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Aloe flexilifolia Christian

Journ. S. African Bot. 8(2): 167 (1942).
Origin and geographic distribution
Aloe flexilifolia is endemic to the Usambara Mountains of north-east Tanzania.
Sap from crushed roots and leaves of Aloe flexilifolia is applied by the Shambaa people of Tanzania to reduce swelling of the testicles and scrotum.
The distinctive constituents in Aloe are phenolic compounds, notably chromone, anthraquinone or anthrone derivatives. The exudate of Aloe flexilifolia is known to be caustic, and is rich in aloin. Aloin is the active ingredient and has purgative properties. Other compounds of interest for their medicinal activity in this and other Aloe species are the polysaccharides contained in the gel from the core of the leaves, and lectins found in several plant parts.
Succulent perennial shrub; stem stout, erect and up to 1 m tall or slender, pendulous and up to 2 m long, much branched from the base forming large clumps. Leaves laxly crowded at top of branches, hanging down; stipules absent; petiole absent; blade narrowly lanceolate, up to 50 cm × 7 cm, apex long-acuminate, margin hard and tough, with pale brown sharp teeth 1–2 mm long, 1–2 cm apart, blade pale bluish green with a few white spots when young; exudate drying brown. Inflorescence consisting of erect, cylindrical racemes, 10–15(–30) cm × 8 cm, densely flowered; peduncle horizontal to down-curved, 50–65 cm long, with 6–8 branches, lowest branches occasionally rebranched; bracts ovate-lanceolate, 5–6 mm long. Flowers bisexual, regular, 3-merous; pedicel 12–18 mm long; perianth tubular, up to 3.5 cm long × c. 8 mm, lobes 6, 10–12 mm long, bright red or brownish red, sometimes yellow; stamens 6, exserted; ovary superior, 3-celled, style filiform, stigma head-shaped, exserted. Fruit unknown.
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 flexilifolia belongs to a group of species with decumbent, sprawling or pendulous stems. Several other East African species in this group have medicinal uses. The leaf sap of Aloe carolineae L.E.Newton is used in Kenya to cure eye disorders. Aloe pulcherrima M.G.Gilbert & Sebsebe, which is endemic to central Ethiopia, is used medicinally and has become scarce in the wild due to harvesting, but is increasingly cultivated in gardens. According to CITES, Aloe scabrifolia L.E.Newton & Lavranos from Kenya is threatened as a result of overexploitation for medicinal use and exudate extraction; the leaf exudate is brown and contains much aloin A. The So people of Uganda use the exudate of Aloe wilsonii Reynolds from north-western Kenya and north-eastern Uganda externally to cure eye infections, headache and body pains, while an infusion of the whole plant is taken as an emetic; pounded roots and leaves are applied to aching teeth. The leaf exudate is yellow and turns brownish when drying.
Aloe flexilifolia occurs on rocky slopes and cliff-faces at 1000–1250 m altitude.
Aloe flexilifolia can easily be propagated by suckers and stem cuttings.
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, except Aloe vera (L.) Burm.f. are listed by CITES. The status of Aloe flexilifolia is classified as ‘Undetermined’. However, in view of its restricted range and a general decline in Tanzania of populations of medicinally used Aloe species, ‘Vulnerable’ would probably be a more appropriate classification.
Research into the chemical composition and affinities of Aloe species is well underway. However, the ethnobotanical aspects of less important species such as Aloe flexilifolia are poorly documented. The high aloin content makes Aloe flexilifolia a potential crop plant. Growing Aloe 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.
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] 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.
• Reynolds, T., 1996. Chemotaxonomy of Aloe turkanensis and Aloe scabrifolia from Kenya. Biochemical Systematics and Ecology 24(4): 347–352.
Other references
• 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.
• Groom, Q.J. & Reynolds, T., 1987. Barbaloin in Aloe species. Planta Medica 53: 345–348.
• Heine, B. & König, C., 1988. Plant concepts and plant use; an ethnobotanical survey of the semi-arid and arid lands of East Africa. Part 2. Plants of the So (Uganda). Cologne Development Studies 7. Breitenbach, Saarbrücken, Germany. 140 pp.
• Kokwaro, J.O., 1993. Medicinal plants of East Africa. 2nd Edition. Kenya Literature Bureau, Nairobi, Kenya. 401 pp.
• 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.
• Reynolds, T., 1997. Comparative chromatographic patterns of leaf exudate components from Aloe Section Pachydendron Haw. Botanical Journal of the Linnean Society 125(1): 45–70.
C.H. Bosch
PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands

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 flexilifolia Christian. In: Schmelzer, G.H. & Gurib-Fakim, A. (Editors). Prota 11(1): Medicinal plants/Plantes médicinales 1. [CD-Rom]. PROTA, Wageningen, Netherlands.