On Quebracho Bark.


Translated and abridged from "Archiv der Pharmacie," Bd. xv, pp. 81 to 102, Feb., 1881., BY FREDERICK B. POWER.

As in the case of jaborandi, much confusion has prevailed in medical and pharmaceutical circles with relation to this new medicinal drug, which can only be prejudicial to the proper application or judgment of a possibly valuable medicament. Those interested in the subject will therefore welcome the very serviceable monograph of Dr. A. Hansen in Erlangen ("Die Quebracho-Rinde, botanisch-pharmacognostische Studie," Berlin: J. Springer), by which it has been made possible to distinguish the genuine quebracho bark from the various false barks, which have long enough maintained the field nearly alone, and by the procuration and pharmaceutical application of the genuine drug, to clear the path for rational medical experiences and judgment in regard to this novelty. The above-mentioned essay, which, besides being accompanied by several explanatory anatomical tables, contains also a series of further pharmacologically important communications, and is deserving, therefore, of special consideration in pharmaceutical circles.

In the following the most important deductions from Hansen's pamphlet will be produced, accompanied by some special notes of the author.

In regard to the derivation of the genuine quebracho bark, it is supposed to be known that it was first, in the course of the year 1878, sent by a resident German in the Argentine Republic, F. Schickedanz, together with other products of the country, to Erlangen, with the observation that the bark had served for a long time in those districts, and particularly in Tucuman and the surrounding country, as a fever remedy, and in many instances in its action was accorded an equal position with cinchona bark. While the bark sent by Schickedanz was obtained from the western portion of the Argentine Republic, where the quebracho tree is said to occur chiefly in the province of Santiago and in the district of Catamarca, it appears, according to other reports, to occur also in neighboring Chili, and may possibly be also found in Bolivia and some districts of southern Brazil.

The above-mentioned quantitatively not significant export was subjected to a double seizure, as simultaneously a chemical examination of the drug was made in Munich, and a series of therapeutical experiments with pharmaceutical preparations of the bark performed by Dr. Penzoldt in Erlangen.

The result of the chemical examination was the isolation of an alkaloid, aspidospermia, by Fraude (see this journal, 1879, p. 192), who, supported by the composition (C22H30N2O2) and the chemical behavior of this new vegetable base, proved on the one hand its close relation to quinia, and on the other to strychnia.

The medico-clinical experiments, without indeed confirming a decided anti-febrile action, led to the discovery of its beneficial properties in difficulty of respiration, which had not remained unknown in the native country of the bark, and after the declaration of these results there soon followed from medical and pharmaceutical sections a demand for quebracho bark. In consequence of the difficulty of quickly procuring the genuine drug the supplies were much less than the demand, and as the result of a deficiency of knowledge in regard to its true derivation, various substitutes were created leading to manifold contradictions in regard to the medicinal activity of quebracho bark, which, for nearly two years, had partially found application in the form of two or three other barks, without any certain knowledge prevailing as to their spurious nature.

A very essential part in the confusion with regard to quebracho bark is due to the circumstance that in South America, and particularly in the southern districts, the name "Quebracho" (the etymology of which is derived from the Spanish words "quebrar" [to break] and "hacha" [axe] ) is a common designation, a peculiar vulgar name for various heterogenous trees with very hard wood, whereby occasionally the different species of wood and the trees from which they are derived are given in addition thereto, and further distinguished by special adjectives as "blanco, flojo," etc. But even these more complete designations can serve by no means as a criterion, and may vary with the country or province. While the genuine quebracho bark is derived from the apocynaceous Aspidosperma quebracho, Schlechtendal, in the western part of the Argentine Republic at least two other trees, a Terebinthacea and an Ilicinea, are designated as "Quebracho," the former with the surname "Colorado" and the latter with the attribute "flojo" (soft, loose), the tree Aspidosperma quebracho being known as "Quebracho blanco," and, according to the trustworthy statement of Professor Hieronymus of Cordoba, exclusively so. It was chiefly the tree known in the Argentine Republic as Quebracho Colorado which was confused with the Quebracho blanco, and the bark and wood of which was medicinally applied in Europe as "Quebracho" instead of the original Q. blanco bark, the two plants appearing to be closely connected both in relation to their history as also in their technical application.

