Lobeline is an oily, yellowish fluid with a strong alkaline reaction, especially when in solution. In the pure state it smells slightly of the plant, but more strongly when mixed with ammonia. Its taste is pungent and tobacco-like, and when taken in minute doses, it exercises in a potent manner the poisonous action of the drug. Lobeline is to some extent volatile, but its decomposition begins when it is heated to 100° C. either pure or in presence of dilute acids or caustic alkalis. Lobeline dissolves in water, but more readily in alcohol or ether, the latter of which is capable of removing it from its aqueous solution. It neutralizes acids, forming with some of them crystallizable salts, soluble in water or alcohol.
The herb likewise contains traces of essential oil (the Lobelianin of Pereira?), resin and gum. The seeds afforded Procter about 30 per cent. of fixed oil, sp. gr. 0·940, which was found to dry very rapidly. The Lobeliin of Reinsch appears to be an indefinite compound.
In 1871 Enders at our request performed some researches on Lobelia in order to isolate the acrid substance to which the herb owes its taste. He exhausted the drug with spirit of wine and distilled the liquid in presence of charcoal, which then retained the acrid principle. The charcoal was washed with water, and then treated with boiling alcohol. This on evaporation yielded a green extract, which was further purified by means of chloroform. Warty tufts were thus finally obtained, yet always of a brownish colour. The tufts are readily soluble in ether and chloroform, but only slightly in water; they possess the acrid taste of lobelia. This substance, which we may term Lobelacrin, is decomposed if merely boiled with water; by the influence of alkalis or acids it is resolved into sugar and Lobelic Acid. The latter is soluble in ether, water, and alcohol, and is non-volatile; it yields a soluble salt with baryum oxide, whereas its plumbic salt is insoluble in water.
Lewis suggests that lobelacrin is nothing else than lobeliate of lobeline, which he believes to exist ready formed in the plant. From a decoction of the drug, on addition of sulphate of copper, lobeliate of copper is precipitated. By decomposing the latter with sulphuretted hydrogen, concentrating the solution and shaking it with warm ether, Lewis obtained a yellow solution affording on evaporation a crystalline mass of lobelic acid.
Uses—Lobelia is a powerful nauseating emetic; in large doses an acro-narcotic poison. It is prescribed in spasmodic asthma.
ERICACEÆ.
FOLIA UVÆ URSI.
Bearberry Leaves; F. Feuilles de Busserole; G. Bärentraubenblätter.
Botanical Origin—Arctostaphylos Uva-ursi Sprengel (A. officinalis Wimmer et Grabowsky, Arbutus Uva-ursi L.), a small, procumbent, evergreen shrub, distributed over the greater part of the northern hemisphere. It occurs in North America, Iceland, Northern Europe, and Russian Asia, and on the chief mountain chains of Central and Southern Europe. In Britain it is confined to Scotland, the north of England, and Ireland.
History—The bearberry was used in the 13th century by the Welsh “Physicians of Myddfai,” described by Clusius in 1601, and recommended for medicinal use in 1763 by Gerhard of Berlin and others.[1466] It had a place in the London Pharmacopœia for the first time in 1788.