Kigelia africana (PROSEA)

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Plant Resources of South-East Asia
Introduction
List of species


Kigelia africana (Lamk) Benth.


Protologue: Hook., Niger Fl.: 463 (1849).
Family: Bignoniaceae
Chromosome number: n= 20, 21, 2n= 40

Synonyms

Kigelia aethiopica (Fenzl) Decne. (1845), Kigelia pinnata (Jacq.) DC. (1845).

Vernacular names

  • Sausage tree (En). Saucissonnier, faux baobab (Fr)
  • Thailand: sai krok africaa (Bangkok)
  • Vietnam: dồi, bí dặc.

Origin and geographic distribution

K. africana originates from tropical Africa, where it is widespread. It is widely cultivated in other tropical regions as an ornamental tree in parks and along roads. It is locally planted in South-East Asia, e.g. in Vietnam, Thailand, Peninsular Malaysia, Java and the Philippines.

Uses

In Africa, K. africana is a true multipurpose tree. It is highly esteemed for ritual purposes as well as for medicinal applications, as a shade and ornamental tree, and for its wood. In traditional medicine, the fruits are most commonly used and sold on markets, and their uses are often interwoven with ritual uses as they are considered a strong fetish. A decoction of the fruit is administered as a galactagogue, internally as well as externally, and is also used to treat oedema of the legs and cancer. The fruit is purgative and toxic, and is applied in poultices to treat syphilis and rheumatism, and as a sexual stimulant. A decoction with peppers is used to treat constipation and piles, and powdered fruits are applied to ulcers and to treat rheumatism. The fruit is commonly used in the preparation of beer, to make it stronger. The leaves and bark are sometimes applied to treat dysentery, and stomach and kidney complaints. The slightly bitter bark is used in mixtures with other plants to treat epilepsy, and also to treat snakebites, rheumatism, asthma, syphilis, gonorrhoea, and externally to treat wounds, sores and ringworm. The likewise bitter root is administered as a remedy for boils, sore throat, constipation and tapeworm.

The wood is whitish to yellowish with a pale brown heart, and medium-weight. It is used in Africa for dugout canoes, tool-handles, small implements and boxes, and occasionally for fence posts.

In South-East Asia, it is apparently only planted as a roadside tree and in parks, and no medicinal uses have yet been recorded. It is a conspicuous ornamental tree, with extremely large flowers and fruits.

Properties

Chemical investigations showed that the aqueous extracts of the stem bark contain iridoids as major components. These extracts showed significant antimicrobial activity. The naphthoquinones kigelinone, isopinnatal, dehydro-α-lapachone and lapachol and the phenylpropanoids p-coumaric acid and ferulic acid have been isolated as the compounds responsible for the observed antibacterial and antifungal activity of the roots, as well as kigelinone and caffeic acid from the fruits. Flavonoids such as luteolin and quercetin have been isolated from the leaves and fruits.

Aqueous leaf extracts protected rats and mice from castor oil-induced diarrhoea; they reduced faecal output and decreased the propulsive movement of the gastro-intestinal contents. Oral administration of an ethanolic extract of the fruits to mice resulted in a significant inhibition in the tumour incidence and burden in the benzo[a]pyrene-induced forestomach tumourigenesis model. The extract also evinced anti-inflammatory effects in rats against albumen-induced paw inflammation. A dichloromethane extract of the stem bark showed significant and dose-dependent inhibitory activity on the growth of melanoma and renal carcinoma cell lines in vitro, with norviburtinal as the most active compound. Lapachol showed similar activity, and therefore might be one of the active compounds too. Dichloromethane extracts of the root bark and stem bark exhibited antitrypanosomal activity against Trypanosoma brucei in vitro. Some naphthoquinones have been determined as active compounds. Naphthoquinones were also identified as the active compounds in a hexane extract of K. africana exhibiting antimalarial activity against Plasmodium falciparum .

A bark extract showed acute toxicity to fish, and it also has molluscicidal activity. It caused total suppression of larval hatching of Meloidogyne incognita . The observed cytotoxicity of the root bark in the brine shrimp assay was attributed to the presence of γ-sitosterol, which showed activity similar to lapachol.

Botany

A small to medium-sized tree up to 20 m tall, widely branched; branchlets with large leaf scars. Leaves decussately opposite or whorled, usually in whorls of 3, pinnately compound, up to 50 cm long; stipules absent; leaflets 7-13, ovate to elliptical, up to 20 cm × 7 cm, entire or serrate distally. Inflorescence a terminal, pendent panicle up to 200 cm long. Flowers bisexual, large; pedicel 8-18 cm long, apically upcurved; calyx 3.5-5 cm long, irregularly lobed, greenish; corolla above the narrow base funnel-shaped, 10-14 cm long, with tube as long as calyx or longer, 2-lipped, upper lip 2-lobed, lower lip 3-fid, outside veined, yellowish, inside dark wine-red; stamens 4, inserted at the top of the narrow part of the corolla tube, 1 large staminode present; ovary superior, 2-celled. Fruit a large sausage-like, pendulous berry, 25-50 cm × 7.5-15 cm, shortly beaked, often on still flowering panicles, many-seeded. Seeds obovoid, wingless.

K. africana trees are in general fast-growing. In bud, the calyx contains much watery slime. The flowers open in the evening, have a disagreeable acid smell, and are much visited by bats, although hawkmoths apparently also provide pollination. The corolla falls off the next morning. In Java, the trees can be found flowering throughout the year.

The genus Kigelia is now usually considered to comprise only one single extremely variable species.

Ecology

In Africa, K. africana occurs naturally in rain forest and in remnants of forest in the savanna, usually in damp sites, often along rivers. In South-East Asia, it is planted in the lowlands, up to 700 m altitude. However, it has been observed to flower poorly in the per-humid climate of Singapore.

Management K. africana is easily cultivated. Fresh seeds germinate well, and seedlings grow reasonably fast and straight upwards, beginning to branch only after some years.

Genetic resources

There are no large ex situ germplasm collections of K. africana . In Africa, it is widespread and subject to some protection because it is often considered valuable by the local population. The extremely great variation in morphology and chemical composition is remarkable and warrants further research. The genetic basis of the planted K. africana trees in South-East Asia is not known, but is likely to be quite narrow.

Prospects

Although up to the present time K. africana has only been used as an ornamental tree in South-East Asia, it has fairly good prospects as a medicinal plant. The results of tests on pharmacological activities in animal models add credence to the folklore use of K. africana fruits for the treatment of cancer and oedema in traditional systems of medicine in Africa. The antimicrobial activity deserves more attention. It may be tried for planting on a larger scale in South-East Asia as a multipurpose tree.

Literature

26, 29, 61, 93, 120, 247, 372, 406, 986.

Other selected sources

62, 121, 468, 639, 760.

Main genus page

Authors

R.E. Nasution & R.H.M.J. Lemmens