Related entry: Jalapa (U. S. P.)—Jalap
Preparation.—"Jalap, in No. 60 powder, one thousand grammes (1000 Gm.) [2 lbs. av., 3 ozs., 120 grs.]; alcohol, water, each, a sufficient quantity. Moisten the powder with three hundred (300) cubic centimeters [10 fl℥, 69♏] 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 48 hours. Then allow the percolation to proceed, gradually adding alcohol, until twenty-five hundred (2500) cubic centimeters [84 fl℥, 257♏] of tincture are obtained, or until the tincture ceases to produce more than a slight turbidity when dropped into water. Distill off the alcohol, by means of a water-bath, until the tincture is reduced to four hundred (400) grammes [14 ozs. av., 48 grs.], and add the latter, with constant stirring, to nine thousand (9000) cubic centimeters [304 fl℥, 155♏] of water. When the precipitate has subsided, decant the supernatant liquid, and wash the precipitate twice, by decantation, with fresh portions of water. Place it upon a strainer, and, having pressed out the liquid, dry the resin with a gentle heat, stirring occasionally until the moisture has evaporated"—(U. S. P.). The yield by this process is officially required to be not less than 12 per cent (see Jalapa), but this figure is now seldom attained with jalap imported from Mexico, about 7 to 8 per cent being the average yield. Prof. Flückiger ascribes the decrease in yield to fraudulent abstraction of resin by means of alcohol, probably practiced by some Mexican dealers. He advocates the cultivation of jalap in Europe, pointing out that the tubers in one instance where jalap was cultivated, yielded 22.7 per cent of resin, referred to dry material (Amer. Jour. Pharm., 1890, p. 141; also see E. R. Squibb, Ephemeris, Vol. III, pp. 1095 and 1248). Mr. F. H. Alcock proposes an assay of jalap for resin by means of amyl alcohol (Amer. Jour. Pharm., 1892, p. 534).
Description and Tests.—As officially demanded resin of jalap should be in "yellowish-brown or brown masses or fragments, breaking with a resinous, glossy fracture, translucent at the edges, or a yellowish-gray or yellowish-brown powder, having a slight, peculiar odor, and a somewhat acrid taste. Permanent in the air. Its alcoholic solution has a faintly acid reaction. Soluble in alcohol in all proportions; insoluble in carbon disulphide, benzol, and fixed or volatile oils. Not more than about 10 per cent of it is soluble in ether. On evaporating the ethereal solution, and dissolving the residue in potassium hydrate T.S., a reddish-brown liquid is formed, from which the resin is reprecipitated by acids. If that portion of resin of jalap which remained undissolved by ether be dissolved in potassium hydrate T.S., the addition of an acid does not precipitate it" (U. S. P.). The resinous portion, not soluble in ether, is usually called convolvulin (W. Mayer). (For details regarding the chemistry of the resin, see Jalapa.) "Resin of jalap should not suffer any material loss of weight when heated at 100° C. (212° F.) (absence of water). Water triturated with it should neither become colored, nor take up anything soluble from it (absence of soluble impurities). On digesting 1 Gm. of resin of jalap, for about an hour, with frequent agitation, in a glass-stoppered vial, with 10 Cc. of ammonia water, at a temperature of about 80° C. (176° F.), it should yield a solution which does not gelatinize on cooling (absence of common resin)"—(U. S. P.).
Action, Medical Uses, and Dosage.—Jalap owes its cathartic powers to its resin; while its mucilage or gum has been reputed diuretic. The dose of the resin prepared, as stated above, is from 1 to 6 or 8 grains; it, is apt to occasion much pain and griping, which may be frequently obviated by trituration with castile soap, resin of caulophyllum, or loaf-sugar.
King's American Dispensatory, 1898, was written by Harvey Wickes Felter, M.D., and John Uri Lloyd, Phr. M., Ph. D.