LIGNUM GUAIACI.

Botanical Origin—This wood is furnished by two West Indian species of Guaiacum, namely:—

1. G. officinale L., a middle-sized or low evergreen tree, with light blue flowers, parapinnate leaves having ovate, very obtuse leaflets in 2, less often in 3 pairs, and 2-celled fruits. It grows in Cuba, Jamaica (abundantly on the arid plains of the south side of the island), Les Gonaives in the N.W. of Hayti (plentiful), St. Domingo, Martinique, St. Lucia, St. Vincent, Trinidad, and the northern coast of the South American continent. This tree affords the Lignum Vitæ of Jamaica (of which very little is imported), a portion of that shipped from the ports of Hayti, and probably the small quantity exported by the United States of Colombia.

2. G. sanctum L., a tree much resembling the preceding, but distinguishable by its leaves having 3 to 4 pairs of leaflets which are very obliquely obovate or oblong, passing into rhomboid-ovate, and mucronulate; and a 5-celled fruit. It is found in Southern Florida, the Bahama Islands, Key West, Cuba, St. Domingo (including the part called Hayti) and Puerto Rico, and is certainly the source of the small but excellent Lignum Vitæ exported from the Bahamas as well as of some of that shipped from Hayti.

History—There can be no doubt but that the earliest importations of Lignum Vitæ were obtained from St. Domingo, of which island, Oviedo[403] who landed in America in 1514 mentions the tree, under the name of Guayacan, as a native. He points out its fruits as yellow and resembling two joined lupines, which could only be said with reference to G. officinale, and would not apply to the ovoid five-cornered fruits of G. sanctum. Oviedo appears however to have been aware of two species, one of which he found in Española (St. Domingo) as well as in Nagrando (Nicaragua) and the other in the island of St. John (Puerto Rico), whence it was called Lignum sanctum.

The first edition of Oviedo was printed in 1526; but some years before this the wood must have been known in Germany, as is evident by the treatises written in 1517, 1518, and 1519 by Nicolaus Poll,[404] Leonard Schmaus[405] and Ulrich von Hutten.[406] The last which gives a tolerable description of the tree, its wood, bark, and medicinal properties, was translated into English in 1533 by Thomas Paynel, canon of Merton Abbey, and published in London in 1536 under the title—“Of the wood called Guaiacum that healeth the Frenche Pockes and also helpeth the gout in the feete, the stoone, the palsey, lepree, dropsy, fallynge euyll, and other dyseases.” It was several times reprinted.

In the old pharmacy the products of destructive distillation of guaiacum wood were known as Oleum ligni sancti. It must have consisted of the substances which we mention further on in the following article.

Description—The wood (always known in commerce as Lignum Vitæ) as imported consists of pieces of the stem and thick branches, usually stripped of bark, and often weighing a hundredweight each. It is remarkably heavy and compact. Its sp. gr. which exceeds that of most woods is about 1·3.

Lignum Vitæ is mostly imported for turnery,[407] and the chips, raspings and shavings are the only form in which it is commonly seen in pharmacy. A stem 7 to 8 inches in diameter cut transversely exhibits a light-yellowish zone of sapwood about an inch wide, enclosing a sharply defined heartwood of a dark greenish brown. Both display alternate lighter and darker layers, which especially in the sapwood are further distinguished by groups of vessels. In this manner are formed a large number of circles resembling annual rings, the general form of which is evident, though the individual rings are by no means well defined. More than 20 such rings may be counted in the sapwood of a log such as we have mentioned, and more than 30 in the heartwood. The pithless centre is usually out of the axis. The medullary rays are not visible to the naked eye, but may be seen by a lens to be very numerous and equidistant. The pores of the heartwood may be distinguished as containing a brownish resin, while those of the outermost layer of sapwood are empty.

In the thickest pieces sapwood is wanting, and even in stems of about a foot in diameter it is reduced to ⅕ of an inch. It is of looser texture than the heartwood and floats on water, whereas the latter sinks. Both sapwood and heartwood owe their tenacity to an extremely peculiar zigzag arrangement[408] of the woody bundles. The sapwood is tasteless. The heartwood has a faintly aromatic and slightly irritating taste, and when heated or rubbed emits a weak agreeable odour.

The bark which was formerly officinal but is now almost obsolete, is very rich in oxalate of calcium and affords upon incineration not less than 23 per cent. of ash. It contains a resin distinct from that of the wood, and also a bitter acrid principle.[409]

The Lignum Vitæ of Jamaica (G. officinale) and that of the Bahamas (G. sanctum), of which authentic specimens have been kindly placed at our disposal by Mr. G. Shadbolt, display the same appearance as well as microscopic structure.[410]

Microscopic Structure—The wood consists for the most part of pointed, not very long, ligneous cells (libriform), traversed by one-celled rows of medullary rays. There are also thin layers of parenchymatous tissue, to which the zones apparent in a transverse section of the drug are due. The pitted vessels are comparatively large but not very numerous. The structure of the sapwood is the same as that of the heartwood, but in the latter the ligneous cells are filled with resin. The parenchymatous cells contain crystals of oxalate of calcium.

