_Marshmallow Root_; F. _Racine de Guimauve_; G. _Eibischwurzel_.
=Botanical Origin=—_Althæa officinalis_ L., the marshmallow, grows in
moist places throughout Europe, Asia Minor, and the temperate parts of
Western and Northern Asia, but is by no means universally distributed.
It prefers saline localities such as in Spain the salt marshes of
Saragossa, the low-lying southern coasts of France near Montpellier,
Southern Russia, and the neighbourhood of salt-springs in Central
Europe. In southern Siberia Althæa has been met with by Semenoff (1857)
ascending as high as 3,000 feet in the Alatau mountains, south of the
Balkash Lake.
In Britain it occurs in the low grounds bordering the Thames below
London, and here and there in many other spots in the south of England
and of Ireland.
The cultivated marshmallow thrives as far north as Throndhjem in
Norway, and has been naturalized in North America (salt marshes of
New England and New York) and Australia. It is largely cultivated in
Bavaria and Württemberg.
=History=—Marshmallow had many uses in ancient medicine, and is
described by Dioscorides as Άλθαία, a name derived from the Greek verb
ἀλθειν, _to heal_.
The diffusion of the plant in Europe during the middle ages was
promoted by Charlemagne who enjoined[373] its culture (A.D. 812) under
the name of “_Mismalvas_, id est alteas quod dicitur ibischa.”
=Description=—The plant has a perennial root attaining about a foot in
length and an inch in diameter. For medicinal use the biennial roots
of the cultivated plant are chiefly employed. When fresh they are
externally yellowish and wrinkled, white within and of tender fleshy
texture. Previous to drying, the thin outer and a portion of the middle
bark are scraped off, and the small root filaments are removed. The
drug thus prepared and dried consists of simple whitish sticks 6 to 8
inches long, of the thickness of the little finger to that of a quill,
deeply furrowed longitudinally and marked with brownish scars. Its
central portion, which is pure white, breaks with a short fracture, but
the bark is tough and fibrous. The dried root is rather flexible and
easily cut. Its transverse section shows the central woody column of
undulating outline separated from the thick bark by a fine dark outline
shaded off outwards.
The root has a peculiar though very faint odour, and is of rather
mawkish and insipid taste, and very slimy when chewed.
[373] Pertz, _Monumenta Germaniæ historica_, Legum tom. i. (1835)
181.—_Ibischa_ from the Greek ὶβίσκος.
=Microscopic Structure=—The greater part of the bark consists of liber,
abounding in long soft fibres, to which the toughness of the cortical
tissue is due. They are branched and form bundles, each containing from
3 to 30 fibres separated by parenchymatous tissue. Of the cortical
parenchyme many cells are loaded with starch granules, others contain
stellate groups of oxalate of calcium, and a considerable number of
somewhat larger cells are filled with mucilage. The last named on
addition of alcohol is seen to consist of different layers.
The woody part is made up of pitted or scalariform vessels, accompanied
by a few ligneous cells and separated by a parenchymatous tissue,
agreeing with that of the bark. On addition of an alkali, sections of
the root assume a bright yellow hue.
=Chemical Composition=—The mucilage in the dry root amounts to about
25 per cent. and the starch to as much more. The former appears from
the not very accordant analysis of Schmidt and of Mulder to agree
with the formula C₁₂H₂₀O₁₀, thus differing from the mucilage of gum
arabic by one molecule less of water. It likewise differs in being
precipitable by neutral acetate of lead. At the same time it does not
show the behaviour of cellulose, as it does not turn blue by iodine
when moistened with sulphuric acid, and it is not soluble in ammoniacal
solution of oxide of copper.
The root also contains pectin and sugar (cane-sugar according to
Wittstock), and a trace of fatty oil. Tannin is found in very small
quantity in the outer bark alone.
In 1826 Bacon, a pharmacien of Caen, obtained from althæa root crystals
of a substance at first regarded as peculiar, but subsequently
identified with _Asparagin_, C₄H₈N₂O₃, H₂O. It had been previously
prepared (1805) by Vauquelin and Robiquet from Asparagus, and is now
known to be a widely diffused constituent of plants.[374] Marshmallow
root does not yield more than 0·8 to 2·0 per cent. Asparagin
crystallizes in large prisms or octohedra of the rhombic system; it is
nearly tasteless, and appears destitute of physiological action. Its
relation to succinic acid may be thus represented:—
Succinic acid: C₂H₄ {COOH; Asparagin: C₂H₃(NH₂) {CONH₂
{COOH {COOH.
Asparagin is quite permanent whether in the solid state or dissolved,
but it is easily decomposed if the solution contains the albuminoid
constituents of the root, which act as a ferment. Leguminous seeds,
yeast or decayed cheese induce the same change, the final product of
which is succinate of ammonium, the asparagin taking the elements of
water and hydrogen set free by the fermentation, thus—
C₄H₈N₂O₃ + H₂O + 2H = 2NH₄, C₄H₄O₄
Asparagin. Succinate of Ammonium.
Under the influence of acids or bases, or even by the prolonged boiling
of its aqueous solution, asparagin is converted into _Aspartate of
Ammonium_, C₄H₆(NH₄)NO₄, of which the hydrated asparagin contains the
elements.
[374] It plays an interesting part in the germination of the seeds of
papilionaceous and other plants. It is abundant in the young plants,
but in most it speedily disappears. Its presence can be proved in the
juice by means of the microscope and absolute alcohol, in which latter
asparagin is insoluble. See Pfeffer in Pringsheim’s _Jahrb. f. wiss.
Bot._ 1872. 533-564.—Borodin in _Bot. Zeitung_, 1878. 801 and seq.
These transformations, especially the former, are undergone by the
asparagin in the root, if the latter has been imperfectly dried, or has
been kept long, or not very dry. Under such conditions, the asparagin
gradually disappears, and the root then yields a brownish decoction,
sometimes having a disagreeable odour of butyric acid. There is no
doubt that a protein-substance here acts as a ferment. The sections
of the root when touched with ammonia or caustic lye should display a
bright yellow, not a dingy brown, colour.
The peeled root dried at 100° C. and incinerated afforded us 4·88 of
ash, rich in phosphates.
=Uses=—Althæa is taken as a demulcent; it is sometimes also applied as
an emollient poultice. It is far more largely used on the continent
than in England.