Tragacantha. U. S., Br. Tragacanth.
Trag. [Gum Tragacanth]
"The spontaneously dried gummy exudation from the stems of Astragalus gummifer Labillardiere, or from other Asiatic species of Astragalus (Fam. Leguminosae)." U. S. "Tragacanth is a gummy exudation obtained by incision from Astragalus gummifer, Labill., and some other species of Astragalus. Known in commerce as Syrian tragacanth." Br.
Gummi Tragacantha vel Astragalorum; Gomme Adragante, Fr. Cod.; Tragacantha, P. G.; Tragant, Traganth, G.; Gomma adragante, Dragante, It.; Gomo tragacanto, Sp.
Numerous species belonging to this genus yield a gummy matter having the properties of tragacanth. The drug known in commerce by that name was at first erroneously supposed to be obtained from A. Tragacantha of Linnaeus (A. massiliensis of Lamarck), which grows in Southern Europe and Northern Africa and is now said to yield no gum. It was afterwards ascribed, on the authority of Tournefort, to a species (A. creticus of Lamarck) which grows in Crete and lonia, and on that of Olivier, to A. verus, which inhabits Asia Minor, Armenia, and Northern Persia. Labillardiere described a species by the name of A. gummifer which he found growing on Mount Libanus in Syria, and from which tragacanth exudes, though not that of commerce. Only recently it has been denied that Astragalus gummifer is the source of tragacanth. (Cons. and Tr. Rep., 1910, p. 728.)
Sieber denies that any of the above-mentioned species yields the official tragacanth, which he ascribes to A. aristatus, growing in Anatolia, especially upon Mount Ida, where the gum is most abundantly collected. This plant, however, is not the A. aristatus of Villars, which, according to Sibthorp, furnishes tragacanth in Greece. (Merat and De Lens.) Lindley received two specimens of plants, said to be those which furnish tragacanth in Turkestan, one of which proved to be A. gummifer of Labillardiere which was said to yield a white variety, and the other a new species, which he called A. strobiliferus, and which was said to yield a red and inferior product. The fact seems to be that the commercial drug is collected from various sources; and it is affirmed that all the species of Astragalus with thorny petioles are capable of producing it. These form a natural group, and so closely resemble one another that botanists have found some difficulty in distinguishing them. They are very abundant on the mountains of Asia Minor, and, according to information received by M. J. Leon Soubeiran from Balansa, a scientific traveller who derived his knowledge from personal observation, the gum-producing species are closely analogous to the A. creticus of Lamarck. It is in the Anti-Taurus range that the gum is chiefly collected. Transverse incisions are made, near the base of the stem, into the medullary tissues, which alone yield the gum. This exudes very slowly, flowing at night, and ceasing during the day; two weeks usually elapse before the pieces are large enough for collection. The shape of the pieces is influenced by the rapidity of the exudation, and the lines on their surface indicate the daily concretion. The section Tragacantha of the genus Astragalus includes the principal species which yield gum tragacanth.
According to Haussknecht, tragacanth is yielded by the following species of Astragalus: A. adscendens Boiss. et Hausskn. (Southern Persia); A. leioclados Boiss. (in Middle and Western Persia, by Ispahan and Hamadan); A. brachycalyx Fisch. (Kurdistan and Luristan); A. gummifer Labill. (widely distributed from Lebanon to Armenia and in the northern regions of the Euphrates and Tigris); A. microcephalus Willd. (the same as A. gummifer Labill., and also in Asia Minor); A. pycnocladus Boiss. et Hausskn. (particularly in Western Persia); A. stromatodes Bge. (in Achyr Dagh, in Northern Syria); A. kurdicus Boiss. (Aintab). Other species that yield a tragacanth gum are A. heratensis Bge., of the Khorasan Mountains, which yields a gum known as "kutira," and A. Parnassi Boiss., var. cyllenea, found on the mountains of Peloponnesus.
