_Radix Curcumæ_;[2365] _Turmeric_; F. _Curcuma_; G. _Gelbwurzel_,
_Kurkuma_.
=Botanical Origin=—_Curcuma longa_[2366] L.—Turmeric is indigenous to
Southern Asia, and is there largely cultivated both on the continent
and in the islands.
=History=—Dioscorides mentions an Indian plant as a kind of _Cyperus_
(Κύπειρος) resembling ginger, but having when chewed a yellow colour
and bitter taste: probably turmeric was intended. Garcia de Orta
(1563), as well as Fragoso (1572), describe turmeric as _Crocus
indicus_. A list of drugs sold in the city of Frankfort about the year
1450, names _Curcuma_ along with zedoary and ginger.[2367]
In its native countries, it has from remote times been highly esteemed
both as a condiment and a dye-stuff; in Europe, it has always been less
appreciated than the allied spices of the ginger tribe. In an inventory
of the effects of a Yorkshire tradesman, dated 20th Sept., 1578, we
find enumerated—“_x. owncis of turmeracke, x d._”[2368]
[2364] Statist. Abstract (as quoted p. 633, note 3), p. 71.
[2365] _Curcuma_ from the Persian _kurkum_, a name applied also to
saffron. The origin of the word _Turmeric_ is not known to us; _Terra
merita_ seems to be a corruption of it.
[2366] Fig. in Bentley and Trimen’s _Med. Plants_, part 9. (1876).
[2367] Flückiger, _Die Frankfurter Liste_, Halle, 1873. 11.
[2368] Raine, _Wills and Inventories of the Archdeaconry of Richmond_
(Surtees Society), 1853. 277.
=Description=—The base of the scrape thickens in the first year into
an ovate rootstock; this afterwards throws out shoots, forming lateral
or secondary rhizomes, each emitting roots, which branch into fibres
or are sometimes enlarged as colourless spindle-shaped tubers, rich in
starch. The lateral rhizomes are doubtless in a condition to develope
themselves as independent plants when separated from the parent.
The central rhizomes formerly known as _Curcuma rotunda_, and the
elongated lateral ones as _Curcuma longa_, were regarded by Linnæus as
the production of distinct species.
The radical tubers of some species of _Curcuma_, as _C. angustifolia_
Roxb., are used for making a sort of arrowroot (p. 637). Sometimes
they are dried, and constitute the peculiar kind of turmeric which the
Chinese call _Yuh-kin_.[2369]
The turmeric of commerce consists of the two sorts of rhizome just
mentioned, namely, the _central_ or _round_ and the _lateral_ or
_long_. The former are ovate, pyriform or subspherical, sometimes
pointed at the upper end and crowned with the remains of leaves, while
the sides are beset with those of roots and marked with concentric
ridges. The diameter is very variable, but is seldom less than ¾ of
an inch, and is frequently much more. They are often cut and usually
scalded in order to destroy their vitality and facilitate drying.
The lateral rhizomes are subcylindrical, attenuated towards either end,
generally curved, covered with a rugose skin, and marked more or less
plainly with transverse rings. Sometimes one, two or more short knobs
or shoots grow out on one side. The rhizomes, whether round or long,
are very hard and firm, exhibiting when broken a dull, waxy, resinous
surface, of an orange or orange-brown hue, more or less brilliant. They
have a peculiar aromatic odour and taste.
Several varieties of turmeric distinguished by the names of the
countries or districts in which they are produced, are found in the
English market: but although they present differences which are
sufficiently appreciable to the eye of the experienced dealer, the
characters of each sort are scarcely so marked or so constant as to
be recognizable by mere verbal description. The principal sorts now
in commerce are known as _China_, _Madras_, _Bengal_, _Java_, and
_Cochin_. Of these the first-named is the most esteemed, but it is
seldom to be met with in the European market.[2370]
_Madras Turmeric_ is a fine sort in large, bold pieces. Sometimes
packages of it contain exclusively round rhizomes, while others are
made up entirely of the long or lateral.
_Bengal Turmeric_ differs from the other varieties chiefly in its
deeper tint, and hence is the sort preferred for dyeing purposes.
_Java Turmeric_ presents no very distinctive features; it is dusted
with its own powder, and does not show when broken a very brilliant
colour. Judging by the low price at which it is quoted it is not
in great esteem. It is the produce of _Curcuma longa_ var. β.
_minor_[2371] Hassk.
[2369] Hanbury, _Pharm. Journ._ iii. (1862) 206; also _Science Papers_,
254, fig. 11.—It is not wholly devoid of yellow colouring matter.
[2370] A good deal is exported from Takow in Formosa, but mostly to
Chinese ports.—_Returns of Trade at the Treaty Ports of China for
1872._ p. 106.
[2371] From information communicated by Mr. Binnendyk, of the Botanical
Garden, Buitenzorg, Java.
=Microscopic Structure=—The suberous coat is made up of 8 to 10 rows
of tabular cells; the parenchyme of the middle cortical layer of large
roundish polyhedral cells. Towards the centre the transverse section
exhibits a coherent ring of fibro-vascular bundles representing a kind
of medullary sheath. The parenchyme enclosed by this ring is traversed
by scattered bundles of vessels, and in most of its cells contains
starch in amorphous, angular, or roundish masses, which are so far
disorganized that they no longer exhibit the usual appearance in
polarized light, but are nevertheless turned blue by iodine. The starch
has been reduced to this condition by scalding.
