Prota 11(1): Medicinal plants/Plantes médicinales 1
Bot. Reg. 8: tab. 683 (1823).
2n = 18, 36
Bush cane, ginger lily, spiral ginger (En). Costus, gingembre spirale (Fr). Fia ipqueté (Po).
Origin and geographic distribution
Costus afer is found in the forest belt from Senegal east to Ethiopia and south to Tanzania, Malawi and Angola. It is often planted in home gardens for medicinal purposes.
Costus afer is commonly used as a medicinal plant throughout tropical Africa. An infusion of the inflorescence is taken to treat tachycardia. The same infusion or a rhizome infusion is taken to treat stomach complaints. A stem decoction, the mashed or chewed stem or the pounded fruit, sometimes mixed with sugar cane juice, are taken to treat cough, respiratory problems and a sore throat. The smoke of the dried stem is also inhaled to treat cough. Leaf sap is used as eye drops to treat eye troubles and as nose drops to treat headache with vertigo, and in frictions to treat oedema and fever. Leaf sap or a rhizome decoction is taken to treat malaria. Stem sap is applied to treat urethral discharges, venereal diseases, jaundice and to prevent miscarriage. Stem sap is acid and rubefacient and burns on open wounds, but it is also anodyne and healing, and is applied to different skin ailments. A stem decoction is widely taken to treat rheumatoid arthritis. An infusion of the dried aerial parts is taken to treat hypertension. The powdered stems are used as an enema to treat worms and haemorrhoids. The pulped stems taken in water are strongly diuretic. In Nigeria the debarked stem is chewed to treat nausea and to quench thirst. A cold water extract of the stem is taken to treat small epileptic attacks. Rhizome pulp is applied to abscesses and ulcers to mature them, applied to teeth to cure toothache, and mixed with water it is taken to treat diarrhoea and amoebic dysentery. A rhizome decoction or the raw rhizome is taken to treat leprosy and venereal diseases. In Gabon the stem sap is rubbed on the body to treat colic.
In Togo Costus afer is sometimes cultivated for the stem bark which is used to make table mats and baskets. Experiments in Uganda to use it for making paper were successful. In DR Congo the stems are used in house construction. The sap can be used to coagulate latex and is also used in skin nourishing creams. In West Africa Costus afer is used as a fodder for small ruminants and poultry and the leaves serve as a feed for snails. Costus afer is widely used for ceremonial and religious purposes.
The stem, seeds and rhizome of Costus afer contain several steroidal sapogenins, of which diosgenin is the most important one. The rhizome yields 0.5% diosgenin. Diosgenin is a very important raw material used as a precursor in the synthesis of a number of steroidal drugs, including corticosteroids, sex hormones, oral contraceptives and anabolic agents. The rhizomes also contain the saponins aferosides A–C, as well as dioscin and paryphyllin C and the flavonoid glycoside kaempferol 3-O-α-L-rhamnopyranoside. The last compound showed an ability to potentiate in vitro cisplatin cytotoxicity in a human colon cancer cell line.
Sesquiterpenoids were the most abundant group of volatile compounds in the essential oil of Costus afer leaves from western Nigeria, with sesquilavandulyl acetate (17.0%) as the principal component, followed by β-caryophyllene (12.3%) and Z,E-farnesol (9.9%). The essential oil did not show any antimicrobial activity. A papaverine-like alkaloid is found in the rhizome which causes relaxation of smooth muscle and is anti-spasmodic, diuretic and central nervous system depressant in tests in animals. The saponin fraction from the rhizomes and the methanolic leaf extract showed significant abortifacient activity in rats. The chloroform and methanol extracts from the aerial parts showed a significant reduction of carrageenin-induced rat paw oedema. The methanol extract of the rhizome showed significant topical anti-inflammatory activity in croton aldehyde-induced mouse ear oedema. The chloroform extract ameliorated all signs associated with adjuvant-induced polyarthritis in rats. The extracts delayed arachidonic acid and castor oil-induced diarrhoea in rats.
The aqueous extract of the leaves and stems showed significant antibacterial and amoebicidal activity in vitro. The methanolic leaf extract showed significant cytotoxicity in the brine shrimp test. The same extract showed moderate local anaesthetic activity in guinea pig skin test, and contracted the guinea pig ileum in a concentration-dependent manner. The extract exhibited antihyperglycaemic activity, and decreased the blood glucose level by 50% in streptozotocin (STZ)-induced hyperglycaemia in male rats; high doses, however, increased blood glucose level.
Adulterations and substitutes
Diosgenin is mainly obtained from Dioscorea spp., but it is also present in most Costus spp., and especially obtained from the ornamental Costus speciosus (Fenzl) K.Schum. Another species of which the seed contains high concentrations of diosgenin is fenugreek (Trigonella foenum-graecum L.).
