_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_.
[412] Blue Book—Island of Jamaica for 1871.
[413] Blue Book for Colony of Bahamas for 1871.
[414] _Consular Reports_, Aug. 1873. 746.
[415] The ancient treatment of syphilis by guaiacum which gained for
the drug such immense reputation, consisted in the administration of
vast quantities of the decoction, the patient being shut up in a warm
room and kept in bed.—See Hutten’s pamphlet quoted before, and its
numerous reprints and translations.
[416] Schulz, in the (Chicago) _Pharmacist_, Sept. 1873.
[417] _Op. cit._ at p. 101.
[418] We have to thank Mr. Eugène Nau of Port-au-Prince for the
information given under this head, as well as for some interesting
specimens.
=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.
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.