Source, Etc

Myrrh is a gum-resin obtained from the stem of Commiphora Myrrha, Holmes, and probably other species (N.O. Bur-seraceoe). It is collected chiefly in Somaliland (in the north-east of Africa), brought down to the coast and sent to Aden, whence it is shipped to Europe, either direct or via Bombay. Some myrrh is said also to be collected in the south of Arabia. Several other species of Commiphora are found in Arabia and north-eastern Africa yielding gum-resins that more or less resemble the official myrrh in appearance and odour.

These plants are shrubs or small trees, and, like most other plants belonging to the same natural order, they contain numerous schizo-genous ducts in the bark, in which an oleo-gum-resin is secreted. In the case of the species from which the official myrrh is derived the tissue intervening between the ducts frequently breaks down and thus lysigenous cavities of considerable extent are produced which, together with the ducts that remain intact, are filled with a granular secretion. When the bark is wounded, therefore, the secretion is discharged in considerable quantity. It is first yellowish white and fluid, but soon hardens to a firm, reddish brown mass which constitutes the commercial drug. The secretion also exudes from fissures that are formed in the bark by natural causes; indeed the bulk of the drug is said to be naturally exuded.

It not unfrequently contains other gums and gum-resins from which it is freed by hand picking.

Description

Myrrh occurs in irregular rounded tears, or lumps composed of agglutinated tears, varying in size from small grains up to masses nearly as large as the fist, pieces about the size of a walnut being of common occurrence. They have a reddish yellow or reddish brown colour and a rather rough, dull, dusty surface. They break fairly easily, the fractured surface having a rich brown or reddish brown colour and translucent, unctuous, granular appearance, often exhibiting whitish spots or veins; thin splinters are translucent or almost transparent. The drug has an agreeable aromatic odour and an aromatic, bitter and acrid, but not unpleasant taste. Triturated with water it yields a yellowish emulsion. If one gramme of the coarsely powdered drug is shaken for a few minutes with 10 c.c. of ether and 2 c.c. of the ethereal .solution allowed to evaporate to a thin film in a small porcelain dish, the residue is coloured instantly deep violet-black by the vapour of bromine, or violet by nitric acid diluted with an equal volume of water. The resinous film obtained by evaporating tincture of myrrh will also yield similar reactions.

The student should observe

(a) The unctuous, granular (not uniform or vitreous) fracture,

(b) The translucent (not opaque) appearance of thin fragments,

(c) The aromatic, bitter taste.

The taste and the violet colour-reaction are, perhaps, the most characteristic features of myrrh.

Fig. 242.   Myrrh. Section of a portion of bark, probably of Commiphora Myrrha. P, outer portion (bark) in which layers of sclerenchymatous cells, st, alternate with thin walled cells, d; p, bast parenchyma; b, bast fibres; m, medullary ray; o, oleo resin ducts containing a granular secretion (myrrh); 0, tissue breaking down to form a cavity filled with the secretion. Magnified 280 diam. (Vogl.)

Fig. 242. - Myrrh. Section of a portion of bark, probably of Commiphora Myrrha. P, outer portion (bark) in which layers of sclerenchymatous cells, st, alternate with thin-walled cells, d; p, bast parenchyma; b, bast fibres; m, medullary ray; o, oleo-resin ducts containing a granular secretion (myrrh); 0, tissue breaking down to form a cavity filled with the secretion. Magnified 280 diam. (Vogl).

Constituents

Myrrh consists of a mixture of resin, gum, and volatile oil. The latter can be obtained by distillation with water to the extent of 2.5 to 6.5 per cent. (Schimmel). The resin occurs in amounts varying from 25 to 35 per cent., the remainder of the drug consisting of gum, moisture, and various impurities.

Alcohol dissolves the volatile oil and resin. The volatile oil is yellowish and viscous and resinifies with great rapidity. Both the volatile oil and the resin give the characteristic violet reaction.

The resin is not entirely soluble in ether. The insoluble (smaller) portion is separable into three free resin-acids (α-, β- and γ-commi-phoric acids), a combined resin-acid (commiphorinic acid), and two phenolic resins (a- and β-heerabo-myrrholol). The portion soluble in ether contains α- and β-myrrhololic acids. These constituents are remarkable for exhibiting little analogy with the substances that have been isolated from other resins.

The gum is apparently allied to acacia gum; it yields by hydrolysis arabinose and contains an oxydase enzyme the activity of which is destroyed by a temperature (in solution) of 100,° but not of 90°.

The bitter principle has not yet been isolated.

Good myrrh should yield not more than 70 per cent, of substances insoluble in alcohol and not more than 5 per cent, of ash; commercial powdered myrrh often yields much more ash.

Uses

Myrrh has stimulant and antiseptic properties; it is used as a mouth wash and as a uterine stimulant and emmenagogue.

Varieties

In addition to Somali myrrh (the official drug), as above described, the following varieties may be briefly alluded to:

Fadhli or Arabian myrrh, which occurs in smaller pieces made up of agglutinated tears, presenting a less dusty surface, and free from white markings. The odour is less fragrant and taste less bitter than that of genuine myrrh. It is said to be collected on the mountains to the east of Aden.

Yemen myrrh, which occurs in large pieces of dark reddish brown colour and dusty surface. It exhibits no whitish streaks and exudes no oil. The taste is bitter, the odour resembles that of myrrh but is less aromatic. It is exported from Makullah to Bombay and Aden.

Substitutes And Admixtures

Perfumed bdellium or bissabol which closely resembles myrrh. It breaks with a waxy fracture and yields to the nail, giving an oily exudation like soft myrrh. It has a yellowish colour and exhibits white markings which, however, are traversed by angular interstices filled with a brown resin. It has a taste and odour quite distinct from those of myrrh and it does not yield the violet reaction. It is frequently seen in the London market, where it is offered for sale under various names (scented bdellium). It is probably derived from G. erythroeum, var. glabrescens, Engler.

Opaque bdellium, a very hard, yellow ochre-coloured, opaque gum-resin with but a slight odour and a bitter taste. Portions of a papery bark are frequently found associated with it. The tincture (1 in 6) assumes an intense greenish black colour with solution of ferric chloride.

African bdellium, in hard pieces, translucent in thin layers, and red when viewed by transmitted light. The fracture is dull and slaty, the margins possessing a powdery appearance; it has a bitter taste and an odour recalling pepper. The tincture gives no precipitate with ferric chloride.

Indian bdellium, which occurs in large irregular masses of a dark reddish brown colour. The fractured surface resists the nail, and is covered with characteristic, minute, shiny points of resin which also appear on the outer surface. The odour is feeble and cedar-like; it appears to be developed only on keeping. The taste is slightly acrid and devoid of bitterness.

Gum hotai, liver-coloured, opaque masses, is sent in large quantities to Bombay; used for washing the hair. It contains an acid resin and a saponin.