschirch, however, finds the action of even chrysophanic acid to be decidedly purgative (Archiv der Pharm., 1899, p. 632). Chrysophanic acid (C15H10O4) was first isolated by Rochleder and Heldt, in 1843, from the wall-lichen Parmelia parietina. In 1844 its presence in rhubarb was recognized by Schlossberger and Doepping, who also isolated several resins, aporetin, phaeoretin, and erythroretin, all soluble in alkalies. Chrysophanic acid likewise occurs in the roots of certain species of Rumex (which see) and in goa powder (see Acidum Chrysophanicum). It crystallizes from alcohol in orange-yellow needles, soluble with yellow color in ether, alcohol (in 224 parts of 86 per cent); in petroleum benzin and amylic alcohol, almost insoluble in cold water. It dissolves in caustic alkali with beautiful dark-red color, but is insoluble in solution of sodium carbonate. According to M. Kubli (Amer. Jour. Pharm., 1885, p. 614), chrysophanic acid usually does not exist as such in rhubarb, but occurs in the form of a glucosid called chrysophan (also see Dragendorff, previous page). Treatment of rhubarb with water seems to dissolve a ferment capable of converting chrysophan into chrysophanic acid. The same conversion with liberation of sugar in both cases, takes place upon boiling with diluted acids. Chrysophan is soluble in warm water, insoluble in ether and benzin. Chrysophanic acid is gradually deposited when a tincture of rhubarb weak in alcohol is allowed to stand. Warren de la Rue and Müller, in 1857, discovered in rhubarb a substance analogous to chrysophanic acid which they called emodin (compare Frangulaand Rhamnus Purshiana). It crystallizes in long, red, monoclinic prisms, more easily soluble in alcohol than chrysophanic acid, but less soluble in benzol. It also differs by being soluble in solution of sodium carbonate. It has the formula C15H10O5, and is trioxy-methyl-anthra-quinone, while chrysophanic acid is dioxy-methyl-anthra-quinone, both derivatives of the hydrocarbon anthracene (C14H10) (Liebermann and Waldstein, 1876).
In addition, J. O. Hesse (Amer. Jour. Pharm., 1895, p. 615) obtained a third crystallizable principle rhein (C15H10O6), which seems to be tetra-oxy-methyl-anthraquinone. Like emodin, it dissolves in sodium carbonate solution at ordinary temperature with deep purple-red color, but differs from it in being insoluble in hot toluene. It is physiologically inert. Hesse finds the purgative principle of rhubarb to reside in that portion of its ether extract which is dissolved by 80 per cent alcohol and from the latter extract dissolved by a weaker alcohol. The principle thus obtained is resinous, non-glucosidal, not yielding chrysophanic acid upon boiling with acids. It is somewhat acrid and bitter, acid in alcoholic solution, and strongly purgative.
These results, however, do not seem to be final (see J. O. Hesse, Lieb. Annalen, Vol. CCCIX, 1899, p. 32; also A. Tschirch, Archiv der Pharm., 1899, p. 632). Tschirch takes the ground that in the group of Frangula, Rheum, Senna and Aloe the purgative action is due to the presence of glucosids which are decomposed by the alkaline fluid of the intestines, whereby sugar and oxy-methyl-anthraquinones are formed. Of the latter, emodin in particular is decidedly active. In rhubarb, this glucosid is chrysophan (see above), the presence of which is confirmed also by Gilson (1898).
Action, Medical Uses, and Dosage.—Rhubarb is cathartic, astringent and tonic; as a cathartic, it acts by increasing the muscular action of the intestines, rather than by augmenting their secretions, and affects the whole intestinal canal, especially the duodenum. Its cathartic effect is succeeded by a mild astringency, which has gained for rhubarb the reputation of being secondarily a calmative, as well as a stimulant of the digestive canal; with its astringent influence, it likewise exerts for the most part, a tonic action on the stomach, improving the appetite and digestive powers. It is absorbed in the course of its operation, making the serum of the blood yellow, the sweat tawny, and the urine red, which may be distinguished from bloody urine by heating it. If blood be present it will coagulate, and remove the red color, which will not happen if the tint be owing to rhubarb. Rhubarb applied moist to the skin, or when used to dress ulcers, as it sometimes is, has produced its peculiar purgative effects. Rhubarb is much used as a laxative for infants, in many infantile diseases; its mildness and tonic qualities rendering it peculiarly applicable, especially when enfeebled digestion and irritation of the alimentary canal are present. In acute or chronic diarrhoea or dysentery, in convalescence from exhausting diseases, and in some irritable habits, where the mildest of all other laxatives are apt to excite hypercatharsis, rhubarb is an appropriate medicine. Its combination with soap or an alkali tends to counteract its astringent effects, and it thus becomes valuable in cases of constipation. It is useful in all cases of fecal accumulations, as it produces fecal, more than watery discharges. Sometimes it produces griping, which may be obviated by aromatics. The following pill I have found very beneficial in dyspepsia attended with constipation, chronic diarrhoea and dysentery, habitual constipation, hepatic derangements, piles, etc.: Take extract of rhubarb, extract of leptandra, hydrochlorate of berberine, and castile soap, of each, ½ drachm. Mix them well together, and divide into 30 pills. Of these, 1, 2, 3, or 4 may be taken daily, sufficient to keep the bowels regular, without causing catharsis. When more than 1 are required daily, they should be given in doses of 1 pill at a time at regular intervals through the day (J. King). Prof. Locke recommends it in the constipation of dyspeptics with hepatic torpor, combining the neutralizing cordial with specific podophyllum or aloes. He also recommends it in gout and rheumatism with constipation, and as a gentle laxative after parturition. The cordial is recommended in the nursing sore mouth of infants. Rhubarb is efficient in the bowel disorders following the excessive use of alcoholics. The following is efficient during convalescence from delirium tremens: Rx Leptandra, rhubarb, gentian aa, in powder, ℥i; ginger, ℨii; diluted alcohol, Oj. Macerate. Sig. Dose, 1 teaspoonful (Locke). Rhubarb is generally contraindicated in severe febrile or inflammatory affections. Toasting dissipates its purgative property considerably, but without diminishing its astringency, and it is, thus prepared, recommended by some practitioners in diarrhoea, dysentery, cholera morbus, and other diseases where astringents are indicated. In the ordinary summer diarrhoea of both children and adults, and particularly when an acid condition presents, the neutralizing cordial (Locke's formula preferred) is a most excellent corrective.
