_Tuber Jalapæ_; _Jalap_, _Vera Cruz Jalap_; F. _Racine de Jalap_; G.
_Jalape_.
=Botanical Origin=—_Ipomœa Purga_ Hayne (_Convolvulus Purga_ Wenderoth,
_Exogonium Purga_ Bentham), a tuberous-rooted plant, throwing out
herbaceous, twining stems, clothed with cordate-acuminate sharply
auricled leaves, and bearing elegant salver-shaped, deep pink flowers.
It grows naturally on the eastern declivities of the Mexican Andes,
at an elevation above the sea of 5000 to 8000 feet, especially about
Chiconquiaco and the adjacent villages, and also around San Salvador
on the eastern slope of the Cofre de Perote. In these localities where
rain falls almost daily, and where the diurnal temperature varies
from 15° to 24° C. (60° to 75° F.), the plant occurs in shady woods,
flourishing in a deep rich vegetable soil.
The jalap grows freely in the south of England, if planted in a
sheltered border, but its flowers are produced so late in autumn that
they rarely expand, and the tubers, which develope in some abundance,
are liable to be destroyed in winter unless protected from frost.
The plant has been introduced on the Neilgherry Hills in the south
of India; it succeeds there remarkably well,[1634] and might be
extensively propagated if there were any adequate inducement.
=History=—The use as a purgative of the tuber of a convolvulaceous
plant of Mexico, was made known by the early Spanish voyagers; and so
highly was the new drug esteemed that large quantities of it reached
Europe during the 16th century.
Monardes, writing in 1565, says the new drug was called _Ruybarbo de
las Indias_ or _Ruybarbo de Mechoacan_, the latter name being given
in allusion to the province of Michoacan whence the supplies were
derived. Some writers have advanced the opinion that mechoacan root was
the modern jalap, but in this we do not concur, for the description
given of mechoacan and the place of its production do not apply well
to jalap. Both drugs were moreover well known about 1610; they were
perfectly distinguished by Colin, an apothecary of Lyons (1619),
who mentions jalap (“_racine de Ialap_”) as then newly brought to
France.[1635] They were however often confounded, or at least only
distinguished by their difference of tint. Thus jalap, which at that
period used to be imported cut into transverse slices,[1636] was
termed, from its darker colour, _Black Mechoacan_; and on the other
hand, the paler mechoacan was in later times known as _White Jalap_.
[1634] Thus at Ootacamund, Mr. Broughton, in a letter to one of us (15
January 1870), speaks of receiving “a cluster of tubers” weighing over
9 lb., and remarks that the plant grows as easily as yam.
[1635] Monardes, _Hist. des Medicamens_, trad. par Colin, ed. 2.
16.—The first edition of this work seems to be unknown.
[1636] Hill, _History of the Mat. Med._ Lond. 1751. 549.
Mechoacan root is now known to consist (at least in part) of the large
thick tuber of _Ipomœa Jalapa_ Pursh (_Batatas Jalapa_ Choisy), a plant
of the Southern United States and Mexico. As a drug it has been long
obsolete in Europe, having given place to jalap, which is a more active
and efficient purgative.
The botanical source of jalap was not definitely ascertained until
about the year 1829, when Dr. Coxe of Philadelphia published a
description and coloured figure, taken from living plants sent to him
two years previously from Mexico.[1637]
=Manner of Growth=—Though we have cultivated the jalap plant for many
years, we have had no opportunity of examining the seedling, but
judging from analogy suppose that it has at first a small tap-root
which gradually thickens after the manner of a radish. A root of
jalap, called by some _tuber_ and by others _tubercule_, throws out in
addition to aerial stems, slender, prostrate, underground shoots which
emit roots at intervals. These roots while but an inch or two long
become thickened and carrot-shaped, gradually enlarging into napiform
tuber-like bodies, which emit a few rootlets from their surface and
taper off below in long, slender ramifications. The thickened roots
have no trace of leaf-organs; the aerial stems grow from the shoot from
which they originated.
Fresh jalap roots (tubers) are externally rough and dark brown,
internally white and fleshy.
