Source, Etc

The aconite, monkshood, or wolfsbane, Aconltum Napellus, Linne (N.O. Ranunculaceoe), is a perennial herb growing abundantly on the lower mountain slopes of central Europe. It is cultivated in England as a garden plant as well as for medicinal use, and is found apparently wild in some localities, but in these cases has probably escaped from cultivation. The drug has only recently been introduced into medicine, although the poisonous properties of the plant have long been known. Both the fresh leaves and flowering tops, as well as the dried roots, have been used; the latter are, however, now alone official.

Source Etc 229Fig. 147.   Aconite root. A, parent and daughter roots of the autumnal plant connected together: γ, parent root; δ, daughter root; β, short branch connecting them; e, bud at the apex of the daughter root; natural size. B, longitudinal section through the daughter root: a, bark; 6, cambium; c, wood; natural size. (Berg.)

Fig. 147. - Aconite root. A, parent and daughter roots of the autumnal plant connected together: γ, parent root; δ, daughter root; β, short branch connecting them; e, bud at the apex of the daughter root; natural size. B, longitudinal section through the daughter root: a, bark; 6, cambium; c, wood; natural size. (Berg).

The root should be collected in the autumn after the stem and leaves have died down, but before the bud destined to produce the stem for the following year has begun to develop. This bud is protected by cataphyllary leaves, in the axils of which lateral buds are situated. As the terminal bud grows and forms a flowering stem, certain (usually from one to three) of these lateral buds develop into short lateral shoots, each of which produces a long, slender, descending, adventitious root crowned with a bud. These roots rapidly enlarge and fill with reserve material produced by the parent plant, the root of which shrivels and perishes in proportion as the daughter roots increase in size. Towards the autumn the parent plant dies down, and the daughter roots, which have then attained their maximum development, are plump and full of starch. If allowed to remain in the soil the buds that crown the daughter roots begin to grow in the late winter or very early spring, and this growth is effected at the expense of the starch in the root, which for that purpose is converted into sugar. The root therefore becomes gradually exhausted of its reserve material, and it is generally assumed that the proportion of alkaloid it contains simultaneously diminishes, although this assumption has not been confirmed by analysis, such assays as have been made having shown but little difference. In some continental countries the wild plant is considered to be more active than the cultivated, and as experiments have shown that A. Napellus is more toxic than A. variegatum, Linne, and its varieties, the root is directed to be gathered from wild plants when in flower, at which time they can be most easily distinguished. Hence the aconite root that is imported in large quantities from Germany consists chiefly of the partially exhausted summer (parent) roots of the wild flowering plants.

After collection the roots are washed, freed from the rootlets and dried, sometimes entire, sometimes longitudinally sliced.

Description

Aconite root of commerce varies usually from 5 to 10 cm. in length, although the entire root is often considerably longer. At the upper extremity, where it is crowned with an undeveloped bud enclosed by scaly leaves (daughter root), or by the remains of the aerial stem (parent root), it is about 1 or 2 cm. in diameter, tapering rapidly downwards. It is dark brown in colour, and marked with the scars of rootlets. The surface is usually longitudinally wrinkled, especially if it has been dried entire. The root breaks with a short fracture, and should be whitish and starchy internally. The smoothed transverse section exhibits a thick bark, separated from the inner portion by a well-marked, darker, stellate line (cambium), with a group of vessels distinctly visible at each of the projecting angles, usually five to seven in number. Commercial aconite root is, however, often yellowish or brownish internally, and does not readily show the stellate cambium; this is probably due to its having been collected too early. The taste is at first slight, but is followed by a persistent sensation of tingling and numbness in the mouth. Although the daughter roots are usually more active than the parent root, the British Pharmacopoeia admits the use of either, uniformity being ensured by the assay.

Fig. 148.   Aconite root. Transverse section of daughter root, a, bark; b, cambium; c, wood. Magnified 3 diam. (Berg.)

Fig. 148. - Aconite root. Transverse section of daughter root, a, bark; b, cambium; c, wood. Magnified 3 diam. (Berg).

The student should observe

(a) The elongated conical shape,

(b) The starchy interior and stellate cambium,

(c) The characteristic tingling taste.

Constituents

Aconite root contains three closely allied alkaloids, viz. aconitine, picraconitine (benzoylaconine), and aconine.

