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 |
| COOH; | ||
| Asparagin: C₂H₃(NH₂) | | CONH₂ |
| 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.
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.