Dioclea hexandra (PROSEA)
Introduction |
Dioclea hexandra (Ralph) Mabb.
- Protologue: Taxon 29: 605 (1980).
- Family: Leguminosae
- Chromosome number: 2n= 22
Synonyms
- Dioclea reflexa Hook.f. (1849),
- Dioclea javanica Benth. (1852).
Vernacular names
- Marbles vine (En)
- Malaysia: kacang laut, pinang kesa, kacang pinggang.
Origin and geographic distribution
D. hexandra has an extremely wide area of distribution: West and Central Africa, tropical America, throughout tropical Asia, and tropical Australia.
Uses
In Peninsular Malaysia the root of a papilionaceous liana, probably D. hexandra, is boiled and the decoction drunk for pain in the region of the heart. In West and Central Africa the powdered seed is used as an external application for itch and rheumatism; it is also included in prescriptions to be taken orally to treat cough and asthma. The seed, alone or together with Aframomum seeds, is taken as a tonic and stimulant, and in Nigeria it is used against splenitis and applied externally to kill head lice. Locally, the seeds, either roasted or boiled, are used as a thickener for soup. In Africa the seeds are widely used in games (e.g. as marbles), as ornaments (e.g. in necklaces) and as a good-luck charm.
Properties
Research on Dioclea has focused on neotropical species, in particular on their lectins, which, for example, induce histamine release (interacting with sugars in the antibodies bound to the mast cells), and their flavonoids, such as dioclein, which showed analgesic and vasorelaxant effects.
A root extract of D. hexandra (at 100 ppm) resulted in 70% mortality in the freshwater snail Bulinus globulus. Roots contain considerable amounts of rotenone. The seeds contain toxic substances such as phytic acid (320 mg/100 g), tannin (150 mg/100 g) and hydrogen cyanide (2 mg/100 g). Heating apparently reduces the toxic effects for human consumption.
Botany
- A large liana up to 30 m long; young stems covered with spreading, brown, short and long hairs, later glabrescent, ridged and lenticellate.
- Leaves alternate, 3-foliolate; petiole up to 15 cm long; stipules 8-12 mm long; leaflets oblong to oblong-elliptical, 6.5-15 cm × 4-12 cm, base rounded to slighly subcordate, apex acuminate, variably hairy on both surfaces.
- Inflorescence an axillary pseudoraceme, rachis 10-30 cm long, peduncle 15-55 cm long; bracts 4-16(-20) cm long, patent, early caducous.
- Flowers bisexual, pedicellate; calyx campanulate, 1-1.5 cm long, 5-toothed with 2 upper teeth connate, pubescent; corolla papilionaceous, 1.5-2.5 cm long, purple-blue, standard rounded or ovate, with basal auricles, wings about as long as keel, keel incurved, obtuse or beaked; fertile stamens 6, sterile ones 4, 9 connate and 1 free; ovary superior, subsessile, 1-celled, style incurved.
- Fruit a linear-oblong to semi-orbicular pod, compressed or turgid, 6.5-12(-16) cm × 2-6.5 cm, indehiscent,1-5-seeded.
- Seeds rounded, compressed, 2.7-3.5 cm × 2.4 cm, with very large hilum encircling c. 3/4 of the seed.
D. hexandra can be found flowering and fruiting throughout the year. Dioclea is primarily a neotropical genus comprising some 50 species, with 3 species indigenous in South-East Asia. D. hexandra is a very variable species, formerly proposed to be divided, but no combination of characters can be found to justify a division at any level in South-East Asia.
Ecology
D. hexandra is often encountered in forest margins, often not far from water, but also in open forest and brushwood, from sea-level up to 450(-1100) m altitude. The seed has considerable buoyancy and can be dispersed by sea currents.
Genetic resources
In view of its wide distribution and presence in secondary habitats, D. hexandra does not appear to be threatened by genetic erosion. The genetic diversity is probably considerable, considering its extremely wide distribution and variability.
Prospects
Future research on the pharmacological activities of Dioclea in South-East Asia seems justified, given the wide application in traditional medicine in Africa and the interesting compounds and activities found in tropical American species. The future use of the roots of D. hexandra in South-East Asia for their rotenone content is not expected to be important.
Literature
62, 120, 121, 965.
Other selected sources
7, 25, 75, 244, 935.
Main genus page
Authors
L.J.G. van der Maesen