=Collection=—Jalap is said to be dug up in Mexico during the whole
year.[1638] The smaller roots are dried entire; the larger are cut
transversely, or are gashed so that they may dry more easily. As drying
by sun-heat would be almost impracticable owing to the wetness of the
climate, the roots are placed in a net, and suspended over the almost
constantly burning hearth of the Indian’s hut, where they gradually
dry, and at the same time often contract a smoky smell. Much of the
jalap that has of late arrived has been more freely sliced than usual,
and has obviously been dried with less difficulty.
According to Schiede, whose account was written in 1829,[1639] the
Indians of Chiconquiaco were at that period commencing the cultivation
of jalap in their gardens.
=Description=—The jalap of commerce consists of irregular, ovoid
roots, varying from the size of an egg to that of a hazel-nut, but
occasionally as large as a man’s fist. They are usually pointed at the
lower end, deeply wrinkled, contorted and furrowed, and of a dark brown
hue, dotted over with numerous little, elongated, lighter coloured
scars, running transversely. The large roots are incised lengthwise, or
cut into halves or quarters, but the smaller are usually entire. Some
of the small roots are spindle-shaped or cylindrical; others can be
found which are nearly globular, smooth and pitchy-looking, but these
latter are seldom solid. Good jalap is ponderous, tough, hard and often
horny, becoming brittle when long kept, and breaking with a resinous
non-fibrous fracture; internally it is of a pale dingy brown or dirty
white. It has a faint smoky, rather coffee-like odour, and a mawkish
taste, followed by acridity.
[1637] _American Journal of Med. Sciences_, v. (1829) 300. pl. 1-2.
[1638] It is plain that such a proceeding is irrational. The roots
should be dug up when the aerial stems have died down.
[1639] _Linnæa_, iii. (1830) 473; _Pharm. Journ._ viii. (1867) 652.—We
are not aware of any more recent account.
=Microscopic Structure=—Seen in transverse section, jalap exhibits no
radiate structure, but numerous small concentric rings, which in many
pieces are very regularly arranged. They are due to the laticiferous
cells, differing from the surrounding parenchyme only by their contents
and rather large size. These laticiferous cells traverse the tissue in
a vertical direction, constituting vertical bands, as may be observed
on a longitudinal section; the single cells are simply placed one
on the other, and do not form elongated ducts as in _Lactuca_ or
_Taraxacum_.
The fibro-vascular bundles of jalap are neither numerous nor large;
they are accompanied by thin-walled cells, so that firm woody rays do
not occur. Parenchymatous cells are abundant, and, on a longitudinal
fracture especially, if subsequently moistened, are seen to constitute
concentric layers. The laticiferous cells are always found in the outer
part of each layer. The suberous coat with which the drug is covered is
made up of the usual tabular cells.
The parenchyme of jalap is loaded with starch grains; in the pieces
which have been submitted to heat in order to dry them, the starch
appears as an amorphous mass, and the drug then exhibits a horny
consistence and greyish fracture, instead of being mealy. Crystals of
calcium oxalate are frequently met with. The laticiferous cells contain
the resin of jalap in a semi-fluid state, even in the dry drug; drops
of the resinous emulsion flow out of the cells, if thin slices are
moistened by any watery liquid.
=Chemical Composition=—Jalap owes its medicinal efficacy to a resin,
which is extractable by exhausting the drug with spirit of wine,
concentrating the alcoholic solution to a small bulk, and pouring
it into water. The resin precipitated in this manner is then washed
and dried; it is contained in jalap to the extent of 12 to 18 per
cent.[1640]
From this crude resin, which is the _Resina jalapæ_ of the
pharmacopœias, ether or chloroform extracts 5 to 7 (12, Umney) per
cent. of a resin which, according to Kayser,[1641] partially solidifies
when in contact with water in crystalline needles. We can by no means
confirm Kayser’s statement. The residue (insoluble in ether) is one
of the substances to which the name _Jalapin_ has been applied.[1642]
W. Mayer, 1852-1855, who designated it _Convolvulin_,[1643] found it
to have the composition C₃₁H₅₀O₁₆. When purified, it is colourless;
it dissolves easily in ammonia as well as in the fixed alkalis, and
is not re-precipitated by acids, having been converted by assumption
of water into amorphous Convolvulic Acid, which is readily soluble in
water. Both convolvulin and _convolvulic acid_ are resolved by moderate
heating with dilute acids, or with emulsin, into crystallizable
_Convolvulinol_, C₂₆H₅₀O₇, and sugar. Convolvulinol in contact with
aqueous alkalis is converted into _Convolvulinolic Acid_, C₂₆H₄₈O₆,
which is slightly soluble in water and crystallizable.
