XI.—Curarine.
§ 504. Commercial curare is a black, shining, resinoid mass, about 83 per cent. of which is soluble in water, and 79 in weak spirit. It is a complicated mixture of vegetable extracts, from which, however, a definite principle possessing basic characters (curarine) has been separated.
The extract is an arrow poison[545] prepared by different tribes of Indians in South America, between the Amazon and the Orinoco; therefore, samples are found to vary much in their poisoning properties, although it is noticeable that qualitatively they are the same, and produce closely analogous symptoms. It is supposed that some of the curare is derived from different species of strychnos. This is the more probable, because, as before stated, the South American strychnines paralyse, and do not tetanise. It is not unlikely that the active principles of curare (or woorari) may be methyl compounds similar to those which have been artificially prepared, such as methyl strychnine and methyl brucine, both of which have a curare-like action.
[545] A constituent of the Borneo arrow poison is “derrid,” a toxic principle obtained from a leguminous plant, the Derris elliptica; it is a resinous substance, which has not yet been obtained in the pure state. It is said not to be a glucoside, nor to contain any nitrogen (Greshoff, Ber., xxiii. 3537-3550).
The Comalis on the east coast of Africa prepare an arrow poison from the aqueous extract of the root of Oubaion, a tree closely related to Carissa Schimperii.
Oubain is prepared by treating the aqueous extract with lead acetate, getting rid of excess of lead by SH2, and concentrating in a vacuum. The syrup is boiled with six times its volume of alcohol of 85°, and allowed to cool in shallow vessels; crystals are obtained which are recrystallised, first from alcohol, and afterwards from water.
Oubain, C30H46O12, forms thin white nacreous lamellæ. It is tasteless, odourless, and neutral, almost insoluble in cold water, and soluble in boiling water; it dissolves readily in moderately concentrated alcohol, is almost insoluble in absolute alcohol, and insoluble in ether and chloroform. Its melting-point is 200°. The solution of oubain in water is lævorotatory [α]D = -340. It is a glucoside, yielding on boiling with dilute acids a sugar. It is very poisonous; 2 mgrms. will kill a dog of 12 kilos. weight in a few minutes, if subcutaneously injected; but, taken by the stomach, it produces no effect.—Arnaud, Compt. Rend., cvi. 1011-1014.
Curarine was first separated by Preyer in a crystalline form in 1865. He extracted curare with boiling alcohol, to which a few drops of soda solution had been added, evaporated off the alcohol, took up the extract with water, and, after filtration, precipitated by phosphomolybdic acid, which had been acidified with nitric acid. The precipitate was dried up with baryta water, exhausted with boiling alcohol, and curarine precipitated from the alcoholic solution by anhydrous ether. It may also be obtained by precipitating with mercuric chloride solution, and throwing out the mercury afterwards by means of hydric sulphide, &c.