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.
Gentian root is the dried root and rhizome of the yellow gentian, Gentiana lutea, Linne (N.O. Gentianeoe), a stately herb with large, opposite, broadly ovate leaves and yellow flowers. It is indigenous to central Europe, growing abundantly on the lower slopes of the Jura and Vosges mountains, in the Black Forest, in the Pyrenees and European Turkey. Large quantities are imported from Spain. The root has long been used as a medicine.
The plant produces an erect rhizome, from which large fleshy roots are given off; the latter take a more or less horizontal course a short distance below the surface of the earth, and attain a considerable length. Both rhizome and roots are collected in the autumn and dried; they are occasionally, but not often, sliced longitudinally. When fresh they are whitish internally and almost odourless, but during the slow drying to which they are subjected the colour changes to a yellowish brown, and a distinctive odour is developed. So much are the particular colour and odour required, that in some districts the practice prevails of heaping the fresh root and allowing it to heat and ferment before drying it; by this treatment it darkens in colour and acquires the desired odour. Gentian root that has been longitudinally sliced or strung upon strings and quickly dried is paler and more bitter, and has an odour less strong than that which has not been so treated.
Gentian root is usually seen in nearly cylindrical pieces of varying length and thickness, but seldom more than 15 mm. in diameter. The roots, which differ in appearance from the rhizomes, are of a yellowish brown colour, and much shrivelled and wrinkled longitudinally. They are tough and flexible when slightly moist, but when quite dry they are brittle. They break with a very short fracture, and internally are usually of a reddish brown colour and spongy. The transverse section exhibits a dark line (cambium) separating a rather thick bark from a large central portion (wood) in which vascular tissue can with difficulty be discerned, as, like the bark, it consists almost entirely of parenchyma; neither bark nor wood exhibits any radiate structure.
The rhizome is easily distinguished from the root by the absence of conspicuous longitudinal wrinkles, and the presence of close, transverse annulations. It often exceeds the root in diameter, and may attain a length of 30 cm. or more. Each transverse annulation represents a year's growth, and bears the scars of fallen leaves, the minute fibro-vascular bundles of which are evident under a lens. The rhizome, which occasionally branches, is usually crowned with a large bud protected by dry, scaly leaves.
Fig. 179. - Gentian root. A, root, showing surface with longitudinal wrinkles. B, rhizome, showing fine transverse lines (leaf scars), and dividing into two branches, each terminating in a bud. Natural size.
Roots that have been longitudinally sliced before they were dried frequently exhibit transverse instead of longitudinal wrinkles, and are paler internally; otherwise they correspond to the description given.
Both roots and rhizome have the same distinct and characteristic odour, and a sweetish, afterwards agreeably bitter, taste. The student should observe
(a) The uniform yellowish brown colour,
(b) The longitudinal wrinkles of the root, the transverse annulations and leaf scars on the rhizomes,
(c) The absence of any evident structure in the transverse section,
(d) The absence of starch (see below).
The transverse section exhibits a narrow cork and a largely developed cortex which, like the bast-ring, is free from scleren-chymatous cells or fibres, and from more than an occasional starch grain. The cells have rather thick walls and contain small oil globules, and, frequently collected at one end of the cell, groups of very minute acicular crystals of calcium oxalate. The wood consists principally of parenchymatous tissue; the vessels are isolated or in small groups. In longitudinal section the vessels exhibit porous, annular, or reticulate thickening.
The powder is characterised by the abundant parenchymatous cells with rather thick walls, inclined to swell in water, and containing oily globules and minute calcium oxalate crystals, by the vessels with characteristic thickening, and by the absence of sclerenchymatous cells and fibres and of more than an occasional starch grain. Imported powdered gentian root is frequently much adulterated, particularly with ground almond shells which are readily detected by the sclerenchymatous tissue of which they consist.
Fresh gentian root contains two bitter principles, viz. gentiopicrin and gentiin. During the drying of the root, however, the gentiopicrin disappears and the dry root contains gentiin and gentiamarin, the latter not being present in the fresh root; this decomposition is induced by the fermentative processes which take place during the drying; carefully dried root retains its gentiopicrin intact, but still contains enzymes which act upon the gentiopicrin when the tincture is made.
Gentiopicrin is a pale yellow crystalline bitter substance, and is hydrolysed by emulsin and also by dilute mineral acids to gentiogenin and dextrose; it is present in G. punctata, G. asclepiadea and certain other species as well as in Chlora perfoliata, Linne. Gentiin is also a crystalline glucoside, but gentiamarin is amorphous.
Gentian root contains a yellow crystalline acid, gentisic (gentianic) acid, sucrose, and (in the fresh state) a sugar gentianose, together with pectin and oily globules, probably of a cholesterol compound; it is free from starch, or contains at most but minute traces of the latter. It yields from 3 to 4 per cent. of ash.
Fig. 180. - Gentian root. Transverse section. a, bark; b, wood. Magnified 2 diam. (Berg).
Gentianose is a hexatriose yielding by partial hydrolysis gentiobiose and levulose; further hydrolysis converts the gentiobiose into two molecules of dextrose. During the drying of the root the sucrose completely disappears and the gentianose is converted into dextrose, levulose, and gentiobiose. If the root is unduly exposed to fermentation these sugars are further converted into carbon dioxide and alcohol, so that highly fermented root may yield as little as 13 per cent. of extract to cold water, whereas good gentian root should yield 40 per cent. or even more. The British Pharmacopoeia requires not less than 33 per cent. The darkening that takes place on the addition of ferric chloride to an infusion of gentian root is probably due to gentin.
Fresh gentian root is largely used in Germany and Switzerland for the production of an alcoholic beverage. The roots are cut, macerated with water, fermented and distilled; the distillate contains alcohol and a trace of volatile oil which imparts to it a characteristic odour and taste.
Gentian is a favourite bitter tonic.
The roots of other species of gentian are often collected and dried; Gentiana purpurea, Linne (Switzerland &c), G. pannonica, Scopoli (Austria), G. punctata, Linne (Austria), all yield gentian roots. They are, however, all smaller than those of G. lutea. The roots of G. purpurea, which approach nearest to the official gentian, attain about half the size and are crowned with several (eight to ten) aerial stems clothed below with many scaly remains of leaves. The top of the root has thus a peculiar branched appearance never found in the root of G. lutea (Pharmacographia). All these species appear to possess similar properties.
The rhizomes of Rumex alpinus, Linne, have also been found; they are reddish brown, astringent and bitter, and give a deep red colour with caustic alkalies. Laserpitium latifolium, Linne, yields the white gentian of Continental commerce. White gentian of English commerce is said to be derived from G. Burseri, Lapeyr.