Botanical Origin—Guaiacum officinale L., [see preceding article.]
History—Hutten[417] in 1510 stated that guaiacum wood when set on fire exudes a blackish resin which quickly hardens, but of which he knew no use. The resin was in fact introduced into medicine much later than the wood. The first edition of the London Pharmacopœia in which we find the former named is that of 1677.
Production[418]—In the island of St. Domingo, whence the supplies of guaiacum resin are chiefly derived, the latter is collected from the stems of the trees, in part as a natural exudation, and in part as the result of incisions made in the bark. In some districts as in the island of Gonave near Port-au-Prince, another method of obtaining it is adopted. A log of the wood is supported in a horizontal position above the ground by two upright bars. Each end of the log is then set on fire, and a large incision having been previously made in the middle, the melted resin runs out therefrom in considerable abundance. 36,350 lbs. of it have been exported in 1875 from Port-au-Prince.
The resin is collected chiefly from G. officinale, which affords it in greater plenty than G. sanctum.
Description—The resin occurs in globular tears ½ an inch to 1 inch in diameter, but much more commonly in the form of large compact masses, containing fragments of wood and bark. The resin is brittle, breaking with a clean, glassy fracture; in thin pieces it is transparent and appears of a greenish brown hue. The powder when fresh is grey, but becomes green by exposure to light and air. It has a slight balsamic odour and but little taste, yet leaves an irritating sensation in the throat.
The resin has a sp. gr. of about 1·2. It fuses at 85° C., emitting a peculiar odour somewhat like that of benzoin. It is easily soluble in acetone, ether, alcohol, amylic alcohol, chloroform, creosote, caustic alkaline solutions, and oil of cloves; but is not dissolved or only partially by other volatile oils, benzol or bisulphide of carbon. By oxidizing agents it acquires a fine blue colour, well shown when a fresh alcoholic solution is allowed to dry up in a very thin layer and this is then sprinkled with a dilute alcoholic solution of ferric chloride. Reducing agents of all kinds, and heat produce decoloration. An alcoholic solution may be thus blued and decolorized several times in succession, but it loses at length its susceptibility. This remarkable property of guaiacum was utilized by Schönbein in his well-known researches on ozone.
Chemical Composition—The composition of guaiacum resin was ascertained by Hadelich (1862) to be as follows:—
| Guaiaconic Acid, | 70·3 | per cent. |
| Guaiaretic Acid, | 10·5 | ” |
| Guaiac Beta-resin, | 9·8 | ” |
| Gum, | 3·7 | ” |
| Ash constituents, | 0·8 | ” |
| Guaiacic Acid, colouring matter | ||
| (Guaiac-yellow), and impurities, | 4·9 | ” |
If the mother-liquor obtained in the preparation of the potassium salt of guaiaretic acid (vide infra) is decomposed by hydrochloric acid, and the precipitate washed with water, ether will extract from the mass Guaiaconic Acid, a compound discovered by Hadelich, having the formula C₃₈H₄₀O₁₀. It is a light brown, amorphous substance, fusing at 100° C. It is without acid reaction but decomposes alkaline carbonates, forming uncrystallizable salts easily soluble in water or alcohol. It is insoluble in water, benzol, or bisulphide of carbon, but dissolves in ether, chloroform, acetic acid or alcohol. With oxidizing agents it acquires a transient blue tint.
Guaiaretic Acid, C₂₀H₂₆O₄, discovered by Hlasiwetz in 1859, may be extracted from the crude resin by alcoholic potash or by quicklime. With the former it produces a crystalline salt; with the latter an amorphous compound: from either the liquid, which contains chiefly a salt of guaiaconic acid, may be easily decanted. Guaiaretic acid is obtained by decomposing one of the salts referred to with hydrochloric acid, and crystallizing from alcohol. The crystals, which are soluble also in ether, benzol, chloroform, carbon bisulphide or acetic acid, but neither in ammonia nor in water, melt below 80° C., and may be volatilized without decomposition. The acid is not coloured blue by oxidizing agents.