Description—The flower of the saffron crocus has a style 3 to 4 inches long, which in its lower portion is colourless, and included within the tube of the perianth. In its upper part it becomes yellow, and divides into three tubular, filiform, orange-red stigmas, each about an inch in length. The stigmas expand towards their ends, and the tube of which they consist is toothed at the edge and slit on its inner side. The stigma is the only part officinal, and alone is rich in colouring matter.
Commercial saffron (Hay Saffron of the druggists) is a loose mass of thread-like stigmas, which when unbroken are united in threes at the upper extremity of the yellow style. It is unctuous to the touch, tough and flexible; of a deep orange-red, peculiar aromatic smell, and bitter and rather pungent taste. It is hygroscopic and not easily pulverized; it loses by drying at 100° C. about 12 per cent. of moisture, which it quickly reabsorbs.[2488]
The colouring power of saffron is very remarkable: we have found that a single grain rubbed to fine powder with a little sugar will impart a distinct tint of yellow to 700,000 grains (10 gallons) of water.
Microscopic Structure—The tissue of the stigma consists of very thin, sinuous, closely-felted, thread-shaped cells, and small spiral vessels. The yellow colouring matter penetrates the whole, and is partly deposited in granules. The microscope likewise exhibits oil-drops, and small lumps, probably of a solid fat. Large isolated pollen grains are also present.
Chemical Composition—The splendid colouring matter of saffron has long been known as Polychroit; but in 1851 Quadrat, who instituted some fresh researches on the drug, gave it the name of Crocin, which was also adopted in 1858 by Rochleder. Weiss in 1867[2489] has shown that it is a glucoside, for which he retains the name of Polychroit, while the new colouring matter which results from its decomposition he terms Crocin. It agrees with the Crocetin of Rochleder.
Polychroit was prepared by Weiss in the following manner: saffron was treated with ether, by which fat, wax, and essential oil were removed; and it was then exhausted with water. From the aqueous solution, gummy matters and some inorganic salts were precipitated by strong alcohol. After the separation of these substances, polychroit was precipitated by addition of ether. Thus obtained, it is an orange-red, viscid, deliquescent substance, which, dried over sulphuric acid, becomes brittle and of a fine ruby colour. It has a sweetish taste, but is devoid of odour, readily soluble in spirit of wine or water, and sparingly in absolute alcohol. By dilute acids, it is decomposed into Crocin, sugar, and an aromatic volatile oil having the smell of saffron. Weiss gives the following formula for this decomposition:—
| C₄₈H₆₀O₁₈ + H₂O = | 2(C₁₆H₁₈O₆) | · C₁₀H₁₄O · | C₆H₁₂O₆. |
| polychroit | crocin | essential oil | sugar |
Crocin is a red powder, insoluble in ether, easily soluble in alcohol, and precipitable from this solution on addition of ether. It is only slightly soluble in water, but freely in an alkaline solution, from which an acid precipitates it in purple-red flecks. Strong sulphuric and nitric acids occasion the same colours as with polychroit; the former producing deep blue, changing to violet and brown, and the latter green, yellow, and finally brown. It is remarkable that hydrocarbons of the benzol class do not dissolve the colouring matter of saffron.
The oil obtained by decomposing crocin is heavier than water; it boils at about 209° C., and is easily altered,—even by water. It is probably identical with the volatile oil obtainable to the extent of one per cent. from the drug itself, and to which its odour is due.
Saffron contains sugar (glucose?), besides that obtained by the decomposition of polychroit. The drug leaves after incineration 5 to 6 per cent. of ash.