Harris states that the best Smyrna tragacanth is produced in Asia Minor. It is not, however, collected in the immediate vicinity of Smyrna, but comes from Karahissar, Jalowadsch, and even farther in the interior, where the plant grows wild. This kind of gum consists of white, yellow, and red, hardened pieces, which have become congealed after oozing out of the bush or tree in the hot sun of a Levantine summer. The gum is secured in a similar manner as opium by an incision in the branch. This is done in the spring and summer of each year, and the gum is usually scraped in September, when the first rains begin to fall. During the last twenty years the gum tragacanth trade of Smyrna bas decreased. It has been estimated that the trade has fallen from 600,000 pounds to 55,000 pounds in that length of time. (Oil, Paint and Drug Reporter, lxxiii, p. 633.)
Properties.—Tragacanth is odorless and nearly tasteless. It occurs either in flaky, leaf-like pieces, irregularly oblong or roundish, or in tortuous vermicular filaments, rounded or flattened, rolled up or extended, of a whitish, yellowish-white, or slightly reddish color, marked by parallel lines or ridges, somewhat translucent, and resembling horn in appearance. In commerce certain varieties of tragacanth are recognized and usually known by the name of the locality from which they have been produced or through which they have entered commerce. The ordinary tragacanth, tragacanth in sorts, sometimes known as traganton, occurs in irregular pieces; Smyrna tragacanth appears usually in broad thick flakes, yellowish or brownish; Syrian tragacanth, in thin, ribbon-like, white flakes, is said really to be obtained in Kurdistan and Persia. Tragacanth is officially described as <( in flattened, lamellated fragments varying from ribbon-shaped bands to long and linear pieces, which may be either straight or spirally twisted, and from 0.5 to 2.5 mm. in thickness; whitish to light brown in color, translucent and horny; fracture short; rendered more easily pulverizable by heating to 50° C. (122° F.); inodorous; taste insipid, mucilaginous. Under the microscope, sections made from Tragacanth, previously softened in water, and mounted in glycerin, show the lamellae of mucilaginous walls and a few starch grains, the latter being mostly spherical and single, occasionally 2- to 3-compound, the individual grains from 0.003 to 0.025 mm. in diameter and colored blue with iodine. Indian Gum, derived from plants of uncertain origin, upon similar treatment and examination, shows numerous threads of a granular substance, sometimes the hyphae of a fungus and chains of bacteria, and occasional fragments of a yellowish-brown or reddish-brown color, containing lignified wood-fibers, a few rosette aggregates of calcium oxalate, from 0.02 to 0.03 mm. in diameter, and a few spherical starch grains, from 0.003 to 0.007 mm. in diameter. Add 1 Gm. of Tragacanth to 50 mils of distilled water; it swells and forms a smooth, nearly uniform, stiff, opalescent mucilage free from cellular fragments. Indian Gum upon similar treatment forms an uneven mucilage containing a few reddish-brown fragments, and on stirring separates in the form of coarse, uneven strings. Shake 2 Gm. of Tragacanth with 100 mils of water until fully swollen and free from lumps, and then add 2 Gm. of powdered sodium borate and shake the mixture thoroughly until the salt is dissolved; the mucilage does not lose its transparency, nor exhibit any change in consistence, and on pouring is . not slimy or stringy, even after standing twenty-four hours (foreign gums). Boil 1 Gm. of Tragacanth with 20 mils of water until a mucilage is formed, then add 5 mils of hydrochloric acid and again boil the mixture for five minutes; it develops no pink or red color (Indian Gum). The powder is whitish; forming with water a translucent mucilage and under the microscope exhibiting numerous starch grains, from 0.003 to 0.025 mm. in diameter, varying from spherical to elliptical, -with occasional 2-to 4-compound grains, many of the grains being swollen and more or less altered, due to the drying of the Tragacanth before powdering. Powdered Indian Gum shows numerous fragments of lignified vegetable tissue. Tragacanth yields not more than 3.5 per cent. of ash." U. S.
