Cetraria. Iceland Moss.
Iceland moss consists of the dried lichen, Cetraria islandica, Acharius (N.O. Discomycetes). The plant is indigenous to Britain, and widely distributed over the Northern Hemisphere. The drug consists of the dried cartilaginous foliose thallus, the branches of which have fringed lobes. It is brownish or greenish-brown above, greyish below, and marked with small white depressed spots. The apothecia, which are sometimes present, appear as slightly depressed circular, reddish-brown spots on the upper surface of the thallus. The lichen is hard when dry, but becomes softer when moist. It has no odour, but a mucilaginous bitter taste. A 5 per cent. decoction gelatinises on cooling. The drug should be free from pine leaves, moss and other lichens, which are frequently present.
Constituents.—The chief constituent of Iceland moss is the carbohydrate lichenin, which is accompanied by its isomer isolichenin. Lichenin is soluble in hot water, but the solution gelatinises as it cools; isolichenin is soluble in cold water, and resembles a soluble modification of starch. Both lichenin and isolichenin are converted into dextrose by boiling with a dilute mineral acid. The drug also contains a crystalline bitter principle named cetraric acid, bitter protocetraric acid, and tasteless licheno-stearic acid. The bitterness of the lichen can be removed by prolonged maceration with water, or by macerating the powdered drug in a dilute solution of an alkali carbonate.
Action and Uses.—In the northern countries of Europe, Iceland moss is used as a food, either made into bread or boiled with milk, the bitterness being to some extent removed by previous washing with water. The decoction made with milk forms a nutritious and demulcent drink. Iceland moss is administered chiefly as decoction, for its demulcent properties, and in the form of jujube, the bitter cetraric acid being removed. Jellies are also prepared with sugar and water. The bitter principle has been given in pills as a tonic, in doses of 1 to 2 decigrams (2 to 4 grains).
- Decoctum Cetrariae, B.P., 1885.—DECOCTION OF ICELAND MOSS.
- Iceland moss, washed, 5; distilled water, to 100. This decoction contains a large quantity of mucilage, and is demulcent and nutritive. Dose.—30 to 120 mils (1 to 4 fluid ounces).