Canthium (PROSEA Medicinal plants)
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Introduction |
Canthium Lamk
- Protologue: Encycl. Meth., Bot. 1: 602 (1785).
- Family: Rubiaceae
- Chromosome number: x= unknown
Origin and geographic distribution
Canthium in the broad sense is a large genus of over 200 species, which occurs in the African and Asian tropics. In Asia, Canthium sensu stricto is restricted to India, Sri Lanka, Burma (Myanmar), Indo-China, southern China, Thailand and western Malesia (east to Java, Borneo and the Philippines). Several dozen species are found in Malesia.
Uses
There are several records on the uses of C. horridum in traditional medicine in South-East Asia. Decoctions of several parts of the plant are used to treat wounds and fever, and after childbirth; the leaves are used to treat eye diseases; a decoction of the leaves and bark is used as an emmenagogue, and a decoction of bark and young twigs to treat dysentery. The fruit is edible and sometimes used to make confections. In Java the leaves are pounded in water to prepare a sweet jelly. C. horridum is sometimes planted in hedges. Two doubtful records on medicinal uses of C. aciculatum have been noted for Peninsular Malaysia.
In tropical Africa many species of Canthium and related genera are used in traditional medicine to treat a wide array of ailments, the most important being cough, diabetes and hypertension.
The wood of some Canthium species that grow to timber size is used locally in house and boat building, and for flooring and implements.
Properties
Biological screening of an ethanol-water (1:1) extract of C. coromandelicum in India showed analgesic, spasmolytic and hypotensive activities.
Botany
- Spiny or unarmed climbers or shrubs to small or medium-sized trees up to 25 m tall.
- Leaves opposite, simple and entire, short-stalked; stipules triangular.
- Inflorescence axillary, cymose or umbellate, stalked, or flowers solitary.
- Flowers usually bisexual, sometimes unisexual, 4-5(-6)-merous; calyx with triangular lobes; corolla with a short tube and valvate lobes; stamens inserted in the throat of the corolla tube; ovary inferior, 2(-3)-celled, style with globose to cylindrical stigma.
- Fruit a drupe, ovoid, obovoid to globose, often strongly 2-lobed and laterally compressed.
- Pyrenes 2(-3), plano-convex.
- Seedling with epigeal germination; cotyledons leafy, green.
Canthium belongs to the tribe Vanguerieae which is renowned for its very closely related genera with poorly defined limits. Many genera have been split off from Canthium in the broad sense, such as the South-East Asian genera Meyna, Perakanthus and Psydrax (the latter is also present in Africa, the Pacific and Australia). Many Psydrax specimens collected in Malesia have been named Canthium didymum Gaertner or Canthium diococcum (Gaertner) Merr. However, the true Psydrax diococca Gaertner (synonym: Canthium didymum Gaertner) occurs only in Sri Lanka and southern India. Research is needed to delimit sound genera for South-East Asia, a task that has already been accomplished for Africa. Only then will it be possible to decide whether the species treated here belong to Canthium sensu stricto or to one of the other genera.
C. horridum seems closely related to C. coromandelicum (Burm.f.) Alston (synonym: C. parviflorum Lamk) from India and Sri Lanka. However, the taxonomic relationships of the spiny small-leaved Canthium plants need further study.
Ecology
In general, Canthium occurs scattered in lowland forest or lower montane forest. C. horridum is mainly found in forest edges and brushwood, C. aciculatum on limestone rocks.
Genetic resources
As long as botanical knowledge of Canthium in South-East Asia is poor, it will remain difficult to establish the extent of genetic erosion for the different species. Although the exact areas of distribution are unclear, C. horridum seems widely spread and common, whereas C. aciculatum is a rare narrow endemic.
Prospects
Knowledge of Canthium and related genera is scarce. A taxonomic revision of the genera and species for South-East Asia, therefore, is required to interpret the literature and to serve as a basis for further research. The reported medicinal uses of C. horridum in different parts of South-East Asia warrant studies on the phytochemistry and pharmacological properties.
Literature
2, 114, 115, 121, 671, 760.
Selection of species
Authors
- Fitmawati
