Extractum Pruni Virginianae Fluidum.
By CYRUS M. BOGER, PH. G.
Read at the Pharmaceutical Meeting April 19, 1887.
Perhaps no other drug in the pharmacopoeia has been investigated as much and written upon as often as Wild Cherry Bark.
While many valuable additions have from time to time been made to our knowledge concerning it, yet its preparations remain for the most part unsatisfactory.
The design of this paper is the discussion of its fluid-extract; the chief objects to be attained in making this are:
- 1. To develop all the hydrocyanic acid the bark is capable of yielding.
- 2. To have as little tannic acid present when finished as possible.
- 3. To have it free from a precipitate—The U. S. Pharmacopeia process fulfils none of these requirements; why does it not?
- 1. Because the time allowed for maceration is too short.
- 2. The addition of glycerin hinders the development of prussic acid during maceration.
- 3. The drug is not moistened sufficiently to develop all the acid.
Experience has proven that sixty hours at least must be allowed for the full development of the acid and that seventy-two hours is not too long.
The viscidity and therefore the immobility of a liquid materially affects the rapidity of chemical action; the advantage to be gained from the addition of glycerin to the macerate is therefore not apparent and experience has shown its influence to be inimical in this process.
The hydrocyanic acid does not develop well when the bark is not moistened sufficiently, any more than it does when made too wet; actual practice has shown that the U. S. Pharmacopeia process does not allow sufficient moistening. Just here it may be remarked that after the addition of the macerate the bark should not be packed at all but put loosely into a percolator until it is time to pack it for the percolation.
The matter of tannic acid has puzzled a great many persons and it is quite enough to say that the addition of a large quantity of glycerin to the formula has not reduced the amount dissolved, even if it has helped to hold it in solution; seeing that the acid is freely soluble in both, water and alcohol them is little hope that very much can be accomplished in the direction of ridding the product of this constituent of the drug, unless indeed we should have resort to an expedient of perhaps questionable propriety and add to the macerate a small quantity of some acid, thus rendering the tannin less soluble; experiments in this direction have however not been made.
The presence of a precipitate is due to the fact that the menstruum of dilute alcohol is not allowed to thoroughly mix with the macerate before percolation begins, thus the first part of the percolate differs from the last part; this must naturally cause a precipitate.
The following formula has yielded excellent results and develops all the prussic acid; there is no precipitate nor does any form on standing as will be seen from the specimen which is seven months old and has never been filtered; and I had a specimen, which has unfortunately been mislaid, which was over a year old and is identical in appearance and odor with this:
|Take of Ground Wild Cherry Bark||16 ounces.|
|Water and Alcohol, each||10 fl. ounces.|
|Glycerin||4 fl. ounces|
Moisten the bark with 10 ounces of water and put loosely in the percolator, close tightly and allow it to macerate sixty hours; then pack very firmly, mix the ten fluidounces of alcohol and four of glycerin and pour it upon the bark, now cork up the percolator tightly and macerate twenty-four hours longer; at the expiration of this time remove the cork and about twelve fluidounces of percolate will come through; water should now be poured on to force the other four fluidounces out when the percolation should be stopped and the product will be finished. After an extended experience the conclusion was reached that to continue the percolation beyond this point is worse than useless as it necessitates subsequent evaporation; nor does it add any medicinal strength to the preparation. It does add quite a considerable quantity of tannin and gallic acid, which latter results from the conversion of the tannin by heat.