Viburnum prunifolium and Viburnum opulus.

By L. E. Sayre,
Member of Research Committee C, Revision Committee of U. S. P.

The two barks, Viburnum prunifolium and Viburnum opulus, have been for some time almost equally popular among practitioners. Wherein lies the advantage of one over the other, therapeutically, is, perhaps, difficult for one to say without more data than is at present at our command; but, as far as my investigations have gone, it appears that the prunifolium is more frequently depended upon in neuralgia of the ovaries, that the opulus is most useful in uterine and ovarian pain, in dysmenorrhea and pains of that class, and that it is more often depended upon for prevention of abortion whether accidental or habitual. But it is not so much a question of therapeutical merits of the one or the other of these barks which so much engages the attention of the pharmacist, as it is the physical characteristics which will enable one to assure himself of their purity.

The Pharmacopoeia describes these two barks as follows:

Viburnum opulus.

"In flattish or curved bands, or occasionally in quills, sometimes 30 centimetres long, and from 1 to 1.5 millimetres thick; outer surface ash-gray, marked with scattered, somewhat transversely elongated warts of a brownish color, due to abrasion, and more or less marked with blackish dots, and chiefly in a longitudinal direction, with black, irregular lines or thin ridges; underneath the easily-removed corky layer of a pale brownish or somewhat reddish-brown color; the inner surface dingy white or brownish; fracture tough, the tissue separating in layers; inodorous; taste somewhat astringent and bitter."

Viburnum prunifolium.

"In thin pieces or quills, glossy purplish-brown, with scattered warts and minute black dots; when collected from old wood, grayish-brown; the thin, corky layer easily removed from the green layer; inner surface whitish, smooth; fracture short; inodorous; somewhat astringent and bitter."

Among the problems presented to Research Committee C by its chairman, Dr. H. H. Rusby, is one which relates to the question of discrimination of these two barks, particularly in the crushed or powdered condition, and one relating to the distinction between the bark of the root and bark of the stem of Viburnum prunifolium. Entering upon the investigation, I have formulated the problem as follows:

(1) What are the distinguishing characteristics which will identify the bark of the stem and the bark of the root of Viburnum prunifolium?

(2) How can one distinguish between the bark of Viburnum prunifolium and V. opulus?

(3) What are the differential characteristics of these barks which will enable one to distinguish between them in the crushed condition or in the state of powder?

Before seriously taking up the third question, it is necessary to have clearly before one the gross characteristics of these barks, and to understand the relation between them structurally as well. At the same time, it is essential that such a knowledge of the constituents be had as shall enable one to compare them pharmaceutically.

It is the object of this paper to lay before those who desire to contribute to the work a statement of what has been done thus far in answering the first and second questions. I am gratified to state that there are those, even outside of the committee, who have interested themselves in the work, and who desire such a statement. It is this that has suggested this paper.

For authentic specimens for the investigation I am indebted to Dr. H. H. Rusby. These were as follows:

Name of Specimen and Physical Characteristics.

I. Viburnum opulus.—Trunk bark, commercial specimen from Parke, Davis & Co. Curved pieces from 6 to 10 inches (150 to 250 mm.) in length, and about 1/12 inch (2 mm.) in thickness, the inner surface usually with strips of the white wood adhering. The bark consists of three layers, the periderm, a green chlorophyll layer, and a yellowish or brownish-yellow inner bark. The periderm is nearly smooth, especially on the younger bark, greenish or greenish-gray, marked with greenish and whitish patches, and with brown, corky warts. Fracture short through the outer layer; the inner layer tears in long, fibrous strips

II. Viburnum prunifolium.—Trunk-bark collected by Dr. H. H. Rusby, at Franklin, N. J., May, 1894. Curved pieces and fragments about 1/6 inch (4 mm.) thick; outer surface very rough, greenish or grayish, covered here and there with gray lichens; inner surface yellowish-white, about half as thick as the corky layer, free from adhering wood; the cork is thick, reddish, and shows, on a cross-section, small white spots dotted throughout its tissue. Fracture short.

III. Viburnum prunifolium.—Bark collected from small branches. Small curved pieces, very thin; periderm brownish-gray, smooth, overlaying a green chlorophyll layer; inner layer whitish, its inner surface yellowish-brown from exposure to air. Fracture short. It seems to possess the bitter principle to a greater extent than any of the preceding.

IV. Viburnum prunifolium.—Bark of root collected at Franklin, N. J., May, 1894, by Dr. H. H. Rusby. Quills or fragments, sometimes with strips of the yellowish-white wood adhering to the inner surface, which is brownish by exposure to air. The corky layer is grayish-brown, somewhat ridged so as to form more or less distinct meshes. The inner layer is thick, breaking with a short, or sometimes waxy, white fracture, easily cut or scraped with the fingernail.

V. Bark of root (source unknown).—Flattish or curved pieces, from 1/8 to 1/6 inch (3 to 4 mm.) in thickness, covered by (or sometimes deprived of) a reddish or grayish-red cork. Inner layer of about equal thickness to the outer, breaking with a short, brownish-white or white fracture.

All of these specimens have a pronounced, peculiar odor, difficult to describe, differing quite considerably among themselves in this respect. The root-bark of Viburnum prunifolium has a somewhat disagreeable odor. All contain a bitter principle, this bitterness being particularly prominent in the root-bark and bark of small branches of V. prunifolium. In the trunk-bark the bitterness is noticeably less. In Viburnum opulus there is not much bitterness, but there is quite an astringent taste.

Structural Characteristics.

