Prota 11(1): Medicinal plants/Plantes médicinales 1
Cat. afr. pl. 1(3): 674 (1898).
Oncinotis glandulosa Stapf (1902).
Origin and geographic distribution
Oncinotis glabrata is widespread in West and Central Africa, from Guinea east to Uganda and western Tanzania, and south from Cameroon to Angola.
In Cameroon and Equatorial Guinea the latex of the grated bark of Oncinotis glabrata is sprinkled into yaws sores to cure them. The plant is of distinct decorative value. The stems are used as bowstrings in southern Nigeria.
No chemical data are recorded for Oncinotis glabrata. In several other Oncinotis species polyamine alkaloids of the spermidine type have been found. Spermidine derivatives show structural similarities to spider and wasp toxins, which are potent inhibitors of glutamate receptors in the central nervous system.
Climbing shrub or liana up to 50 m long, with milky latex; stem up to 12 cm in diameter; bark smooth, later longitudinally fissured, greyish brown, with large pale brown lenticels. Leaves opposite, simple and entire; stipules absent; petiole 5–25 mm long, glabrous, upper side with small triangular glands up to 1 mm long; blade elliptical to ovate, up to 15.5 cm × 7.5 cm, base cuneate, apex acuminate, papery to leathery, glabrous, with small domatia in axils of lateral veins. Inflorescence an axillary or terminal panicle, 4–12.5 cm × 2–5 cm, many-flowered, rusty brown hairy but glabrescent; bracts ovate to triangular. Flowers bisexual, regular, 5-merous; pedicel 2–5 mm long; sepals ovate, 1.5–3.5 mm long; corolla yellow to greenish yellow, tube urn-shaped, 3–5 mm long, lobes triangular, 2–6 mm long, spreading, with a belt of hairs inside the tube just below the insertion of the stamens; stamens inserted at the base of the tube, filaments short; ovary half-inferior, 2-celled, style very short, pistil head at apex with 2 appendages. Fruit composed of 2 spreading, spindle-shaped follicles 10–30 cm long, pendulous, opening by longitudinal slits, longitudinally winged, many-seeded. Seeds 5–25 mm long, smooth, with tuft of hairs 10–75 mm long at apex; cotyledons thin, leafy.
Oncinotis comprises 7 species, 6 occurring in continental Africa and 1 in Madagascar. It is related to Baissea and Motandra. The West African Oncinotis nitida Benth. is used in Côte d’Ivoire to prevent abortion. From the stem bark the spermidine derivative oncinotine has been isolated as the major alkaloid. The bark decoction of the Central and East African Oncinotis hirta Oliv. is applied in Gabon to wounds to promote healing. In the Central African Republic root bark, stem bark and seeds of different Oncinotis spp. are added to arrow poison and have the reputation of being extremely effective. Oncinotis gracilis Stapf is a decorative climber in West and Central Africa, and in Ghana the stems are used for bowstrings.
Oncinotis glabrata occurs in rainforest, swamp forest, secondary deciduous forest and gallery forest. It grows on clay and rocky outcrops, from sea-level up to 2200 m altitude.
Genetic resources and breeding
Oncinotis glabrata is widespread and it does not appear to be threatened.
Very little information is available on Oncinotis including Oncinotis glabrata. More research on the phytochemistry and pharmacological properties is needed before their prospects as medicinal plants can be judged.
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Correct citation of this article:
Boone, M.J., 2006. Oncinotis glabrata (Baill.) Stapf ex Hiern. In: Schmelzer, G.H. & Gurib-Fakim, A. (Editors). Prota 11(1): Medicinal plants/Plantes médicinales 1. [CD-Rom]. PROTA, Wageningen, Netherlands.