CHAPTER XXIV.

OLEORESINS AND RESINS.

OLEORESINS.

SOLUTIONS of this class represent the medicinal virtues of the drugs from which they are made, in a more concentrated form than is possible in any other. They possess the power of self-preservation, and in this respect are superior to fluid extracts. Oleoresins consist chiefly of fixed or volatile oils associated with resin and other constituents; those officially recognized in the Pharmacopoeia are all prepared by the same process, which consists in slowly percolating the drug in fine powder, with ether, to exhaustion, recovering the greater part of the ether by distillation, and finally removing the remaining ether by spontaneous evaporation. The percolation of drugs with ether requires the use of special apparatus (see page 134) to prevent loss of the very volatile solvent, and several attempts have been made to economize ether by repeatedly using the same liquid until the material is exhausted, the best device for this purpose being the ether-extraction apparatus designed by Prof. Flückiger, illustrated in Fig. 216. The extractor A passes by means of the tube D through a cork into the receiving flask E; at C is a septum or disk, upon which the material to be extracted is packed, and which communicates by means of a small funnel-shaped tube with D. The lateral tube BF passes into the tube G, which is provided with a properly cut cork, K, so that the ether vapor may pass from the receiving bottle to a spiral condenser H, fitted by means of a cork to the top of the extractor; the ether vapor can also be made to pass upward through the powder by pushing the cork deeper into the tube G, thus closing the orifice of the lateral tube BF. A loose pledget of cotton is placed in the funnel tube at C, or a piece of filter-paper is placed over the small opening to prevent the material from passing down. The whole apparatus may be made of any convenient size, of glass or tinned copper, and when in use the receiving flask is placed in warm water, for the purpose of vaporizing the ether, which is condensed above the extractor and drops back upon the powder, the process being continued until the material is exhausted. Another desirable feature of this apparatus is the recovery of the ether from the marc when the extraction of the drug has been completed. The lateral communication between D and BF is closed by means of the cork, and, applying a cold

wet sponge to the receiving flask, the ether vapor therein is condensed and a partial vacuum produced, which withdraws all the ether from the mare in the percolator above.

FIG. 216.

H

B

FK

Experience has shown that when 2 Cc. of percolate have been obtained for each Gm. of drug used, the latter will be practically exhausted, therefore percolation beyond this point is unnecessary; with the continuous extraction apparatus, half the quantity of ether can be made to accomplish the same results.

Considerable care is necessary in the recovery of ether by distillation, as official ether, which is directed to be used in the process, boils at about 37° C. (98.6° F.); the recovered ether should be but very slightly impregnated with the odor of volatile oil, and may be used for a subsequent operation. Oleoresins are not used to any great extent at present, and are rarely made by the pharmacist himself; small quantities for use in prescriptions may be conveniently obtained by percolating some of the finely powdered drug in the barrel of a glass syringe and allowing the ether to evaporate in a warm place. The yield of oleoresins ranges from 5 to 60 per cent. for different drugs, and their consistence varies from liquid to a soft solid, dependent upon the amount of resin present.

On account of the volatile and inflammaable character of ether, efforts have frequently been made to find a suitable substitute for the same; mixtures of ether and alcohol have been tried, as also petroleum benzin, but not with general satisfaction. The experiments of Mr. G. M. Beringer, in 1892, with pure acetone, have, however, conclusively proved the value of this solvent. Acetone is a product of the destructive distillation of calcium or barium acetate, and is now available in a very pure state; it is somewhat heavier than ether, and boils at a point about 20 degrees C. higher than that liquid. It is miscible in all proportions with water or alcohol, and possesses remarkable solvent properties. Drugs exhausted with

E

Flückiger's ether-extraction

apparatus.

acetone, when subsequently percolated with ether, have been found: to yield nothing of value, and the oleoresins prepared with acetone are perfectly soluble in ether or alcohol and practically identical with those made with ether.

The Pharmacopoeia recognizes 6 oleoresins prepared with ether, and in every case, with one exception, the drug is packed firmly into On account: the percolator, previous moistening being unnecessary. of the large proportion of resin in lupulin, this drug must be packed lightly, otherwise the mass will become impacted. The following is an alphabetical list of the official oleoresins, showing the fineness of powder used and the average yield.

Oleoresina Aspidii.-This preparation is known also by the names oleoresina filicis, extractum filicis æthereum, and oleum filicis maris. As the root rapidly deteriorates upon keeping, only that having a fresh green color should be used. The oleoresin of male fern generally deposits, on standing, a granular crystalline substance largely composed of filicic acid, upon which depends the activity of the preparation; hence the necessity for thoroughly incorporating the deposit before dispensing the oleoresin. By percolation with acetone the drug has yielded as much as 18 per cent. of oleoresin. This preparation is recognized in the British Pharmacopoeia as Extractum Filicis Liquidum, and in the German Pharmacopœia as Extractum Filicis.

fatty matter.

