Blue Flag. N. F. IV. (U. S. P. 1890.) Iris Versicolor.—"The dried rhizome of Iris versicolor Linne (Fam. Iridaceae), without the presence of more than 5 per cent. of the roots and leaf bases." y. F. In all the species belonging to this genus, so far examined, the roots are more or less acrid, and possessed of cathartic and emetic properties. In Europe, Iris foetidissima L., I. florentina L. , I. germanica L., I. pseudoacorus L., and I. tuberosa L. have at various times been admitted into use, and the unpeeled roots of I. germanica are still sold in the Indian bazaars under the name of Irisia. Iris versicolor L., or blue flag, is found in all parts of the United States, flourishing in low wet places in meadows. The flowers afford a fine blue infusion, which serves as a test for acids and alkalies. The recent root is without odor, and has a nauseous, acrid taste, which is imparted to water by decoction, and still more perfectly to alcohol, the acrimony as well as medicinal activity is impaired by age. If cut, when fresh, into slices, dried at the temperature of about 37.8 ° C. (100° F.), then powdered and kept in bottles excluded from the air, the root retains its virtues unimpaired for a considerable time (Andrews). It is described as follows in the National Formulary IV:
"Rhizome frequently branched, up to 10 cm. in length and 2 cm. in thickness, usually cut into longitudinal pieces; outer surface grayish-brown to purplish-brown, somewhat annulate, the upper surface with markings of leaf bases, the lower with numerous root scars and remnants; fracture short, the broken surface pale purplish-brown and exhibiting a central stele with whitish fibro-vascular bundles distributed throughout, a distinct endodermis, and cortex. Odor slight, not distinctive; taste acrid, nauseous. The powder is light purplish-brown and, when examined under the microscope, exhibits numerous resin cells filled with yellow to brown resin; starch grains few, or, in some specimens, abundant, simple, or two-to four-compound, the simple grains being spherical or elliptical, up to 0.022 mm. in diameter; calcium oxalate in prisms, up to 0.35 mm. in length; tracheae with spiral or reticulate markings or with bordered pores; sclerenchymatous fibers few, lignified and with oblique pores. Blue flag yields not more than 7 per cent. of ash." N. F.
D. W. Cressler found in this plant starch, gum, tannin, sugar, and acid resin, fixed oil, and indications of an alkaloid. (A. J. P., 1881, p. 602.)
Blue flag is a cathartic and emetic, said to have been used by the Southern Indians, and may be given in doses of from ten to twenty grains (0.65-1.3 Gm.). Iridin, or irisin, of the eclectics, is an oleoresin obtained by precipitating a tincture of the root with water, and mixing the precipitate with an equal weight of some absorbent powder. Wm. E. Jenks (A. J. P., 1881, p. 601) prepares the oleoresin of iris by exhausting the root with alcohol, sp. gr. 0.835, and distilling off the alcohol. (See also a paper on the constituents of the oleoresin by W. L. Cliffe, A. J. P., 1884, p. 616.) The so-called irisin is undoubtedly purgative and is generally believed to have a very decided action upon the liver. Power and Salvay (A. J. P., 1911, 14) isolated isophthalic acid, C6K4(CO2H)2. It may be given in pill in the dose of from three to four grains (0.20-0.26 Gm.).
The Pharmacopoeia formerly recognized a solid extract (Extractum Iridis), made by the following process: "Iris, in No. 60 powder, one thousand grammes [or 35 ounces av., 120 grains]; Alcohol, a sufficient quantity. Moisten the powder with four hundred mils [or 13 fluidounces, 252 minims] of Alcohol, and pack it firmly in a cylindrical percolator; then add enough Alcohol to saturate the powder and leave a stratum above it. When the liquid begins to drop from the percolator, close the lower orifice, and, having closely covered the percolator, macerate for forty-eight hours. Then allow the percolation to proceed, gradually adding Alcohol, until three thousand mils [or 101 fluidounces, 3 ½ fluidrachms] of tincture are obtained, or the Iris is exhausted. Distil off the Alcohol from the tincture by means of a water-bath, and evaporate the residue, on a water-bath, to a pilular consistence." U. S., 1890. The dose of the extract of iris is one to two grains (0.065-0.13 Gm.).
A fluidextract is official in the N. F. (see Part III).