In addition to these alkaloids the root contains starch and aconitic acid, C3H3(COOH)3, an acid fairly widely distributed in plants. The drug yields about 5 per cent, of ash.

Aconitine, C34H47NO11 (m.pt. 198° ), is the only one of these three that is crystalline and extremely toxic, the lethal dose being about 0.00013 gm. per kilo weight. It produces even in minute quantity the persistent tingling on the tongue that characterises aconite root. It is very readily hydrolysed by acids as well as by alkalies, yielding first acetic acid and picraconitine; the latter by further hydrolysis yields benzoic acid and aconine. Aconitine is, therefore, acetylbenzoylaconine, and picraconitine is benzoylaconine. Aconitine may be distinguished from benzoylaconine and aconine by its taste, by its melting point, by its solubility in ether, and by its being readily crystallisable.

Picraconitine (benzoylaconine), C32H45NO10, is amorphous, but yields crystalline salts; it has a bitter taste, is much less toxic than aconitine, and is insoluble in ether.

Aconine, C25H41N09, is also amorphous, bitter, and insoluble in ether; it is practically non-toxic.

The relation in which these alkaloids stand to one another may be made clear by the following equations:

C34H47NOn

+

H1O

=

CH3.COOH

+

C32H45NO10

aconitine

acetic acid

benzoylaconine

C32H45NO10

+

H1O

=

C6H5.COOH

+

C25H41NO9

benzoylaconine

benzoic acid

aconine

The amount of total alkaloid present in the root appears to be subject to great variation, from 0.2 to 1.5 per cent, having been reported. No process has yet been devised by which the aconitine can be accurately determined in the presence of the other alkaloids. That portion of the total alkaloid that is dissolved by ether is, however, mostly crystalline, and consists almost entirely of aconitine. The ether-soluble alkaloid in aconite root of good quality ranges usually from about 0.3 to 0.5 per cent.

Uses

Preparations of aconite and its principal alkaloid, aconitine, when applied to the skin, produce tingling followed by numbness; they are used in certain forms of neuralgia and rheumatism. Administered internally, aconite produces a steady fall of temperature, moistening of the skin, increase in the amount of urine, and lowering of the sensibility; it is given in cases of fever and pain, usually in the form of small doses of the tincture frequently repeated.

Varieties And Substitutes

English Aconite Root, as described above, may generally be recognised by the bud which crowns most of the roots, indicating that the root is a daughter root and not a parent root.

Foreign Aconite Root

Much aconite root is imported from Germany. It is collected from wild plants when in flower, and consists largely of the parent roots, as shown by their being crowned with the lower portions of the stems. Comparative assays of German and English aconite root tend to show that the German is scarcely inferior to the English in the proportion of ether-soluble alkaloid it contains.

Japanese Aconite Root (A. uncinatum, Linne, var. japonicum, Regel), is regularly imported in considerable quantities. It tapers gradually, and is either dark grey and nearly smooth (daughter root) or brownish, and marked with not very prominent, paler, longitudinal ridges (parent root). Both kinds of root are smaller than the English; they are, however, very starchy, less wrinkled than the English root, and exhibit, in transverse section, the groups of vessels arranged in a more regular circle. It contains japaconitine, which closely resembles, but is not identical with, aconitine, being acetylbenzoyl-japaconine.

Indian Aconite Root (A. laciniatum, Stapf) is much larger than the English, measuring frequently 15 cm. in length and 4 cm. in thickness near the crown; it is crowned with the remains of a bud and is coarsely wrinkled; internally it may be either starchy or yellowish and horny; the horny character is due to the starch having been completely gelatinised by the prolonged application of heat, the roots being, according to some accounts, boiled in cow's urine to preserve them. The drug contains pseudaconitine (acetylveratroyl-pseudaconine), which is about twice as toxic as aconitine.

Atis Root (A. heterophyllum, Wallich), small, ovoid, greyish roots with a bitter but not numbing taste, contain the alkaloid atisine.

The root of A. chasmanthum, Stapf, contains indaconitine which resembles aconitine in action; that of A. paniculatum, Lamark, is much less toxic than that of A. Napellus and is believed to contain benzoylaconine only. The rhizome of A. lycoctonum, Linne, contains lycaconitine and myoctonine: its action resembles that of atis root.