Aganosma (PROSEA)

Plant Resources of South-East Asia Introduction

List of species

Aganosma (Blume) G. Don

Protologue: Gen. Syst. 4: 77 (1837).

Family: Apocynaceae

Chromosome number: x= unknown;A. dichotoma: 2n= 22

Aganosma comprises 8 species and is distributed from India and Sri Lanka, through Indo-China, southern China, Thailand and western Malesia to the Philippines and the Moluccas. Only 2 species occur naturally in Malesia, but a third one ( A. dichotoma ) is cultivated in gardens. 6 species have been found in Thailand, and 4 in Vietnam.

In India, A. dichotoma is credited with antiseptic, emetic and anthelmintic properties and is also used to treat bronchitis. The leaves are used against biliousness, and the flowers for treating eye troubles. In Malaysia, a decoction of A. marginata roots is commonly used internally to treat urinary troubles, as a tonic during fever, and as an emmenagogue. In Thailand, roots, stems, leaves, flowers and fruits of the latter species are applied against fever. In India, A. wallichii is said to be useful in diseases of the bile and blood. The latex of some species is occasionally used as rubber in Indo-China. The fibrous bark is sometimes used for binding purposes.

The leaves of A. marginata have a sweetish taste. Flavonoids such as rutin, robinin and other glycosides of kaempferol and quercetin have been isolated from Aganosma .

Lianas or scramblers, producing latex; stems often lenticellate. Leaves opposite, simple and entire, petiolate; stipules absent, but often with an interpetiolar ridge bearing glands. Inflorescence a terminal or sometimes axillary panicle. Flowers bisexual, 5-merous, actinomorphic, usually fragrant; sepals with free lobes; corolla gamopetalous, with narrowly cylindrical tube sometimes somewhat inflated below and spreading to erect lobes in bud overlapping to the right, white, sometimes yellowish; stamens inserted to a slightly widening part of the corolla tube, included, attached in a ring to the pistil head; disk of 5 fused, occasionally free lobes surrounding the ovary; ovary superior, consisting of 2 separate carpels united into a common style, pistil head ovoid with a short sharp projection on top. Fruit consisting of 2 linear or somewhat fusiform follicles, longitudinally dehiscent, many-seeded. Seeds narrowly elliptical, flattened, with numerous long hairs at apex.

The flowers are pollinated by insects such as bees and flies. Aganosma belongs to the subfamily Apocynoideae . A. caryophyllata G. Don is a synonym of A. wallichii , but the name A. caryophyllata has also often been used for A. dichotoma .

A. marginata occurs in many different habitats, but especially in drier evergreen and deciduous forest and in scrub vegetation, up to 850 m altitude. A. wallichii is found in evergreen forest up to 400 m altitude.

Management Aganosma is usually propagated by seed; stem cuttings can also be used.

A. marginata and A. wallichii have fairly large areas of distribution, but they seem to be rare in some regions, e.g. in Sumatra, Java and Borneo for the first species, and in Peninsular Malaysia and Sumatra for the second. A. dichotoma is almost only known from cultivation; only few collections seem to represent wild specimens, and these come from a small area in eastern India (near Puri, Orissa). Several other Aganosma species from Vietnam and Thailand, which are scattered in occurrence, seem vulnerable to genetic erosion.

Too little is known about properties and phytochemistry of Aganosma to be specific about its prospects. However, the widespread use of some species, e.g. A. marginata , in traditional medicine warrants modern research.

182, 331, 625.

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Tran Dinh Ly & Tran The Bach