Argyreia (PROSEA)
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Introduction |
Argyreia Lour.
- Protologue: Fl. cochinch.: 95, 134 (1790).
- Family: Convolvulaceae
- Chromosome number: x= 14, 15;A. nervosa: 2n= 30
Origin and geographic distribution
Argyreia comprises about 100 species, and occurs in tropical Asia and Madagascar (4 species). In the Malesian region, about 45 species have been found. Peninsular Malaysia, Sumatra and the Philippines are richest in species, with 13, 12 and 10, respectively. Most species are narrow endemics, but A. capitiformis (Poir.) v. Ooststroom (synonym: A. capitata (Vahl) Choisy) and A. mollis are widely distributed. A. nervosa is native to India, but widely planted in South-East Asia.
Uses
Argyreia is used occasionally in traditional medicine in South-East Asia; most commonly a decoction of the roots or leaves is applied externally to treat rheumatism, wounds, abscesses, boils and skin diseases. In India, A. nervosa is a well-known medicinal plant used for similar purposes, and also as tonic, diuretic and aphrodisiac. However, it is planted as an ornamental in South-East Asia and elsewhere in the tropics.
The leaves of A. capitiformis are used externally to treat trauma in China.
A decoction of the leaves of A. acuta Lour. is used in Vietnam as a diuretic, emmenagogue and antitussive, and is also applied to abscesses. A. acuta roots and stems are used against fever, cough, leucorrhoea and carbuncles. Dried aerial parts of A. populifolia Choisy are considered astringent and antiseptic in Sri Lanka.
Properties
The chemical compounds isolated from A. nervosa belong to the ergot (ergoline type) alkaloids, lipids, flavonoids, steroids and triterpenoids. Activities of several parts of A. nervosa plants in India include anti-ulcer, antitumour, antidiabetic, hypoglycaemic, hypotensive, spasmolytic, antifilarial, antimicrobial and central nervous system depressant activities. Ergoline alkaloids have hallucinogenic activity. Hexadecanyl p-hydroxycinnamate and scopoletin have been isolated from the roots; these compounds showed antifungal activity, and were highly active against Alternaria alternata . The main component of the oil from seeds of A. nervosa is oleic acid (about 27.5%). This oil showed moderate activity against several gram-positive and gram-negative bacteria and phytopathogenic fungi. The seeds also contain ergot alkaloid constituents, with ergine and isoergine in the highest concentration (up to 0.2%). The hypotensive activity of the seeds is due to this mixture of alkaloids, which also includes e.g. ergometrine. Biosynthetically, the ergot alkaloids are derived from the amino acid tryptophan, containing an indole residue. Aqueous and alcoholic extracts of A. nervosa leaves showed in-vitro antifilarial activity against Setaria cervi , a parasitic worm of cattle.
Several flavonoids have been isolated from the roots of A. mollis , as well as the tropane alkaloids calystegin B1 and B2, loline alkaloids and simple pyrrolidine alkaloids.
Botany
Lianas or shrubs with twining branches. Leaves arranged spirally, simple and entire, glabrous or hairy, petiolate; stipules absent. Inflorescence an axillary cyme, loose or compact, few- to many-flowered; bracts minute to large. Flowers bisexual, regular, 5-merous; sepals free, imbricate, often hairy outside, persistent; corolla campanulate, funnel-shaped or tubular, limb nearly entire to deeply lobed, usually with 5 hairy bands outside, purple, red, pink or white; stamens inserted on the corolla, included or exserted, with filiform filaments often dilated at base; ovary superior, 2- or 4-celled, style filiform, stigma biglobular. Fruit an ellipsoid to globose berry, fleshy, leathery or mealy, purple, red, orange or yellow, few-seeded. Seeds glabrous, with endosperm.
Argyreia belongs to the tribe Ipomoeeae , and differs from the largest genus in this tribe, Ipomoea , in the woody stems, the usually hairy corolla and the indehiscent fruit.
Ecology
Argyreia occurs most commonly in forest margins, secondary forest and brushwood at low to medium altitudes, up to 1500(-1700) m.
Management As an ornamental, A. nervosa is propagated by seed or softwood/greenwood cuttings. Special attention is given to training because rapid growth will lead to an impenetrable tangle if it becomes enmeshed in other plants.
Genetic resources
Most Argyreia species have small areas of distribution, and consequently may easily become endangered. Only few species are widely distributed, e.g. A. mollis , or widely planted, e.g. A. nervosa .
Prospects
Argyreia is comparatively little used in traditional medicine in South-East Asia. A. nervosa is a well-known medicinal plant in India, and research on its pharmacological properties has shown interesting results. Although it is only planted as an ornamental in the Malesian region, A. nervosa may have good prospects as a medicinal plant, similar to those of indigenous Argyreia species, which will probably have similar biological activities.
Literature
36, 247, 671, 887.
Selection of species
Authors
Trimurti H. Wardini
