Prota 11(1): Medicinal plants/Plantes médicinales 1
Prodr. 9: 507 (1845).
Ehretia coerulea Gürke (1900).
Sandpaper bush, big-leaved puzzle bush (En). Mkilika (Sw).
Origin and geographic distribution
Ehretia obtusifolia occurs in almost all countries of eastern and southern Africa and in Madagascar. It extends into Asia up to Pakistan and northwest India.
In Zimbabwe the leaves of Ehretia obtusifolia are used as an infusion to treat sore throat and are rubbed on the gums of infants suffering from teething pains. In Zimbabwe powdered root is added to porridge to treat painful menstruation and infertility in women and an infusion of the roots is taken against retained placenta. A decoction of the roots is taken as a painkiller, specifically against abdominal pain in Zimbabwe and in Tanzania. The wood is used to make pestles for pounding grain in Zimbabwe. In Pakistan the leaves are used as a fodder and the wood as firewood.
Ehretia obtusifolia has so far escaped attention of pharmacological research, but several Asian species of the genus (e.g. Ehretia philippinensis DC.) have been the subject of tests and analyses. In tests with mice, a crude stem bark extract of Ehretia philippinensis was found to be moderately toxic when administered intraperitoneally and slightly toxic when administered orally. A decrease in motor activity and slight analgesia were observed as well. Extracts of the stem bark showed inhibitory activity against compound 48/80, a potent histamine liberator. Rosmarinic acid was identified as the active constituent. A stem bark extract was also tested for anti-inflammatory activity using animal models, and was found comparable in potency to an aspirin reference. Five cyanoglucosides have been isolated: ehretiosides A1, A2, A3 and B, and simmondsin.
Deciduous shrub or small tree up to 6 m tall; often straggling or with several branches from base; bark grey. Leaves alternate, simple; petiole up to 2 cm long; blade elliptical, oblong-elliptical or obovate, 1–9(–11) cm × 0.5–6(–8.5) cm, pubescent to velvety; base cuneate; apex obtuse to shortly acuminate. Inflorescence a corymbose cyme, terminal or on short lateral shoots, c. 2.5 cm wide, many-flowered, axes densely glandular pubescent. Flowers bisexual, regular, 5-merous, fragrant; pedicel up to 4.5 mm long; calyx lobes ovate, elliptical or narrowly triangular, 2 mm × 1 mm, puberulous, only joined at the base; corolla pink, blue, pale lilac or mauve, tube cylindrical, 4–4.5 mm long, lobes narrowly triangular to oblong, 3–4.5 mm × 1 mm, acute or obtuse; stamens exserted for 2–4 mm; ovary superior, 2-celled, style 3–6 mm long, deeply forked. Fruit a globose drupe 5–6 mm in diameter, orange or red, splitting into two 2-seeded pyrenes.
The genus Ehretia comprises about 33 species, most of them in tropics and subtropics of the Old World and a few in Central America and the West Indies. Ehretia is sometimes placed in the small family Ehretiaceae. Several other African Ehretia species are used in traditional medicine as well as for timber. A root decoction of Ehretia bakeri Britten, a species restricted to Kenya and Tanzania, is used as a cure for gonorrhoea in Kenya. Ehretia coerulea is sometimes distinguished as a separate species differing in its much-branched inflorescence and blue to purplish blue corolla colour (versus the white tube and mauve or blue lobes in Ehretia obtusifolia). However, as both species occur in Zimbabwe and it is not clear to which one the information on uses refers, they are kept together here, with Ehretia coerulea as a synonym of Ehretia obtusifolia.
Ehretia obtusifolia is found in woodland, wooded grassland and in thickets, often in rocky localities at of 700–1500 m altitude.
Genetic resources and breeding
Ehretia obtusifolia is widespread but obviously not common in most of its range. In Madagascar the species is only known from 4 collections and hence qualified there as ‘Endangered’ according to the IUCN Red List categories.
Research on the pharmacological compounds of Ehretia obtusifolia may prove worthwhile, because Asian Ehretia species have compounds with interesting activities.
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• Martins, E.S. & Brummitt, R.K., 1990. Boraginaceae. In: Launert, E. & Pope, G.V. (Editors). Flora Zambesiaca. Volume 7, part 4. Flora Zambesiaca Managing Committee, London, United Kingdom. pp. 59–110.
• Retief, E. & van Wyk, A.E., 2001. The genus Ehretia (Boraginaceae: Ehretioideae) in southern Africa. Bothalia 31(1): 9–23.
Correct citation of this article:
Bosch, C.H., 2006. Ehretia obtusifolia DC. In: Schmelzer, G.H. & Gurib-Fakim, A. (Editors). Prota 11(1): Medicinal plants/Plantes médicinales 1. [CD-Rom]. PROTA, Wageningen, Netherlands.