DIGITA′LIN. Syn. Digita′lia. A vegetable principle discovered by M. Royer in Digitalis purpurea, or purple foxglove.
Prep. 1. (Majendie.) Foxglove leaves (powdered), 1 lb., are digested in ether, first in the cold, and then heated under pressure; when the whole has again become cold, the liquor is filtered (rapidly), and the ether is distilled off in a water bath; the residuum is dissolved in water, the filtered solution treated with hydrated oxide of lead, the whole gently evaporated to dryness, and the dry residuum again digested in hot ether; from this solution the alkali is obtained, by evaporation and repeated resolutions, in a crystalline form.
2. (Homolle and Henry.) Foxglove leaves (carefully dried and powdered), 21⁄2 lbs., are digested in rectified spirit, and the tincture expressed in a tincture press; the spirit is then distilled off, and the residual extract treated with distilled water, 1⁄2 pint, acidulated with about 2 fl. dr. of acetic acid, a gentle heat being employed; some animal charcoal is then added, and the whole filtered; the filtrate is then diluted with water, and partly neutralised with ammonia; a fresh-made, strong decoction of galls is next added; a copious precipitation of tannate of digitalin ensues; the precipitate is washed with water, and mixed with a little alcohol, after which it is triturated with litharge (in fine powder) and exposed to a gentle heat; the whole is now digested in alcohol, the tincture treated with animal charcoal, and evaporated; the dry residuum is, lastly, treated with cold sulphuric ether, which takes up some foreign matter, and leaves the digitalin. 2 lbs. 8 oz. of the dried leaves yield 140 to 150 gr. of the digitalin.
Prop., &c. White, inodorous, porous masses, or small scales; it crystallises with difficulty, is intensely bitter, and excites violent sneezing when smelled to; dissolves freely in alcohol; scarcely soluble in cold ether; and takes 2000 parts of water for its solution; it is neither basic nor alkaline; concentrated colourless hydrochloric acid dissolves it, forming a characteristic solution which passes from yellow to a fine green. (Homolle.) It is one of the most powerful of known poisons, being fully 100 times stronger than the powdered leaves of the dried plant. It is used in the same cases.—Dose, 1⁄60 to 1⁄30 gr.; either made into pills or dissolved in alcohol and formed into a mixture. Owing to the difficulty and uncertainty connected with dispensing such small quantities, it is now seldom employed in this country.
Digitalin, Crystallised. Digitalis leaves from the Vosges, in rather fine powder, 1000 grams; neutral lead acetate, 250 grams; distilled water, 1000 grams. The digitalis should be collected in its second year just when the first flowers appear. With respect to the lead acetate, it is very important that it should not have an alkaline reaction; a slight acidity would be preferable. The lead salt is dissolved in the cold water, the powder added and thoroughly mixed, the whole passed through a sieve and left in contact twenty-four hours, taking care to mix it from time to time. The mixture is then packed sufficiently in a displacement apparatus, and exhausted with 50° alcohol, until it no longer yields any bitterness. About six parts of liquor are thus obtained, and this is neutralised exactly with sodium bicarbonate dissolved to saturation in cold water; about 25 to 30 grams will be required. When effervescence ceases, the alcohol is distilled, and the liquor remaining is evaporated
in a water bath down to 2000 grams; it is then left to cool and diluted with its weight of water. Two or three days afterwards the clear liquor is decanted off, by means of a syphon, and the precipitate drained upon a linen filter. When freed from the extractive liquor the precipitate weighs about 100 grams. It is suspended in 1000 grams of 80° alcohol, and the whole passed through a metal sieve or a fine cloth; the turbid liquor obtained is heated to ebullition, and to it is added a solution containing 10 grams of neutral lead acetate; the heating is continued a few moments, and the liquor is then left to cool and filtered. The deposit in the filter is washed with alcohol to remove any liquor it may retain, and then pressed. To this liquor is added 50 grams of finely powdered vegetable charcoal that has been washed with acid and afterwards with water until quite neutral, and it is then distilled, the residue being heated for some time in a water bath, it being very important that all the alcohol should be driven off. A little water is added to replace what may evaporate; the residue is allowed to cool, then drained upon the cloth that was used to separate the precipitate, and the carbonaceous mass is washed with a little water to remove the last portion of the coloured liquor. The carbonaceous residue is then dried completely in a stove at a temperature not exceeding 100° C., and exhausted by displacement with pure chloroform until it passes colourless. This liquid is distilled to dryness, and a few grams of 95° alcohol are placed in the retort, and evaporated to drive off the last traces of chloroform.
