_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.
[1115] _De Medicina_, lib. iv. c. 17.
[1116] Lib. i. c. 153.
[1117] Lib. xxiii. c. 60.
[1118] _Edinb. Med. and Surg. Journ._, iii. (1807) 22.
[1119] Debeaux, _Pharmacie et Mat. Méd. des Chinois_, 1865. 70.
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.