Both trees, the "blanco" as also the "Colorado," were signalized by former travelers in the La Plata States, particularly by Burmeister, who, however, considered the two Quebracho trees as simple varieties, which were distinguished to some extent by the form of the leaf, and particularly by the color of the wood. The portion of the white quebracho sent by Burmeister to Europe induced Schlechtendal to determine the species, which he accordingly named "Aspidosperma quebracho blanco" and, misled by the relationship of names, he connected the red quebracho tree as a further species with the name of "Aspidosperma quebracho Colorado."

It was more than ten years later that this error was corrected by the publication by Grisebach of the "Plantae Lorentzianse" (a revision of the Argentine plants collected by Prof. Lorentz in Cordoba), and, at the same time, reported that the Q. Colorado plant, supposed to belong to "Aspidosperma," was a Terebinthacea, and related to the genus "Anacardium." It thereby received a correct description and the botanical name "Loxopterygium Lorenztii, Grisebach..

From a technical view, it remains to be said that the wood of both trees, Q. blanco and Q. Colorado, is employed in South American countries for tanning purposes, and has repeatedly figured as such at the world's expositions. The very small amount of tannin contained in the aspidosperma wood (about 3 per cent.) does not permit of its competition with other similar materials, while the loxopterygium wood, with 15 to 20 per cent. of tannin, was introduced some time since into Europe, where it is employed either in the rasped condition or in the form of extract. As this tanning wood occurs in trade under the simple name of quebracho wood, its substitution for the preparations of the bark and wood of Q. blanco, as recommended from Erlangen, was not difficult, and the above-mentioned extract of the Q,. Colorado wood was therefore also drawn into medicinal use.

The mother-plant of the genuine quebracho bark Aspidosperma quebracho, Schl., is connected with other likewise South American aspidosperma species, amounting in number to as many as 40, and is described as a high, perpendicular tree, with a finely branched summit, the habitus of which is said to resemble the crown of the weeping willow.

The leathery, smooth, lanceolate leaves, whose points terminate in a spine, are arranged to the number of three on each branch. The dichotomously-branched inflorescence shows flowers with a calyx composed of five sepals and a five-partite corolla, five anthers, one style and a superior ovary.

The Quebracho blanco bark from the Argentine Republic, as it occurs in commerce, appears to consist of pieces from the older trees, about 70 years of age, and shows an average thickness of 2 centimeters. Less frequently younger barks are found with a very moderately developed periderm, or the latter even entirely wanting.

The most striking peculiarity in the outer structure of the quebracho bark is the relatively exceedingly strongly developed cork, which penetrates very deeply into the bark, often to the extent of over one-half. Upon a cross-section of pieces of the bark a boundary line passing approximately through the middle of the bark separates very distinctly the two portions of tissue, the cork and the unchanged bark tissue, which are also sharply distinguished by their color and internal structure. The lens permits of recognition on a cross-section of the cork, the outer surface of which is grayish, or in scarified places reddish, a yellowish-red fundamental mass with tangentially penetrating serpentine lines, differing in color, and between the same plainly evident white points. The inner cortical layer consists for the most part of a light brown, or occasionally also of a much lighter dirty yellow tissues, with very numerous and irregularly distributed whitish dots corresponding to those of the cork tissues.

While the outer bark, which has been converted into bork, possesses a somewhat crumbly consistence, the inner portion of the bark connected with the stem is hard and composed of long, splint-like fragments.

By a microscopical observation of the quebracho bark on a cross section, the outer cortical tissue shows in a marked degree the structural relations which appear in the preponderating cork. In the parenchymatous tissue with brown, often carmine colored cell walls, the above indicated secondary corky layers appear, consisting of uniform rows of smaller, almost colorless cells, and between the same the white points or grains, which are at once recognized as sclerenchyma, or groups of strongly thickened cells, with a small lumen. A very similar structure is shown by the inner cortical layer, situated between the bork and the cambium, although deviating somewhat in the coloration of the cellular tissue; and here also the groups of stone cells, which microscopically form large white points, are dispersed in a brown colored, often also lighter, parenchymatous tissue containing starch, although the tangential cork bands are wanting; and of the radially extending medullary rays, in consequence of the irregular structure of this tissue only a few are plainly recognizable.

Among the mentioned sclerenchyma cells there are many which are distinguished from the others by a particularly uniform circular outline of the cross section, and are, in part, combined with them in groups or occur isolated throughout the bark. These peculiar cells, which aggregate particularly in the inner portion of the bark and which cause its fibrous, splint-like structure, prove themselves true sclerenchyma fibres of considerable length, and are characterized by being surrounded by a closed integument, which consists of numerous small cells and each of which contains an oxalate crystal. These integument cells surround, as well upon the cross as upon the longitudinal section, the contour of the thickened fibres most closely, and are organically connected with them, so that the separate fibres, isolated from the tissue, present an over-surface consisting entirely of these small crystal cells.

