Some Constituents of Yerba Santa.
By R. ROTHER.
A syrup prepared from Eriodictyon leaves is extensively used for the administration of quinine in a bitterless form. It also affords the further advantage of extinguishing the bitter taste of quinine when taken immediately after the use of mixtures in which it would otherwise be chemically incompatible. In order to disguise the bitterness of quinine when given in a fluid state, it has been variously exhibited in the condition of insoluble salts. The great objection to this mode of procedure is that these quinium compounds remain partially insoluble, and hence inoperative, in both alkaline and acidine contacts. Some of these combinations, although remarkably insoluble in the main, are by no means destitute of the nauseous bitter taint.
The important advantage possessed by Yerba Santa consists not only in the phenomenal suppression of the bitterness of quinine, but also in its presentation in a readily assimilable state.
A certain resinous component of Eriodictyon leaves is characterized by the property of forming in contact with some bases very soluble seemingly saline compacts. These, when merged with quinium salt generate by double decomposition an ordinarily insoluble quinium-resin salt. This compound is promptly decomposed by the stronger acids, and is peculiarly soluble in ammonia.
When coarsely ground Eriodictyon leaves are percolated with water, a moderately dark brown colored and somewhat bitter percolate is obtained. On evaporating this to a syrupy consistence and treating this residue with alcohol, a light brown liquor and dark brown pasty residue results. The alcoholic solution has acquired all of the peculiar bitterness of the percolate whilst the pasty mass is practically tasteless. On treating this residue, or the original one resulting from the percolate, with potassium carbonate, an ammoniacal odor becomes quite pronounced. The addition of an acid to the dark brown mass, separated by alcohol, yields a profuse precipitate which is wholly but slowly dissolved to a dark brown solution by a large volume of water.
When the residuary leaves in the percolator are treated with water rendered strongly alkaline with ammonia, the first portion of the new percolate is very turbid, but becomes clear as the free ammonia descends into the precipitate. A considerable proportion of alkaline menstruum is needed to extract the color-giving substance wholly. Evaporation of the percolate to a syrupy residue and treatment of this with alcohol, yields a brown red bitter solution, and a profuse dark brown precipitate. The solution and precipitate are in all respects identical to those obtained in the first percolation. The alcoholic solution contains the quinine precipitant in union with ammonia as an acidic salt. The addition of water causes a dense milkiness, and acidulation with a strong acid precipitates the acidic resin in curdy flakes. Excess of ammonia added to the alcoholic solution causes no precipitate, but the color is very perceptibly deepened. On exposure of this mixture the excess of ammonia and much of the alcohol is dissipated, whilst a red-brown tarry acidic ammonium salt deposits.
The precipitate given by alcohol appears to be an acidic ammonium salt of the tasteless and nor-quinine precipitating acidic component of the leaves. When treated with water an inconsiderable proportion dissolves, leaving a large residue. Addition of ammonia or potassium carbonate and much water dissolves this wholly to a deep red-brown solution. The tinctorial power of this body is its most remarkable property. In its natural condition it is very probably in great part an acidic anhydrate, which is dissolved by aqueous solutions of alkalis and their carbonates. Under these circumstances no perceptible effervescence occurs, when carbonates are employed. With the use of monocarbonates the solution contains bicarbonate, showing that the reaction is like to that resulting in similar cases with analogous matter from other plants. On adding ferric chloride to such a solution, no precipitate at first appears. The continued addition of it, however, causes an abundant brown-black precipitate soluble to a great, extent in an excess of the reagent. It is also partially soluble in ammonia with a deep red-brown color. The addition of ammonia to a mixture containing excess of ferric chloride gives a precipitate utterly insoluble in ammonia. These results show that the various proportions of the tinctorial body appended to basic radicles determine the degree of solubility and insolubility of the compound. As already stated, strong acids occasion a precipitate when added to alkaline solutions of this substance. Boiling of the mixture with dilute sulphuric acid appears to generate a new insoluble substance readily soluble in alcohol and in ammonia, with intense red-brown color. The solutions are characteristically tasteless.
The tarry acidic ammonium salt of the quinine precipitant is readily and perfectly soluble in a sufficiency of alcohol. It is also readily and completely soluble in excess of ammonia. When treated with ether, a portion of the acidic component is dissolved. A correspondingly less acidic salt, however, remains undissolved. The action of chloroform is precisely similar in this. The acidic resin thus separated has an all-proportional solubility in these menstrua. It remains as a green-yellow transparent mass after the spontaneous volatilization of the respective solvents. It reacts with monad monocarbonates, converting them into bicarbonates. It is readily soluble in bicarbonates, evolving no carbonic anhydrate except on heating. When the solution obtained with sodium bicarbonate, for instance, is evaporated, a portion of the resin separates and is readily taken up by ether or chloroform. Alcohol, however, dissolves an acidic sodium salt of the resin.
Treatment of Eriodictyon leaves with alcohol, dilute or strong, wholly removes the quinine precipitant. But this method of isolating it is neither economical nor practical.
A fluid extract of Yerba Santa limpidly miscible with simple syrup is a desideratum. The writer has heretofore employed ammonia as a part menstruum in preparing syrup of Yerba Santa. In order to secure an effective extraction an excess of ammonia is essential. It is difficult, however, to adjust a proper proportion, and hence the ammonia may preponderate in the finished syrup. The writer would suggest a fluid extract of Yerba Santa for preparing the syrup to be used in the proportion of one fluidounce for one pint of the syrup. This fluid extract is merely an alcoholic solution of normal potassium eriodictyonate uncontaminated by the dark colored non-quinine precipitant. The following is the process recommended:
|Yerba Santa leaves, coarsely ground||16 Troy ounces.|
|Potassium carbonate||3 Troy ounces.|
|Water. Of each sufficient to make one pint.|
Mix ammonia water and water in the proportion of me measure of the first and seven measures of the second. Mix the Yerba Santa with eight fluidounces of this mixture and pack it firmly into a cylindrical glass percolator. After due maceration pour on menstruum until 3 pints of percolate has slowly passed. To this add the potassium carbonate and evaporate it until a pasty residue is left. Stir this well with 8 fluidounces of alcohol, gradually added; let the pasty precipitate subside and decant the supernatant liquor. To the residue gradually add 8 fluidounces of alcohol, as before, pour this mixture upon a strainer and force the liquid out. Should this second extraction measure more than is needed to complete the intended volume of fluid extract, dissipate the excess of alcohol by appropriate means; unite the residue with the first extraction, set the mixture aside for twenty four hours, and decant the clear fluid extract from the scant crystalline deposit meanwhile formed.
The American Journal of Pharmacy, Vol. 59, 1887, was edited by John M. Maisch.