§ 551. The Active Principles of the Hellebores.—The Christmas rose (Helleborus niger), as well as H. viridis, H. fœtidus, and, in short, all the species of hellebore, are poisonous, and if the root is treated with alcohol, from the alcoholic extract may be separated two glucosides, helleborin and helleborein.
Helleborin is in the form of white, glittering needles, which, if placed on the tongue, are almost tasteless, but if dissolved in alcohol, and then tasted, give a burning, numbing sensation. By boiling with zinc chloride, helleborin splits up into sugar and a resin—helleboresin. Concentrated sulphuric acid dissolves the crystals with the production of a beautiful red colour; on standing, the solution after a while becomes colourless, and a white powder separates.
Helleborein forms colourless crystals, mostly consisting of fine needles; they have a bitter taste, excite sneezing, and are very hygroscopic. The crystals easily dissolve in water and dilute alcohol, but are with difficulty soluble in absolute alcohol, and not soluble in ether. They dissolve in fatty oils. Helleborein splits by the action of mineral acids into sugar and amorphous helleboretin.
Helleboretin is in the moist condition of a beautiful violet-blue colour, becoming, when dried at 100°, dirty green. Concentrated sulphuric acid dissolves it with the production of a brown-yellow colour, which on standing passes into violet and then into brown.
Marmé separated from H. fœtidus, in addition, a white, intensely odorous substance, but too small in quantity to thoroughly investigate its properties.
§ 552. There is little doubt that hellebore owes its properties to the glucosides just described. There are several instances of poisoning by hellebore root,[583] and by the pharmaceutical preparations, but none of poisoning by the pure active principles. Morgagni mentions a case in which 2 grms. (nearly 31 grains) of the watery extract of H. Niger caused death within eight hours; and Ferrari saw, after the use of the wine in which the root had been boiled, two persons poisoned with a like result. A more recent case was recorded by Felletar, in 1875, in which a person died from an infusion of hellebore; there was, however, old standing heart-disease, so that there may be a doubt as to the real cause of death in this instance. Schauenstein mentions a case in which the roots of hellebore were accidentally used in soup, but the bitter taste prevented any quantity being eaten. The physiological action, especially of helleborein, is that of an intense heart poison, and the symptoms produced by the hellebores are so strikingly like those of the digitalins that it might be difficult to distinguish clinically between them. In any case of poisoning, the active principle must be separated in the form of an alcoholic extract, and identified as a heart poison by physiological experiment.
[583] There used to be a tincture officinal in our pharmacopœia; the root of H. viridis is officinal in the German pharmacopœia, maximum single dose, ·3 grm.; maximum total quantity in twenty-four hours, 1·2 grm. The tincture is also officinal on the Continent.
§ 553. Euonymin is found in a resin obtained from the Euonymus atropurpureus; it is crystalline, crystallising in colourless, cauliflower-like masses consisting of groups of stellate needles, which are soluble in water, but with difficulty in alcohol. It is a glucoside, and a powerful heart poison, 1 mgrm. causing the heart of a frog to cease in diastole.[584]