The residue is crude digitalin with viscous and oily matter. It is dissolved with heat in 100 grams of 90° alcohol, and 1 gram of neutral lead acetate dissolved in a little water added, together with 10 grams of animal charcoal in fine granules without powder that has been treated with hydrochloric acid, and washed until the washings are no longer acid. After boiling for ten minutes it is allowed to cool and settle, and then filtered in a glass cylinder furnished with a tight cotton plug, through which it passes quickly and clear. The black deposit is added last, and exhausted of all bitterness with alcohol. After distillation the digitalin remains as a grumous crystalline mass, now only contaminated with the coloured oil. A little aqueous liquor that occurs with it is separated and the weight of the impure digitalin is taken in the previously tarred vessel. The digitalin is then dissolved with heat in exactly sufficient 90° alcohol for its solution (from 6 to 12 grams). Any alcohol evaporated is replaced, and then to the cooled solution is added, sulphuric ether rectified at 65°, to half the weight of the alcohol employed; after mixing, distilled water equal to the weight of the alcohol and ether combined is added, and the flask is closed and shaken. Two layers are formed: the upper is coloured, and consists of the ether which has taken up the fat oil; the lower is colourless, and contains the digitalin, which being now free quickly crystallises. The flask is placed in a cool place. Two days afterwards the whole is thrown into a small cylinder furnished with a moderately tight cotton plug; the mother liquor runs off, and then the coloured layer, and the small quantity that remains adherent to the crystals, is removed by a little ether. Thus obtained, this first crystallisation of digitalin is slightly coloured; it is sufficiently pure, however, for its weight to be taken in an analysis; one tenth being deducted for the digitalin it still contains. To obtain it perfectly white, two purifications are necessary, but first a treatment with chloroform is indispensable to separate the remainder of the digitalin which injures its purity.
The digitalin, well dried and reduced to a fine powder, is dissolved in 20 parts of chloroform, and the solution is filtered in a cylinder through a tight cotton plug. The liquor passes limpid; it is distilled to dryness, and a little alcohol is poured into the retort, and evaporated to remove the last traces of chloroform.
The digitalin is dissolved in 30 grams of 90° alcohol, 5 grams of washed granular animal black added, and the whole boiled for 10 minutes; the liquor is filtered and the charcoal exhausted as before indicated; and, lastly, it is distilled, the digitalin in dry crystals is found on the sides of the vessel, but it is still slightly coloured. To obtain it perfectly white it is dissolved with heat in exactly sufficient 90° alcohol (about 6 to 8 grams); to the solution is added ether equal to half the weight of alcohol employed, and double the quantity of distilled water, and the flask is closed and agitated; the crystallisation commences quickly. The ether does not separate. It is exposed to the coolness of the night, and by the next day nearly the whole of the digitalin is deposited in small groups of white needles, that which retains colouring matter remaining in the mother liquor. The whole is thrown into a cylinder and the crystals washed with ether as before described. 1000 grams of Vosges digitalis of good quality yields about 1 gram of crystallised digitalin. Digitalin occurs under the form of very white light crystals, consisting of short slender needles, grouped around the same axis. It is very bitter and scarcely soluble in water. 90° alcohol dissolves it well, anhydrous alcohol dissolves it less freely. Pure ether dissolves only traces. Chloroform is its best solvent. Brought into contact with a small quantity of hydrochloric acid, digitalin is coloured emerald green, and this reaction is favoured by a very slight heat. From ‘Formulæ for New Medicaments, adopted by the Paris Pharmaceutical Society.’
DILL. Syn. Anethum (Ph. L. & E.), L. The fruit (seed) of Anethum graveolens, or garden dill, Anethi fructus, B. P. Dill is an aromatic