Castanospermum australe

Castanospermum australe

Black bean (Castanospermum australe A.Cunn. ex Mudie 1829) is a tree species belonging to the Fabaceae family.

Systematics –
Domain Eukaryota,
Kingdom Plantae,
Division Magnoliophyta,
Class Magnoliopsida,
Order Fabales,
Family Fabaceae,
Subfamily Faboideae,
Tribe Sophoreae,
Genus Castanospermum,
Species C. australe.
The terms are synonymous:
– Castanospermum australe A. Cunn. & C. Fraser, (1830);
– Castanospermum australe A. Cunn. & C. Fraser ex Hook.;
– Castanospermum australe var. australe Hook.;
– Castanospermum australe var. brevivexillum F.M.Bailey;
– Castanospermum brevivexillum Domin;
– Castanospermum cunninghamii J.M.Wood.

Etymology –
The term Castanospermum comes from the Latin “Castanea”, chestnut and from the Greek “σπέρμα”, sperm, for the seeds that resemble chestnuts in shape and color.
The specific epithet australe comes from the Latin australis, auster, austro name of the wind coming from the southern hemisphere, as the species was discovered in Australia.

Geographic Distribution and Habitat –
Castanospermum australe is a plant native to the coastal rainforests and beaches of Australia, from New South Wales to the Iron Range, from the Cape York Peninsula, on the coast of Queensland, up to 150 km west of the Bunya Mountains.
The plant is also present in the Pacific islands of Vanuatu, New Caledonia and the island of New Britain (Papua New Guinea); It has also been spread by humans in India, Africa and other tropical and subtropical areas of the world, mainly as an ornamental plant.
However, anthropological studies have shown that the distribution area of ​​the species has been greatly influenced by prehistoric populations who, between 40,000 and 65,000 years ago, began to colonize Australia.
This was possible during the Pleistocene glaciations because the Torres Strait had emerged from the sea. The sea returned to occupy the strait between 12,000 and 8,000 years ago and Australia remained isolated for a long time, even though the Australian Aborigines traded with the inhabitants of the islands of the strait.
Its natural habitat is that of humid, fertile and well-drained soils, on terraces, on the side of mountains in the rainforest or along the banks of rivers and streams from sea level up to 800 m above sea level.

Description –
Castanospermum australe is an evergreen tree, with a very dense crown of abundant, dark green and glossy foliage that grows up to 40 m and with a trunk diameter of up to 1.2 m; its roots live in symbiosis with some soil bacteria that form nodules inside which atmospheric nitrogen is fixed to be used, in part, by the growing plant.
The trunk is characterized by a very dark grayish bark, slightly rough and supports a very dense crown for the abundant dark green and glossy foliage. The branches have numerous and showy lenticels that ensure gas exchanges between the internal tissues of the plant and the external environment.
The leaves are arranged alternately; they are compound, odd-pinnate, 20-35 cm long, with 8-17 leaflets, with entire margins, supported by petioles 0.4-0.7 cm long. The leaf blades are elliptical, sometimes oval in shape, about 8-17 x 3-6 cm, often unequal at the base, glossy green on the upper surface.
The leaves and twigs are poisonous and if crushed they smell of cucumber or courgette.
In nature on the branches and trunk, in the months of October-November, large inflorescences appear, up to 15 cm long, on thin pedicels of about 2.5 cm. The flowers are 4-5 cm large, very attractive and have the characteristic papilionaceous shape. The calyx is yellowish, bell-shaped, with 5 lobes at the apex, weakly covered with brown hair. The corolla is formed by leathery petals, yellow that turn reddish to intense orange when fully bloomed. The upper petal (flag) is lobed at the apex and measures 3-4 x 3 cm. The stamens are yellow, usually ten in number, all free, curved, about 0.4 x 0.15 cm. The ovary, on a peduncle about 1.5-2 cm long, carries 3-4 ovules. The style is 1-2 cm long, glabrous with a terminal stigma.
The flowers are rich in pollen and nectar and in nature they are pollinated by lorikeets such as Trichoglossus haematodus (Linnaeus, 1771), by butterflies and sometimes also by the “spectacled flying fox” bat (Pteropus conspicillatus Gould, 1850) which is fond of nectar. The nectar is abundant and sometimes parrots, very greedy, can become poisoned.
The fruits are large and woody, they are cylindrical pods, 15-25 x 4-5 cm.
Inside there are 3-5 round or compressed seeds, 3-5 cm in size, brown in color that form from March to May. They are often present in abundance on the ground under large trees. The pods are floating and exposure to salt water does not hinder the germination of the seeds.

