CHAPTER XLVIII

RESINS AND NEUTRAL PRINCIPLES

THIS chapter deals with plant principles, of which less is known than any other group of chemical substances-in truth, the only reason why these bodies are grouped into this chapter is because they have not been sufficiently studied to know to what classes of chemicals they belong, and as its composition is worked out, each body will be placed in its appropriate position in systematic chemistry, leaving nothing for discussion in this chapter.

This work is already begun. It is now known that resin of jalap owes its activity to the glucoside, convolvulin; while resin of scammony is active because of its glucoside, scammonin; therefore, these two so-called resins are considered among the glucosidal drugs.

The phrase "resin acid" is here used in the attempt to classify the important constituent found in the several plant products which we call resins. These bodies are best defined as plant substances soluble in alcohol, insoluble in water, and dissolving in alkalis to form "resin soaps." Hence they are acid in character. Whether all the resins considered in this chapter will on investigation comply with this definition remains to be seen, and let it be distinctly understood that practically all resins are far more complex than the above definition implies.

Tschirch has attempted a classification of resins as follows:
Resin Esters or Their Saponification Products: (Resines.)

These esters are combinations of aromatic acids, such as benzoic, cinnamic,
and ferulic acids, with resin alcohols (resinoles).

The resin alcohols can be grouped into two classes, according as they do or do not give the tannin reaction, the latter class being called resin-tannols. Among the tannin-free resinols may be mentioned storesin in storax; while as examples of resin tannols may be cited toluresin tannol in balsam of tolu. Resinol Acids:

Resin acids, such as abietinic acid in rosin, guaiaconic acid in guaiac, and copaivic acid in copaiba.

Resenes:

Indifferent substances of unknown composition, such as dracoresene in dragon's blood.

Aliphato-resins (esters of aliphatic acids), chromo-resins (containing coloring matter); enzymo-resins (containing enzymes such as laccase); glucoresins (esters of resin acids with sugars, such as the glucosides found in Jalap) are known; while the so-called "milk juices" (india rubber, etc.) are now considered as lacto-resins.

Resins are sometimes extracted from drugs by means of solvents (example: the resin from phytolacca); sometimes represent practically entire plant exudation (example: mastic); frequently exude from plants combined with volatile oils, then forming the class of drugs called oleoresins (example: turpentine, U.S.P.); and often exuding mixed with gummy substances, such as exudation being called a gum-resin (example: asafetida). Occasionally, the resin which exudes is aromatic by reason of the benzoic and cinnamic acid it contains, the example of such a balsamic resin being benzoin (p. 776), while natural oleoresin similarly flavored with benzoic and cinnamic acid is called a balsam (example: balsam of tolu (p. 769). The last two classes of drugs as well as the oleoresins were discussed in the preceding chapter. It is advisable. right here again to call attention to the distinction between natural and pharmaceutic oleoresins, already discussed on p. 253.

Neutral principles are plant principles of whose structural chemistry -of whose position in systematic chemistry-we know little or nothing. They are usually bitter and crystalline, are neither basic like alkaloids nor derivatives of glucose, as are the glucosides. That the grouping is purely artificial and temporary is shown by the fact that the most carefully studied neutral principle, santonin, is now known to be a lactone derived from hexahydrodimethyl-naphthalin and will soon be considered in text-books among the naphthalin derivatives, even as coumarin, a lactone of oxycinnamic acid, is studied among the derivatives of allylbenzene (p. 721).

RESINS, GUM-RESINS, AND DRUGS CONTAINING NEUTRAL PRINCIPLES

GUAIACUM-Guaiac

(Guaiac.-Guaiac Resin)

The resin of the wood of Guaiacum officinale Linné, or of Guaiacum sanctum Linné (Fam. Zygophyllacea).

Summarized Description.

Irregular, homogeneous masses; brown to greenish-gray-brown; balsamic odor, acrid taste; melts between 85° and 90°; readily soluble in alcohol, ether, chloroform, creosote, in solutions of alkalies and of hydrated chloral. For details see U.S.P., p. 211.

For tests for identity, for impurities: Rosin (petroleum benzene solution not turned green by cupric solution) see U.S.P.

Constituents.-Guaiaconic acid, (now said to be a mixture), guaiaretic acid, C20H2104, guaiacinic acid (or beta-resin) vanillin, volatile oil, etc. Tschirch inclines to the belief that these so-called "acids" are resin alcohols.

Remarks.-The alcoholic solution is characterized by turning blue in the presence of oxidizing agents, such as ferric chloride (U.S.P. test). By reason of this property filter-paper steeped in tincture of guaiac is used as a test-paper for ozone and for blood, the hematin of the latter as the oxidizing agent.

Medical Properties.-Alterative in syphilis and rheumatism. The tincture (p. 227) and the ammoniated tincture (p. 227) are official. Dose. Of drug, 1 gramme (15 grains).

Guaiacum Lignum (U.S.P. 1890; N.F. IV) or guaiac wood, the wood from which the above resin is derived. It owes its properties almost entirely to the resin, although it is said to also contain a saponin.

