Entada (PROSEA)

Plant Resources of South-East Asia Introduction

List of species

Entada Adanson

Protologue: Fam. pl. 2: 318 (1763).

Family: Leguminosae

Chromosome number: x= 14; E. phaseoloides: 2n= 28

Major species

• Entada rheedii Spreng.,
• E. phaseoloides (L.) Merr.

Origin and geographic distribution

Entada has a pantropical distribution and comprises about 30 species; species diversity is highest in Africa. In Malesia, 5 species are indigenous and an additional 2 species are confined to Indo-China.

Uses

Entada is one of the chief sources of traditional hair wash throughout South-East Asia. Contact with the eyes should be avoided as it is rather painful and irritating. The juice of the bark proper may cause conjunctivitis. However, its cleansing properties mean that it is applied as a remedial wash for pityriasis, wounds and itch. In Fiji, likewise, chewed or pounded leaves are externally applied as a remedy for filariasis or elephantiasis. In the Philippines, both stem pieces and seeds of E. rheedii and E. phaseoloides are used as a fish poison. The macerated seeds are used for poulticing abdominal complaints such as colic in children. In India, a paste of pounded E. rheedii seeds is externally applied to relieve inflammatory glandular swellings in the armpits, pains in the loins and joints, and swollen hands and feet. The seed kernels, in small doses, are taken in various ways and mixtures for abdominal complaints, apparently for their emetic and purging properties. In Peninsular Malaysia little distinction is made between E. spiralis Ridley and E. rheedii, although the pods and leaflets are very different. In the Philippines, the stems of E. parvifolia Merr. are also occasionally used as a substitute for soap. Young leaves of Entada are eaten, raw or cooked. The seed kernels can be consumed after careful preparation to get rid of the toxic principles. The long vine is sometimes harvested to obtain drinking water, the bark fibres are used as rope and raw material for basketry.

Properties

The medicinal use of Entada is largely due to the presence of saponins in the bark, wood and seeds. The seeds of E. phaseoloides contain 2 sulphur-containing amides, entadamide A and entadamide B. Furthermore, entadamide C has been isolated from the leaves of E. phaseoloides together with entadamide A. Its stereostructure has been established as (R)-(+)-trans-N-(2-hydroxyethyl)-3-methylsulphinylpropenamide, thus being the sulphoxide form of entadamide A. Both entadamide A and B inhibit 5-lipoxygenase activity of RBL-1 cells at 10^-4 g/ml in vitro. Trans-N-(2-hydroxyethyl)-3-methylthiopropenamide has been isolated and patented as an anti-asthma medicine.

Other components isolated from E. phaseoloides displaying pharmacological activity include 2-hydroxy-5-butoxyphenylacetic acid and 2,5-dihydroxyphenylacetic acid methyl ester, which are cytotoxic to P-388 cells in vitro, and a crystalline saponin (empirical formulae C₄₅H₈₂O₂₇), which shows significant activity against Walker 256 carcinosarcoma in rats.

Bioassay-guided fractionation of a dichloromethane extract of E. abyssinica Steud. ex A. Rich. root bark, a plant used by traditional healers in Uganda for the treatment of sleeping sickness, led to the isolation of a diastereoisomer of the clerodane type diterpene kolavenol. It showed a trypanocidal activity with an IC₅₀value of 2.5 μg/ml against Trypanosoma brucei rhodesiense, the causative agent of the acute form of human African trypanosomiasis.

E. phaseoloides extracts possess strong molluscicidal activity, but are also toxic to fish, thereby limiting their potential for controlling transmission of fascioliasis. Water extracts of E. phaseoloides bark cause 100% mortality at 200 ppm after 24 hours in Pomacea snails, an activity similar to berries of Phytolacca dodecandra L’Hér. Analytical work also indicated that the active fraction contained at least 2 kinds of saponins. However, molluscicidal activity against Oncomelania quadrasi, the snail intermediate host of Schistosoma japonicum, was not realistic under field conditions as 40 g/m² would be needed for a satisfactory result.

E. phaseoloides seeds were found to be highly toxic in a series of feeding trials with rats. Since they had low levels of essentially non-toxic lectins it was suggested that the toxicity was due to other antinutritional factors.