Cultivation –
Castanospermum australe is a tree whose seeds are a traditional staple food of the Australian Aborigines and are also collected in the wild by other people. The tree is most attractive when in bloom with sprays of red-orange flowers and also when bearing its large, cylindrical, bean-like, pendant fruits.
For this reason it is therefore often planted as an ornamental in warm temperate and tropical areas.
In cultivation the plant develops a rounded, dense crown reaching a height of 8-20 m with a spread of 4-8 m. It is, therefore, an ideal shade tree in driveways, parks and gardens. Its extensive root system and preference for moist soils, makes it a useful tree for stabilising the banks of watercourses, however, due to its extensive root system, it should not be planted within 10 metres of pipes, sewers, house foundations, garages or swimming pools.
Castanospermum australe is a tree of humid tropical and subtropical climates and lowlands, it grows best at an altitude of between 50 and 750 meters and in areas where annual daytime temperatures are between 20 and 32 °C, but can tolerate temperatures between 10 and 41 °C.
It prefers an average annual rainfall of between 1,600 and 3,200 mm, but tolerates 1,000 and 3,800 mm.
From a pedological point of view it requires a high quality soil very well drained but moist and a very sunny position when grown in areas cooler than its natural climate; it also prefers a pH between 5 and 6, tolerating 4.5 and 6.5.
It is also a widely available indoor plant in florists and nurseries. It tolerates low and filtered light up to full sun if adapted gradually.
Among the adversities we point out the possible attacks of scale insects and psyllids. To avoid problems of this type, it is best to use a broad-spectrum pesticide during the winter.
Avoid excessive irrigation because it can cause root rot due to the development of fungi.
The flowers, which are produced on old wood, are rich in nectar and are pollinated by parrots in nature. The plant has a symbiotic relationship with some soil bacteria, these bacteria form nodules on the roots and fix atmospheric nitrogen. Part of this nitrogen is used by the growing plant, but part can also be used by other plants growing nearby.
The propagation of this species is done from fresh seed and germination requires a temperature of 18-25 °C.
Sowing is done in individual pots using a mixture of three parts of river sand and one part of perlite.
After the formation of the first pairs of leaves, it is necessary to transplant into a bed of well-loosened and moist soil, with a slightly acidic pH.
It is advisable to mulch around the base of the plant and water regularly.

