2701

12(3): Medicinal and poisonous plants 3

Indigofera L.

Sp. pl. 2: 751 (1753) ; Gen. pl. ed. 5: 333 (1754).

LEGUMINOSAE

x = 8;Indigofera linnaei, Indigofera tinctoria: 2n = 16

Indigofera consists of about 700 species, and is widely distributed in the tropics and subtropics of Africa, the Americas, Asia and Australia. Africa is richest in species, but the southern Himalaya region is also comparatively rich. Approximately 35 species occur naturally in South-East Asia, 16 of which are found in the Malesian region. Additionally, several species have been introduced in South-East Asia.

Indigofera is used in traditional medicine in South-East Asia for various complaints, externally, e.g. to treat sores, ulcers and aphthae, as well as internally, e.g. to treat epilepsy and as a diuretic. Some Indigofera species are well-known dye plants throughout the world, especially Indigofera arrecta Hochst. ex A. Rich. and Indigofera tinctoria L., the leaves of which are also used in traditional medicine to treat epilepsy and nervous disorders, and to heal sores and ulcers. Several Indigofera species are used as a cover crop, green manure or fodder, e.g. Indigofera hirsuta L. and Indigofera suffruticosa Miller, both of which have medicinal applications: the leaves of the first are used to treat stomach complaints in the Philippines and Thailand, the roots of the second to treat stomach-ache and diarrhoea, the leaves against fever and the juice against diarrhoea in Malaysia. Seeds are used occasionally as a famine food, including those of Indigofera linifolia and Indigofera linnaei.
In Taiwan the roots ofIndigofera zollingeriana Miq. are used to treat stomach-ache and snakebites. In Burma (Myanmar) the roots of Indigofera cassioides Rottler ex DC. (synonym: Indigofera pulchella Roxb.) are applied to treat cough.

An ethanol extract from the leaves of Indigofera oblongifolia showed in-vitro antibacterial activity against Enterococcus faecalis, Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus. Small proteins or peptides in the leaves of Indigofera oblongifolia show considerable in-vitro antibacterial and antifungal activity. These compounds probably play a role in the defence mechanism of the plant.
An extract of the above ground parts of Indigofera tinctoria shows hypoglycaemic and central nervous system-depressant effects in rats, and potentiates pentobarbital sodium-induced sleep in mice. An ethanol extract possesses protective effects against carbon tetrachloride-induced liver damage in rabbits, rats and mice, as confirmed by histopathological studies.
Pharmacological research on Indigofera arrecta supports its traditional use in Ghana, where an aqueous extract of leaves from immature shoots is administered orally to patients with diabetes mellitus. This extract prevented the development of hyperglycaemia in genetically obese diabetic mice. In tests with rats, an intraperitoneal administration of a hot water extract of dried leaves decreased the plasma glucose levels of fasting normoglycaemic rats, but did not prevent the rise in plasma glucose after an oral glucose load. It was suggested that the extract is insulinotropic and may require functional ß-cells to be active. The extract was devoid of acute and subchronic toxic effects in tests with mice. Clinical test data suggest that the plant may not have overt toxic reactions in humans but could affect the immune status of users. A medicine based on Indigofera arrecta for the management of peptic ulcer has been patented.
Many Indigofera species contain toxic compounds. The toxic effects of Indigofera linnaei may well be attributed to the presence of nitropropanoyl esters that upon hydrolysis yield 3-nitropropanoic acid. This compound inhibits succiniate dehydrogenase and other essential respiratory enzymes. Several flavonoids have been isolated from Indigofera, including Indigofera linifolia.

