§ 462. Properties of Solanine.—The reaction of the crystals is weakly alkaline; the taste is somewhat bitter and pungent. Solanine is soluble in 8000 parts of boiling water, 4000 parts of ether, 500 parts of cold, and 125 of boiling alcohol. It dissolves well in hot amyl alcohol, but is scarcely soluble in benzene. An aqueous solution froths on shaking, but not to the degree possessed by saponine solutions.
The amyl alcohol solution has the property of gelatinising when cold. It does this if even so little as 1 part of solanine is dissolved in 2000 of hot amyl alcohol. The jelly is so firm that the vessel may be inverted without any loss. This peculiar property is one of the most important tests for the presence of solanine. The hot ethylic alcohol solution will, on cooling, also gelatinise, but a stronger solution is required. From very dilute alcoholic solutions (and especially with slow cooling) solanine may be obtained in crystals. In dilute mineral acids solanine dissolves freely, and forms salts, which for the most part have an acid reaction and are soluble in alcohol and in water, but with difficulty in ether. The compounds with the acids are not very stable, and several of them are broken up on warming the solution, solanine separating out from the aqueous solutions of the solanine salts. The alkaloid may be precipitated by the fixed and volatile alkalies, and by the alkaline earths. Solanine will stand boiling with strongly alkaline solutions without decomposition; but dilute acids, on warming, hydrolyse. By heating solanine in alcoholic solution with ethyl iodide in closed tubes, and then treating the liquid with ammonia, ethyl solanine in well-formed crystals can be obtained. Solanine is precipitated by phosphomolybdic acid, but by very few other substances. It gives, for example, no precipitate with the following reagents:—Platinic chloride, gold chloride, mercuric chloride, potassic bichromate, and picric acid. Tannin precipitates it only after a time. Sodic phosphate gives a crystalline precipitate of solanine phosphate, if added to a solution of solanine sulphate. Both solanine and solanidine give with nitric acid at first a colourless solution, which, on gentle warming, passes into blue, then into light red, and lastly becomes weakly yellow. Solanine, dissolved in strong sulphuric acid, to which a little Fröhde’s reagent is added, at first colours the fluid light brown; after standing some time the edges of the drop becomes reddish-yellow, and finally the whole a beautiful cherry-red, which gradually passes into dark violet when violet-coloured flocks separate.
§ 463. Solanidine.—Solanidine has stronger basic properties than solanine. Its formula is C40H61NO2. It is obtained from an alcoholic solution in amorphous masses interspersed with needles; m.p. 191°. It dissolves readily in hot alcohol, with difficulty in ether. With hydrochloric acid it forms a hydrochloride—3(C40H61NO2HCl)HCl + H2O or 11⁄2H2O. This hydrochloride is a slightly yellow powder, only sparingly soluble in water, and carbonising without melting when heated to 287°. Solanidine also forms a sulphate, 3(C40H61NO2H2SO4)H2SO4 + 8H2O; this salt is in the form of scaly plates, melting at 247°; it dissolves readily in water.
The sugar obtained from the hydrolysis of solanidine is a yellow amorphous mass dissolving readily in water and wood spirit, and has a specific rotatory power of [α]D = + 28·623. With Phenylhydrazine hydrochloride and sodium acetate in aqueous solution it forms a glucosazone, melting at 199°. It is probably a mixture of sugars.
Solaneine is the name that has been given to the amorphous substance accompanying solanine; on hydrolysis it yields solanidine and the same sugar as solanine. Its formula is C52H82NO13 with 4H2O.
§ 464. Poisoning from Solanine.—Poisoning from solanine has been, in all recorded cases, induced, not by the pure alkaloid (which is scarcely met with out of the laboratory of the scientific chemist), but by the berries of the different species of Solanum, and has for the most part been confined to children. The symptoms in about twenty cases,[517] which may be found detailed in the medical literature of this century, have varied so greatly that the most opposite phenomena have been witnessed as effects of poisoning by the same substance. The most constant phenomena are a quick pulse, laboured respiration, great restlessness, and hyperæsthesia of the skin. Albumen in the urine is common. Nervous symptoms, such as convulsions, aphasia, delirium, and even catalepsy, have been witnessed. In some cases there have been the symptoms of an irritant poison—diarrhœa, vomiting, and pain in the bowels: in many cases dilatation of the pupil has been observed.
[517] See “Death of Three Children by S. nigrum”; Hirtz., Gaz. Med. de Strasbourg, 1842; Maury, Gaz. des Hôp., 1864; J. B. Montane, Chim. Med., 1862; Magne, Gaz. des Hôp., 1869; Manners, Edin. Med. Journ., 1867. Cases of poisoning by bitter-sweet berries are recorded in Lancet, 1856; C. Bourdin, Gaz des Hôpitaux, 1864; Bourneville, the berries of S. tuberosum, Brit. Med. Journ., 1859.