Prota 11(1): Medicinal plants/Plantes mιdicinales 1
Kew Bull. 43(2): 340 (1988).
Caesalpiniaceae (Leguminosae - Caesalpinioideae)
2n = 28
Cassia petersiana Bolle (1861).
Dwarf cassia, eared cassia, monkey pod (En). Mbaraka, mpingawaume (Sw).
Origin and geographic distribution
Senna petersiana occurs from Cameroon east to Ethiopia and south to South Africa. It has been introduced in several Indian Ocean islands and is widely naturalized in Madagascar.
Senna petersiana is widely used as a purgative to treat constipation, stomach-ache and intestinal worms by drinking an infusion or decoction of the roots, or less often, by using fresh leaves. In southern Africa medicinal uses include the treatment of malaria, schistosomiasis, gonorrhoea and syphilis. In southern Africa the sweet fruit pulp is eaten raw by children and in Malawi the pods are soaked, boiled and eaten as a gruel. In Mozambique the seeds and fruits are made into an alcoholic drink. In Zambia and probably elsewhere, the wood is used as firewood.
The active constituents of leaves, bark, roots and pods of Senna petersiana are anthraquinone glycosides. These compounds are responsible for the purgative activity. The seeds contain the flavone luteolin. The ethanol extract of the seeds and luteolin were tested for antiviral activity and showed some activity at the highest non-toxic concentrations; luteolin also showed antibacterial activity. The methanol and water extract of the leaves showed some schistosomicidal activity in vitro. Both leaves and roots have shown antimalarial activity in vitro.
Anthraquinone glycosides are also found in other species of Senna, Cassia and Aloe and these are also used for their laxative and purgative properties.
Shrub or small tree up to 12 m tall. Leaves arranged spirally, paripinnately compound, with 410(13) pairs of leaflets; stipules kidney-shaped, 12.5 cm long, acuminate, persistent; petiole up to 4 cm long; leaflets lanceolate or ovate-lanceolate, 310 cm Χ 14 cm, apex acuminate, variably hairy. Inflorescence an erect, terminal or axillary panicle 1520 cm long, many-flowered. Flowers bisexual, zygomorphic, 5-merous; sepals unequal, up to 6 mm long, rounded at apex; petals unequal, obovate, 1.53 cm long, bright yellow; stamens 10, 3 long, 4 medium-sized and 3 rudimentary; ovary superior. Fruit a somewhat compressed, linear pod 1225 cm Χ 11.5 cm, indehiscent, sutures transversely cracked, many-seeded. Seeds compressed, ovoid to orbicular, 57 mm Χ 46 mm, with an olive-coloured areole.
Until the early 1980s, Cassia was considered a very large genus of about 550 species, but was then split into 3 genera: Cassia s.s. with about 30 species, Chamaecrista with about 250 species and Senna with about 270 species. Senna is very similar to Cassia, but is distinguished from it by the possession of 3 adaxial stamens which are short and straight, and the pedicels which have no bracteoles. Senna petersiana is very variable and in East Africa 3 types can be distinguished that are geographically separated and differ by their hairiness. In southern Africa intermediates between the 3 types occur and therefore a formal distinction between them is not justified.
Senna petersiana occurs at the margins of rainforest, in riverine forest, deciduous woodland, coastal evergreen bushland and wooded grassland up to 2500 m altitude.
Genetic resources and breeding
In view of its wide distribution Senna petersiana is not considered threatened. In areas where the roots and bark are intensively used, monitoring of the populations is recommended. It will be worthwhile to try to link the medicinal uses to the variation in morphology, as there are no recorded medicinal uses in Ethiopia, few in Kenya and Tanzania, but many in southern Africa.
Senna petersiana will remain locally important as a purgative, but has many substitutes. More research into its potential as an anti-malaria and anti-bilharzia medicine is recommended.
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Correct citation of this article:
Bosch, C.H., 2007. Senna petersiana (Bolle) Lock. In: Schmelzer, G.H. & Gurib-Fakim, A. (Editors). Prota 11(1): Medicinal plants/Plantes mιdicinales 1. [CD-Rom]. PROTA, Wageningen, Netherlands.