Senna italica (PROTA)
|Geographic coverage Africa|
|Geographic coverage World|
|Cereal / pulse|
|Dye / tannin|
|Forage / feed|
Senna italica Mill.
- Protologue: Gard. dict. ed. 8: Senna n. 2 (1768).
- Family: Caesalpiniaceae (Leguminosae - Caesalpinioideae)
- Chromosome number: n = 7, 14
- Cassia italica (Mill.) Spreng. (1800),
- Cassia obovata Collad. (1816).
- Senegal senna, Italian senna, Tripoli senna, Port Royal senna, Jamaica senna, Aleppo senna, eland’s pea, wild senna, dog senna (En).
- Séné du Sénégal (Fr).
- Sene (Po).
Origin and geographic distribution
Senna italica is a native of many African countries from Cape Verde east to Somalia and south to South Africa. In Benin it is only recorded as a cultivated plant. It is also native in Asia, from the Middle East through Iraq, Iran, Pakistan and India to Sri Lanka, and has been introduced and is naturalized in the Caribbean and Venezuela.
Throughout its range the leaves, pods and mature seeds of Senna italica are used as a purgative. They are taken, usually as a decoction or maceration, to cure stomach complaints, fever, jaundice, venereal diseases and biliousness, as an abortifacient and against intestinal worms. The leaves, either fresh or dried and pulverized, are used as a dressing for skin problems such as burns and ulcers. A tea made from the flowers is used as a purgative and to induce labour. A maceration of the roots is taken to cure colic and influenza, and boiled roots are used as a wound dressing. A root infusion is used as eye drops for sore eyes. The roots also enter in treatments of indigestion, liver complaints, gall bladder disorders, nausea, vomiting and dysmenorrhoea. In Malawi a root infusion is given to infants to cure diarrhoea.
Reports on the value of Senna italica as a browse are contradictory. In East Africa it seems to be eaten by most livestock, whereas in West Africa livestock seems to avoid it. Although mature seeds have a purging activity, young seeds are eaten as a snack or as a vegetable in the Sahel region. The seeds are smoked in Mauritania. The leaves, traded as ‘neutral henna’ or ‘blonde henna’, are used as a hair conditioner to make the hair glossy. It may impart a yellowish colour rather than a reddish one.
Production and international trade
Both dried leaves and pods of Senna italica are traded locally as a purgative. Dried, powdered leaves for use as a hair conditioner are nowadays traded internationally. The origin of this product is Sudan, Egypt or India.
From leaves and pods of Senna italica a number of anthraquinones have been isolated, which are responsible for the purgative effect: aloe emodin, chrysophanol, rhein, sennosides and their aglucons sennidins. Chrysophanol is also the active ingredient of ‘neutral henna’. The anthraquinone content of the leaves ranges from 1.1–3.8% on a dry weight basis. The pods have a lower anthraquinone content than the leaves. Leaves further contain flavonoids (quercetin, kaempferol and apigenin) and steroids (stigmasterol, α-amyrin and β -sitosterol).
An ethanol extract of the whole plant has anti-inflammatory and antipyretic properties. 1,5-dihydroxy-3-methoxy-7-methylanthraquinone, isolated from Senna italica, showed activity against several gram-positive and gram-negative bacteria, as well as anticarcinogenic activity in vitro.
Toxicity tests on goats and rabbits fed with foliage proved negative. Rats and chicks fed with seeds at 10% of their intake showed symptoms of toxicity, but did not die during the 6-week test period. Feeding chicks with seeds at 2% of their intake promoted growth. The seeds yield a water soluble gum (about 20% of dry matter), mainly composed of D-galactose and D-mannose.
Adulterations and substitutes
Anthraquinone glycosides, including sennosides, are also found in other species of Senna, Cassia and Aloe and are used for their laxative and purgative properties as well. Senna italica is popular as a substitute for Senna alexandrina Mill., but is considered inferior.
Deciduous, perennial herb or small shrub up to 60 cm tall, often with prostrate stems. Leaves arranged spirally, paripinnately compound with 4–6 pairs of leaflets; stipules narrowly triangular to ovate-triangular, 3–9 mm long, early deflexed, somewhat persistent; petiole 1.5–2.5 cm long; leaflets oblong-obovate or narrowly elliptical to elliptical, 1–6.5 cm × 0.5–1.5 cm, base cuneate, unequal, apex rounded to obtuse, shortly hairy on both sides. Inflorescence an erect, axillary raceme 2–25 cm long, up to 20-flowered; bracts rhombic to ovate, shortly pointed, up to 5 mm long. Flowers bisexual, zygomorphic, 5-merous; sepals unequal, oblong-elliptical, up to 1 cm long, obtuse at apex; petals obovate, up to 13 mm long, yellow; stamens 10, the 2 lower ones largest, 5 medium-sized, 3 short and sterile; ovary superior, with short, stiff hairs, style up to 6 mm long. Fruit a flattened, oblong pod 2.5–6 cm × 1.5–2 cm, with a ridge running along the middle of each valve, tip upcurved, dehiscent by 2 valves, many-seeded. Seeds oblong-ovate, compressed, 6–7.5 mm × 1.5–2.5 mm, with a small areole on each face.