Resin likewise occurs in separate cells, forming dark yellowish-red
particles. The entire tissue is penetrated with yellow colouring
matter, and shows numerous drops of essential oil, which in the fresh
rhizome is no doubt contained in peculiar cells.
=Chemical Composition=—The drug yielded us (1876) one per cent. of a
yellow essential oil, which contains a portion boiling at 250° C.,
answering to the formula C₁₀H₁₄O; this liquid differs from carvol (p.
306) by being unable to combine with SH₂. The other constituents of
curcuma oil boil at temperatures much above 250°; we found the crude
oil and its different portions slightly dextrogyrate.
The aqueous extract of the drug tastes bitter, and is precipitated by
tannic acid.
The colouring matter, _Curcumin_, C₁₀H₁₁₀O₃, may be obtained to the
amount of ⅓ per cent. by depriving first the drug of fat and essential
oil. The powder, after that treatment with bisulphide of carbon, is
gradually exhausted, according to Daube (1871), with warm petroleum
(boiling point 80°-90° C.). On cooling chiefly the last portions of
petroleum deposit the crystalline curcumin. Its alcoholic solution
is purified by mixing it cautiously with basic acetate of lead, not
allowing the liquid to assume a decidedly acid reaction. The red
precipitate thus formed is collected, washed with alcohol, immersed
in water, and decomposed with sulphuretted hydrogen. From the dried
mixture of sulphide of lead and curcumin the latter is lastly removed
by boiling alcohol.
By Ivanow-Gajewsky (1873) the best produce of curcumin is stated to be
obtained by washing an ethereal extract of turmeric with weak ammonia,
dissolving the residue in boiling concentrated ammonia, and passing
into the solution carbonic acid, by which the curcumin is precipitated
in flakes.
After due recrystallization from alcohol curcumin forms yellow
crystals, having an odour of vanilla, and exhibiting a fine blue in
reflected light. They melt at 165° C. Curcumin is scarcely soluble,
even in boiling water, but dissolves readily on addition of an alkali
either caustic or carbonate. On acidulating these solutions, a yellow
powder of curcumin is precipitated. Curcumin is not abundantly
dissolved by ether, very sparingly by benzol or bisulphide of carbon.
It is not volatile; heated with zinc dust it yields an oil boiling at
290°; fused with caustic potash, curcumin affords protocatechuic acid
(page 243).
Paper tinged with an alcoholic solution of curcumin displays on
addition of an alkali a brownish-red coloration, becoming violet on
drying. Boracic acid produces an orange tint, turning blue by addition
of an alkaline solution.[2372] This behaviour of (impure) curcumin was
pointed out by Vogel as early as 1815, and has since that time been
utilized as a chemical test.
[2372] The following is a striking experiment, showing some of these
changes of colour:—Place a little crushed turmeric or the powder on
blotting paper, and moisten it repeatedly with chloroform, allowing the
latter to evaporate. There will thus be formed on the paper a yellow
stain, which on addition of a slightly acidulated solution of borax and
drying assumes a purple hue. If the paper is now sprinkled with dilute
ammonia it will acquire a transient blue. This reaction enables one to
recognize the presence of turmeric in powdered rhubarb or mustard.
Borax added to an alcoholic solution of curcumin gives rise to a
crystallizable substance, which Ivanow-Gajewsky (1870) isolated by
heating an alcoholic extract of turmeric with boracic and sulphuric
acids. It forms a purple crystalline powder with a metallic green
lustre, insoluble in water, but soluble in alcohol. Its solution is
coloured dark blue by an alkali.
According to the same chemist there also exists in curcuma an alkaloid
in very small quantity. Kachler (1870) found in the aqueous decoction
an abundance of _bioxalate of potassium_.
=Commerce=—In the year 1869 there were imported into the United Kingdom
64,280 cwt. of turmeric; in 1870, 44,900 cwt.,—a very large proportion
being furnished by Bengal and Pegu. The export from Calcutta[2373] in
the year 1870-71 was 59,352 cwt.
Bombay exported in the year 1871-72, 29,780 cwt., of which the greater
portion was shipped to Sind and the Persian Gulf, and only 910 cwt. to
Europe.[2374]
=Uses=—Turmeric is employed as a condiment in the shape of curry
powder, and as such is often sold by druggists; but as a medicine it is
obsolete. It is largely consumed in dyeing.
=Substitute=—_Cochin Turmeric_ is the produce of some other species of
_Curcuma_ than _C. longa_. It consists exclusively of a bulb-shaped
rhizome of large dimensions, cut transversely or longitudinally
into slices or segments. The cortical part is dull brown; the inner
substance is horny and of a deep orange-brown, or when in thin shavings
of a brilliant yellow. Mr. A. Forbes Sealy of Cochin has been good
enough to send us (1873) living rhizomes of this _Curcuma_, which he
states is mostly grown at Alwaye, north-east of Cochin, and is never
used in the country as _turmeric_, though its starchy tubers are
employed for making arrowroot. The rhizomes sent are thick, short,
conical, and of enormous size, some attaining as much as 2½ inches in
diameter. Internally they are of a bright orange-yellow.
The beautiful figures of Roscoe[2375] show several species of Curcuma
and Zingiber provided with yellow tubers or rhizomes, all probably
containing curcumin.
[2373] Returns quoted at p. 571, note 2.
[2374] _Statement of the Trade and Navigation of Bombay for_ 1871-72,
pt. ii. 95.
[2375] _Monandrous Plants of the order Scitamineæ_, Liverpool, 1828,
especially _Zingiber Cossumunar_.