In order to ascertain the percentage of the alkaloid in any part of the plant, the process followed by Thorey has the merit of simplicity. The substance is first exhausted by petroleum ether, which frees it from fat; after drying, it is extracted with 85 per cent. alcohol at a temperature not exceeding 40°. The alcoholic extracts are then united, the alcohol distilled off, and the residue filtered. The filtrate is now first purified by agitation with petroleum ether, then saturated by ammonia, and shaken up with chloroform. The latter, on evaporation, leaves the alkaloid only slightly impure, and, after washing with distilled water, if dissolved in dilute sulphuric acid, a crystalline sulphate may be readily obtained.
A tincture and an extract of henbane leaves and flowering tops are officinal in most pharmacopœias; an extract of the seeds in that of France.
An oil of hyoscyamus is officinal in all the Continental pharmacopœias, but not in the British.
Henbane juice is recognised by the British pharmacopœia; it is about the same strength as the tincture.
An ointment, made of one part of the extract to nine of simple ointment, is officinal in the German pharmacopœia.
The tincture (after distilling off the spirit) and the extracts (on proper solution) may be conveniently titrated by Mayer’s reagent ([p. 263]), which, for this purpose, should be diluted one-half; each c.c. then, according to Dragendorff, equalling 6·98 mgrms. of hyoscyamine. Kruse found 0·042 per cent. of hyoscyamine in a Russian tincture, and ·28 per cent. in a Russian extract. Any preparation made with extract of henbane will be found to contain nitrate of potash, for Attfield has shown the extract to be rich in this substance. The ointment will require extraction of the fat by petroleum ether; this accomplished, the determination of its strength is easy.
The oil of hyoscyamus is poisonous, and contains the alkaloid. An exact quantitative research is difficult; but if 20 grms. of the oil are shaken up for some time with water acidified by sulphuric acid, the fluid separated from the oil, made alkaline, shaken up with chloroform, and the latter removed and evaporated, sufficient will be obtained to test successfully for the presence of the alkaloid, by its action on the pupil of the eye.
§ 458. Dose and Effects.—The dose of the uncrystalline hyoscyamine is 6 mgrms. (1⁄10 grain), carefully increased. I have seen it extensively used in asylums to calm violent or troublesome maniacs. Thirty-two mgrms. (1⁄2 grain) begin to act within a quarter of an hour; the face flushes, the pupils dilate, there is no excitement, all muscular motion is enfeebled, and the patient remains quiet for many hours, the effects from a single dose not uncommonly lasting two days. 64·8 mgrms. (1 grain) would be a very large, and possibly fatal, dose. The absence of delirium or excitement, with full doses of hyoscyamine, is a striking contrast to the action of atropine, in every other respect so closely allied; yet there are cases on record showing that the henbane root itself has an action similar to that of belladonna, unless indeed one root has been mistaken for another; e.g., Sonnenschein relates the following ancient case of poisoning:—In a certain cloister the monks ate by error the root of henbane. In the night they were all taken with hallucinations, so that the pious convent was like a madhouse. One monk sounded at midnight the matins, some who thereupon came into chapel could not read, others read what was not in the book, others sang drinking songs—in short, there was the greatest disturbance.
§ 459. Separation of Hyoscyamine from Organic Matters.—The isolation of the alkaloid from organic tissues or fluids, in cases where a medicinal preparation of henbane, or of the leaves, root, &c., has been taken, is possible, and should be carried out on the principles already detailed. Hyoscyamine is mainly identified by its power of dilating the pupil of the eye. It is said that so small a quantity as ·0083 mgrm. (1⁄4000 grain) will in fifteen minutes dilate the eye of a rabbit. It is true that atropine also dilates the pupil; but if sufficient of the substance should have been isolated to apply other tests, it can be distinguished from atropine by the fact that the latter gives no immediate precipitate with platinic chloride, whilst hyoscyamine is precipitated by a small quantity of platinic chloride, and dissolved by a larger amount, and also by the characters of the gold salt.