INDIGO IS A HEALTH-GIVING PLANT: HISTORY AND USES OF TRUE INDIGO

INDIGO OR TRUE INDIGO, INDIGOFERA TINCTORIA

Indigo has been used as a dye for millennia as have woad (Isatis tincotria) and madder, (Rubia tinctoria). Indigo is native to Asia and was the blue dye used there, while woad was used in Europe. In India indigo has been used in Ayurveda and other traditional medicine systems to cure a number of ailments, despite the fact that the whole plant contains indican, which is a carcinogenic glucoside. The plant also contains rotenoids which are effective insecticides against mosquito larvae.

  Because of its use in traditional medicine there have been studies to attempt to support these uses. Indigotin, the substance responsible for the blue of the dye is thought to have antiseptic and astringent properties, and there are studies currently underway on indirubin, also found in woad, to discover if it has anti-cancer properties. Early studies have shown that the alcohol extracts of indigo’s stems and leaves protect the liver from damage by chemicals such as carbon tetrachloride, found in cleaning agents, refrigerants and aerosols and the leaves can help to lower blood pressure. One study reported in the International Journal of Pharmacology vol 7 (3) pages 356-63 2011 by Renukadevi, K.P. and Suhani Sultana, S. suggests that the plant’s extracts from the leaves have potent antioxidant actions and antibacterial and anti-cancer ones. However the studies were carried out on animals and in vitro, no tests have been done on human subjects in any of the research quoted here.

  In the same study the leaves were analyzed and found to contain flavonoids, saponins, tannins, steroidal terpenes, phenols and anthroquinone, and were found to be effective against lung cancer cells in vitro. The report concludes with this sentence “This study suggests that ethanol extract (sic) of Indigofera tinctoria have profound antibacterial, antioxidant and cytotoxic effect. (sic)”

  In another study, “Anti-hyperglycaemic activity of ethanol extract and chloroform extract of Indigofera tinctoria leaves in streptozotocin induced diabetic mice (Family Papilionaceae)” published in the  Research Journal of Pharmaceutical. Biological and Chemical Sciences Jan-March 2011, Bangar, A.V. and Saralaya M.G. conclude “…from the present study that Indigofera tinctoria leaves alcoholic extract long-term treatment may be beneficial in the management of type-1, type-2 diabetes.”                            

Yet another study looked at the traditional use of the plant in treating epilepsy and in the Tropical Journal of Pharmaceutical  Research published 2010 vol9 (2) pages 149-56, it is concluded that extracts from the whole plant were “useful in controlling lithium/pilocarpine-induced status epilepticus in albino rats.”

  Indigofera tinctoria means dyer’s indigo-bearing plant (tinctoria means dyer and indigofera means indigo bearing). There are many plants in the genus; it is thought that there are around 700, which is of the Fabaceae family, making indigo a relative of the pea. Marco Polo wrote about the indigo dying industry in the 13^th century on his travels around what is now Quilon in the Indian state of Kerala in 1298. However we know that indigo was used as a dye by the people of the Indus Valley Civilization between the 4^th and 2^nd millennia BC. In the Industrial Revolution the dye was used for European military uniforms and of course has been used in the US to dye blue jeans their distinctive colour. However imported indigo was banned in many countries in Europe in the 17^th century so that it did not compete with woad, as dyers and cultivators of this native European plant protested against the importing of indigo. Later indigo and woad were used together to strengthen the colour of the dye.

  In India indigo has been used to colour paper used for writing letters as well as for ink and oil-based paints for artists. A Persian rug dating back to the 5^th century BC has been found to have indigo-dyed fibres and at Thebes Egyptian mummies were found to have indigo-dyed cloth with them. The Greek historian Herodotus (who wrote rather fancifully of the collection of cinnamon bark, claiming it was from the nest of the fabled bird, the phoenix), writing circa 450 BC described the use of indigo in the Mediterranean region at that time, and we know that ancient Greeks and Romans used indigo imported from India in “cakes”. The ancient Egyptians and Romans applied it to wounds and ulcerous sores.

  In traditional Chinese medicine indigo has been used as a pain reliever, for fever, inflammation and to purify the liver and blood. In Indian traditional medicine it has been used to promote hair growth and is used as a hair dye for black hair, just as henna is used for red hair. It has been used for centuries in Ayurveda to treat depression, for cancer, bronchitis and other respiratory problems such as asthma, hemorrhaging, as well as problems with the spleen, lungs and kidneys. Some research suggests that it has liver protective properties. In other traditional medicine systems in the Indian subcontinent it has also been used for cardio-vascular problems, urinary tract problems and the paste made with the leaves is applied to sores, ulcers and piles and a decoction of the leaves was applied to the stings and bites of venomous creatures as well as to relieve pain and aid fast healing of burns and scalds. At one time in India it was used to cure bites from rabid dogs and the resulting hydrophobia.

  Indigo is sometimes used as ground cover in tea, coffee and rubber plantations and often food crops such as potatoes are interspersed with cultivated indigo.

  It is likely that many of these treatments will be the basis for future research into Indigofera tinctoria and other related indigo bearing plants.