Source, Etc

Mezereon bark may, according to the British Pharmacopoeia 1898, be obtained from either of the following species of Daphne (N.O. Thymeloeacoe):

1. Daphne Mezereum, Linne, Mezereon, a small shrub attaining a metre in height, growing in moist woods in hilly parts of Europe, and found also in the southern counties of England. It bears in early spring, before the leaves appear, purple, sweet-scented flowers on the preceding year's shoots. The bark is collected chiefly in Thuringia.

2. Daphne Laureola, Linne,' Spurge Laurel, a small indigenous evergreen shrub, not uncommon in woods; it bears inconspicuous green odourless flowers in the axils of the leaves, the latter being crowded towards the summit of the stem. The bark is seldom collected.

3. Daphne Gnidium, Linne, a small shrub with numerous straight slender branches and small white flowers; it is a native of the south of France and the north coast of Africa, and is found generally on the shores of the Mediterranean. It is largely collected in Algeria and the south of France, and has been long known and used as an irritant.

The bark of all these plants is collected in the winter or early spring, when it separates readily from both stem and root in long flexible strips. These are dried, and either sold loose or made into small bundles or flat disc-like rolls.

Description

The bark of Daphne Mezereum sometimes occurs in quills of varying length, but more usually in long, thin, more or less flattened fibrous strips that are remarkable for their extreme toughness and flexibility; they can easily be torn lengthwise, but it is almost impossible to break them.

The outer surface (cork) is of a yellowish or olive brown colour, very thin, and transversely wrinkled, that of the stem-bark being marked with scattered rounded scars of leaves and buds, and often bearing the minute black apothecia of small lichens. It easily separates in papery fragments from the cortex, which is either green (stem-bark) or yellowish (root-bark) in colour. The inner portion of the bark (bast) has a pale yellowish or nearly white and silky inner surface; it is extremely tough and fibrous from the presence of numerous strands of tough bast fibres.

Fig. 138.   Mezereon bark. Slightly reduced.

Fig. 138. - Mezereon bark. Slightly reduced.

The dry bark has little or no odour, but a persistent burning acrid taste. So marked is the acrid nature of the bark that, moistened and applied to the skin, it produces inflammation and even vesication.

Spurge laurel bark is very similar to the foregoing; it may be distinguished by the purplish grey colour of the cork and by elongated, pointed oval leaf- and bud-scars which are crowded at intervals.

The bark of D. Gnidium has a dark purplish brown cork; the leaf-scars resemble those of D. Mezereum.

The student should observe

(a) The thin, easily separable cork,

(b) The silky inner surface,

(c) The extreme toughness and flexibility.

Constituents

Mezereon bark contains a greenish brown amorphous resin, mezerein, possessing extremely acrid and sternutatory properties. It easily changes into an acid bitter resin, mezereic acid, which is present in the ethereal and alcoholic extracts of the bark.

A crystalline bitter glucoside, daphnin, has also been isolated, as well as a fixed oil, and a substance resembling euphorbone, neither of which is acrid.

Uses

Mezereon is a powerful local irritant capable of producing vesication. Internally it is stimulant, and in large doses an irritant poison; it is, however, seldom administered internally, and although frequently employed in the south of France as an irritant, finds but little use in this country.