Oleoresina Capsici.-Owing to the large amount of fat present in capsicum, it is not desirable to carry percolation to complete exhaustion; experience, in fact, has taught that, if collected slowly, 150 Cc. of percolate will have practically exhausted 100 Gm. of the drug, and that further treatment simply loads the percolate with Oleoresin of capsicum is a dark, brownish-red liquid, which, shortly after being made, deposits granular fat; this is best removed by decanting the clear liquid and straining the residue, or washing the deposit rapidly with a little ether. Although the average yield of oleoresin has been reported as not over 5 or 6 per cent., from 12 to 16 per cent. of a very excellent preparation has very frequently been obtained.

Oleoresina Cubebæ.-Cubeb yields all its medicinal virtues to

alcohol as well as ether; very satisfactory oleoresin has been made with alcohol alone, and this menstruum is now used by many manufacturers. In Germany the oleoresin is officially recognized under the name Extractum Cubebarum, and is prepared with a mixture of equal volumes of ether and alcohol. All oleoresin of cubeb deposits, upon standing, waxy matter and a crystalline body, cubebin, which, as the Pharmacopoeia directs, should be rejected, only the liquid portion being dispensed. It is of a green or brownish-green color, and when made with acetone has been obtained to the extent of 25 per cent.

Oleoresina Lupulini.-Lupulin is very rich in resin, hence a large yield of oleoresin is to be expected; it is of a reddish-brown color and has the consistence of a soft solid extract. While the average yield is about 60 per cent., as much as 70 per cent. has been obtained with both ether and acetone, by complete exhaustion.

Oleoresina Piperis.-Commercially this preparation is known also as oil of black pepper, which latter, however, is usually obtained as a by-product in the manufacture of piperin. Oleoresin of pepper, when first made, deposits piperin in crystalline form, which is separated by straining, leaving a thick, very black liquid. The yield with ether or acetone rarely exceeds 6.5 per cent.

Oleoresina Zingiberis.-When made from uncoated (Jamaica) ginger the yield of oleoresin is less than from coated ginger, and is also lighter in color, thinner, and of a more agreeable flavor. The name piperoid has sometimes been applied to this preparation. From coated ginger as much as 10 per cent. of oleoresin has been obtained, while from Jamaica ginger the yield rarely exceeds 6 per cent.

RESINS.

Under the title Resince the Pharmacopoeia recognizes 5 preparations, 2 of which, however, are simply residuary products obtained in the distillation of the volatile oil from natural oleoresins. For the remaining 3 an official process of manufacture is given, alcohol being used as a solvent in each case; the resin is obtained by pouring a concentrated alcoholic tincture of the respective drugs into cold water and subsequently washing the precipitate repeatedly with

Resina Jalapæ.-The amount of resin in jalap root varies considerably, ranging from 8 to 18 per cent., and it is not always possible to find commercial jalap which meets the official requirement of not less than 12 per cent. Resin of jalap differs from the official extract of jalap in being free from water-soluble matter, of which the latter preparation contains quite an appreciable quantity; hence the official direction to wash the precipitated resin twice with water should be repeated until the washings are colorless; the adhering water is removed by drying the resin with a gentle heat. Not more than 10 per cent. of the resin of jalap should be soluble in ether, nor more than 7 per cent. in chloroform. The presence of common resin may be detected by solubility in oil of turpentine and by gelatinization upon cooling a solution made by digesting the suspected resin in 10 parts of ammonia-water at 80° C. (176° F.). Since resin of jalap has a slightly acrid but not bitter taste, an adulteration with aloes may be suspected if a pronounced bitter taste is observed. If resin of jalap be moistened with alcohol and then with a solution of ferric chloride, a green color should not be developed, nor should a blue color be observed if the inner surface of a fresh potato paring be rubbed with the resin, otherwise guaiac is present. That portion of jalap resin insoluble in ether, when dissolved in caustic alkali solution, is not reprecipitated upon addition of an acid; this property distinguishes jalap resin from other resins except that of scammony, and from the latter it differs in its insolubility in ether and oil of turpentine. While resin of scammony might become accidentally mixed with jalap resin, it would never be added as an adulterant, since it is far more expensive.

Resin of jalap may be obtained free from color by treatment with animal charcoal; the best plan is to mix the charcoal with the powdered jalap before percolation, and also to pass the percolate through animal charcoal.

Resina Podophylli.-The object of adding hydrochloric acid to the water before adding the alcoholic solution is simply to facilitate the separation of the resinous matter. The yield of resin of podophyllum rarely exceeds 4 or 5 per cent., and its color should be from grayish white to yellowish green, provided no heat higher than 35° C. (95° F.) is used in drying it. According to Prof. Lloyd, who has had large experience in the manufacture of this resin, the con