The stem about a foot high, bears a large, solitary, white flower, rising from between two leaves of the size of the hand composed of 5 to 7 wedge-shaped divisions, somewhat lobed and toothed at the apex. The yellowish pulpy fruit of the size of a pigeon’s egg is slightly acid and is sometimes eaten under the name of May Apple. The leaves partake of the active properties of the root.
History—The virtues of the rhizome as an anthelminthic and emetic have been long known to the Indians of North America. The plant was figured in 1731 by Catesby[166] who remarks that its root is an excellent emetic. Its cathartic properties were noticed by Schöpf[167] and Barton[168] and have been commented upon by many subsequent writers. In 1820, podophyllum was introduced into the United States Pharmacopœia, and in 1864 into the British Pharmacopœia. Hodgson published in 1832 in the Journal of the Philadelphia College of Pharmacy[169] the first attempt of a chemical examination of the rhizome, which now furnishes one of the most popular purgatives, the so-called Podophyllin, manufactured on a large scale at Cincinnati and in other places in America, as well as in England.
Description—The drug consists of the rhizome and rootlets. The former creeps to a length of several feet, but as imported is mostly in somewhat flattened pieces of 1 to 8 inches in length and 2 to 4 lines in longest diameter: it is marked by knotty joints showing a depressed scar at intervals of a few inches which marks the place of a fallen stem. Each joint is in fact the growth of one year, the terminal bud being enclosed in papery brownish sheaths. Sometimes the knots produce one, two, or even three lateral buds and the rhizome is bi- or tri-furcate. The reddish-brown or grey surface is obscurely marked at intervals by oblique wrinkles indicating the former attachment of rudimentary leaves. The rootlets are about ½ a line thick and arise from below the knots and adjacent parts of the rhizome, the internodal space being bare. They are brittle, easily detached, and commonly of a paler colour. The rhizome is mostly smooth, but some of the branched pieces are deeply furrowed. Both rootstock and rootlets have a short, smooth, mealy fracture; the transverse section is white, exhibiting only an extremely small corky layer and a thin simple circle of about 20 to 40 yellow, vascular bundles, enclosing a central pith which in the larger pieces is often 2 lines in diameter.
The drug has a heavy narcotic, disagreeable odour, and a bitter, acrid, nauseous taste.
Microscopic Structure—The vascular bundles are composed of spiral and scalariform vessels intermixed with cambial tissue. From each bundle a narrow-tissued, wedge-or crescent-shaped liber-bundle projects a little into the cortical layer. This, as well as the pith, exhibits large thin-walled cells. The rootlets are as usual of a different structure, their central part consisting of one group of vascular bundles more or less scattered.[170] The parenchymatous cells of the drug are loaded with starch granules; some also contain stellate tufts of oxalate of calcium.
Chemical Composition—The active principles of podophyllum exist in the resin, which according to Squibb[171] is best prepared by the process termed re-percolation. The powdered drug is exhausted by alcohol which is made to percolate through successive portions. The strong tincture thus obtained is slowly poured into a large quantity of water acidulated with hydrochloric acid (one measure of acid to 70 of water), and the precipitated resin dried at a temperature not exceeding 32° C. The acid is used to facilitate the subsidence of the pulverulent resin which according to Maisch settles down but very slowly if precipitated by cold water simply, and if thrown down by hot water fuses into a dark brown cake. The resin redissolved in alcohol and again precipitated by acidulated water, after thorough washing with distilled water and finally drying over sulphuric acid, amounts to about 2 per cent.
Resin of podophyllum is a light, brownish-yellow powder with a tinge of green, devoid of crystalline appearance, becoming darker if exposed to a heat above 32° C., and having an acrid, bitter taste; it is very incorrectly called Podophyllin. The product is the same whether the rhizome or the rootlets are exclusively employed.[172] It is soluble in caustic, less freely in carbonated alkalis, even in ammonia, and is precipitated, apparently without alteration, on addition of an acid. Ether separates it into two nearly equal portions, the one soluble in the menstruum, the other not, but both energetically purgative. From the statements of Credner[173] it appears that if caustic lye is shaken with the ethereal solution, about half the resin combines with the potash, while the other half remains dissolved in the ether. If an acid is added to the potassic solution a red-brown precipitate is produced which is no longer soluble in ether nor possessed of purgative power. According to Credner, the body of greatest purgative activity was precipitated by ether from an alcoholic solution of crude podophyllin.
By exhausting the resin with boiling water, Power found that finally not more than 20 per cent. of the resin remained undissolved. By melting the crude resin with caustic soda, a little protocatechuic acid was obtained.
F. F. Mayer[174] of New York stated podophyllum to contain, beside the resin already mentioned, a large proportion of Berberine, a colourless alkaloid, an odoriferous principle which might be obtained by sublimation in colourless scales, and finally Saponin. From all these bodies the resin as prepared by Power,[175] was ascertained by him to be destitute; he especially proved the absence of berberine in Podophyllum.
Uses—Podophyllum is only employed for the preparation of the resin (Resina Podophylli) which is now much prescribed as a purgative.