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Aloe turkanensis Christian

Protologue
Journ. S. African Bot. 8(2): 173 (1942).
Family
Asphodelaceae
Chromosome number
2n = 14
Origin and geographic distribution
Aloe turkanensis occurs in north-western Kenya and in the Karamoja District of Uganda.
Uses
The Turkana people of Kenya apply the leaf sap of Aloe turkanensis to wounds and as a cure for eye diseases. The juice from boiled roots is added to a drink to induce vomiting, which is said to relieve persistent headaches. The roots are used to flavour beer.
Production and international trade
The trade of Aloe extract from East Africa is illegal. The dried exudate, marketed under the name ‘Kenya aloes’ or ‘bitters’, is usually a mixture of the exudate of several species. In Kenya Aloe turkanensis is harvested from the wild at a large scale.
Properties
The main components of leaf exudate of Aloe turkanensis are aloin A, aloin B and aloesone. From about 70 Aloe species checked, Aloe turkanensis had the highest aloin content, both in the exudate and in the leaf (31% and 6.6% of dry weight, respectively). Aloin is a mixture of the stereoisomers aloin A (barbaloin) and aloin B (isobarbaloin), and is responsible for the laxative properties.
Botany
Succulent sprawling shrub; stem ascending, becoming decumbent, up to 70 cm long, branching from the base and forming large clumps. Leaves 14–18 in a dense rosette, erect to spreading; stipules absent; petiole absent; blade lanceolate, up to 70 cm × 9 cm, apex long-acuminate, margin with sharp deltoid teeth, 2 mm long, whitish, brown-tipped, 12–18 mm apart, blade pale bluish green with elongated white spots on both surfaces; exudate drying yellow. Inflorescence consisting of cylindrical racemes 15–26 cm long; peduncle up to 1 m long, with up to 8 branches; bracts ovate, 5–7 mm long. Flowers bisexual, regular, 3-merous; pedicel 8–10 mm long; perianth tubular, c. 2.5 cm long, lobes 6, c. 12 mm long, bright coral-pink, paler at mouth; stamens 6, exserted; ovary superior, 3-celled, style filiform, stigma head-shaped, exserted. Fruit an oblong-ovoid capsule c. 2 cm × 1 cm, dehiscing loculicidally, yellowish brown, many-seeded. Seeds blackish with whitish, sparsely black-speckled wings.
Aloe comprises about 450 species in Africa and Arabia, of which c. 315 occur in mainland Africa, c. 100 are endemic to Madagascar or the Indian Ocean islands (including the former Lomatophyllum) and c. 50 occur in Arabia. Aloe turkanensis belongs to a group of East African species forming large clumps, with leaves wider than 2 cm. Several other species in this group have medicinal uses and are considered by CITES to be under threat because of the risk of overexploitation. Aloe calidophila Reynolds from Ethiopia and Kenya has become rare due to harvesting for medicinal purposes. Aloe camperi Schweinf. (synonym: Aloe eru A.Berger) is one of the most important medicinal plants in Eritrea. In Egypt it is widely cultivated for its exudate. The main components of the exudate are emodin and aloenin. The exudate has significant antifungal properties. Aloe elgonica Bullock, from Kenya, has become vulnerable due to harvesting. The leaf exudate contains aloe-emodin, aloenin, aloesin, aloeresin B and homonataloin. In Somalia the exudate of Aloe microdonta Chiov. is dissolved in water and drunk to treat jaundice. The leaf juice is applied topically to cure skin diseases. The leaf exudate contains aloin A and B, and microdontin A and B.
Ecology
Aloe turkanensis grows on stony, sandy soil or lava, usually in the shade of shrubs in arid areas at 600–1250 m altitude.
Management
To harvest the exudate from Aloe turkanensis and other Aloe species, a hole is dug in the ground and lined with a container. Cut leaves are arranged around the edge of the hole at an angle allowing the exudate to drain into the container. The exudate is transferred to bottles or jerry cans for sale to a dealer. It is placed in a large drum and boiled down until it becomes reddish black and very viscous. It is then transferred from the drum to sacks, in which it is left to cool and harden. After a day of cooling the material is solid and black, called ‘bitters’, and is ready for sale to a middle man, who will sell it to an exporter. Harvesting from wild plants is generally destructive. Development of properly managed plantations will lead to conservation of the wild plants and substantial yields from the plantations. Aloe turkanensis can easily be propagated by suckers. It is being cultivated on a small scale in Kenya for exudate production, but no details are available on its management.