A cross-section of the stem bark of Viburnum opulus under the microscope shows the following structure: Immediately interior to the periderm are numerous irregular clusters of stone cells. These are succeeded in the inner or bast layer by large clusters of bast fibres associated with a few stone cells. These clusters are arranged in bands parallel to the surface of the bark, and are separated from each other radially by narrow, one or two-rowed, straight medullary rays. The clusters are also partly or wholly encased in thin-walled crystal cells, each usually containing a single crystal of calcium oxalate. These interrupted bands of bast fibres and stone cells are separated from each other by rather broader bands of soft bast, in which also a few scattered stone cells and bast fibers occur.

Tests by means of ferric solutions show the presence of considerable quantities of tannic matters in the middle bark, in the soft bast and in the medullary rays.

A cross-section of the stem bark of V. prunifolium shows groups of stone cells somewhat irregularly disposed, but no bast fibres. These groups appear in this section rounded or somewhat elongated in a tangential direction, or sometimes irregular in outline, but in longitudinal view they appear mostly fusiform, and sometimes five or ten times as long as thick. The component cells are also of large size.

The clusters of stone cells occur both in the middle and in the inner layers of the bark, but are larger in the latter.

The medullary rays, which in this species are also straight and composed of one or two rows of cells, are much less easily traceable than in the former species, because the cells differ little in size and shape from adjacent parenchymatous elements. They are best recognized by means of iodine solution, their cells containing more starch than those of adjacent tissues.

Freely sprinkled through the parenchymatous regions of this bark are cells containing stellate crystalline masses of calcium oxalate, but cells containing single crystals are rare or wanting, and there is no crystal sheath about the masses of stone cells.

Tannin is also present in this bark, but apparently somewhat less abundant than in the former species.

The bark of the young stems or branches differs from that of older ones, in the fact that the stone cells are in smaller groups. This is because in the old bark the earlier formed masses of stone cells have been cut off by the secondary cork formations, and the later formed groups of stone cells in the inner layers of the bark are of larger size than the older ones farther exterior.

The bark of the root of V. prunifolium differs from that of the stem chiefly in the fact that its groups of stone cells are farther apart and average somewhat larger in size. The outer bark is also thicker and more spongy in its texture. [It appears possible to distinguish between the two species, V. opulus and V. prunifolium, by the presence or absence of stone cells. A further report will be made on this point when some experience has been obtained in practically distinguishing the powders of the two species.]

Pharmaceutical examination.

Five grammes of each of the powdered drugs were taken, and, by means of the continuous extracting apparatus, chloroformic extracts were obtained. The amount of the extractive obtained from the two official drugs by this means was quite different, that of the prunifolium being nearly twice that of the opulus. The physical characteristics of these chloroformic extracts were similar, resin-like, yellow to green in color, sticky to the touch, and having a very bitter taste. The extractives were then allowed to evaporate down and their solubility in water was taken. Of the Viburnum opulus 0.00459 gramme was dissolved, and of the Viburnum prunifolium, 0.005 gramme, showing both to contain about the same amount of the principles soluble in water. This extractive was of a clear, greenish color and very bitter, that of the opulus being the more bitter of the two.

The residues remaining after treating the chloroformic extracts with water were next treated with a small quantity of petroleum spirit and filtered, the total extractive of the Viburnum opulus being 0.0834 gramme, and that of the V. prunifolium 0.3915 gramme. These figures show a marked difference in the amounts of the fixed oil (?) contained in the two barks. The physical properties of this fatty material from the different barks were similar in most respects. Both were of a pale green to yellow color, rather sticky, showing the presence of a small quantity of resinous matter; hard to saponify, darkened with sulphuric acid, and, in case of the opulus, a slight reaction was obtained with hydrochloric acid.

The chloroformic residues which remained, after extracting with water and petroleum spirit, were macerated for two days in 80 per cent. alcohol. The quantity of extractives obtained thereby was, of Viburnum opulus, 0.122 gramme, and of the V. prunifolium, 0.0375 gramme, showing the extractive of the opulus to be considerably larger than that of the prunifolium. The physical characteristics were similar. Evaporated to small bulk and poured into acidulated water gave a large precipitate of resin from the solution of Viburnum opulus, but scarcely any with the prunifolium.

The powdered drugs which had been treated with chloroform were dried and subjected to the action of alcohol for fourteen hours. The quantity of extractive from each was as follows: Viburnum opulus, 1.515 gramme, and V. prunifolium, 0.969. The only distinguishable point of difference in these extracts was the very astringent taste in that of the opulus, which was almost entirely lacking in the extractive of the prunifolium. Evaporating to small bulk, and pouring into a large volume of water, a precipitate of resin came down from both solutions, but much larger from the prunifolium than from the opulus.

The analysis was continued through an alcoholic and aqueous solution of the dregs in turn, and an examination was also made of all the barks in order to compare them; but as this part of the examination did not yield results which appear of special significance now, they need not be here recorded. The examination of the chloroformic extract proves the most interesting, and is worthy of mention at this time.

Tabulation of Results.

For this comparison of constituents I am indebted to the assistance of Mr. E. E. Cowman, who performed the work under my direction. The figures are his. Work on the proximate analysis of the different specimens is still in progress, and what is here presented must be regarded as preliminary.

These preliminary results seem to justify the hope that a means may soon be discovered by which the different barks may be distinguished even in the state of powder. The practical details for this discrimination are not yet worked out. It is hoped this preliminary report will be a help to those who may desire to offer assistance in perfecting these details.

The American Journal of Pharmacy, Vol. 67, 1895, was edited by Henry Trimble.