Agave americana (PROTA)
- Protologue: Sp. pl. 1: 323 (1753).
- Family: Agavaceae
- Chromosome number: 2n = 60
- Century plant, American agave, American aloe (En).
- Agave d’Amérique (Fr).
- Piteira de boi, piteira brava (Po).
Origin and geographic distribution
Agave americana is a native of Mexico and the southern United States. It has been distributed throughout the world for its ornamental value. Its distribution in Africa is not reflected by collections in herbaria as it is introduced and not easy to collect. However, it is probably found throughout tropical Africa.
In DR Congo and Mauritius the leaf sap of Agave americana is drunk for its laxative and diuretic properties and as an emmenagogue. It is applied to wounds and cuts to promote healing. A decoction of the roots is taken, mixed with honey, to cure syphilis and it also has diuretic properties. In South Africa the leaves are used to treat cardiac problems, high blood pressure and gastro-intestinal problems. The leaves are split, heated and applied externally to relieve rheumatic pain. The leaf sap is used as an insecticide, e.g. against termites in Tanzania.
As an ornamental, Agave americana is planted in private and public gardens and on roadsides. It is used as a hedge plant and planted along contours for erosion control and for reclamation of denuded and overgrazed land. The leaf fibres are used locally to make textiles.
Two different derivatives of triacontanol, isolated from the leaves, were shown to have antibacterial activity against Staphylococcus spp., Pseudomonas aeruginosa and Escherichia coli. Leaf extracts showed molluscicidal and insecticidal properties. The leaves contain angiotensin-converting enzymes that are a potent medicine to treat hypertension. The leaves also contains several sapogenins, e.g. hecogenin, which can be used in the manufacture of semisynthetic corticosteroids, but only if they do not contain too much tigogenin, because this results in losses in product quality and yield. In Nigerian plants tigogenin was only found in trace amounts in the leaves. Tigogenin itself is a base material for the production of other steroids.
The leaves contain needle-like calcium oxalate crystals, called raphides, which can cause contact dermatitis and conjunctivitis.
Robust, perennial herb up to 9 m tall when flowering, producing suckers; stem short and thick, up to 20 cm in diameter, with a dense rosette of leaves at apex. Leaves arranged spirally, succulent, sessile, lanceolate, 1–2 m × 15–25 cm, base fleshy, triangular in cross section, apex with sharp, dark brown spine up to 5 cm long, margin wavy to toothed with teeth up to 10 mm long, pale blue-grey to green, sometimes variegated. Inflorescence a very large, terminal, rather open panicle; peduncle 2–8 m long. Flowers bisexual, regular; perianth tubular, 8–20 mm long, 6-lobed, pale yellow; stamens 6, attached above the middle of the perianth tube, 6–9 cm long; ovary inferior, 3-celled, style 1, longer than the stamens, stigma 3-lobed. Fruit an oblong capsule 4–5 cm long, shortly beaked, many-seeded. Seeds flat, disk-shaped, 7–8 mm × 5–6 mm, curved, shiny black. Seedling with epigeal germination.
Agave americana follows the Crassulacean Acid Metabolism (CAM) pathway. CAM plants are able to fix CO2 at night and photosynthesize with closed stomata during the day, thus minimizing water loss. Agave comprises 100–200 species, all native to Central America and Mexico.
Agave americana is adapted to a wide range of conditions. In East Africa it is found from sea-level to 2500 m altitude. It is found in both low and high rainfall areas. In many countries in southern Africa, including South Africa, it is considered a noxious invasive weed.
Multiplication of Agave americana is done by suckers or seeds. The hecogenin content of the leaves increases with age of the plant and is highest during dry periods.
As Agave americana is widely distributed and cultivated no threats are envisaged. Many ornamental cultivars have been developed, including a cultivar with pale yellow leaf margins, known as ‘Marginata’, which is widely planted. Breeding and selection for ornamental properties is ongoing.
As a source of medicine for hypertension, Agave americana is promising. Hypertension, often regarded as a disease of well-to-do populations, is on the increase in urban populations in Africa.
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- P. Oudhia, SOPAM, 28-A, Geeta Nagar, Raipur, 492001, C.G., India
Correct citation of this article
Oudhia, P., 2007. Agave americana L. [Internet] Record from PROTA4U. Schmelzer, G.H. & Gurib-Fakim, A. (Editors). PROTA (Plant Resources of Tropical Africa / Ressources végétales de l’Afrique tropicale), Wageningen, Netherlands. <http://www.prota4u.org/search.asp>.
Accessed 29 November 2022.
- See the Prota4U database.