Family: Fabaceae (Leguminosae), Indigofera species
Source: Simon, J.E., A.F. Chadwick and L.E. Craker. 1984.
Herbs: An Indexed Bibliography. 1971-1980. The Scientific Literature
on Selected Herbs, and Aromatic and Medicinal Plants of the Temperate
Zone. Archon Books, 770 pp., Hamden, CT.
Indigo refers to several species of Indigofera, famous
for the natural blue colors obtained from leaflets and branches
of this herb. Of primary importance are French indigo, Indigofera
tinctoria L., and Guatemalan indigo, Indigofera suffruticosa
Mill., which was formerly classified as Indigofera anil
L. These plants are perennial shrubs with an erect stem reaching
a height of 1 to 2 meters. The French and Guatemalan indigo differ
in size and shape of the leaflets and pods (14.1-3). Prior
to the development of synthetic aniline and indigo dyes, the indigo
species were grown commercially in the East Indies, India, and
parts of North, South, and Central America for export and domestic
use. Popularity and economic value of the plant reached a peak
during the Middle Ages, when indigo was the most important dye
plant for blue color in the western portion of the world (9.1-5).
The reported life zone of Indigofera tinctoria is 16 to
27 degrees centigrade with an annual precipitation of 0.7 to 4.2
meters and a soil pH of 5.0 to 7.3 (4.1-31). Indigo is generally
grown as a perennial shrub, although in Morocco it grows as a
biennial herbaceous plant (13.1-76).
The blue dyestuff is produced during fermentation of the leaves,
commonly with caustic soda or sodium hydrosulfite. A paste that
exudes from fermenting plant material is processed into cakes
and finely ground. The blue color develops as the material is
exposed to air (13.1-76). The indigo dye is a derivative
of indican, a natural constituent of several of the Indigofera
species (14.1-19). Indican is enzymatically converted to
blue indigotin (14.1-35). The colorfast dye is mixed with
different mordants and other plant materials to produce a wide
range of colorants. The species name tinctoria refers to
tinctorius, meaning "of dyes" or "belonging to
dyes" (14.1-3). Today almost all indigo for dyeing cotton
and wool is synthesized commercially.
As a medicinal plant, indigo has been used as an emetic. The Chinese
use Indigofera tinctoria L. to clean the liver, detoxify
the blood, reduce inflammation, alleviate pain, and reduce fever
(11.1-10). The powdered root of Indigofera cf. patens
is used in South Africa to alleviate toothache (11.1-96).
Indigofera spirata is known as a plant teratogen because
of the presence of indospicine (11.1-96). Indigofera endecaphylla
plant, creeping indigo, is poisonous and has been responsible
for livestock death (11.1-96). Indigofera arrecta
Hochst. ex A. Rich and Indigofera caroliniana Mill.
are used as dye plants (9.1-5).
False, wild, and bastard indigo are names for Baptisia tinctoria
L., a native North-American member of the Leguminosae family,
whose leaves, pods, and bark are used to make a blue color. Medicinally,
it is employed as an astringent, emetic, stimulant, and antiseptic.
Fake indigo and Baptisia leucantha are reported to have
caused poisonings, diarrhea, vomiting, and loss of appetite (11.1-96,
11.1-136). Strobilanthes flaccidifolis and Dalea
emoryi L., known as indigo bush, have been used as indigo
[Note: References listed above in parentheses can be found in
full in the original reference].
Last modified 6-Dec-1997