Senna occidentalis (PROSEA)
Senna occidentalis (L.) Link
- Protologue: Handb. 2: 140 (1831).
- Family: Leguminosae
- Chromosome number: 2n= 28 (26)
- Cassia occidentalis L. (1753),
- C. foetida Persoon (1805),
- Ditremexa occidentalis (L.) Britton & Rose ex Britton & Wilson (1924).
- Negro coffee, coffee senna, stinking weed (En).
- Café nègre, casse-café, casse puante (Fr)
- Indonesia: menting (Javanese), kasingsat (Sundanese), kopi andelan (Sumatra)
- Malaysia: kachang kota, ketepeng hutan
- Philippines: balatong-aso (Tagalog), andadasi (Ilokano), duda (Bisaya)
- Cambodia: sânndaèk khmaôch
- Laos: kh'ét, lang kh'ét
- Thailand: khilek-thet (northern), khilek-pi (central), chumhet-thet (peninsular)
- Vietnam: vọng giang nam, muồng cốt khí.
Origin and geographic distribution
The origin of S. occidentalis is unknown; tropical South America and the Old World tropics are thought to be possible candidates. Now it is a common weed throughout the tropics and subtropics. In South-East Asia it occurs everywhere, so if it has been introduced this must have happened in ancient times. In Indonesia it is sometimes also cultivated.
Roasted seed of S. occidentalis is used as a substitute for coffee (sometimes also for tea), pure or in a mixture with true coffee. In Indonesia young leaves and fruits are eaten steamed as a vegetable; the young fruits are also said to be consumed raw as a side-dish with rice. Non-woody plant parts are used as green manure and the plant has some ornamental value. It is not eaten by animals and the seed is deadly poisonous when eaten in quantity. In traditional medicine S. occidentalis is considered a panacea, especially in Africa its medicinal applications are numerous. All plant parts are said to have tonic, diuretic, stomachic and febrifuge properties and are especially used for dropsy, rheumatism, fevers and venereal diseases. An ointment prepared from S. occidentalis is also used to treat all kinds of skin diseases (e.g. ringworm, eczema). Although the seed is considered to contain the most effective ingredients, the roots are especially used as an anthelmintic and against malaria and haematuria. An infusion of the bark is applied as a remedy for diabetes. The leaves are used as a purgative and antiherpetic, and a poultice is administered against toothache in Indonesia and against headache in Malaysia.
Production and international trade
In the past there has been some international trade in seed and medicinal products of S. occidentalis , e.g. between Africa and Europe. At present the only trade is local and there are no statistics.
It is remarkable that the use of roasted seed of S. occidentalis as a coffee substitute has been established independently in America, Africa and Asia, even though the infusion does not contain caffeine. Fresh seed is poisonous but the toxicity seems to disappear after heating. The chemistry of S. occidentalis is badly known. Fresh seed is said to contain tannins, a toxalbumin, the alkaloid N-methyl-morpholine, chrysophanol (chrysophanic acid), chrysarobine, emodin, rhein, physcion and more anthroquinone derivatives, a fixed oil and a volatile oil. Several of those constituents are also present in the leaves and the roots. The cathartic and diuretic action of plant parts is explained by chrysophanol and chrysarobine, which are irritant to mucous membranes. Chrysarobine and the toxalbumin cause kidney and liver damage in livestock. The essential oil has shown antibacterial activity.
- Erect, annual or perennial, malodorous, subglabrous herb, up to 2.5 m tall, with black roots. Stem obtusely angled or sulcate, often richly branched.
- Leaves arranged spirally, pinnately compound; stipules triangular to long lanceolate, more or less falcate, 3-13 cm × 1.5-5 cm, early caducous; petiole 2.5-5.5 cm long, grooved, bearing a large, sessile, subovoid, reddish gland at base just above the pulvinus; rachis 4-14 cm long, with 3-6 pairs of leaflets, size of leaflets increasing from base to apex of rachis; petiolule 2-4 mm long; leaflet ovate to ovate-oblong, 2.5-17 cm × 1-4 cm, more or less unequal-sided, base rounded, margin entire, apex acuminate, lower surface pruinose to finely puberulous.
- Inflorescence racemose, axillary or terminal, 2-4-flowered; peduncle 1-7 mm long; bracts lanceolate, 5-18 mm × 1-4.5 mm, caducous.
