_Lobelia_, _Indian Tobacco_; F. _Lobelie enflée_; G. _Lobeliakraut_.
=Botanical Origin=—_Lobelia inflata_ L., an annual herb, 9 to 18
inches high, with an angular upright stem, simple or more frequently
branching near the top, widely diffused throughout the eastern part
of North America from Canada to the Mississippi, growing in neglected
fields, along roadsides, and on the edges of woods, and thriving well
in European gardens.
=History=—_Lobelia inflata_ was described and figured by Linnæus[1460]
from specimens cultivated by him at Upsala about 1741, but he does not
attribute to the plant any medicinal virtues.
The aborigines of North America made use of the herb, which from this
circumstance and its acrid taste, came to be called _Indian Tobacco_.
In Europe it was noticed by Schöpf,[1461] but with little appreciation
of its powers. In America it has long been in the hands of quack
doctors, but its value in asthma was set forth by Cutler in 1813. It
was not employed in England until about 1829, when, with several other
remedies, it was introduced to the medical profession by Reece.[1462]
=Description=—The leaves are 1 to 3 inches long, scattered, sessile,
ovate-lanceolate, rather acute, obscurely toothed, somewhat pubescent.
The edge of the leaf bears small whitish glands, and between them
isolated hairs which are more frequent on the under than on the upper
surface. They are usually in greater abundance on the lower and middle
portions of the stem.
The stem of the growing plant exudes when wounded a small quantity of
acrid milky juice, contained in laticiferous vessels running also into
the leaves. The inconspicuous blossoms are arranged in a many-flowered,
terminal, leafy raceme. The five-cleft, bilabiate corolla is bluish
with a yellow spot on the under lip, its tube being as long as the
somewhat divergent limb of the calyx.
The capsule is ovoid, inflated, ten-ribbed, crowned by five elongated
sepals which are half as long as the ripe fruit. The latter is
two-celled, and contains a large number of ovate-oblong seeds about
¹/₅₀ of an inch in length, having a reticulated, pitted surface.
The herb found in commerce is in the form of rectangular cakes, 1
to 1¾ inches thick, consisting of the yellowish-green chopped herb,
compressed as it would seem while still moist, and afterwards neatly
trimmed. The cakes arrive wrapped in paper, sealed up and bearing the
label of some American druggist or herb-grower.
[1459] Stillé, _Therapeutics and Mat. Med._ i. (1868) 756. Garrod
(_Med. Times and Gazette_, 26 March, 1864), gave lactucarium in drachm
doses, repeated 3 or 4 times a day, without being able to perceive that
it had any effect either as an anodyne or hypnotic.
[1460] _Acta Soc. Reg. Scient. Upsal._ 1746. 23.
[1461] _Mat. Med. Americana_, Erlangæ, 1787. 128.
[1462] _Treatise on the Bladder-podded Lobelia_, Lond. 1829.
Lobelia has a herby smell and, after being chewed, a burning acrid
taste resembling that of tobacco.
=Chemical Composition=—Lobelia has been examined by Procter, Pereira
(1842), Reinsch (1843), Bastick (1851), also by F. F. Mayer.[1463]
The first-named chemist[1464] traced the activity of the plant to
an alkaloid which he termed _Lobelina_, and his observations were
confirmed by the independent experiments of Bastick.[1465] Lewis (1878)
obtained it by mixing the drug with charcoal and exhausting the powder
with water containing a little acetic acid. The liquid is cautiously
evaporated to the consistency of an extract and triturated with
magnesia, from the excess of which the aqueous solution of lobeline is
separated by filtration. It is agitated with amylic alcohol (or ether),
which by spontaneous evaporation affords the alkaloid. The latter is
again dissolved in water and filtered through animal charcoal; from the
dried powder lobeline is to be removed by ether.
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.
[1463] _American Journ. of Pharm._ xxxvii. (1866) 209; also
_Jahresbericht_ of Wiggers and Husemann, 1866. 252.
[1464] _Am. Journ. of Pharm._ iii. (1838) 98; vii. (1841) 1; _Pharm.
Journ._ x. (1851) 456.
[1465] _Pharm. Journ._ x. (1851) 270.
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.