An aqueous extract of nux vomica, officinal in the German pharmacopœia, appears to contain principally brucine, with a small percentage of strychnine; the proportion of brucine to strychnine being about four-fifths to one-fifth. Blossfield found in a sample 4·3 per cent. of total alkaloid, and two samples examined by Grundmann consisted (No. 1) of strychnine, 0·6 per cent.; brucine, 2·58 per cent.—total, 3·18 per cent.; (No. 2) strychnine, 0·68 per cent.; brucine, 2·62 per cent.—total, 3·3 per cent. A sample examined by Dragendorff yielded—strychnine, 0·8 per cent.; brucine, 3·2 per cent.—total, 4 per cent. The maximum medicinal dose is put at ·6 grm. (91⁄14 grains).
The spirituous extract of nux vomica, officinal in the British and all the Continental pharmacopœias, differs from the aqueous in containing a much larger proportion of alkaloids, viz., about 15 per cent., and about half the total quantity being strychnine. The medicinal dose is 21·6-64·8 mgrms. (1⁄3 grain to a grain).
There is also an extract of St. Ignatius bean which is used in the United States; nearly the whole of its alkaloid may be referred to strychnine.
The tincture of nux vomica, made according to the British Pharmacopœia, contains in 1 fl. oz. 1 grain of alkaloids, or 0·21 part by weight in 100 by volume, but the strength of commercial samples often varies. Lieth found in one sample 0·122 per cent. of strychnine and 0·09 per cent. brucine; and two samples examined by Wissel consisted respectively of 0·353 per cent. and 0·346 per cent. of total alkaloids. Dragendorff found in two samples ·2624 per cent. and ·244 per cent. of total alkaloids, about half of which was strychnine.
Analysis.—Either of the extracts may be treated for a few hours on the water-bath, with water acidulated by sulphuric acid, filtered, the residue well washed, the acid liquid shaken up with benzene to separate impurities, and, on removal of the benzene, alkalised with ammonia, and shaken up two or three times with chloroform; the chloroform is then evaporated in a tared vessel, and the total alkaloids weighed. The alkaloids can then be either (a) treated with 11 per cent. of nitric acid on the water-bath until all the brucine is destroyed, and then (the liquid being neutralised) precipitated by potassic chromate; or (b) the alkaloids may be converted into picrates. Picrate of strychnine is very insoluble in water, 1 part requiring no less than 10,000 of water.[423] The tincture is analysed on precisely similar principles, the spirit being got rid of by distillation, and the residue treated by acidified water, &c.
[423] Dolzler, Arch. Pharm. [3], xxiv. 105-109.
The nux vomica powder itself may be valued as follows:—15 to 20 grms., pulverised as finely as possible, are treated three times with 150 to 300 c.c. of water, acidified with sulphuric acid, well boiled, and, after each boiling, filtered and thoroughly pressed. The last exhaustion must be destitute of all bitter taste. The united filtrates are then evaporated to the consistence of a thick syrup, which is treated with sufficient burnt magnesia to neutralise the acid. The extract is now thoroughly exhausted with boiling alcohol of 90 per cent.; the alcoholic extract, in its turn, is evaporated nearly to dryness, and treated with acidulated water; this acid solution is freed from impurities by shaking up with benzene, and lastly alkalised with ammonia, and the alkaloids extracted by shaking up with successive portions of chloroform. The chloroformic extract equals the total alkaloids, which may be separated in the usual way.