[1640] Guibourt obtained of it 17 per cent., Umney 21·5, Squibb 11 to
16, T. and H. Smith “not more than 15,” D. Hanbury 11 to 15·8. Jalap
grown in Bonn afforded to Marquart 12 per cent.; a root cultivated at
Münich gave Widnmann 22 per cent.; from plants produced in Dublin W. G.
Smith got 9 to 12 per cent.; and fine tubers from Ootacamund in India
yielded to one of us 18 per cent. of resin. Broughton is of opinion
that exposure of the sliced tuber to the air in the process of drying,
favours the formation of resin, by the oxidation of a hydrocarbon.
[1641] Gmelin, _Chemistry_, xvi. (1864) 159.
[1642] As by Pereira, _Elem. of Mat. Med._ ii. (1850) 1463.
[1643] Gmelin, _op. cit._ xvi. 154.
When convolvulin or its derivatives is treated with nitric acid, it
yields several acids, one of which is the _Sebacic Acid_,
C₈H₁₆ {COOH
{COOH
which is to be obtained by treating castor oil or other fatty
substances in the same manner. Sebacic acid forms crystalline scales,
soluble in boiling water, melting at 128°. That from jalap was first
thought to be a peculiar acid, and therefore termed _ipomic_ or
_ipomœic acid_. Its identification is due to Neison and Bayne (1874).
Convolvulin (dry) melts at 150° C., but a small amount of water renders
it fusible below 100° C. It is insoluble in oil of turpentine and in
ammonia. It dissolves in dilute nitric acid without becoming coloured
or evolving gas. Convolvulin possesses in a high degree the purgative
property of jalap, but this is not the case with convolvulinol.
The other constituents of jalap include starch, uncrystallizable sugar,
gum, and colouring matter. The sugar, according to Guibourt, exists to
the extent of 19 per cent.
=Commerce=—We have no means of knowing to what extent jalap is produced
in Mexico. The imports of the drug into the United Kingdom amounted in
1870 to 169,951 lb. Very considerable quantities have of late (1873)
appeared in the London drug-sales.
=Uses=—Jalap is employed as a brisk cathartic.
Other kinds of Jalap.
Besides true jalap, the roots of certain other _Convolvulaceæ_ of
Mexico have been employed in Europe, either in the form of jalapin, or
as adulterants of the more costly, legitimate drug. The two following
have been extensively imported and have been traced to their botanical
source; but there are others, of more occasional occurrence, the origin
of which has not been ascertained.[1644]
1. _Light_, _Fusiform_, or _Woody Jalap_, _Male Jalap_, _Orizaba Root_,
_Jalap Tops_ or _Stalks_, _Purgo macho_ of the Mexicans.
This drug is derived from _Ipomœa orizabensis_ Ledanois,[1645] a
plant of Orizaba, which is but imperfectly known. It is described as
a pubescent climber, having a spindle-shaped root about two feet long
of woody and fibrous texture. The drug occurs in irregular rectangular
or block-like pieces, evidently portions of a very large root,
divided transversely and longitudinally. Sometimes it is more like
true jalap, being in entire roots, of smaller size, spindle-shaped,
not spherical. It has a somewhat lighter colour than jalap, and much
deeper longitudinal wrinkles. The larger pieces often exhibit deep
cuts from an axe or knife; transverse slices are of rare occurrence.
