These fruits removed from their stalks and dried have the aspect of little round berries, and constitute the Cocculus Indicus of commerce. As met with in the market they are shortly ovoid or subreniform, ⁴/₁₀ to ⁵/₁₀ of an inch long, with a blackish, wrinkled surface, and an obscure ridge running round the back. The shorter stalk, when present, supports the fruit very obliquely. The pericarp, consisting of a wrinkled skin covering a thin woody endocarp, encloses a single reniform seed, into which the endocarp deeply intrudes. In transverse section the seed has a horseshoe form; it consists chiefly of albumen, enclosing a pair of large, diverging lanceolate cotyledons, with a short terete radicle.[147]
The seed is bitter and oily, the pericarp tasteless. The drug is preferred when of dark colour, free from stalks, and fresh, with the seeds well-preserved.
Microscopic Structure—The woody endocarp is built up of a peculiar sclerenchymatous tissue, consisting of branched, somewhat elongated cells. They are densely packed, and run in various directions, showing but small cavities. The parenchyme of the seed is loaded with crystallized fatty matter.
Chemical Composition—Picrotoxin, a crystallizable substance occurring in the seed to the extent of ⅖ to 1 per cent., was observed by Boullay, as early as 1812, and is the source of the poisonous property of the drug. Picrotoxin does not neutralize acids. It dissolves in water and in alkalis; the solution in the latter reduces cupric or bismutic oxide like the sugars, but to a much smaller extent than glucose. The alcoholic solutions deviate the ray of polarized light to the left. The aqueous solution of picrotoxin is not altered by any metallic salt, or by tannin, iodic acid, iodohydrargyrate or bichromate of potassium—in fact by none of the reagents which affect the alkaloids. It may thus be easily distinguished from the bitter poisonous alkaloids, although in its behaviour with concentrated sulphuric acid and bichromate of potassium it somewhat resembles strychnine, as shown in 1867 by Köhler.
Picrotoxin melts at 200° C.; its composition, C₉H₁₀O₄, as ascertained in 1877 by Paternò and Oglialoro, is the same as that of everninic, hydrocoffeïc, umbellic and veratric (or dimethyl-protocatechuic acid—see Semen Sabadillæ) acids.
Pelletier and Couerbe (1833) obtained from the pericarp of Cocculus Indicus two crystallizable, tasteless, non-poisonous substances, having the same composition, and termed respectively Menispermine and Paramenispermine. These bodies, as well as the very doubtful amorphous Hypopicrotoxic Acid of the same chemists, require re-examination.
The fat of the seed, which amounts to about half its weight, is used in India for industrial purposes. Its acid constituent, formerly regarded as a peculiar substance under the name of Stearophanic or Anamirtic Acid, was found by Heintz to be identical with stearic acid.
Commerce—Cocculus Indicus is imported from Bombay and Madras, but we have no statistics showing to what extent. The stock in the dock warehouses of London on 1st of December, 1873, was 1168 packages, against 2010 packages on the same day of the previous year. The drug is mostly shipped to the Continent, the consumption in Great Britain being very small.
Uses—In British medicine Cocculus Indicus is only employed as an ingredient of an ointment for the destruction of pediculi. It has been discarded from the British Pharmacopœia, but has a place in that of India.