The occurrence of these spindle-shaped fibres covered with crystal cells, accompanied by the approximately parenchymatous stone cells, which, upon a longitudinal section, appear through the cork as bright, punctate cells, is highly characteristic of the genuine quebracho bark, and a priori adapted to distinguish it from the false barks which have appeared in commerce, which is even possible with the use of a strong lens.

It may be observed that, according to Hansen, in the younger barks of the quebracho plant very deviating anatomical relations prevail. the integuments of the crystal ducts first exist after the complete formation of the sclerenchyma fibres and, indeed, from the surrounding parenchyma cells. The formation of the entire duct tissue proceeds quite slowly. Cross sections through younger barks show that nowhere a ring of cells containing crystals surrounds a younger fibre, but that this is closely surrounded by the parenchyma cells of the cortical tissue.

The author subsequently considers the microscopical structure of the wood of quebracho, which, in the case of the true Q. blanco, like the bark, possesses some medicinal activity, although to a very slight extent, and together with the wood of Q, Colorado, on account of its extreme hardness, is much employed in its native country for building purposes.

In consideration of the most important false quebracho barks which have served as substitutions for the aspidosperma bark there is to be mentioned, in the first place, a bark which has been much sold and applied as quebracho, although deviating so much from the true Q. blanco bark that its continued substitution is scarcely to be thought of. The bark in question was soon recognized as belonging to the genus Croton (Euphorbiaceae) by Pohl, and was afterwards identified by Hansen a copalchi bark, which was long known in the drug market, although now obsolete in pharmacy; it belongs to the group of cascarilla barks and is derived from the Mexican Croton pseudochina, Schl. (Croton niveus, Jacq.). As is known, the copalchi bark agrees with this false quebracho by occurring in tubular pieces several inches long, provided with a grayish-white powdery periderm, and varies in thickness from ½ to 2 lines. The cross section of the bark shows with the lens a structure entirely different from the aspidosperma bark, i. e., a homogenous yellowish-white outer bark, and a brown bast portion, which, by means of the small bast bundles becoming pointed towards the periphery assumes a flame-like appearance. Moreover, the croton bark possesses a spicy odor and taste, which is not present in true quebracho. Another bark of undetermined botanical derivation consists of dark-brown pieces with a grayish or gray-brown cork layer, and shows many furrows on the inner side, without, however, possessing a similarity with aspidosperma bark. The same may be said of a bark of unknown botanical derivation, which as "Cortex Quebracho verus" has been sold at a high price, and has been found by Hansen to differ from all previous quebracho varieties. This bark, which is also distinguishable from the aspidosperma by a microscopical examination, consists of pieces from 1 to 1 ½ inch in thickness, of a brown color and firm consistence, characterized by numerous light-colored cork bands on a cross section, and with a slightly developed inner bark. It appears to contain a large amount of tannin, but does not possess the remarkable bitterness of the genuine quebracho bark. Finally, the bark of the Q,. Colorado tree appears occasionally to have taken the place of the "Q. blanco" bark, although it can hardly be confound with the true quebracho.

The Q. Colorado bark is of a brown or dark-brown color on the exterior and possesses frequently a covering of lichens. The cross section is light-brown and shows concentric darker cork bands, as also light radially extending lines, which prove to be the medullary rays. Between these latter uniformly arranged groups of sclerenchyma fibres are situated, which groups, several in number and standing behind each other, impart to the bark a checkered appearance. Although these fibres show a structure similar to the crystal-covered fibres of the aspidosperma bark, they are, however, considerably smaller and are situated not alone, but, as stated, in bundles of nearly right angular form. By the use of a lens, or by microscopical examination, the bark of Q. Colorado may thus be easily distinguished from the Q. blanco, even when the difference in taste is not considered;

In concluding his valuable review of quebracho bark the author gives also a sketch of the development of the chemistry of the subject, for the principal results of which the reader is referred to abstracts in this journal (1879, p. 192 and 554-557), as also to the more recent contribution of O. Hesse, contained in the last number.

The American Journal of Pharmacy, Vol. 53, 1881, was edited by John M. Maisch.