_Indian Liquorice_; F. _Liane à réglisse_, _Réglisse d’Amérique_.
=Botanical Origin=—_Abrus precatorius_ L., a twining woody shrub[747]
indigenous to India, but now found in all tropical countries.
=History=—The plant is mentioned in the Sanskrit medical writings of
Susruta, whence we may infer that it has long been employed in India.
Its resemblance to liquorice was remarked by Sloane (1700), who called
it _Phaseolus glycyrrhites_. As a substitute for liquorice, the root
has been often employed by residents in the tropical countries of both
hemispheres. It was introduced into the _Bengal Pharmacopœia_ of 1844,
and into the _Pharmacopœia of India_ of 1868.
The seeds, of the size of a small pea, well known for their polish and
beautiful black and red colours, have given their name of _Retti_ to a
weight (= 2³/₁₆ grains) used by Hindu jewellers and druggists.
=Description=—The root is long, woody, tortuous and branching. The
stoutest piece in our possession is as thick as a man’s finger, but
most of it is much more slender. The cortical layer is extremely thin
and of a light brown or almost reddish hue. The woody part breaks with
a short fibrous fracture exhibiting a light yellow interior. The root
has a peculiar, disagreeable odour, and a bitterish acrid flavour
leaving a faintly sweet after-taste. When cut into short lengths it has
a slight resemblance to liquorice, but may easily be distinguished by
means of the microscope.
Mr. Moodeen Sheriff,[748] who says he has often examined the root of
_Abrus_ both fresh and dried, remarks that it is far from abounding in
sugar as generally considered;—that it does not possess any sweetness
at all until it attains a certain size, and that even then its sweet
taste is not always well marked. As it is often mixed in the Indian
bazaars with true liquorice, he thinks the latter may have sometimes
been mistaken for it.
[747] Fig. in Bentley and Trimen, _Medicinal Plants_, part 25 (1878).
[748] _Supplement to the Pharmacopœia of India_, Madras, 1869. 16.—The
author has kindly sent us specimens of the root. We are also indebted
for authentic samples to Mr. Thwaites of the Royal Botanical Garden,
Ceylon, and to Mr. Prestoe of the Botanical Garden, Trinidad. The last
named gentleman remarks—“I do not find any liquorice property in the
root, even fresh, but it is very strong in the green leaves.”
=Microscopic Structure=—On a transverse section the bark exhibits some
layers of cork-cells, loaded with brown colouring matter, and then,
within the middle zone of the bark, a comparatively thick layer of
sclerenchymatous tissue. Strong liber-fibres are scattered through
the interior of the cortical tissue, but are not distributed so as to
form wedge-shaped rays as met with in liquorice. In the latter the
sclerenchyme (thick-walled cells) is wanting. These differences are
sufficient to distinguish the two roots.
=Chemical Composition=—The concentrated aqueous infusion of the root of
Abrus has a dark brown colour and a somewhat acrid taste accompanied
by a faint sweetness. When it is mixed with an alkaline solution of
tartrate of copper, red cuprous oxide is deposited after a short
time: hence we may infer that the root contains sugar. One drop of
hydrochloric or other mineral acid mixed with the infusion produces a
very abundant flocculent precipitate, which is soluble in alcohol. If
the infusion of Abrus root is mixed with a very little acetic acid,
an abundant precipitate is likewise obtained, but is dissolved by an
excess. This behaviour is similar to that of glycyrrhizin (see p. 181).
Berzelius observed, so long ago as 1827, that the _leaves_ of Abrus
contain a sweet principle similar to that of liquorice.
=Uses=—The root has been used in the place of liquorice, for which it
is in our opinion a very bad substitute.