Chemical Composition—The only constituent of any interest is the resin which the heartwood contains to the extent of about a fourth of its weight. The sapwood afforded us 0·91 and the heartwood 0·60 per cent. of ash.

Commerce—Lignum Vitæ varies much in estimation, according to size, soundness, and the cylindrical form of the logs. The best is exported from the city of Santo Domingo, whither it is brought from the interior of the island. The quantity shipped from this port during 1871 was 1494 tons;[411] 220 tons were exported in 1877 from Puerto Plata on the northern coast of the island. The wood obtained from the Haytian ports (of the western part of the same island) is much less esteemed in the London market.

Some small wood of good quality comes from the Bahamas, and an ordinary quality, also small, from Jamaica. From the latter island, the quantity exported in 1871 was only 14 tons;[412] from the Bahamas in the same year 199 tons.[413] Lignum Vitæ was shipped from Santa Marta in 1872 to the extent of 115 tons.[414]

Hamburg is also an important place for the wood under notice; in 1877 there were imported 22,404 centners from S. Domingo and 3551 centners from Venezuela.

Uses—Guaiacum wood is only retained in the pharmacopœia as an ingredient of the Compound Decoction of Sarsaparilla. It is probably inert, at least in the manner in which it is now administered.[415]

Adulteration—In purchasing guaiacum chips it is necessary to observe that the non-resinous sapwood is absent, and still more that there is no admixture of any other wood. A spurious form of the drug seems to be by no means rare in the United States.[416]

RESINA GUAIACI.

Guaiacum Resin; F. Résine de Gaïac; G. Guaiakharz.

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:—

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.

By exhausting guaiacum resin with boiling bisulphide of carbon a slightly yellowish solution is obtained (containing chiefly guaiaretic acid?), which, on addition of concentrated sulphuric acid, turns beautifully red.

After the extraction of the guaiaconic acid there remains a substance insoluble in ether to which the name Guaiac Beta-resin has been applied. It dissolves in alcohol, acetic acid or alkalis, and is precipitated by ether, benzol, chloroform or carbon bisulphide in brown flocks, the composition of which appears not greatly to differ from that of guaiaconic acid.

Guaiacic Acid, C₁₂H₁₆O₆, obtained in 1841 by Thierry from guaiacum wood or from the resin, crystallizes in colourless needles. Hadelich was not able to obtain more than one part from 20,000 of guaiacum resin.

Hadelich’s Guaiac-yellow, the colouring matter of guaiacum resin, first observed by Pelletier, crystallizes in pale yellow quadratic octohedra, having a bitter taste. Like the other constituents of the resin, it is not a glucoside.

The decomposition-products of guaiacum are of peculiar interest. On subjecting the resin to dry distillation in an iron retort and rectifying the distillate, Guaiacene (Guajol of Völckel), C₅H₈O, passes over at 118° C. as a colourless neutral liquid having a burning aromatic taste.

At 205°-210° C., there pass over other products, Guaiacol, C₆H₄·OCH₃·OH, (methylic ether of pyrocatechin), and Kreosol C₆H₃·OH(CH₃)₂. Both are thickish, aromatic, colourless liquids, which become green by caustic alkalis, blue by alkaline earths, and are similar in their chemical relations to eugenic acid. Guaiacol has been prepared synthetically by Gorup-Besanez (1868) by combining iodide of methyl, CH₃I, with pyrocatechin, C₆H₄(OH)₂.

After the removal by distillation of the liquids just described, there sublime upon the further application of heat pearly crystals of Pyroguaiacin, C₃₈H₄₄O₆, an inodorous substance melting at 180° C. The same compound is obtained together with guaiacol by the dry distillation of guaiaretic acid. Pyroguaiacin is coloured green by ferric chloride, and blue by warm sulphuric acid. The similar reactions of the crude resin are probably due to this substance (Hlasiwetz).

Beautiful coloured reactions are likewise exhibited by two new acids which Hlasiwetz and Barth obtained (1864) in small quantity together with traces of fatty volatile acids, by melting purified resin of guaiacum with potassium hydrate. One of them is isomeric with pyrocatechuic acid.

Uses—Guaiacum resin is reputed diaphoretic and alterative. It is frequently prescribed in cases of gout and rheumatism.

Adulteration—The drug is sometimes imported in a very foul condition and largely contaminated with impurities arising from a careless method of collection.