Mastiche (U.S.P. VIII; Ñ.F. IV) or mastic is a concrete resinous exudation from Pisticia Lentiscus Linné (Fam. Anacardiaceœ).

Mastic contains masticic acids (two isomeres, C23H36O4); masticonic acids (two isomeres, C32H4804); masticolic acid, C23H3604; mastico-resenes (the "beta" variety formerly called masticin); volatile oil 2 per cent. It is used as a carminative (dose, 30 grains) and is a constituent of pills of aloes and mastic, N.F.

Burgundy pitch is no longer official, having been dropped in the last revision. It is a resin prepared from a species of fir, and is used in medicine exclusively for the preparation of plasters.

Resin of copaiba (U.S.P. 1890), while considered as a pharmaceutic on p. 283, is worthy of a few lines devoted to its chemistry. It is the residue left on distillation of official copaiba, and consists largely of a solid acid-in this case, copaivic acid. As mentioned on p. 305, this acid combines with moist magnesium oxide to form a salt, and to this action is due the solidification of oleoresin in making mass of copaiba.

RESINA-Rosin

(Resin.-Colophony)

The residue left after distilling the volatile oil from the concrete oleoresin obtained from Pinus palustris Miller and from other species of Pinus (Fam. Pinaceœ). Summarized Description.

Sharp, angular, translucent, amber-colored fragments; brittle at ordinary temperatures; terebinthinate odor and taste; freely soluble in alcohol, ether, benzene, glacial acetic acid, fixed and volatile oils and in diluted alkaline hydroxide solutions; sp. gr. 1.07 to 1.09. For details see U.S.P. p. 357.

Acid Number.-Not less than 150. Details in Part V.

Constituents.-Chiefly abietic acid anhydride. Abietic acid, C19H2802, is obtained by digesting rosin with 70 per cent. alcohol, freeing the solution of impurities by filtration, and then dissolving the residue in hot methyl alcohol from which the abietic acid crystals separate on cooling.

Tschirch and Koritschoner, on the other hand, claim that the resin acids are palabietinic acid, C20H30O2, palabieninic acid, C13H20O, and a- and ß-palabietinolic acids, C16H2402.

Remarks. As already mentioned (p. 765), rosin is the resinous constituent of the natural oleoresin, turpentine, and is obtained by distilling the volatile oil-the so-called "spirit of turpentine"-therefrom.

Medical Properties.-Mild irritant. Use chiefly externally as constituent or plasters, cerates, and ointments. Official preparation: Rosin cerate (p. 329).

Elastica (U.S.P. VIII) or rubber is the prepared milk-juice of several species of Hevea. It is a polymerized isoprene having the formula

Constituents. Since rubber consists largely of isoprene, the condensation (polymerization) of this hydrocarbon should produce rubber. This condensation has now been accomplished, though who was the first to obtain genuine rubber by this method is a matter of controversy. The synthesis has not as yet become financially feasible, although work to prepare cheap isoprene from dimethyl-butadiene

CH2 =C — C =CH2
CH3 CH3

gives promise of ultimate success in the commercial manufacture of rubber. The "preparation" of the milk juice mentioned in the official definition consists of submitting the fresh juice to the action of smoke made by burning fatty fuel-like palm fruit-which is allowed to smoulder with but slight access of air. The milk juice is held over the smoke on a wooden paddle, which has been dipped into a bucket containing the juice, and by deft manipulation the liquid juice is prevented from dripping from the paddle until it solidifies. The paddle containing the dried rubber is again dipped into the fresh juice, and the paddle once more rotated over the smoke until that layer has solidified, and this process continued until the paddle holds a large mass of rubber.

When heated to above 125°C., it becomes a sticky mass, and the products made from it should, therefore, be kept from undue heat. Rubber goods can best be preserved by keeping immersed in water.

Rubber is made more durable by the process of vulcanization. In making soft rubber it is kneaded with 10 per cent. sulphur (or a metallic sulphide) at a temperature of 120° to 136°C., while in making hard rubber the crude rubber is heated with 30 to 35 per cent. sulphur to 140° to 142°C., and further hardened with rosin, chalk,

etc.

Rubber used in medicine is the pure native unvulcanized variety. The only medical use of rubber is as a plaster base.

Gutta Percha (N.F.) is the prepared milk-juice of various trecs of the genus, Palaquium. It resembles rubber in many respects, although it is less elastic and does not readily vulcanize. It is used in surgery for preparing splints. A recipe for solution of gutta percha is given in the National Formulary (p. 190).

BENZOINUM-Benzoin

(Benzoin.-Gum Benjamin)

A balsamic resin obtained from Styrax Benzoin Dryander and some other species of Styrax (Fam. Styracaceae) growing in the East Indies and known in commerce as Sumatra Benzoin and Siam Benzoin.

Constituents.-Resin, benzoic acid, cinnamic acid, vanillin, etc.