Specifically rhubarb is employed for a different action from that given above which represents the old but excellent uses of the drug. The specific object sought is the control of gastro-intestinal irritation, and this is nicely accomplished by the use of small doses of specific rheum. The red-pointed tongue, evidencing gastro-intestinal irritation, is the direct indication for its use. Add to this vomiting, nervous irritability as manifested by restlessness, screaming and convulsive muscular contractions, and the specific field of rhubarb is clearly set forth. The common method of administration is as follows: Rx Specific rheum, ℨi; water, ℥iv. Dose, a teaspoonful every ½ or 1 hour. The same doses given less often act as an excellent gastro-intestinal tonic, giving better digestion and controlling the papescent diarrhoea of indigestion when present. In chronic constipation with a sense of constriction in stomach and bowels and contraction of the abdominal muscles, 10 drops of specific rheum may be given in a full glass of cold water in the morning. Fatty inunction of the abdomen adds to its efficacy. In conjunction with cod-liver oil and phosphorus preparations Prof. Scudder administered rhubarb where an "increased nutrition of nerve tissue" was demanded.
Dose of the powder as a purgative, from 10 to 30 grains; as a laxative, from 5 to 10 grains; as a tonic, from 1 to 5 grains; of the tincture or syrup, 1 or 2 fluid drachms; of neutralizing cordial, 1 to 4 fluid drachms. For specific effects, from 1/10 to 5 drops of specific rheum.
Specific Indications and Uses.—Gastric irritation, nausea, vomiting, elongated tongue reddened at tip and edges; irritative diarrhoea with tenderness on pressure; sour smelling discharges imparting to the child a sour odor; gastrointestinal irritation with nervous irritability, restlessness, screaming and convulsive muscular contractions; constipation, with a sense of intestinal constriction and abdominal contraction; light-colored fecal discharges.
Related Species.—Rheum Emodi, Wallich (R. australe, Don.) R. Moorcroftianum, R. speciforme and R. Webbianum are Himalayan species of rhubarb. (For a description of these and the following species see Lindley, Flora Medica, p. 354).
Rheum palmatum, Linné.—This plant inhabits the country near the great wall of China. It was cultivated in Russia soon after 1750, when a Tartarian merchant supplied Dr. Boerhaave, physician to the emperor of Russia, with what were believed to be the seeds of genuine rhubarb. Guibourt strongly held that R. palmatum was the botanical source of genuine rhubarb of China, a view supported by the Russian Colonel Przewalski, who observed this species and collected specimens thereof in 1872-73 in the Chinese province of Kansu. The specimens, however, by analysis of Dragendorff (see Rheum) proved to be different from authentic specimens of the genuine root.
Rheum hybridum, Murray, and its variety Colinianum are cultivated, the former in Europe and the latter in Asia. Their roots agree with rhubarb.
Rheum undulatum (Bucharian rhubarb) and R. compactum are two species cultivated in France. The petioles of the latter species are used for pies.
Rheum rhaponticum, Linné, Common garden rhubarb.—This plant inhabits the borders of the Black Sea and is more abundant north of the Caspian, in the deserts between the Volga and the Yaik; also on the mountains of Krasnojar in Siberia. This has a more disagreeable smell than rhubarb, and is not so gritty to the taste. It is cultivated in this country and Europe, for pies, etc. The prepared root has the resemblance of true rhubarb, but not its medicinal properties. R. Otto believes the continued use of the petioles of rhubarb for pies, etc., to be injurious to health owing to the oxalic acid (0.2 to 0.3 per cent) it contains in soluble form in addition to insoluble calcium oxalate (Drug. Cir., 1895, p. 150).
Perezia adnata, Gray (Trixis Pipitzahoac, Schaffner. (Nat. Ord.—Compositae).—The rhizome of this plant is employed as a laxative and contains a violently purgative acid, which also imparts to the urine a greenish color. Pipitzahoic acid (C15H10O3) is obtained by extracting the roots with alcohol of 82 per cent and precipitating with water. It forms beautiful yellow or reddish scales (vegetable gold) soluble in alcohol, ether, chloroform and carbon disulphide, nearly insoluble in water. It is sublimable. In alkali it dissolves with beautiful violet color. It has also been obtained from Perezia Wrightii, Gray, and Perezia nana, Gray, both from southwestern Texas. As a drastic cathartic the dose is from 4 to 8 grains. The acid is an oxyquinone (Anschütz).
Rhinacanthus communis, Nees (Acanthaceae).—India and China. Root-bark of this shrub contains viscous, tasteless, rhinacanthin (C14H18O4), not a glucosid (Liborius). In some respects it resembles chrysophanic acid. The leaves and woody root have been employed in ringworm and other skin affections (see complete analysis, by P. Liborius, in Jahresb. der Pharm., 1883-84, p. 152).