Genetic resources and breeding
Harvesting from the wild for medicinal and ornamental uses and habitat destruction are major threats to many Aloe species. All Aloe species are listed by CITES, except Aloe vera (L.) Burm.f. As Aloe turkanensis is still being harvested on a large scale from the wild, it is certainly threatened.
Prospects
Research into the chemical composition and affinities of Aloe species is well underway. However, the ethnobotanical aspects of less important Aloe species are poorly documented. Growing Aloe species as a commercial crop might take the pressure off wild populations, but more research is needed to identify the species best suited for domestication and their requirements in cultivation. Aloe turkanensis and other species that develop many suckers seem good candidates for domestication. The high aloin content of Aloe turkanensis makes it even more interesting as a potential crop plant.
Major references
• Carter, S., 1994. Aloaceae. In: Polhill, R.M. (Editor). Flora of Tropical East Africa. A.A. Balkema, Rotterdam, Netherlands. 60 pp.
• CITES, 2003. Review of significant trade: East African Aloes. [Internet] http://www.cites.org/ eng/com/ PC/14/E-PC14-09-02-02-A4.pdf. Accessed May 2004.
• Morgan, W.T.W., 1981. Ethnobotany of the Turkana: use of plants by a pastoral people and their livestock in Kenya. Economic Botany 35(1): 96–130.
• Newton, L.E., 2001. Aloe In: Eggli, U. (Editor). Illustrated handbook of succulent plants: Monocotyledons. Springer-Verlag, Berlin, Germany. pp. 103–186.
• Newton, L.E. & Lavranos, J.J., 1990. Two new aloes from Kenya, with notes on the identity of Aloe turkanensis. Cactus and Succulent Journal 62(5): 215–221.
Other references
• Ali, M.I.A., Shalaby, N.M.M., Elgamal, M.H.A. & Mousa, A.S.M., 1999. Antifungal effects of different plant extracts and their major components of selected Aloe species. Phytotherapy Research 13(5): 401–407.
• Conner, J.M., Gray, A.I., Waterman, P.G. & Reynolds, T., 1990. Novel anthrone anthraquinone dimers from Aloe elgonica. Journal of Natural Products 53: 1362–1364.
• Dagne, E., Abiy Yenesew, Senait Asmellash, Sebsebe Demissew & Stephen Mavi, 1994. Anthraquinones, pre-anthraquinones and isoeleutherol in the roots of Aloe species. Phytochemistry 35(2): 401–406.
• Demissew Sebsebe & Gilbert, M.G., 1997. Aloaceae. In: Edwards, S., Mesfin Tadesse, Demissew Sebsebe & Hedberg, I. (Editors). Flora of Ethiopia and Eritrea. Volume 6. Hydrocharitaceae to Arecaceae. The National Herbarium, Addis Ababa University, Addis Ababa, Ethiopia and Department of Systematic Botany, Uppsala University, Uppsala, Sweden. pp. 117–135.
• Farah, M.H., Andersson, R. & Samuelsson, G., 1992. Microdontin A and B: two new aloin derivatives from Aloe microdonta. Planta Medica 58: 88–93.
• Groom, Q.J. & Reynolds, T., 1987. Barbaloin in Aloe species. Planta Medica 53: 345–348.
• Neuwinger, H.D., 2000. African traditional medicine: a dictionary of plant use and applications. Medpharm Scientific, Stuttgart, Germany. 589 pp.
• Reynolds, T., 1996. Chemotaxonomy of Aloe turkanensis and Aloe scabrifolia from Kenya. Biochemical Systematics and Ecology 24(4): 347–352.
• Reynolds, T. & Nicholls, E., 1986. An examination of phytochemical variation in Aloe elgonica Bullock. Botanical Journal of the Linnean Society 92: 393–397.
• Tawfik, K.M., Sheteawi, S.A. & El-Gawad, Z.A., 2001. Growth and aloin production of Aloe vera and Aloe eru under different ecological conditions. Egyptian Journal of Biology 3 (Botany): 149–159.
Author(s)
C.H. Bosch
PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands


Editors
G.H. Schmelzer
PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands
A. Gurib-Fakim
Faculty of Science, University of Mauritius, Réduit, Mauritius
Associate editors
C.H. Bosch
PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands
M.S.J. Simmonds
Royal Botanic Gardens, Kew, Richmond, Surrey TW9 3AB, United Kingdom
R. Arroo
Leicester School of Pharmacy, Natural Products Research, De Montfort University, The Gateway, Leicester LE1 9BH, United Kingdom
A. de Ruijter
PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands
General editors
R.H.M.J. Lemmens
PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands
L.P.A. Oyen
PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands

Correct citation of this article:
Bosch, C.H., 2006. Aloe turkanensis Christian. In: Schmelzer, G.H. & Gurib-Fakim, A. (Editors). Prota 11(1): Medicinal plants/Plantes médicinales 1. [CD-Rom]. PROTA, Wageningen, Netherlands.