Perennial, rhizomatous herb up to 4 m tall. Leaves arranged spirally, simple and entire; sheath tubular, closed, green with purple blotches; ligule 4–8 mm long, leathery, glabrous; petiole 4–12 mm long; blade elliptical to obovate, 15–35 cm × 3.5–9.5 cm, base rounded to subcordate, apex acuminate, margin sparsely hairy, usually glabrous above, sometimes shortly hairy beneath. Inflorescence a very compact, terminal, conical spike 2.5–7.5 cm long, sessile; bracts oblong, convex, c. 3.5 cm long, densely imbricate, upper ones often smaller, apex truncate to rounded, green with purple markings, each subtending 2 flowers; bracteoles boat-shaped, c. 2.5 cm × c. 1 cm, keel thick and ridged, pale green with pink markings and thin pink papery margin. Flowers bisexual, zygomorphic, 3-merous; calyx tube 1.5–2 cm long, teeth c. 5 mm long, triangular, margin pink; corolla tube c. 2 cm long, hairy inside, enclosed by bract, lobes oblong to ovate, 3–4 cm long, hooded at apex, transparent to white, labellum (lip) broadly triangular, funnel-shaped, c. 2.5 cm × 2.5 cm, opposite the stamen, white or tinged pink towards the margin with an orange-yellow central line to the base of the corolla tube; stamen 1, free, petaloid, ovate, c. 3 cm × 1 cm, entire, white, anther c. 7 mm long, attached at the middle to the filament; ovary inferior, 3-celled, style 1, filiform. Fruit an ellipsoid capsule c. 1 cm long, dehiscing loculicidally, many-seeded. Seeds black, with aril.
Other botanical information
Costus is pantropical and comprises about 70 species, of which about 40 species in tropical America, about 25 in tropical Africa and about 5 in South-East Asia. The African Costus spp. are much in need of revision, especially the large forest species which are difficult to collect for herbarium collections. Costus afer and Costus lucanusianus J.Braun & K.Schum. are closely related species, mainly differing in the form of the inflorescence, the number of flowers enclosed by the bracts and the colour of the flowers. In Costus afer the inflorescence is cone-like, each bract covers 2 flowers and the corolla is white with a yellow throat, whereas in Costus lucanusianus the inflorescence is globose, each bract covers 1 flower and the corolla is white with a red lip and yellow throat. In southern Nigeria Costus afer and Costus lucanusianus produce hybrids.
Other Costus spp. with medicinal uses in West Africa are Costus deistelii K.Schum., Costus dubius (Afzel.) K.Schum., Costus englerianus K.Schum., Costus schlechteri Winkler and the ornamental Costus spectabilis (Fenzl) K.Schum. An extract of the inflorescences and stems of all species is taken to treat cough and stomach complaints. Leaf and stem sap is used as eye drops to treat eye infections and as nose drops to cure headache, in frictions or a vapour bath to treat oedema and fever, or applied to treat urethral discharges, venereal diseases, jaundice and to prevent miscarriage. Rhizome pulp is applied to abscesses, ulcers and Guinea worm to mature them. The rhizome decoction of Costus dubius is taken to treat epilepsy; it is also a diuretic and febrifuge. The boiled leaves of Costus schlechteri are also applied to smallpox and are taken to treat diabetes. The rhizomes of Costus deistelii yield 0.25% total steroidal sapogenins, with 0.15% diosgenin.
Growth and development
Costus afer is a very vigorous grower. It flowers and fruits throughout the year, depending on the humidity of the soil.
Costus afer occurs in moist localities in forest and forest edges, up to 1400 m altitude. In southern Nigeria Costus afer is a weed in rice fields. In cultivation it requires a rich well-drained, moist soil (2 parts peat moss to 1 part loam to 1 part sharp sand). It does well in partial shade to full sun.
Propagation and planting
Costus afer can be propagated by seed, and also by stem cuttings or rhizome cuttings. The stems and rhizomes are cut into pieces 2.5 cm long and planted in a mixture of sand and peat moss. In-vitro storage of multiple shoot cultures of Costus afer was successful; after 1 year of storage under liquid paraffin, high survival rates (70–100%) were found, and even after 2 years, 75% of the cultures of Costus afer remained viable.
Diseases and pests
In Cameroon Costus afer is a host of the African root and tuber scale Stictococcus veyssierei.
The stems and rhizomes of Costus afer are harvested from the wild or from plants grown in home gardens whenever the need arises.
In Ethiopia Costus afer is harvested on a large scale from the wild for medicinal purposes, resulting in diminishing numbers. As demand for medicinal plants rises, harvest rates also increase. The situation is further aggravated by habitat destruction caused by slash-and-burn, commercial logging and firewood collection. In West and Central Africa, Costus afer remains a common species in forest undergrowth, and is not liable to genetic erosion.
Costus afer is widely used as a medicinal plant in tropical Africa and several uses have been confirmed by pharmacological tests, although no systematic evaluation of the active compounds of the different plant parts has been effected. The diosgenin content needs further study as well, especially because the content is higher than commercially grown diosgenin-producing Costus spp. Costus afer has some value as an ornamental plant.
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Sources of illustration
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Correct citation of this article:
Aweke, G., 2007. Costus afer Ker Gawl. In: Schmelzer, G.H. & Gurib-Fakim, A. (Editors). Prota 11(1): Medicinal plants/Plantes médicinales 1. [CD-Rom]. PROTA, Wageningen, Netherlands.
wild and planted
1, flowering shoot; 2, base of leaf with ligule; 3, bract with 2 flowers.
Redrawn and adapted by Achmad Satiri Nurhaman