Prota 3: Dyes and tannins/Colorants et tanins
Gen. hist. 4: 39 (1837).
Diospyros macrocalyx Klotzsch (1861), Royena macrocalyx (Klotzsch) Gürke (1895), Diospyros usambarensis F.White (1963).
Dye diospyros (En). Nhamodema (Po). Mdaa, mdala mweupe (Sw).
Origin and geographic distribution
Diospyros loureiriana is common and widespread in Kenya, Tanzania, Malawi, Zimbabwe and Mozambique.
In Kenya a black dye for mats and wickerwork is extracted from the roots of Diospyros loureiriana by pounding and boiling. The fibres to be dyed are steeped into the solution and then mordanted in black ferruginous mud, iron sulphate or iron rust dissolved in organic acid. A black dye for raffia and cotton cloth can also be extracted from the pounded bark and applied in the same way. In Mozambique a dark red dye used to redden lips and teeth is obtained by crushing the roots into a pulp. The fruits are edible. The wood is hard and white and can be used for small utensils and as firewood. Chewed fresh roots and a root extract are applied externally to snakebites, or the extract is drunk.
The dyeing properties of the bark and roots are due to a combination of naphthoquinones and naphthoquinone dimers and trimers, among which 7-methyljuglone, a derivate of juglone, the dye present in walnut trees (Juglans spp.). The proportions of these colorants have been found to vary according to the seasons. The main components isolated from the root bark of Diospyros loureiriana collected in the rainy season in Tanzania (January) are the naphthoquinones diosindigo A, 7-methyljuglone, mamegakinone, diosindigo B and bis-isodiospyrin. The main component of dried powdered root bark collected during the dry season (September) was 7-methyljuglone. The stem bark contains diosindigo A and 7-methyljuglone. Dried powdered root bark has fungicidal and molluscicidal properties. In bioassays it was found that 5 ppm 7-methyljuglone was lethal to Biomphalaria glabrata snails within 24 hours, and 0.025 μg was sufficient to prevent growth of the fungus Cladosporium cucumerinum. Triterpenoids (including α-amyrin, betulinic acid and various mixtures) were isolated from the leaves.
Dioecious, semi-deciduous shrub or small tree up to 6(–10) m tall; bark corky, rough, deeply fissured, grey or black; twigs with reddish hairs. Leaves alternate, simple and entire; stipules absent; petiole up to 1.5 cm long; blade oblong to obovate-oblong, 1–12 cm × 1–7 cm, base rounded to slightly cordate, apex rounded to acute, almost glabrous to densely pubescent below, lateral veins in 5–6 pairs. Inflorescence an axillary cyme, few-flowered. Flowers unisexual, regular, 4-merous; pedicel up to 1.5 cm long; calyx 3–4 mm long, deeply lobed, lobes triangular, reflexed, accrescent in fruit; corolla 4-lobed almost to the base, 4–6 mm long, white, yellow-white or green-white; disk undulate; male flowers with 8 stamens and rudimentary ovary; female flowers with superior, 8-celled ovary crowned by 4 styles united at base, and 8 staminodes. Fruit a globose berry up to 3 cm in diameter, yellow, shortly hairy, up to 8-seeded, enclosed by the calyx lobes. Seeds up to 14 mm × 7 mm, dull brown, smooth.
Diospyros is a large, pantropical genus of about 500 species; in tropical Africa about 90 species occur and several species produce valuable timber or edible fruits. Many species are used as a dye source in Africa, e.g. the roots of Diospyros lycioides Desf. yield a popular yellow-brown dye in southern Africa, but the species is most important for its fibrous roots and twigs used as toothbrush sticks. A leaf decoction of Diospyros soubreana F.White gives a black ink that is used in Côte d’Ivoire, but the species is more important medicinally. Two subspecies have been distinguished in Diospyros loureiriana, mainly based on differences in hairiness, but intermediates exist.
Diospyros loureiriana is very common on poor soils in sunny locations in wooded or grassy savanna, often in Brachystegia-Julbernardia woodland, from sea-level up to 750 m altitude.
Genetic resources and breeding
Diospyros loureiriana is widespread and not in danger of genetic erosion.
Diospyros loureiriana is a good source of fast reddish brown to black dyes that will remain locally useful in the basket-weaving craft. The medicinal properties need further investigation.
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Correct citation of this article:
Jansen, P.C.M., 2005. Diospyros loureiriana G.Don In: Jansen, P.C.M. & Cardon, D. (Editors). PROTA 3: Dyes and tannins/Colorants et tanins. [CD-Rom]. PROTA, Wageningen, Netherlands.