Annual or perennial herbs or shrubs, with a taproot; branches spreading or ascending; indumentum consisting of 2-branched hairs. Leaves alternate, imparipinnate, sometimes trifoliolate or unifoliolate; stipules usually persistent. Inflorescence an axillary raceme, bracteate. Flowers bisexual, pedicellate; calyx campanulate, 5-toothed; corolla papilionaceous, standard without appendages, usually pubescent outside, wings usually with an auricle at base, keel with auricles at base and with lateral pockets; stamens 10, 9 connate and 1 free, all fertile, alternatingly shorter and longer; ovary superior, sessile, 1-celled, style curved upwards. Fruit a linear to globose pod, 1—20-seeded, dehiscent or not. Seeds globose to ellipsoid, cylindrical or quadrangular. Seedling with epigeal germination; cotyledons thick, short-lasting.
In Java flowering and fruiting of Indigofera linifolia is limited to March—June, whereasIndigofera linnaei and Indigofera oblongifolia can be found flowering and fruiting throughout the year. Indigofera linifolia and Indigofera linnaei both have nodulating ability.
The large number of species makes a worldwide taxonomical study of Indigofera a daunting task. In many regions the genus has been incompletely studied, and in regions where a taxonomic revision has been accomplished, comparisons with other regions have usually not been done.

Most Indigofera species occur in open locations, such as grassland, roadsides and open deciduous forest, in the lowland. In South-East Asia several species are bound to monsoon areas.Indigofera linifolia prefers an extremely dry monsoon climate.

Propagation of the Indigofera species treated here is by seed. Soaking for 5 minutes in concentrated H₂SO₄ increased the germination rate of Indigofera oblongifolia seeds from 10% to 90%, whereas gibberellic acid was ineffective. In Indigofera linifolia pretreatment with KNO₃, 1-naphthalene acetic acid (NAA) and 3-indole acetic acid (IAA) proved to be effective in breaking seed dormancy, whereas for Indigofera linnaei this did not work. Thiourea proved to be effective in both species.

In view of their wide distribution and presence in dry open habitats, the Indigofera species treated here do not appear to be threatened by genetic erosion.

Several fractions of Indigofera showed various interesting pharmacological effects, both in vitro and in vivo. Further research is needed to fully evaluate these preliminary results for future applications.

[198]de Kort, I. & Thijsse, G., 1984. A revision of Indigofera in Southeast Asia. Blumea 30(1): 89—151.
[239]Faridah Hanum, I. & van der Maesen, L.J.G. (Editors), 1997. Plant Resources of South-East Asia No 11. Auxiliary plants. Backhuys Publishers, Leiden, the Netherlands. 389 pp.
[542]Lemmens, R.H.M.J. & Wulijarni-Soetjipto, N. (Editors), 1991. Plant Resources of South-East Asia No 3. Dye and tannin-producing plants. Pudoc, Wageningen, the Netherlands. 196 pp.
[688]Nyarko, A.K., Sittie, A.A. & Addy, M.E., 1993. The basis for the antihyperglycaemic activity of Indigofera arrecta in the rat. Phytotherapy Research 7(1): 1—4.
[731]Perry, L.M., 1980. Medicinal plants of East and Southeast Asia. Attributed properties and uses. MIT Press, Cambridge, Massachusetts, United States & London, United Kingdom. 620 pp.
[870]Sittie, A.A. & Nyarko, A.K., 1998. Indigofera arrecta: safety evaluation of an antidiabetic plant extract in non-diabetic human volunteers. Phytotherapy Research 12(1): 52—54.

Sudibyo Supardi & Hurip Pratomo

Indigofera linifolia
Indigofera linnaei
Indigofera oblongifolia

Supardi, S. & Pratomo, H., 2003. Indigofera L.. In: Lemmens, R.H.M.J. and Bunyapraphatsara, N. (Editors): Plant Resources of South-East Asia No 12(3): Medicinal and poisonous plants 3. PROSEA Foundation, Bogor, Indonesia. Database record: prota4u.org/prosea

The following species in this genus are important in this commodity group and are treated separatedly in this database:
Indigofera linifolia
Indigofera linnaei
Indigofera oblongifolia