- Pedicel 0.5-2 cm long; sepals 5, unequal, white, outer ones orbicular, 5-7.5 mm in diameter, inner ones ovate, 6.5-10 mm long; petals 5, obcordate (ventral one), obovate (2 lateral ones) or oblanceolate (2 dorsal ones), longest one 12-17 mm long, bearing a short claw, yellow with violet veins, 2 outer ones largest; stamens 10, unequal in size, 2 long ones with filaments 5-7 mm and anthers 4-7 mm long, 4 with filaments 2-3 mm and anthers 3-5 mm long, 4 staminodes with filaments 3-4 mm long and very small anthers; pistil with tomentose ovary, glabrous style (3-5 mm long) and small lateral stigma.
- Fruit a flattened-cylindrical legume, 8-13 cm × 0.7-1 cm, straight or slightly incurved, brown with pale margins, subglabrous, 30-45-seeded.
- Seed flattened-orbicular, 3-5 mm in diameter, olive-brown, with an elliptical areole on either side.
Growth and development
In temperate or seasonal climates S. occidentalis is an annual and dies with the onset of the cold or the dry period. Under warm, humid conditions, it can become a much branched, subwoody shrub, living 2-3 years. Under favourable conditions it flowers throughout the year; in temperate climates it flowers in midsummer and autumn.
Other botanical information
In older literature S. occidentalis is best known as Cassia occidentalis. Until the beginning of the 1980s, Cassia L. was considered to be a genus with over 500 species. The large genus Cassia L. emend. Gaertner has since been subdivided into 3 genera: Cassia (trees, some filaments curved, bracteoles present, no areoles on seed), Senna Miller (herbs, shrubs or trees, all filaments straight, bracteoles present, areoles on seed) and Chamaecrista Moench (herbs or shrubs, all filaments straight, bracteoles present, no areoles on seed). Cassia now has about 30 species, Senna and Chamaecrista comprise about equal numbers of species.
S. occidentalis is sometimes easily confused with the also widespread S. obtusifolia (L.) Irwin & Barneby. The basal petiolar gland, the usually ovate leaflets and the shorter wider pod are distinctive for S. occidentalis.
S. occidentalis mainly occurs below 500 m, with 1750 m as its altitudinal limit. It grows as a weed in disturbed forest areas, on waste land, fields, roadsides and around villages and farms. It is especially abundant in ditches and seasonally wet depressions. Although it is resistant to dry conditions it grows best in a moist environment.
S. occidentalis is predominantly a weed, so it is hardly cultivated. Propagation by seed is very easy. When needed, desired plant parts are collected from wild plants. Seeds are dried in the sun, roasted and pounded before being used as a coffee substitute.
Genetic resources and breeding
There are no known germplasm collections and breeding programmes for S. occidentalis . Despite its wide geographical distribution, the plants seem to be rather genetically uniform.
S. occidentalis will continue to be used locally as a stimulant and in other ways. Most promising perhaps are its attributed medicinal properties, but more research is needed, e.g. on possible adverse side-effects.
- Burkill, H.M., 1995. The useful plants of West tropical Africa. Edition 2. Vol. 3. Families J-L. Royal Botanic Gardens, Kew, United Kingdom. pp. 160-163.
- Duke, J.A., 1981. Handbook of legumes of world economic importance. Plenum Press, New York, United States. pp. 47-48.
- Irwin, H.S. & Barneby, R.C., 1982. The American Cassiinae. A synoptical revision of Leguminosae tribe Cassiae subtribe Cassiinae in the New World. Memoirs of the New York Botanical Garden 35. pp. 436-440.
- Larsen, K. & Ding Hou, 1996. Caesalpiniaceae. Senna. In: Kalkman, C., Kirkup, D.W., Nooteboom, H.P., Stevens, P.F. & de Wilde, W.J.J.O. (Editors): Flora Malesiana. Series 1, Vol. 12(2). Rijksherbarium/Hortus Botanicus, Leiden University, the Netherlands. pp. 681-683.
- Larsen, K., Larsen, S.S. & Vidal, J.E., 1980. Légumineuses-Caesalpinioïdées [Leguminosae-Caesalpinioideae]. In: Vidal, J.E. & Vidal, Y. (Editors): Flore du Cambodge, du Laos et du Vietnam [Flora of Cambodia, Laos and Vietnam]. Vol. 18. Muséum National d'Histoire Naturelle, Laboratoire de Phanérogamie, Paris, France. pp. 93-95.
- Nguyen Van Duong, 1993. Medicinal plants of Vietnam, Cambodia and Laos. Mekong Printing, Santa Ana, California, United States. pp. 94-95.
- Quisumbing, E., 1978. Medicinal plants of the Philippines. Katha Publishing, Quezon City, the Philippines. pp. 382-384.