Other botanical information
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.
In Senna italica 3 subspecies are distinguished based on the size of the inflorescence and the length of the petiole. Subsp. italica is found in West Africa, North Africa, Sudan, the Horn of Africa and from Yemen to north-western India. This subspecies is naturalized in parts of South America. Subsp. micrantha (Brenan) Lock is found from southern Ethiopia and Somalia southwards to Namibia, Botswana, Zimbabwe and Mozambique. This subspecies is also found in most of India. Subsp. arachoides (Burch.) Lock is restricted to Namibia, Botswana and South Africa.
Senna truncata (Brenan) Lock, restricted to Ethiopia and Somalia, is used as a purgative. Either seeds are eaten or an infusion of the leaves is drunk. Like Senna italica, the pods have a ridge, but the pods are curved and the leaves have spreading, not appressed, hairs. Confusion of Senna italica with Senna alexandrina Mill. is widespread, but both leaves and pods are readily distinguishable as the former species has wider leaflets and the pods are without ridge.
Growth and development
In experiments, the growth of Senna italica was enhanced by inoculation with a mixture of vesicular arbuscular mycorrhizal (VAM) inoculum. It does not produce root nodules. Flowering usually takes place during the rainy season, but in moist conditions flowers appear throughout the year.
Senna italica is found in grassland of the drier regions of tropical Africa, from sea-level up to 1850 m altitude. It is often found close to streams and in disturbed habitats such as roadsides and waste places.
Propagation and planting
Senna italica is easily propagated by seed. Seed treatment by soaking overnight or abrasion with sand improves germination. Sowing in pockets at 5 seeds per pocket at 75 cm distance within and between rows and thinning to 3 plants per pocket is recommended.
Husbandry practices for Senna italica aim at high leaf yields combined with a high sennoside content. Production of fruits is avoided as their sennoside content is low. Weeding is necessary once or twice in the early stage of the crop. Twenty days after sowing pruning of the main stem to 20 cm will promote the formation of branches. Application of mineral fertilizer was found to be uneconomical in Burkina Faso. Topdressing with farmyard manure after each harvest gave considerable increases in leaf and sennoside yield. In the second year a single weeding should be done early in the growing season. The economic life of the crop is 3 years at the most. The crop can be rejuvenated by natural regeneration.
Diseases and pests
Senna italica is a host of the root lesion nematode (Pratylenchus penetrans). In perennial cultivation serious attacks by termites have been observed.
Senna italica should be harvested early in the morning as the sennoside content drops in the course of the day. Harvesting by cutting branches is recommended for the first harvest, but leaves may also be stripped from the branches. Stripping the leaflets requires more labour than cutting, but this is outweighed by labour saving during processing. Cutting should be at a height of about 20 cm to allow for adequate regrowth. Cutting higher results in a lower leaf yield, but better regrowth and higher yields in consecutive harvests. The first harvest can be done in the year of establishment towards the end of the rainy season. In consecutive years 2–3 harvests per year can be realized.
The highest yields of Senna italica leaflets in Burkina Faso were obtained in the year after establishment with 1300 and 940 kg/ha for the first and second cut, respectively.
Handling after harvest
If whole branches of Senna italica are harvested they are dried as such when it is the first crop, so that the highest possible sennoside content is obtained. In consecutive crops leaflets are stripped before drying. Leaflets should be dried in the shade at temperatures of 20–40°C. When dry, they are packed in compressed bales of about 200 kg.
A few collections of Senna italica are held in gene banks in Israel, the United Kingdom and Namibia. As the species is widespread and common, there is no threat of genetic erosion. It would be worthwhile, however, collecting local selections whenever encountered.
Selection and breeding of Senna italica have not been attempted, but in view of the wide variation would be worthwhile if commercial production is envisaged.
Senna italica is not likely to regain its position in international trade, as this has been taken over by Senna alexandrina. However, for producing a mild laxative for domestic markets in semi-arid regions it does hold promise. The variation of Senna italica in medicinal uses, toxicity and contents of active compounds is not understood. Linking the variation to subspecies, growth stage and climatic and edaphic factors may help obtain a better understanding and a more rational use. Extreme caution is required when adopting medicinal uses of Senna italica from elsewhere.
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Sources of illustration
- Serrato Valenti, G., 1971. Adumbratio florae Aethiopicae 22. Caesalpiniaceae - gen. Cassia. Webbia 26(1): 1–99.
- J.M. Okeyo, TSBF-CIAT, World Agroforestry Centre (ICRAF), P.O. Box 30677, Gigiri, Nairobi, Kenya
- C.H. Bosch, PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands
Correct citation of this article
Okeyo, J.M. & Bosch, C.H., 2007. Senna italica Mill. In: Schmelzer, G.H. & Gurib-Fakim, A. (Editors). PROTA (Plant Resources of Tropical Africa / Ressources végétales de l’Afrique tropicale), Wageningen, Netherlands. Accessed 14 November 2018.
- See the Prota4U database.