Jalap, a well known purgative drug, first introduced into England from Mexico in 1609. The plant grows wild near the city of Jalapa, and was known to the Mexicans as purga de Jalapa; that city being the point of export, the drug retains its name, being known in the pharmacopoeias as jalapa, and in commerce and popularly as jalap. The drug was in use for over two centuries before the plant which furnishes it was known; at one time it was supposed to be the root of a species of mirabilis, now common in our gardens as the four-o'clock, and this was called M. Jalapa, a name which it yet retains. The true jalap plant was first described by Nuttall in the "American Journal of Medical Sciences " for February, 1830; he determined it to belong to the convolvulus family, and gave it the name of ipomaea Jalapa. As botanists have taken different views of the genera of convolvulaceae, this plant has been alternately called ipomaea and convolvulus, but has apparently found a resting place in exogonium, a genus closely related to both of these, and is the E. purga of Bentham. The habit of the plant, with long twining stems, is much like that of some of our garden species of ipo-imaa or morning glory; but, as will be seen from the engraving, it differs in its salver-shaped corolla and protruding stamens; the flowers are purplish and ornamental; the root is perennial, and, according to the age of the plant, differs in size from that of a nut to that of an orange; it is somewhat pear-shaped or oval, externally brownish and white within.
The plant is found in the elevated portions of Mexico, especially in the vicinity of Jalapa, at an altitude of about 6,000 ft. above the sea; it is quite hardy in England and on the continent of Europe, and might without doubt be cultivated in the southern portions of the United States; but as medicinal plants are affected in a marked degree by locality, experiment only could decide if the drug would be equally valuable with that grown in its native habitat. The dried root is the drug of commerce, and it undergoes no other preparation than digging and drying; the smaller roots are dried entire; the largest are divided longitudinally or transversely, sometimes cut in slices, while those of intermediate size are gashed with vertical or crosswire incisions, evidently for the purpose of accelerating the drying. The dried roots are hard and heavy, and, if of good quality, show when broken an undulated resinous fracture, with concentric circles of yellowish gray and dark brown portions. A whitish, mealy fracture may indicate that the root was collected at an improper season, or that a spurious root has been substituted. Jalap has a heavy, rather sweetish odor, and an acrid disagreeable taste; it forms a yellowish gray powder, which is irritating when inhaled and produces sneezing and coughing.
The roots are often worm-eaten, but as their activity depends upon a resin which the worms leave untouched, their value for making extract is not impaired, though if such roots were used for powdering the activity of the drug might be unduly increased. - Jalap when treated with alcohol yields about 17 per cent. of resin, which is found to consist of two distinct resins; one of these, to which the name of jalapine has been given, is hard and insoluble in ether; the other, jalapic acid, is soluble in ether, is soft, and has the peculiar odor of jalap. Besides these resins, the drug contains sugar, a brown extractive soluble in water, gum, starch, and other inert matters. In the powdering of this, as of other drugs, there is an abundant opportunity for adulteration, and those who purchase the ordinary powdered jalap of commerce get a large proportion of sawdust, old ship bread, and the like; and what is known as "overgrown jalap" or "male jalap,'1 the root of ipomaea Orizabensis, a very feebly active purge, is often sold for grinding. Hassall found that nearly half the samples sold in London were thus adulterated.
The extract of jalap is prepared by first exhausting the root with alcohol, and then with water; after distilling off the alcohol from the tincture, and evaporating the watery infusion, the two are mixed and evaporated to form an extract; this has all the medicinal properties of the root, and is employed in half the dose. The resin of jalap is obtained by exhausting the root with alcohol by percolation, distilling off the greater part of the alcohol, and dropping the concentrated tincture thus obtained into water, to precipitate the resin, which is afterward dried and powdered. This preparation is very active, and its dose is one fifth or less of that of the powdered drug. From its action as a hydro-gogue the drug is especially adapted to the treatment of dropsy, and is commonly combined, when thus exhibited, with bitartrate of potassa. In the form of a powder and mixed with calomel, it has been a popular prescription in the United States in bilious fever and congestion of the liver, the usual dose being about 10 grains of each, though in the southern states double this quantity is often given.
Jalap (Exogonium purga).