"Thin flattened flakes, irregularly oblong, or more or less curved, marked on the surface by concentric ridges. Frequently two and a half centimetres long, and twelve millimetres wide. White or pale yellowish-white, somewhat translucent. Horny, fracture short. Inodorous; almost tasteless. Sparingly soluble in water, but swelling into a gelatinous mass, which may be tinged violet or blue by N/10 solution of iodine. Ash not more than 4 per cent." Br.
It is hard and more or less fragile, but difficult of pulverization, unless exposed to a freezing temperature, or thoroughly dried, and powdered in a heated mortar at the temperature of 50° C. (122° F.). Its sp. gr. is 1.384. Introduced into water, it absorbs a certain proportion of that liquid, swells very much, and forms a soft adhesive paste, but does not dissolve. If agitated with an additional quantity of water, this paste forms a uniform mixture; but in the course of one or two days the greater part separates, and is deposited, leaving a portion dissolved in the supernatant fluid. Tragacanth is wholly insoluble in alcohol. It appears to be composed of two different constituents, one soluble in water and resembling gum arable, the other swelling in water, but not dissolving. To separate the soluble from the insoluble part requires agitation with separate portions of water; the solutions are to be decanted and filtered, and the process is to be continued until water ceases to dissolve anything.
Von Sandersleben reported the discovery that when heated with dilute acids tragacanth acquired reducing properties, and formed, along with much syrup, arabinose, which crystallized. (Tollens, Handbuch der Kohlenhydrate, 1888, 218.) The explanation of this observation, now generally accepted, is that in tragacanth, like some other gums, part of the arable acid is present in soluble form, mostly combined with bases, while another part is present in insoluble form, and is known as traganthin. This latter, however, under the influence of certain enzymes, is converted into the soluble form. (Lippmann, Chemie der Zuckerarten, 2te Auf., 1895, 925.) C. O'Sullivan states that tragacanth consists of cellulose, the portion insoluble in boiling water, cold dilute acids, and alkalies; also soluble gum, yielding a series of gum acids of the nature of geddic acid, and which are called polyarabinon-trigalactan-geddic acids; starch granules; bassorin, which yields a-tragacanthan-xylan-bassoric acid, xylan-bassoric acid and bassoric acid. (Proc. Chem. Soc., 1901.) Examined by Kützing by means of the microscope, tragacanth was found to consist of organized cells. (See A. J. P., xxv, 37.) In conformity with this statement is the remarkable fact, discovered by Hugo von Mohl and confirmed by Wigand, that tragacanth is not a secretion of the plant, but the result of the transformation of the cells of the pith and those of the medullary rays which traverse the ligneous part of the stem and older branches. (A. J. P., xxxi, 243.)
It is stated by S. H. Maltass that tragacanth is adulterated, in the Levant, with worthless gums brought from Armenia and Caramania, which, as they are originally of a dark color and destitute of the flaky form of the genuine gum, are broken into small fragments and whitened by means of lead carbonate before being mixed with the tragacanth. Hanbury states, in confirmation of this, that he has detected lead in the small tragacanth imported into London. (P. J., xv, 20.) Gum tragacanth has been recently admixed with and substituted by Indian gum, the product of Cochlospermum gossypium (Fam. Bixaceae). This occurs in vermiform or rounded tears having a dull, rough surface. It is detected by the official tests. The powdered drug is not only adulterated with the Indian gum, but with powdered acacia, dextrin, wheat and cornstarch. Payet gives a test for the detection of acacia in powdered tragacanth which depends on the brown color produced by the oxidase of the former when brought in contact with an aqueous solution of guaiacol in the presence of hydrogen dioxide. (Ann. de Chim. Analyt., x, p. 63.)
Uses.—Tragacanth is demulcent, but, on account of its difficult solubility, is not often given internally. The great viscidity which it imparts to water renders it useful for the suspension of heavy insoluble powders, and it is also employed in pharmacy to impart consistence to troches, for which it answers better than does gum arable, and in making emulsions, although for these purposes it is inferior to acacia. It is also used for its demulcent action in pharyngitis by allowing a piece of the gum to dissolve slowly in the mouth. It is officially employed as the basis of many of the troches.