Indigo

Scientific Name(s): Indigofera tinctoria (French indigo) and I. suffruticosa Mill. (Guatemalan indigo) formerly known as I. anil L. Family: Fabaceae (beans).

Common Name(s): Common or Indian Indigo ; not to be confused with false, wild, or bastard indigo ( Baptisia tinctoria L), a native North American plant from which a blue dye is obtained from the leaves. 1 , 2

Uses

Chiefly a source of dye, indigo also has been used as a nematicide and treatment for a range of ills including scorpion bites and ovarian and stomach cancer.

Dosing

There is no clinical evidence for indigo upon which dosing recommendations can be based.

Contraindications

Contraindications have not yet been identified.

Pregnancy/Lactation

Information regarding safety and efficacy in pregnancy and lactation is lacking. Avoid use.

Interactions

None well documented.

Adverse Reactions

Indigo may irritate the eyes and may cause dermatitis.

Toxicology

Some species are toxic and cause birth defects.

Botany

These plants are perennial shrubs that reach a height of 1 m to 2 m. The French and Guatemalan varieties differ in the shape and size of the leaflets and pods.

History

Indigo refers to several species of Indigofera that are known for the natural blue colors obtained from the leaflets and branches of this herb. 1 Before the development of synthetic aniline and indigo dyes, indigo plants were grown commercially in the East Indies and South and Central America. Indigo was a popular dye during the middle ages. 1 It has been used medicinally as an emetic; the Chinese used the plant to purify the liver, reduce inflammation and fever and to alleviate pain. 1 Extracts of I. tinctoria have been reported to have nematicide activity and the leaf and plant juice have been used to treat cancers, particularly of the ovaries and stomach. 3 In addition, the plant has been used for the treatment of numerous ailments ranging from hemorrhoids to scorpion bites.

Chemistry

The blue dye is produced during the fermentation of the leaves, which is commonly accomplished with caustic soda or sodium hydrosulfite. 1 A paste exudes from the fermenting plant material and this is processed into cakes that are finely ground. The blue color develops as the powder is exposed to air.

Indigo dye is a derivative of indican, a glucoside 3 component of numerous Indigofera species and this is enzymatically converted to blue indigotin. 1 This colorfast dye is combined with stabilizers and other compounds to produce a wide range of colorants. Today, almost all indigo used commercially is produced synthetically.

Uses and Pharmacology

Little is known about the pharmacologic effects of Indigofera species. Preliminary evidence suggests that I. tinctoria may have a protective effect against carbon tetrachloride-induced hepatotoxicity, 4 which is opposite to the hepatotoxic effect observed with other members of this genus. The related I. aspalathoides has been reported to possess anti-inflammatory activity. 5

Dosage

There is no clinical evidence for indigo upon which dosing recommendations can be based.

Pregnancy/Lactation

Information regarding safety and efficacy in pregnancy and lactation is lacking. Avoid use.

Interactions

None well documented.

Adverse Reactions

Indigo appears to be a mild ocular irritant. Dermatitis is common among indigo dyers but there is no direct evidence that this is linked to exposure to the plant or dye. 3

Toxicology

I. spicata is recognized as a teratogen due to the presence of indospicine. Indospicine also is hepatotoxic. 6 , 7 In animals, it causes cleft palate and embryo lethality. 8 I. endacaphylla (creeping indigo) has been responsible for livestock poisonings and deaths. 1

Bibliography

1. Simon JE. Herbs: an indexed bibliography, 1971-1980 . Hamden, CT: Shoe String Press. 1984.
2. Spoerke DG. Herbal Medications . Santa Barbara, CA: Woodbridge Press, 1980.
3. Duke JA. Handbook of Medicinal Herbs . Boca Raton, FL: CRC Press, 1985.
4. Anand KK, Chand D, Ray Ghatak BJ, et al. Histological evidence of protection by Indigofera tinctoria Linn. against carbon tetrachloride induced hepatotoxicity — an experimental study. Indian J Exp Biol 1981;19:298.
5. Amala Bhaskar E, Ganga N, Arivudainambi R, et al. Anti-inflammatory activity of Indigofera aspalathoides Vahl. Indian J Med Res 1982;76(Suppl):115.
6. Liener IE, ed. Toxic Constituents of Plant Foodstuffs . London; Academic Press, 1980.
7. Hegarty MP, Kelly WR, McEwan D, et al. Hepatotoxicity to dogs of horse meat contaminated with indospicine. Aust Vet J 1988;65:337
8. Evans WC. Trease and Evans' Pharmacognosy . 13th ed. London; Bailliere Tindall, 1989.

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