Cortex Granati; Pomegranate Peel; F. Ecorce de Grenades; G. Granatschalen.
Botanical Origin—Punica Granatum L., a shrub or low tree, with small deciduous foliage and handsome scarlet flowers. It is indigenous to North-western India, and the counties south and south-west of the Caspian to the Persian Gulf and Palestine, and grows wild in the hills of Western Sindh in elevations of 4000 feet, in Balutchistan to 6000 feet, also in the east flank of Soliman range. The trunk is short, rarely over 20 feet high. The tree has long been cultivated, and is now found throughout the warm parts of Europe, and in the subtropical regions of both hemispheres.
History—The pomegranate has been highly prized by mankind from the remotest antiquity, as is shown by the references to it in the Scriptures,[1109] and by the numerous representations of the fruit in the sculptures of Persepolis and Assyria,[1110] and on the ancient monuments of Egypt.[1111] It was probably introduced into the south of Italy by Greek colonists, and is named as a common fruit-tree by Porcius Cato[1112] in the 3rd century b.c. The peel of the fruit was recognized as medicinal by the ancients, and among the Romans was in common use for tanning leather,[1113] as it still is in Tunis.
Description—The fruit of the pomegranate tree is a spherical, somewhat flattened and obscurely six-sided berry, the size of a common orange and often much larger, crowned by the thick, tubular, 5-to 9-toothed calyx. It has a smooth, hard, coriaceous skin, which when the fruit is ripe, is of a brownish yellow tint, often finely shaded with red. Membranous dissepiments, about 6 in number meeting in the axis of the fruit, divide the upper and larger portion into equal cells. Below these a confused conical diaphragm separates the lower and smaller half, which in its turn is divided into 4 or 5 irregular cells. Each cell is filled with a large number of grains, crowded on thick spongy placentæ, which in the upper cells are parietal but in the lower appear to be central. The grains, which are about ½ an inch in length, are oblong or obconical and many-sided, and consist of a thin transparent vesicle containing an acid, saccharine, red, juicy pulp, surrounding an elongated angular seed.
The only part of the fruit used medicinally is the peel, Cortex Granati of the druggists, which in the fresh state is leathery. When dry as imported, it is in irregular, more or less concave fragments, some of which have the toothed, tubular calyx still enclosing the stamens and style. It is ⅒ to ¹/₂₀ of an inch thick, easily breaking with a short corky fracture; externally it is rather rough, of a yellowish-brown or reddish colour. Internally it is more or less brown or yellow, and honey-combed with depressions left by the seeds. It has hardly any odour, but has a strongly astringent taste.
Microscopic Structure—The middle layer of the peel consists of large thin-walled and elongated, sometimes even branched cells, among which occur thick-walled cells and fibro-vascular bundles. Both the outer and the inner surface are made up of smaller, nearly cubic and densely packed cells. Small starch granules occur sparingly throughout the tissue, as well as crystals of oxalate of calcium.
Chemical Composition—The chief constituent is tannin, which in an aqueous infusion of the dried peel produces with perchloride of iron an abundant dark blue precipitate. The peel also contains sugar and a little gum. Dried at 100° C. and incinerated, it yielded us 5·9 per cent. of ash.
Uses—Pomegranate peel is an excellent astringent, now almost obsolete in British medicine. Waring[1114] chronic dysentery of the natives of India, as well as in diarrhœa.
Pomegranate-root Bark; F. Ecorce de racine de Grenadier; G. Granatwurzelrinde.
Botanical Origin—Punica Granatum L., see page 289.
History—In addition to the particulars regarding the pomegranate tree given in the preceding article, the following which concern the drug under notice may be stated.
A decoction of the root of the pomegranate was recommended by Celsus,[1115] Dioscorides,[1116] and Pliny[1117] for the expulsion of tapeworm; but the remedy had fallen into complete oblivion, until its use among the Hindus attracted the notice of Buchanan[1118] at Calcutta about the year 1805. This physician pointed out the efficacy of the root-bark, which was further shown by Fleming and others. Pomegranate-root is known to have been long used for a similar purpose by the Chinese.[1119]
Though the medicine is admitted to be efficient, and is employed with advantage in India where it is easily procured both genuine and fresh, it is hardly ever administered in England, the extract of male-fern being generally preferred; but it has a place in several continental pharmacopœias.
Description—The bark occurs in rather thin quills or fragments, 3 to 4 inches long. Their outer surface is yellowish-grey, sometimes marked with fine longitudinal striations or reticulated wrinkles, but more often furrowed by bands of cork, running together in the thickest pieces into broad flat conchoidal scales. The inner surface, which is smooth or marked with fine striæ and is of a greyish yellow, has often strips of the tough whitish wood attached to it. The bark breaks short and granular; it has a purely astringent taste, but scarcely any odour.
Microscopic Structure—On a transverse section, the liber is seen to be the prevailing part of the cortical tissue. The former consists of alternating layers of two kinds of cells—one of them loaded with tufted crystals of oxalate of calcium, the other filled with starch granules and tannic matter. The bark is traversed by narrow medullary rays, and very large sclerenchymatous cells are scattered through the liber. Touched with a dilute solution of a persalt of iron, the bark assumes a dark blackish blue tint.
Chemical Composition—The bark contains, according to Wackenroder (1824), more than 22 per cent. of tannic acid, which Rembold (1867) has ascertained to consist for the most part of a peculiar variety called Punico-tannic Acid, C₂₀H₁₆O₁₃; when boiled with dilute sulphuric acid, it is resolved into Ellagic Acid, C₁₄H₈O₉, and sugar. Punico-tannic acid is accompanied by common tannic acid, yielding, by means of sulphuric acid, gallic acid, which appears sometimes to pre-exist in the bark. If a decoction of pomegranate bark is precipitated by acetate of lead, and the lead is separated from the filtered liquid, the latter on evaporation yields a considerable amount of mannite. This is probably the Punicin or Granatin of former observers.
The tænicide power is due, according to Tanret (1878) to Pelletierine, C₈H₁₅NO, a liquid dextrogyre alkaloid, boiling at 180° to 185° C. It can be obtained colourless by evaporating its ethereal solution in a vacuum, but in the open air becomes yellow. Pelletierine, so called in honour of Pelletier, is readily soluble in water, alcohol or chloroform, and has a somewhat aromatic odour. Several of its salts are crystallizable, yet extremely hygroscopic. The yield of the root-bark was about ½ per cent. of the alkaloid, or about 2 per cent. of crystallized sulphate from trees grown near Troyes, in the Champagne.
Uses—A decoction, followed by a purgative, is stated by Waring[1120] and others to be most efficient for the expulsion of the tapeworm. The fresh bark is said to be preferable to the dried.
Adulterations—The commercial drug frequently consists partly or entirely of the bark of the stem or branches, characterized by its less abundant cork-formation, which exhibits longitudinal bands or ridges of light brownish cork, but not conchoidal exfoliations. The middle cortical layer is somewhat more developed, and contains in the outer cells deposits of chlorophyll. The cambial zone is not distinctly observable. Such bark is reputed to be less active than that of the root, but we are not aware that the fact has ever been proved.
The bark of Buxus sempervirens and of Berberis vulgaris are somewhat similar to the drug under notice, but their decoctions are not affected by salts of iron.