Although generally less ponderous than jalap, the Orizaba drug is
nevertheless of a compact and often horny texture. From jalap it is
easily distinguished by its radiated transverse section, and the
numerous thick bundles of vessels which project as woody fibres from
the fractured surface.
[1644] For information about some of these, consult Guibourt, _Histoire
des Drogues_, ii. (1869) 523.
[1645] _Journ. de Chimie méd._ x. (1834) 1-22. pl. 1. 2. (with
unsatisfactory figures).
In chemical constitution Orizaba root is closely parallel to jalap.
The resin was named by Mayer _Jalapin_; it is the _Jalapin_ of
Gmelin’s _Chemistry_ (xvi. 405), and perhaps the jalapin of English
pharmacy.[1646]
In the pure state it is a colourless amorphous translucent resin,
_dissolving perfectly in ether_,[1647] thus differing from convolvulin
the corresponding resin of jalap. We find that it is readily soluble
also in acetone, amylic alcohol, benzol and phenol, not in bisulphide
of carbon. It has the composition of C₃₄H₅₆O₁₆, so that it is
homologous with convolvulin; the decomposition-products of jalapin
obtained by similar treatment, namely jalapic acid, jalapinol, and
jalapinolic acid, are likewise homologous with the corresponding
substances obtained from convolvulin. All these bodies when treated
with nitric acid yield ipomœic acid. Jalapin has the same fusing point
as convolvulin, and behaves in the same manner with alkalis.
The root afforded us 11·8 per cent. of resin dried at 100° C. When
perfectly washed, decolorized and dissolved in two parts of alcohol,
this resin turned the plane of polarization of a ray of light 9·8°
to the left, in a column of 50 mm. long. Convolvulin under the same
conditions turned it only 5·8°. The resin of Orizaba root is held by
chemists to be identical with that of scammony, of which it has the
drastic action.
2. _Tampico Jalap_,—_Purga de Sierra Gorda_ of the Mexicans. The plant
which affords this drug has been described by one of us (1869) under
the name of _Ipomœa simulans_.[1648] It is closely related to _I.
Purga_ Hayne, from which by its foliage it cannot be distinguished,
but it has a _bell-shaped corolla_ and _pendulous flower-buds_, which
are very different. _I. simulans_ Hanbury grows in Mexico along the
mountain range of the Sierra Gorda in the neighbourhood of San Luis de
la Paz, from which town and the adjacent villages its roots are carried
down to Tampico. It has also been found on the lofty Cordillera near
Oaxaca, but whether there collected we know not.
The drug, to which in trade the name _Tampico Jalap_ is commonly
applied, has been imported during the last few years in considerable
quantities. In appearance it closely approaches true jalap, but the
roots are generally smaller, more elongated or finger-like, more
shrivelled and corky-looking, wanting in the little transverse scars
that are plentifully scattered over the roots of true jalap. Many
pieces occur however which it is impossible to distinguish by the eye
from true jalap, with which it agrees also in odour and taste.
Tampico jalap yielded to one of us 10 per cent. of _purified_ resin,
entirely soluble in ether. Umney[1649] obtained 12 to 15 per cent. of
resin almost wholly soluble in ether; Evans got 13 per cent., but found
only about half of this to be soluble in ether.[1650] According to
Andouard[1651] the resin of Tampico jalap is not deficient in purgative
powers.
[1646] The name is ill-chosen and misleading, but having been adopted
in standard works, it might occasion greater confusion to attempt to
supersede it, and its several derivatives.
[1647] It is at least a fact, that of numerous samples of jalapin that
we have examined (1871), every one is _completely soluble in ether_.
[1648] Hanbury, On a species of _Ipomœa_, affording Tampico Jalap,
_Journ. of Linn. Soc._, Bot. xi. (1871) 279, tab. 2; _Pharm. Journ._
xi. (1870) 848; _American Journ. of Pharm_., xviii. (1870) 330;
_Science Papers_, 1876. 349.
[1649] _Pharm. Journ._ ix. (1868) 282.
[1650] _Ibid._ ix. (1868) 330.
[1651] _Etude sur les Convolvulacées purgatives_ (thèse) Paris, 1864.
31.