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 plant yielding turmeric, Curcuma longa, Linne (N.O. Scitamineoe), is apparently a native of southern Asia, though no longer known in the wild state. It is largely cultivated in India, China, Java, and other tropical countries. The rhizome has long been employed both as a spice and as a colouring agent (Crocus indicus). It was certainly known to Dioscorides, and described by him as a root resembling ginger, but having a yellow colour and bitter taste. During the Middle Ages it fell into disuse, and is now considered much inferior to ginger and other spices, whilst in India it is largely employed as a dye and as a condiment.
The rhizomes are dug up after the herbaceous aerial stems have died down; there is then found an upright, bulb-shaped rhizome, from which the stem has sprung and to which several cylindrical descending branches are attached. One or more of the latter, destined to produce aerial stems in the following year, will curve upwards and thicken to form bulb-shaped organs. The rhizomes so obtained are then steamed in their own juice or boiled in water for a half to one day, by which the vitality that they otherwise obstinately retain is destroyed. They are finally dried either in the sun or in an oven, and (sometimes) sorted into 'fingers' and 'bulbs,' the former being the cylindrical descending branches, the latter the erect, stem-producing ones.
Finger or long turmeric occurs in curved or nearly straight cylindrical pieces bluntly tapering at each end. The outer surface is of a deep yellowish brown colour, longitudinally wrinkled and marked with transverse rings (leaf-scars). Occasionally they bear short knob-like branches, or show large circular scars where these have been broken off. They are hard and heavy, and break with a short fracture; internally they have a uniform dull brownish yellow, waxy appearance and tough horny consistence. The transverse section exhibits little of its structure beyond a paler (or sometimes darker) ring separating the stele from the cortex. This remarkable appearance of the interior of the rhizomes is due to the prolonged boiling they undergo, by which not only is the starch gelatinised and a horny consistence imparted to the drug, but the colouring matter, previously restricted to certain scattered cells, becomes uniformly diffused throughout the rhizome. Bulb or round turmeric resembles the finger variety, but is, as its name indicates, shorter and thicker.
Fig. 198. - Long Turmeric. (Pereira).
Fig. 199. - Round Turmeric. (Pereira).
Fig. 200. - Turmeric rhizome. Transverse section, a, cortex; v, endodermis; b, stele; y, vascular bundles. Magnified 3 diam. (Berg).
The drug has a characteristic aromatic odour and taste, and when chewed colours the saliva yellow. The student should observe
(a) The difference in shape between 'bulbs' and 'fingers,'
(6) The yellowish brown colour,
(c) The horny consistence and waxy appearance of the interior.
Turmeric contains about 5 per cent. of volatile oil-resin, a crystalline yellow body, curcumin. These are confined, in the fresh rhizome, to the particular secreting cells in which they have been produced, but pass during the scalding into the surrounding tissue, the parenchymatous cells of which are filled with amorphous masses of gelatinised starch.
Curcumin, C21H10O6, forms reddish yellow prisms melting at 183°, and readily dissolving in alcohol, forming a deep yellow solution, the colour of which is changed to reddish brown by alkalies. Evaporated after the addition of boric acid the colour is reddish brown, which alkalies then change to blue. A mixture of alcohol and sulphuric acid dissolves it with production of a brilliant crimson red colour and forms an excellent means of detecting powdered turmeric in the presence of many other substances.
Turmeric is used as a condiment and colouring agent.
Several commercial varieties of turmeric are known. The majority of the drug is shipped from India, that from Madras being the most esteemed. Other species of Curcuma (G. angustifolia, Roxburgh, G. leucorhiza, Roxburgh) have paler coloured rhizomes; these are utilised in India for the production of starch, which is known as ' East Indian Arrowroot.'
Zedoary (G. Zedoaria, Roscoe), India; circular slices of a rhizome resembling bulb turmeric; greyish or yellowish; starchy; section exhibiting numerous oleo-resin cells, hairs, and bundles without sclerenchymatous elements; taste and odour resembling ginger but less aromatic.