Source, Etc

The common henbane, Hyoscyamus niger, Linne (N.O. Solanaceœ), is an erect herb attaining a height of about 1 metre, distributed over the whole of Europe and extending to Persia and India. In England it is found chiefly on waste places near buildings; it is cultivated in this country for medicinal use, but much is imported from Germany and Russia. The medicinal use of the plant dates from very remote ages. It was well known to the Anglo-Saxons in the tenth and eleventh centuries, but subsequently fell into disuse. It was omitted from the London Pharmacopoeia in 1746, but restored in 1809 chiefly by the influence of Storck, who also introduced stramonium.

Two varieties of the plant are known, an annual and a binneial, the distinction between them being by no means well marked.

Biennial henbane produces in the first year of its growth simply a rosette of large stalked leaves attaining 30 cm. in length, some of which are frequently collected and form the drug known commercially as ' first biennial henbane.' In the second year the plant sends up a large branching stem attaining a height of about 1.5 metres, which flowers, ripens its seeds, and dies. The smaller branches of this plant with the leaves and flowers constitute the drug from which the green extract of henbane and juice of henbane should be prepared; the flowering tops are dried and sold; the leaves separated from the stalks and dried constitute in part the official drug.

Fig. 33.   Henbane (H. niger). Flowering top of a large second year's plant of biennial Henbane. Reduced.

Fig. 33. - Henbane (H. niger). Flowering top of a large second year's plant of biennial Henbane. Reduced.

Annual henbane is a much smaller plant than the biennial. The stem does not branch as that of the biennial does, nor are the leaves so large or so deeply incised; the corolla is paler in colour and less deeply veined with purple. This variety flowers in the first year of its growth, ripens its seeds, and dies. The dried leaves are included in the official description, but the commercial drug frequently contains a large proportion of the stem.

Four commercial varieties of henbane leaves must therefore be distinguished, viz.:

1 First biennial,' consisting of the leaves of the first year's growth of the biennial variety.

' Second biennial,' or 'biennial.' consisting of the flowering tops of the second year's growth of the biennial variety.

'Annual,' consisting of the stem with leaves and flowers of the annual variety.

'Official' (B.P. 1914), consisting of the leaves collected from the flowering plant, whether biennial or annual.

Description

As previously mentioned, in the second year of its growth the biennial variety of the plant produces a tall, stout, branching stem with leaves and flowers.

The leaves vary considerably in size. The lower attain as much as 25 cm. in length, and are stalked; the upper are smaller and sessile. They are pale green in colour, and, especially when fresh, soft and unpleasantly clammy or sticky to the touch. This peculiarity is due to the soft hairs which are particularly abundant near the veins on the under surface; these hairs possess glandular heads which secrete a resinous substance.

In outline the leaves vary from nearly ovate to elongated triangular; the margin is coarsely dentate or even pinnatifid, and the midrib broad; the stems are rounded, and bear glandular hairs like those of the leaf.

The flowers, which are usually crowded together, arise from the axils of large, hairy, leafy bracts; they possess a hairy, urceolate calyx and a yellowish, gamopetalous corolla deeply veined with purple. The fruit is a two-celled pyxis containing numerous seeds.

The dried flowering tops are commonly found in irregular rounded or flattened masses about 2.5 to 5 cm. in diameter, in which the coarsely dentate hairy bracts, the yellowish corolla, with deep purple veins, and two-celled ovary with numerous ovules can easily be identified.

The fresh plant has a strong heavy odour, which is less perceptible in the dry drug; but the taste of the latter is more distinctly bitter than that of the former.

Microscopical Characters

The epidermis closely resembles that of belladonna and of stramonium, but bears numerous, very long, uniserial, multicellular hairs, some of which are simple, but the majority terminate in oval multicellular glands; the mesophyll contains calcium oxalate chiefly in the form of prismatic, often twin, crystals; in some specimens small cluster crystals are fairly numerous, and sandy crystals may occur in or near the midrib; the bundles are bicollateral, and there are no pericyclic or bast fibres.

Fig. 34.   Annual Henbane. Small specimen. Reduced.

Fig. 34. - Annual Henbane. Small specimen. Reduced.

The student should observe

(a) The hairy leaves with sinuate-dentate outline and broad midrib,

(b) The purple veins of the corolla,

(c) The characteristic fruit (or ovary).

Constituents

The principal alkaloid in henbane leaves is hyos-cyamine, but it appears to be accompanied by small proportions of atropine and scopolamine (hyoscine). The drug contains much less total alkaloid than either belladonna or stramonium, viz. from 0045 to 0.14 or, exceptionally, 0.2 per cent, (of the dry drug). The cultivated plant contains about the same proportion as the wild, but the leaves contain more than the large stems and the extract made from the leaves, more than that made from the stem. The petiole is, however, rather richer than the lamina. Henbane should yield about 8 to 12 per cent, of ash, but commercial samples sometimes afford much more.

Assay

Henbane may be assayed by the process official for belladonna leaves, using 25 gm. of the powdered drug instead of 10.

Uses

The action and uses of henbane closely resemble those of belladonna and stramonium, but the drug is distinctly weaker. The extract has a decided laxative and carminative effect, whilst the tincture has a more marked action on the urinary organs.

Varieties

The first year's leaves of biennial henbane may be recognised by their being longer and relatively narrower, stalked, and free from stem and flower. They are equal in activity to the leaves from flowering plants, and there seems to be no good reason why they should not be used. They are sometimes sold for annual henbane.

Annual henbane is distinguished by its slender simple stem, smaller leaves, and paler corolla, with less distinct purple venation. As in this case the entire plant is usually cut and dried, portions of the stem as well as leaf and flower are often found in the drug. Much imported henbane is of this variety, and it often arrives in very poor condition, probably mixed with other species of Hyoscyamus. Such henbane contains notably less alkaloid than either the first or second biennial, viz. about 003 per cent. English annual henbane consists of such plants as happen under favourable conditions to flower in the first year; such plants are much stronger than the foreign, and being more carefully dried are richer in alkaloid.