Description

• Lianas or scandent shrubs (in Asia), unarmed, up to 150 m long.
• Leaves alternate, bipinnate, the terminal pinnae transformed into tendrils; petiole and rachis without extrafloral nectaries; stipules not spinescent, inconspicuous; leaflets opposite.
• Inflorescence a pedunculate, axillary or supra-axillary spike or spiciform raceme.
• Flowers 5-merous, uniform, male or bisexual; calyx connate, valvate; petals free or shortly united at base, valvate; stamens 10, free, anthers with a caducous gland at the top of the connective.
• Fruit a pod, often large (up to 1 m or more), chartaceous or mostly woody, straight, curved or spirally twisted, at maturity falling apart in one-seeded segments, the exocarp separating from the endocarp, the sutures remaining as an empty frame.
• Seed globular, flattened or irregularly compressed, with a hard testa without areole, wingless, aril absent, endosperm absent.
• Seedling with large cotyledons and curved radicle.

Growth and development

Trunks of E. rheedii and E. phaseoloides are twisted close to the ground, and the trunk base of the latter may reach a girth of 3 m. A growth of 9 m in 4 months has been recorded for E. spiralis in Peninsular Malaysia.

Other botanical information

Confusion surrounding species identity is considerable: in the botanical literature as well as in other disciplines the names E. scandens and E. phaseoloides have often been misapplied.

Ecology

Entada species, except E. parvifolia which is common in thickets, are frequently found in riverine vegetation, the segments of the pods being dispersed by water. E. phaseoloides and E. rheedii are dispersed by sea-currents and are found in habitats at the limits of tidal influence.

Propagation and planting

Natural germination of the hard Entada seeds may take a year or more. Seed treatment by removal of the hilum, including a portion of the testa, and germination in a wet jute sack, results in radicle emergence and seeds ready for potting within 15 days. Seedlings can be planted out in the field after 1 month. E. rheedii can be readily grown from cuttings.

Harvesting

The bark of Entada is cut from the lower part of the trunk, pods can be pulled down, or may simply be collected from the ground. Vines may be cut after 3 years, suckers will develop from the base.

Handling after harvest

When harvested for its application as a traditional hair wash, the stem is cut into short pieces, beaten, dried in the sun, and stored, ready to macerate as needed.

Genetic resources and breeding

Apart from occasional planting in botanical gardens, no material is present in genebanks or germplasm collections. In view of the wide geographical distribution of the medicinally important Entada species, the risk of genetic erosion appears rather limited.

Prospects

Saponins, diterpenes and entadamines from Entada species possess interesting properties as molluscicidal, trypanocidal, anti-asthma and anti-inflammatory compounds respectively. Research is needed to evaluate their future potential.

Literature

• Dai, J., Kardono, L.B.S., Tsauri, S., Padmawinata, K., Pezzuto, J.M. & Kinghorn, A.D., 1991. Phenylacetic acid derivatives and a thioamide glycoside from Entada phaseoloides. Phytochemistry 30(11): 3749-3752.
• Freiburghaus, F., Steck, A., Pfander, H. & Brun, R., 1998. Bioassay-guided isolation of a diastereoisomer of kolavenol from Entada abyssinica active on Trypanosoma brucei rhodesiense. Journal of Ethnopharmacology 61(3): 179-183.
• Ikegami, F., Sekine, T., Aburada, M., Fujii, Y., Komatsu, Y. & Murakoshi, I., 1989. Synthesis of entadamide A and entadamide B isolated from Entada phaseoloides and their inhibitory effects on 5 lipoxygenase. Chemical & Pharmaceutical Bulletin (Tokyo) 37(7): 1932-1933.
• Liu, W.H., Kugelman, M., Wilson, R.A. & Rao, K.V., 1972. A crystalline saponin with anti-tumour activity from Entada phaseoloides. Phytochemistry 11: 171-173.
• Morallo-Rejesus, B. & Punzalan, E.G., 1997. Molluscicidal action of some Philippine plants on golden snails, Pomacea spp. Philippine Entomologist 11(1): 65-79.
• Nielsen, I., 1981. Légumineuses-Mimosoïdées [Leguminosae-Mimosoideae]. In: Vidal, J.E. & Vidal, Y. (Editors): Flore du Cambodge, du Laos et du Viêtnam [Flora of Cambodia, Laos and Vietnam]. Vol. 19. Muséum National d'Histoire Naturelle, Paris, France. pp. 17-25.

Selection of species

• Entada phaseoloides
• Entada rheedii

Authors

• L.J.G. van der Maesen