This section is from the book "A Text Book Of Materia Medica, Being An Account Of The More Important Crude Drugs Of Vegetable And Animal Origin", by Henry G. Greenish. Also available from Amazon: A Text Book of Materia Medica : Being an Account of the More Important Crude Drugs of Vegetable and Animal Origin.
The common dandelion, Taraxacum officinale, Wiggers (N.O. Compositoe), is widely distributed over Europe, Asia, and North America, and is in many cultivated districts a troublesome weed. In this country it has long been used as a domestic medicine.
The fresh root alone is official and is directed to be gathered in the autumn, when, judging from analogy, it may be expected to be most active. This, however, has been denied, the assertion being made that the root is most active in the spring or summer. A method for the quantitative determination of the active constituent not being at present known, this point cannot be definitely settled, but roots collected in the spring or summer contain much sugar, which is more objectionable than inulin, so that, unless positive evidence can be adduced to the contrary, the autumn must be regarded as the proper season in which to collect dandelion root.
The roots are collected from wild plants, washed, and, if necessary, dried. Much of the drug is imported from Germany.
Dandelion root consists of a simple straight root, which, towards the upper part, passes imperceptibly into an erect rhizome; the latter sometimes remains simple, but often divides into several erect branches. It attains a length of 30 cm. or more, and a thickness varying from 15 to 25 mm. Whilst fresh it is yellowish brown externally, whitish and fleshy within.
From the freshly cut surface, as indeed from all parts of the plant, an abundance of a very bitter, milky juice exudes, which on careful examination may be observed to rise from concentric rings of tissue. In the centre of the root is a small yellow wood.
The dried root has a dark brown colour and is much shrivelled and wrinkled longitudinally; it tapers but little below, and often divides in the upper part (rhizome) into several erect branches, the rhizome being distinguishable from the root only by its slightly varying structure. These branches (or the rhizome itself) are crowned with the short remains of the leaves which bear brownish hairs near the point of insertion.
It breaks when dry with a short fracture, the section exhibiting a very small, yellow, porous, central wood surrounded by an abnormally thick, whitish bark in which numerous brownish concentric rings (of latici-ferous tissue) are visible. The root, which is rather hygroscopic, becomes tough when slightly moist. It has no odour, but a bitter taste, which, however, is often not nearly so pronounced as it is in the milky juice that exudes from the fresh root.
Fig. 176. - Dandelion root. Transverse section. a, bark; b, wood; w, cambium Magnified 4 diam. (Berg).
Fig. 177. - Anastomosing latici-ferous vessels of Dandelion root. Magnified 140 diam. (Vogl).
The student should observe
(a) The small, yellow wood,
(b) The thick, whitish bark marked with distinct, darker, concentric rings,
(c) The absence of starch (see below); and should compare the root with
(i) Pellitory root, which has oil glands and a large radiate wood with conspicuous medullary rays, (ii) Liquorice root, which also has a large radiate wood.
Dandelion root contains a small quantity of a crystalline, bitter substance taraxacin, and also an acrid principle, neither of which, however, has been closely examined. The former, taraxacin, appears to be very susceptible of decomposition, which is probably induced by an enzyme, possibly an oxydase; the extract prepared from the fresh root is often almost devoid of bitterness. According to recent researches taraxacin is an indefinite mixture.
The drug also contains choline, resin, the phytosterols, taraxasterol and homotaraxasterol, various fat acids, and in the autumn abundance of inulin. In the fresh root the inulin is dissolved in the cell sap, but in the dry root forms amorphous, transparent lumps not again readily soluble in cold water. The absence of starch, which is so commonly present in roots, especially in the autumn, is a valuable negative character, and is often of service in detecting substitution. The autumn root has been found to contain 25 per cent. of inulin, whereas the spring root contained 18 per cent. of levulin and 17 per cent. of uncrystallisable sugar. Levulin, C6H,0O5, is a soluble carbohydrate converted by hydrolysis into dextrose and levulose.
Dandelion is a simple, bitter, and mild laxative, and is given in atonic dyspepsia attended by habitual constipation.
The root of a species of Lactuca which has the vessels arranged in radial rows has been substituted for dandelion root.