This section is from the book "Materia Medica Pharmacy, Pharmacology And Therapeutics", by W. Hale White. Also available from Amazon: Materia Medica Pharmacy, Pharmacology And Therapeutics..
The tuberous root of Ipomaea Jalapa, Nuttall (nat. ord. Con-volvulacece).
Napiform, pyriform or oblong, varying in size, the large roots incised, more or less wrinkled, dark brown, with lighter-colored spots, and short, transverse ridges; hard, compact; internally pale grayish-brown, with numerous concentric circles composed of small resin-cells; fracture resinous, not fibrous; odor slight, but peculiar, smoky and sweetish; taste sweetish and acrid. On exhausting 100 parts of Jalap by Alcohol, concentrating the tincture, and pouring it into water, a precipitate of resin should be obtained, which, after washing with water and drying, should weigh not less than 12 parts, and of which not over 10 per cent. should be soluble in Ether.
The chief consdtuents are: (1) The official resin (see below), 7 to 22 per cent. mostly Jalapurgin, C62H100O32. (2) A soft resin.
Dose, 5 to 20 gr.; .30 to 1.20 gm.
1. Extractum Jalapae. - Extract of Jalap. By maceration and percolation, with Alcohol, and evaporation.
Extract of Jalap is contained in Pilulae Catharticae Composite and Pilulae Catharticae Vegetabiles.
Dose, 2 to 8 gr.; .12 to .50 gm.
Dose, 1/4 to 1 dr.; 1. to 40. gm.
3. Resina Jalapae. - Resin of Jalap.
By maceration with Alcohol, percolation, distillation of the Alcohol, and precipitation with water, and drying.
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.
The chief constituents are - (1) Jalapurgin, or Con-volvulin C62H100O33, a glucoside, a hard substance insoluble in Ether, more irritant than Jalapin, and probably the most active ingredient of Jalap. (2) Jalapin probably identical with Scammonin. This is a soft resinous substance, soluble in Ether. It is found in Jalap wood and Jalap stalk. (3) Starch and Gum. Resembling Jalap Resin.- Aloes, which is bitter.
Dose, 1 to 5 gr.; .06 to .30 gm.
The mode of action of jalap is precisely the same as that of scammony, with only two exceptions. It causes a greater secretion of intestinal juice, and is therefore more hydragogue; it stimulates the vessels and muscular coat less, and therefore is less irritant and griping.
Jalap is very largely used as a hydragogue purgative when we want to draw off large quantities of fluid; therefore it is especially suitable for patients with Bright's disease, for those suffering from uraemia, and for those with dropsy from any cause. Large doses should not be given if the intestinal mucous membrane is liable to inflame easily. It is occasionally employed for severe constipation. An old prescription consists of equal parts of powdered jalap and calomel, well triturated. The dose is from 5 to 10 gr.; .30 to .60 gm. This is known as Rush's thunderbolt. Curiously enough, it does not gripe..