The resin of Sumatra benzoin consists chiefly of benzoresinol, C16H26O2 and benzoresinotannol, C18H2004. That of the Siam variety contains benzoresinol and siaresinotannol, C12H1403.

Remarks.-Benzoin would be considered a balsam, save that the quantity of volatile oil it contains is so small that its base can hardly be considered as an oleoresin. Accordingly, the pharmacopoeia calls it "a balsamic resin."

Benzoin is interesting as the original source of benzoic acid, which thus received its name.

The pharmacopoeia permits the use of two commercial varieties of benzoin-Siam and Sumatra. Of these, the former possesses a delightful odor of vanilla, and is used by perfumers in preference to the less aromatic Sumatra variety. Medicinally, the two are about equal.

Medical Properties.-Expectorant. Used chiefly externally as an antiseptic and vulnerary. The tincture (p. 224) and the compound tincture (p. 224) are official. It is also used in making benzoinated lard (p. 661).

Dose.-1 gramme (15 grains).

Chicle is the milk-juice of Achras Sapota, a tree growing in Central America. It consists of the alcohols a- and 8-amyrin and lupeol, combined as esters with acetic, capronic, cinnamic and benzoic acids. Its use in chewing gum is well known.

GUM-RESINS

Gum-resins are plant exudations consisting of gum and resin. We have already learned what a gum (p. 633) is, and wherein a resin (p. 773) differs from a gum, the pharmaceutic difference being one of solubility, resins dissolving in alcohols and being insoluble in water, while gums dissolve in water and not in alcohol. Again, resins are terpene derivatives, while gums are dissociation products of cellulose.

The gum of a gum-resin will not dissolve in alcohol; the resin will; and since the resin is the active constituent, tinctures of such drugs are made by maceration in 95 per cent. alcohol and filtration of the resinous solution from the undissolved gum. In water, the gum will dissolve and the resin will not, but by rubbing such a drug with water the mucilage formed by the dissolved gum emulsifies the resin-also the volatile oil, if any be present-making a milky mixture. Such a mixture is formed when asafetida is rubbed with water, and since the preparation is clearly a form of emulsion, it is so termed by the pharmacopoeia. Up to the revision of 1890 they were grouped with the mixtures.

of the pharmacopoeia. Three gum-resins are now official, asafetida, gamboge, and myrrh, and of these, the first is a representative of the Umbelliferæ that family of plants to which belong anise, fennel, coriander, and caraway.

ASAFOETIDA-Asafetida

(Asafœt.-Gum Asafetida)

The gum-resin obtained by incising the rhizomes and roots of Ferula Asafætida Linné and Ferula fætida Regel and of some other species of Ferula (Fam. Umbelliferæ), indigenous to Persia and adjacent countries, and yielding not less than 60 per cent. (or if powdered 50 per cent.) of alcohol-soluble constituents.

Outline of Assay.-The drug is digested with boiling alcohol in a flask with an upright condenser for one hour; the mixture is filtered through counterpoised filters; the insoluble residue is washed with boiling alcohol and is then weighed. Should be not more than 40 per cent. of the original asafetida taken. For details see U.S.P., p. 66.

Constituents.-Resin, 65 per cent.; gum, 25 per cent.; bassorin; vanillin; volatile oil.

The resin consists of the ferulaic acid (p. 721) ester of asaresinotannol, C24H3304OH; while the oil is a mixture of sulphides, C7H14S2, C11H20S2, C8H16S2, and C10H18S2, with terpenes. Powdered asafetida is practically without value, as the amount of heat necessary to dry it drives off practically all of the volatile oil.

Medical Properties.-Antispasmodic (in hysteria), carminative. The emulsion (p. 262), pills (p. 311), and tincture (p. 223) are official, and the tincture is an ingredient of the popular colic cure, Dewee's Carminative (mixture of magnesia, asafetida and opium, N.F.

(See

p. 258.) As this mixture contains opium, its use is not advisable, and some physicians specify the preparation "without opium," in which case it is made exactly as per the Formulary, save that the tincture of opium is omitted.

Dose. Of drug, 250 milligrammes (4 grains).

CAMBOGIA-Gamboge

(Cambog.-Pipe Gamboge)

A gum-resin obtained from Garcinia Hanburii Hooker filius (Fam. Guttifera). Constituents.-Gum, 16 per cent.; resin, 77 per cent. The resin consists of three garcinolic acids. The alpha and gamma varieties have the formula C22H27O4COOH; while the beta acid is C24H3404COOH. The resin on fusion yields phloroglucin and fatty acids.

Medical Properties.-Hydragogue cathartic. Always in combination, since it is very drastic. An ingredient of compound cathartic pills (p. 312).

Dose.-125 milligrammes (2 grains).

MYRRHA-Myrrh
(Myrrh.-Gum Myrrh)

A gum-resin obtained from one or more species of Commiphora (Fam. Burseraceœ). Constituents.-Gum, 60 per cent.; resin, 30 per cent.; volatile oil, 6 to 7 per cent.