§ 401. Brucine (C23H26N2O4 + 4H2O)[453] occurs associated with strychnine in the plants already mentioned; its best source is the so-called false angustura bark, which contains but little strychnine. Its action is similar to that of strychnine. If crystallised out of dilute alcohol it contains 4 atoms of water, easily expelled either in a vacuum over sulphuric acid or by heat. Crystallised thus, it forms transparent four-sided prisms, or arborescent forms, like boric acid. If thrown down by ammonia from a solution of the acetate, it presents itself in needles or in tufts.
[453] Sonnenschein has asserted that brucine may be changed into strychnine by the action of NO3. This statement has been investigated by A. J. Cownley, but not confirmed.—Pharm. Journ. (3), vi. p. 841.
The recently-crystallised alkaloid has a solubility different from that which has effloresced, the former dissolving in 320 parts of cold, and 150 parts of boiling water; whilst the latter (according to Pelletier and Caventou) requires 500 of boiling, and 850 parts of cold water for solution. Brucine is easily soluble in absolute, as well as in ordinary alcohol; 1 part dissolves in 1·7 of chloroform, in 60·2 of benzene. Petroleum ether, the volatile and fatty oils and glycerine, dissolve the alkaloid slightly, amyl alcohol freely; it is insoluble in anhydrous ether. The behaviour of brucine in the subliming cell is described at [p. 260]. Anhydrous brucine melts in a tube at 178°. The alcoholic solution of brucine turns the plane of polarisation to the left [α]r = -11·27°. The taste is bitter and acrid. Soubeiran maintains that it can be recognised if 1 part is dissolved in 500,000 parts of water. If nitric trioxide be passed into an alcoholic solution of brucine, first brucine nitrate is formed; but this passes again into solution, from which, after a time, a heavy, granular, blood-red precipitate separates: it consists of dinitro-brucine (C23H24(NO2)2N2O4). Brucine fully neutralises acids, and forms salts, which are for the most part crystalline. The neutral sulphate (C23H25N2O4SH2O4 + 31⁄2H2O) is in long needles, easily soluble in water. The acetate is not crystalline, that of strychnine is so ([p. 321]).
Brucine is precipitated by ammonia, by the caustic and carbonated alkalies, and by most of the group reagents. Ammonia does not precipitate brucine, if in excess; on the other hand, strychnine comes down if excess of ammonia is added immediately. This has been proposed as a method of separation; if the two alkaloids are present in acid solution, ammonia in excess is added, and the solution is immediately filtered; the quantitative results are, however, not good, the strychnine precipitate being invariably contaminated by brucine.
Chromate and dichromate of potassium give no precipitate with neutral salts of brucine; on the other hand, strychnine chromate is at once formed if present. It might, therefore, be used to separate strychnine from brucine. The author has attempted this method, but the results were not satisfactory.
§ 402. Physiological Action.—The difference between the action of strychnine and that of brucine on man or animals is not great. Mays states that strychnine affects more the anterior, brucine the posterior extremities. In strychnine poisoning, convulsions occur early, and invariably take place before death; but death may occur from brucine without any convulsions, and in any case they develop late. Brucine diminishes local sensibility when applied to the skin; strychnine does not.[454] In a physiological sense, brucine may be considered a diluted strychnine. The lethality of brucine, especially as compared with strychnine, has been investigated by F. A. Falck.[455] He experimented on 11 rabbits, injecting subcutaneously brucine nitrate, in doses of varying magnitude, from 100 mgrms. down to 20 mgrms. per kilogram of body-weight. He found that brucine presented three stages of symptoms. In the first, the respiration is quickened; in 3 of the 11 cases a strange injection of the ear was noticed; during this period the pupils may be dilated. In the second stage, there are tetanic convulsions, trismus, opisthotonus, oppressed respiration, and dilated pupils. In the third stage, the animal is moribund. Falck puts the minimum lethal dose for rabbits at 23 mgrms. per kilo. Strychnine kills 3·06 times more quickly than brucine, the intensity of the action of strychnine relative to that of brucine being as 1 : 117·4. Falck has also compared the minimum lethal dose of strychnine and brucine with the tetanising opium alkaloids, as shown in the following table:—
[454] Journ. Physiol., viii. 391-403.