History—Under the superstitious influence of the so-called doctrine of signatures,[2438] salep[2439] has had for ages a reputation in Eastern countries as a stimulant of the generative powers; and many Europeans who have lived in India, although not prepared to admit the extravagant virtues ascribed to it by Hindus and Mahommedans, yet regard it as a valuable nutrient in the sick-room.
The drug was known to Dioscorides and the Arabians, as well as to the herbalists and physicians of the middle ages, by whom it was mostly prescribed in the fresh state. Gerarde (1636) has given excellent figures of the various orchids whose tubers, says he, “our age useth.”
Geoffroy[2440] having recognized the salep imported from the Levant to be the tubers of an orchis, pointed out in 1740 how it might be prepared from the species indigenous to France.
Collection—The tubers are dug up after the plant has flowered, and the shrivelled ones having been thrown aside, those which are plump are washed, strung on threads and scalded. By this process their vitality is destroyed, and the drying is easily effected by exposure to the sun or to a gentle artificial heat. Though white and juicy when fresh, they become by drying hard and horny, and lose their bitterish taste and peculiar odour.
Salep is largely collected near Melassa (Milas) and Mughla (or Moola), south-east of Smyrna, and also brought there from Mersina, opposite the north-eastern cape (Andrea) of Cyprus. The drug found in English trade is mostly imported from Smyrna. That sold in Germany is partly obtained from plants growing wild in the Taunus mountains, Westerwald, Rhön, the Odenwald, and in Franconia. Salep is also collected in Greece, and used in that country and Turkey in the form of decoction, which is sweetened with honey and taken as an early morning drink.[2441] The salep of India is produced on the hills of Afghanistan, Beluchistan, Kabul and Bokhara;[2442] the Neilgherry Hills in the south, and even Ceylon are said likewise to afford it.
Description—Levant salep, such as is found in the English market, consists of tubers half an inch to an inch in length, of ovoid or oblong form, often pointed at the lower end, and rounded at the upper where is a depressed scar left by the stem; palmate tubers are unfrequent. They are generally shrunken and contorted, covered with a roughly granular skin, pale brown, translucent, very hard and horny, with but little odour and a slight not unpleasant taste. After maceration in water for several hours, they regain their original form and volume. German salep is more translucent and gummy-looking, and has the aspect of being more trimmed and prepared.
Microscopic Structure—The fresh tuber exhibits on transverse section a few outer rows of thin-walled cells rich in starch. These are followed by parenchyme of elongated colourless cells likewise containing starch, and isolated bundles of acicular crystals of oxalate of calcium. In this parenchyme, there are numerous larger cells filled with homogenous mucilage. Small vascular bundles are irregularly scattered throughout the tuber. In Orchis mascula and O. latifolia the starch grains are nearly globular, and about 25 mkm. in diameter. In dried salep the cell-walls are distorted and the starch grains agglomerated.
Chemical Composition—The most important constituent of salep is a sort of mucilage, the proportions of which according to Dragendorff (1865) amounts to 48 per cent.; but it is doubtless subject to great variation. Salep yields this mucilage to cold water, forming a solution which is turned blue by iodine, and mixes clearly with neutral acetate of lead like gum arabic. On addition of ammonia, an abundant precipitate is formed. Mucilage of salep precipitated by alcohol and then dried, is coloured violet or blue, if moistened with a solution of iodine in iodide of potassium. The dry mucilage is readily soluble in ammoniacal solution of oxide of copper; when boiled with nitric acid, oxalic, but not mucic acid is produced. In these two respects, the mucilage of salep agrees with cellulose, rather than with gum arabic. In the large cells in which it is contained, it does not exhibit any stratification, so that its formation does not appear due to a metamorphosis of the cell-wall itself. Mucilage of salep contains some nitrogen and inorganic matter, of which it is with difficulty deprived by repeated precipitation by alcohol.
It is to the mucilage just described that salep chiefly owes its power of forming with even 40 parts of water a thick jelly, which becomes still thicker on addition of magnesia or borax. The starch however assists in the formation of this jelly; yet its amount is very small, or even nil in the tuber bearing the flowering stem, whereas the young lateral tuber abounds in it. The starch so deposited is evidently consumed in the subsequent period of vegetation, thus explaining the fact that tubers are found, the decoction of which is not rendered blue by iodine. Salep contains also sugar and albumin, and when fresh, a trace of volatile oil. Dried at 110° C., it yields 2 per cent. of ash, consisting chiefly of phosphates and chlorides of potassium and calcium (Dragendorff).
Commerce—The shipments of salep from Smyrna are about 5000 okkas (one okka equal to 283·2 lb. avdp. = 128·5 kilogrammes) annually.