Butea (PROSEA)

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Plant Resources of South-East Asia
Introduction
List of species


Butea Roxb. ex Willd.


Protologue: Sp. pl. 3(2): 917 (1802).
Family: Leguminosae
Chromosome number: x= 9;B. monosperma: 2n= 18, 22, 32,B. superba: 2n= 18

Origin and geographic distribution

Butea comprises 2 species and its natural distribution is confined to the drier parts of India and mainland South-East Asia, with the exception of the presence of B. monosperma in Java. The latter species is planted throughout South-East Asia and certain parts of Africa.

Uses

B. monosperma is widely used in Indian and continental South-East Asian folk medicine. The astringent bark exudate is used internally to treat diarrhoea, and is applied externally to boils, sores, ulcers and adenitis. The root bark and seeds are credited with anthelmintic activity, and the seeds, leaves and flowers with antimicrobial activity. Several of the traditional uses are supported by modern research. B. monosperma is well known as a dye and tannin-producing plant. The bark of B. superba is used as a remedy for snakebites and insect stings, and a decoction of stem and leaves is applied to haemorrhoids and is considered sedative. B. superba has recently attracted attention as a possible herbal substitute for Viagra, which is at present the best known oral agent for the treatment of erectile dysfunction. In Thailand over-the-counter preparations have been illegally developed from B. superba both as gel as well as pills.

Properties

Aqueous extracts of B. monosperma roots and leaves showed ocular antiinflammatory activity in rabbits. The petroleum ether extract of flowers of B. monosperma exhibited anticonvulsant activity in mice and rats, and additionally antagonized the behavioural effects of amphetamine and potentiated the pentobarbitalinduced sleep. It was also found to be anxiogenic and a depressant of the central nervous system. A methanol extract of the seeds showed significant in-vitro anthelmintic activity.

An ethanol concentrate of B. monosperma petals exhibited anti-oestrogenic activity in rats, and a flower decoction showed anti-implantation activity. The anti-implantation activity is, at least partly, due to the presence of the flavanone butin. The petroleum and ethyl acetate extracts of B. monosperma stem bark displayed antifungal activity against Cladosporium cladosporioides . The active constituent was identified as (-)medicarpin (an isoflavonoid/pterocarpan). Seed extracts of B. monosperma showed anthelmintic and antispermatogenic activities.

A flavonol glycoside isolated from the stems of B. superba showed antimicrobial activity against numerous plant pathogenic fungi and grampositive as well as gramnegative bacteria. An orally administered seed extract of B. superba showed moderate to strong antispermatogenic effect in mice and rats.

Drugs developed for erectile dysfunction are able to substitute, partially or completely, the malfunctioning endogenous mechanisms that control penile erection. Sildenafil citrate (Viagra) acts as an inhibitor of phosphodiesterase type 5 (PDE-5). This enzyme interferes with the production of cyclic guanosine monophosphate (c-GMP) that is aimed at relaxing the smooth muscles in the corpus cavernosum, thereby increasing the blood flow to the penis. The activity of B. superba is claimed to work according to the same mechanism.

Botany

Lianas, scandent shrubs or trees, with tomentose young branches. Leaves alternate, 3-foliolate; stipules small, linear or subulate, pubescent, caducous; lateral leaflets obliquely ovate, with obtuse to rounded apex, terminal leaflet symmetric, rhomboid-obovate, with obtuse to emarginate apex; stipels present. Inflorescence an axillary or terminal densely fasciculate pseudo-raceme or panicle, bracteolate. Flowers bisexual, pedicellate; calyx broadly campanulate, with 4 short lobes, velvety, olive-green, persistent; petals papilionaceous, densely pubescent outside, brightly coloured, orangered, more rarely yellow or white, standard ovate, auricled at base, acute at apex, strongly reflexed at anthesis, wings equal to or slightly longer than standard, falcate, keel slightly longer than standard and wings, falcate; stamens enclosed within the keel, 9 connate and 1 free; ovary superior, stipitate, woolly, 1-celled, with curved style. Fruit an oblong or broadly linear pod, distinctly stipitate, pendulous, in the lower part flat, with a single seed near the apex. Seed ellipsoid, flattened, c. 3 cm long.

At the beginning of the rainy season B. monosperma is leafless and flowers abundantly. Birds are the chief pollinators. At the end of the flowering period, new leaves develop; these are initially pale bronzetinged green.

Butea is usually classified in the tribe Phaseoleae and seems to be related to Meizotropis and Spatholobus .

Confusion exists with respect to the Thai drug “kwaao khruea”“, reputed for its rejuvenating properties. Contradictory reports on chemical constituents (especially phytoestrogens) of plant material collected under this name can be attributed to a mix-up between B. superba and Pueraria mirifica Airy Shaw & Suvat. The resemblance of the leaves of these species is striking, but they are very different with respect to constituents and activity. Whereas pharmacological interest in P. mirifica focuses on its isoflavones and miroestrol content, B. superba receives special attention for its high levels of flavonoids and flavonoid glycosides. Information with respect to the efficacy of a special selection of B. superba refers to its tuberous root as source of the active principle. However, botanical literature claims that B. superba does not have a tuberous root, whereas Pueraria mirifica does.

Ecology

Butea grows gregariously in open grasslands and scattered in mixed forest, in relatively dry areas up to 1500 m altitude.

Management B. monosperma is propagated by seed. Before the beginning of the rainy season, complete pods are sown in rows 3-6 m apart. The pod opens at the tip and allows the young shoot and root to emerge. The cotyledons remain attached to the seedling for a considerable time. Seedlings thrive best on a rich loamy soil with a neutral pH. Root suckers are freely produced and enable vegetative propagation and easy tree recovery after damage.

Genetic resources

B. monosperma is widely planted and does not seem to be at risk of genetic erosion. Populations of B. superba are locally threatened by over-collecting, especially in Thailand. Plantations of the latter have been established, with a high-yielding selection, that is marketed as a cultivar (Wichai 101), serving as a guarantee of quality.

Prospects

Butea shows several interesting pharmacological properties, including antimicrobial, anthelmintic, anti-inflammatory, anticonvulsant and antifertility activities. These deserve more research, possibly leading to a more adequate usage as a medicinal plant. The basis for the claimed activities of B. superba for the treatment of erectile dysfunction is still unclear. This warrants scientific publications in which the botanical identity of the plant material tested should be indisputably clarified.

Literature

181, 490, 523, 731, 815.

Selection of species

Authors

Raharni