Common Names: Bengal Indigo, Java Indigo, Natal Indigo
Local Names: Elu Aja (Yoruba, Nigeria), Mnili (Swahili, East Africa), Jantari (Hindi, India).
Species ID: NMP-091 | wfo-0000194532 | NCBI_Taxonomy ID: 198859

Kingdom: Plantae

Phylum: Tracheophyta

Class: Magnoliopsida

Order: Fabales

Family: Fabaceae

Genus: Indigofera

Species: I. arrecta

Synonyms: Indigofera indica Lam., Indigofera tinctoria var. arrecta (Hochst. ex A.Rich.) Baker

Indigofera arrecta is a robust, copiously branched perennial shrub or small tree, typically growing 1–3 m tall, occasionally reaching 4 m in optimal conditions. Its key morphological features include:

·       Stem: Erect to spreading, woody at the base, greyish-brown, with short, dense hairs.

·       Leaves: Alternate, pinnately compound, 10–20 cm long, with 7–15 obovate to elliptical leaflets (1–3 cm long, 0.5–1.5 cm wide), dark green, hairy beneath.

·       Flowers: Small, 5–8 mm long, pink to reddish-purple, borne in dense axillary racemes (5–15 cm long); calyx five-lobed, corolla standard petal erect.

·       Fruit: Straight, cylindrical pods, 2–4 cm long, 3–5 mm wide, brown at maturity, containing 6–8 rectangular seeds (2–3 mm long).

The plant’s nitrogen-fixing root nodules and dye precursors (e.g., indican) in leaves are characteristic of the Fabaceae family (Schrire, 2013).

Indigofera arrecta is native to Sub-Saharan Africa, the Arabian Peninsula, and Madagascar, with a naturalized range extending to:

·       Africa: Senegal to Somalia, south to South Africa (annual rainfall 500–2,000 mm).

·       Asia: India, Southeast Asia, Indonesia, Philippines.

·       Australia: Queensland.

It thrives in open deciduous forests, bushlands, savannas, and disturbed areas like roadsides, tolerating drought, waterlogging, and salinity, on sandy to clayey soils (pH 5.0–7.5) from sea level to 2,700 m altitude (Fern, 2024).

Indigofera arrecta is widely valued in traditional medicine. The leaves are employed in treating various ailments, including epilepsy, nervous disorders, diabetes, peptic ulcers, sores, gum infections, snake bites, gonorrhea, and jaundice. Additionally, both leaves and roots are applied externally to address itching. Beyond its medicinal applications, Indigofera arrecta is utilized as a cover crop and green manure, contributing to soil improvement by suppressing weeds and enhancing soil fertility. While these traditional uses are well-documented, specific phytochemical analyses and clinical studies on Indigofera arrecta remain limited, indicating a need for further research to substantiate its medicinal efficacy.

·       Anticonvulsant: Leaf extracts treat epilepsy in Congo

·       Antidiabetic: Leaf infusions manage diabetes in Ghana. Sittie et al. (1998) reported aqueous leaf extracts (500 mg/kg) lowered plasma glucose in normoglycemic rats by 30%, suggesting insulinotropic effects.

·       Antiulcer: Leaf decoctions heal peptic ulcers in Nigeria.

·       Antimicrobial: Leaf poultices treat sores in Senegal. Gerometta et al. (2020) noted broad-spectrum antibacterial activity (MIC 50–100 μg/ml) against Staphylococcus aureus, due to phenolic compounds.

·       Analgesic: Root infusions relieve pain in East Africa. Burkill (1994) documents use, though specific studies on I. arrecta are limited.

Phytochemicals include flavonoids, terpenoids, and indigo precursors (e.g., indican, indirubin), driving its therapeutic potential (Rahman et al., 2020).

⚠  Toxicity Profile: High doses of leaf extracts (>1,000 mg/kg in mice) caused sedation and hepatotoxicity, possibly due to nitropropanoyl esters. Prolonged use may affect immune status in humans, though clinical toxicity is low (Sittie et al., 1998).

·       Dye: Leaves yield indigo dye via fermentation, historically covering 600,000 ha in India (1896) for textiles (Morris, 1999).

·       Agriculture: Used as green manure, cover crop for tea/coffee plantations, and browse for livestock, fixing 50–100 kg N/ha/year (Heuzé et al., 2021).

·       Ecological: Prevents erosion and supports soil health in tropical agroecosystems (Fern, 2024).

• Burkill, H. M. (1994). The useful plants of West Tropical Africa (Vol. 2). Royal Botanic Gardens, Kew.

• Fern, K. (2024). Indigofera arrecta. Useful Tropical Plants Database. Retrieved from https://tropical.theferns.info/viewtropical.php?id=Indigofera+arrecta

• Gerometta, E., Grondin, I., Smadja, J., Frederich, M., & Gauvin-Bialecki, A. (2020). A review of traditional uses, phytochemistry and pharmacology of the genus Indigofera. Journal of Ethnopharmacology, 253, 112608. https://doi.org/10.1016/j.jep.2020.112608

• Heuzé, V., Tran, G., Delagarde, R., & Lebas, F. (2021). Bengal indigo (Indigofera arrecta). Feedipedia, INRAE, CIRAD, AFZ and FAO. Retrieved from https://www.feedipedia.org/node/291

• Morris, J. B. (1999). Legume genetic resources with novel “value added” industrial and pharmaceutical use. In J. Janick (Ed.), Perspectives on new crops and new uses (pp. 196–201). ASHS Press.

• Sittie, A. A., & Nyarko, A. K. (1998). Indigofera arrecta: Safety evaluation of an antidiabetic plant extract in non‐diabetic human volunteers. Phytotherapy Research: An International Journal Devoted to Pharmacological and Toxicological Evaluation of Natural Product Derivatives, 12(1), 52-54.

• Rahman, T. U., Zeb, M. A., Liaqat, W., Sajid, M., Hussain, S., & Choudhary, M. I. (2018). Phytochemistry and pharmacology of genus Indigofera: A review. Records of Natural Products, 12(1), 1-13.

• Schrire, B. (2013). A review of tribe indigofereae (Leguminosae–papilionoideae) in southern Africa (including south Africa, Lesotho, Swaziland & namibia; excluding Botswana). South African Journal of Botany, 89, 281-283.

• Feedipedia - Indigofera arrecta

• World Agroforestry - Indigofera arrecta

• PFAF - Indigofera arrecta

• Plants of the World Online - Indigofera arrecta

• iNaturalist - Indigofera arrecta

• Wikipedia - Indigofera arrecta

• Stigmasterol

Adejoke, S. A., Hassan, H. S., Sule, M. I., Atiku, I., Aduku, O. G., Inusa, B. K., Jimoh, A. A., Dauda, G., & Isah, M. (2020). Isolation and anticonvulsant studies on methanol extract of the aerial part of Indigofera arrecta Hochst. ex A. Rich (Papilionaceae). Nigerian Journal of Pharmaceutical Sciences, 19(2), 94-103.