Uses and Traditions –
Castanospermum australe is the only species of the genus Castanospermum and the tribe Sophoreae. This species was discovered in Australia in Cooktown (North Queensland) in 1770 by botanists Daniel Solander (1733-1782) and Joseph Banks (1743-1820).
The plant has some common names including: black bean, Moreton Bay chestnut, bean tree.
The Aborigines, in their diet, made extensive use of the seeds of C. australe and often stored them underground for several months and, most likely, by doing so, were responsible for the spread of the species beyond its original range. This explains the current presence of this species in the northern part of New South Wales.
However, since the seeds are poisonous and can cause serious gastrointestinal disorders, the Aborigines used them only after a particular treatment. In fact, they were sliced ​​and washed in running water for several days, about ten, then toasted and crushed to obtain flour. In addition to its importance as a food, the black bean tree was, for those people, a seasonal collection point and this served as a catalyst for ceremonies. Furthermore, they used the bark to create traps for fish and animals and the empty pods were used by children as toy boats.
This plant, due to the color of its showy inflorescences and the shade of its foliage, is a species widely used as an ornamental plant throughout the world.
As a potted plant, C. australe is a widespread species in Europe and the Americas, but its roots must be limited in a container to prevent it from growing too tall.
The toxicity of the plant and its seeds derives from the polyhydroxy alkaloid “castanospermine”, discovered in 1981. In fact, poisonings of animals, especially horses, and sometimes even humans, are known.
The alkaloid, however, has medicinal properties because it is an inhibitor of acid alpha-glucosidase, which can be used to combat “Pompe disease”, a rare neuromuscular disorder characterized by a defect in glycogen metabolism that accumulates in tissues, damaging them and causing a slow and progressive weakening of the muscles.
Castanospermine has also been shown to have antiparasitic activity, preventing the adhesion of Plasmodium falciparum Welch, 1897 (a unicellular protozoan parasite that causes malaria) to infected erythrocytes.
In addition, recent studies have shown that castanospermine has inhibitory activity of beta-glucosidase and is proving promising in the fight against cancer and acquired immunodeficiency syndrome (AIDS). Finally, C. australe is a natural resource of therapeutic drugs, alternatives or supplements to synthetic products, including for the treatment of analgesic and inflammatory diseases.
In addition, the seeds have a high content of toxic saponins, which are reportedly toxic to a serious stored grain parasite.
The tree produces wood of high commercial value because it has a walnut-like appearance, is soft, fine-grained and suitable for polishing.
The heartwood is dark brown or almost black; the sapwood varies from white to yellow. The grain is straight, although sometimes interlocked, the texture is slightly greasy. The wood is hard, heavy, durable, resistant to decay. It polishes well and has a high resistance to the passage of electric current. It is used in construction, cabinetry, carving, etc.
It is one of the most valuable woods in Australia, sliced ​​veneers can be a good substitute for teak. The wood has a density of 700 kg/m3 and can be used as a fuel.
Other uses include agroforestry; the large root system is used to protect river banks and harvest areas in Australia.

How to Prepare –
Castanospermum australe is a plant with many uses; from food and medicinal to ornamental, forestry and wood.
The seeds are eaten cooked as the raw fresh seed contains high levels of saponins and can be toxic. The cooked seed tastes like a sweet chestnut.
The Australian Aborigines would finely chop the seeds and soak them in running water for 10 days before toasting and grinding them into a powder. This powder could be stored for later use.
Medicinally, the seeds produce a polyhydroxy alkaloid called castanospermine, which is being studied as an HIV inhibitor and may be useful in the treatment of AIDS.
Parts of the tree contain chemicals that, when carefully extracted, have been shown to have anti-tumor, anti-inflammatory and anti-HIV properties.
The pods are astringent and are used to treat postprandial hyperglycemia in diabetic patients.

Guido Bissanti

Sources
– Acta Plantarum – Flora of the Italian Regions.
– Wikipedia, the free encyclopedia.
– GBIF, the Global Biodiversity Information Facility.
– Useful Tropical Plants Database.
– Conti F., Abbate G., Alessandrini A., Blasi C. (eds.), 2005. An annotated checklist of the Italian vascular flora, Palombi Editore.
– Pignatti S., 1982. Flora d’Italia, Edagricole, Bologna.
– Treben M., 2000. Health from the Pharmacy of the Lord, Advice and experiences with medicinal herbs, Ennsthaler Editore.

Photo source:
– https://inaturalist-open-data.s3.amazonaws.com/photos/240763709/original.jpg

Warning: The pharmaceutical applications and alimurgic uses are indicated for informational purposes only, they do not represent in any way a medical prescription; therefore, any responsibility for their use for curative, aesthetic or nutritional purposes is declined.