This section is from the book "Materia Medica And Therapeutics - Vegetable Kingdom", by Charles D. F. Phillips. Also available from Amazon: Materia Medica And Therapeutics: Vegetable Kingdom.
Active Ingredients. - The chemistry of this plant has not been thoroughly studied. No attempts, so far as we are aware, have been made to isolate its active principles and to determine their ultimate composition; from it, however, is obtained an article, used chiefly by eclectics, called irisin or iridin. It is said by Coe to consist of a resin, a resinoid, alkaloid, and a neutral principle.
Physiological Action. - In the fresh state it possesses acrid properties, lost in part by drying. According to Bigelow,1 "water distilled from the root has a highly nauseous taste and odor," showing that part of its principles are volatile. When taken in sufficient dose, twenty to sixty grains of the fresh root, it produces violent vomiting with purgation and great depression. In smaller doses it is diuretic and cholagogue, and in very small ones it produces annoying constipation from inactivity of the rectum. Faeces accumulate in the lower bowel, but the rectum seems to have lost all power to expel them. This we know by personal experience and complaints of patients to whom we have given it in doses too small to produce full cholagogue effects. Preparations from the dried plant we have seen produce headache and cerebral disturbance. The cholagogue action of iridin was the subject of experiment by Rutherford and Vignal, who write (Brit. Med. Journ., May 5, 1877): "1. Five grains of iridin, mixed with a little bile and water, and placed in the duodenum, very powerfully stimulate the liver. It is not so powerful as large doses (four grains) of podophyllin; but it is more powerful than euonymin, as is shown by the amount of bile secreted per kilogramme of dog; the fractions for the two euonymin experiments being 0.4789 c. c, and 0.4678, whereas in the iridin experiments they are 0.537 c c, and 0.638 c. c. The high fraction in the second iridin experiment probably resulted from a much smaller dog getting the same dose as in the first experiment, the smaller liver being thereby stimulated to a proportionably greater amount of work. 2. Iridin is also a decided stimulant of the intestinal glands. Judging from these experiments, its irritant effects on the intestinal mucous membrane are decidedly less than those of podophyllin, while the purgative effects are greater than in the case of euonymin. The statement of the writer in the Lancet above quoted" (vide infra) "that in man it is gentler in its action than podophyllin, is fully supported by these experiments, and there seems every reason why this substance should be removed from its present obscurity and placed in a prominent position in practical medicine."
1 Am. Med. Botany, vol. i., p. 158, Boston, 1818.
Therapeutic Action. - Blue flag was held in high esteem by the aborigines of this country, and by many tribes was specially cultivated as a medicinal plant. Schoepf (1787) writes: "Mirijice valet in ulceri-bus tibialibus et vulneribus." Iris versicolor cannot be recommended as a simple cathartic, its action being too distressing; but Bigelow speaks highly of its diuretic properties. The writer in the Lancet, above referred to, says: "In our hands iridin has produced effects similar to those occasioned by a combination of blue-pill, rhubarb, and aloes. It seldom fails to produce a mild catharsis with bilious evacuations; it appears to possess the advantages of (1) not requiring the addition of a mercurial; (2) not irritating the rectum, as aloes is apt to do; and (3) it has no as-tringency, and therefore does not produce subsequent costiveness like rhubarb when given alone. In a sluggish state of the bowels, arising from torpidity of the liver, or when the stools are pale, particularly as we find them in the intervals of overt attacks in gouty persons, we have found the iridin one of the best aperients, much gentler than podophyllin, and more reliable when a slight cholagogue action is required to be maintained for a lengthened period."
Personally we have never employed iris versicolor for cathartic or diuretic purposes. But as an hepatic stimulant in those gouty conditions which so frequently give rise to chronic eczema it is invaluable. In these cases we usually prescribe from five to ten minims of the tincture from the fresh root twice daily. If the smaller dose constipates, it is increased or a laxative dose of leptandra is combined with it. In one other distressing condition we have found iris of the utmost service, namely, a blinding headache, the pain occupying the region of the right supra-orbital and accompanied with nausea or vomiting. This form of headache is usually the result of hepatic derangement, and when thus caused may usually be promptly relieved by iris. The dose under these circumstances should not exceed one minim of the tincture, to be repeated every twenty minutes or half hour till three doses are taken. As a rule, the headache will be greatly relieved and perhaps entirely gone before the third dose is taken. If the three doses do not relieve, it is not worth while to continue it longer.
Preparations And Dose. - Although contained in the secondary list of the Pharmacopoeia, no officinal preparations of iris are given. We have employed fluid extracts, "concentrated tinctures," and irisin made from the dry root, but have given them up in favor of the tincture (one part root, two parts alcohol) made from the fresh root. The dry root, as found in the shops, varies so much in quality and activity that tinctures and fluid extracts made from it cannot be thoroughly depended on. If the only variation were in the strength of the preparation, this could be easily rectified by proper adjustment of the dose, but, after a large comparative experience, we are satisfied that the quality and character of the action is not identical in the fresh and dry root. Wet or dry seasons, etc., may influence the proportional amount of active constituents in the plant, but they will probably still preserve their own peculiarities as regards composition and relative proportion. On the other hand, after a plant is gathered, its juices sometimes undergo decomposition and chemical change, and some of them, as we well know, become practically inert; in others there is a change in the kind of effect.