Asclepias Cornuti, Decaisne.
From an Inaugural Essay.
The rhizome of this plant is long and comparatively slender, reaching from one to six feet in length, from one-half to one inch in diameter, and runs horizontally about six inches below the surface of the ground. It is thickened at intervals of ten or twelve inches, where the overground stems shoot out, otherwise it is uniform in size and at the end has generally three rootlets. It has a thick bark, externally brown, the interior white, and contains a number of laticiferous ducts, somewhat scattered, but principally placed in two irregular lines. In drying the bark shrinks very much and is finely wrinkled longitudinally, and somewhat fissured at intervals, leaving the wood exposed. The wood, of a yellow color, is hard and brittle, breaking with a resinous fracture; it contains a large number of medullary rays and also ducts, which are visible to the naked eye. The annexed drawing has been made by Mr. F. L. Slocum. The rhizome has a disagreeable, nauseous taste and a slight odor. The fresh rhizome in air drying loses 70 per cent., the air dry in complete drying 10 per cent., and when completely dried yields 6 per cent. of ash.
A portion of the powdered drug was thoroughly exhausted with petroleum benzin. The benzin was partially distilled off and the remainder allowed to evaporate spontaneously. This left a sticky, yellow extractive, overlaying a fixed oil; these were separated. The oil has a fine yellow color, a bland taste and the odor of the drug. The sticky extract was washed with water and then exhausted with warm 95 per cent. alcohol. This alcoholic solution was concentrated with a low heat and set aside. Upon cooling, yellow, wart-like crystals formed. By numerous solutions and recrystallizations in alcohol these were obtained white. They are wart-like, odorless and tasteless, iridescent in the sunlight, volatilized at a low heat, leaving no residue, have no reaction on litmus paper, are very soluble, in chloroform, soluble in benzin, ether and alcohol, insoluble in water. In contact with strong sulphuric acid and bichromate of potassium they give a green color. With strong sulphuric acid and chlorinated lime they give at. first a brown color, but on standing a short time this turns to a purple.
These crystals may also be obtained by exhausting the sticky benzin extract with ether, but on account of the fatty matter which ether takes up it is difficult to obtain them pure. Another, and probably the best method, is to percolate the drug directly with alcohol, concentrating the tincture and setting aside that crystals may form. The yellow crystals thus obtained are best purified by dissolving in a mixture of chloroform and alcohol, shaking with animal charcoal, filtering and setting aside for spontaneous evaporation, washing with diluted alcohol and drying in a cool place. In all three of the above methods it is important that the least possible amount of heat should be used.
The benzin extract, after having been exhausted with alcohol, ether, water and dilute hydrochloric acid, consists of a yellow, sticky tenacious substance, readily soluble in carbon bisulphide, chloroform and benzin. When heated it gives off the disagreeable odor of burning caoutchouc., When mixed with a small proportion of sulphur and heated the yellow color changes to a dark brown, and it then has the elasticity of ordinary India rubber.
The drug, after exhaustion with benzin, was next treated with 95 per cent. alcohol. From the resulting tincture the alcohol was distilled off, leaving a ruby-red liquid of a syrupy consistence, having with litmus an acid reaction. It has an intensely bitter taste, reminding one of gentian. The liquid, on being slowly mixed with a large bulk of water, yields a precipitate which, after separation and washing, is odorless and tasteless and has the characteristics of a resin. The watery solution left after precipitation of the resin was filtered and boiled to expel the alcohol; tested with solution of gelatin a flocculent precipitate was thrown down, proving the presence of tannin, and after filtering Trommer's test liquid was reduced, showing the presence of glucose. The remainder of the watery solution was evaporated and left a very bitter extractive having an acid reaction. The bitter principle was not isolated.
The drug, after exhaustion with benzin and alcohol, was next treated with hot water; alcohol precipitated gummy matter from the decoction, and compound tincture of iodine gave a deep blue color, indicating starch. The ash, on examination, showed the usual constituents. On distillation of the drug a volatile oil was obtained, but in such a small quantity that it could not be examined. It is probable that the fresh rhizome contains a volatile acrid principle which is poisonous to the skin. In collecting and slicing it the hands are often severely poisoned, small blisters forming, which cause an intense itching.
In conclusion, we find the rhizome to contain the following: Asclepion, caoutchouc, fixed oil, tannin, glucose, a bitter principle, gum, starch, volatile oil and the usual ash constituents.