Commelina (PROSEA Medicinal plants)

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Plant Resources of South-East Asia
Introduction
List of species


Commelina L.

Protologue: Sp. pl. 1: 40 (1753); Gen. pl. ed. 5: 25 (1754).
Family: Commelinaceae
Chromosome number:
x= (8, 9), 11, 14, 15, (21-28), (31-34);
C. benghalensis: 2n= 22, (28, 30, 44, 48, 56, 66, 68),
C. communis: 2n= (16), 22, (28, 32), 36 (40, 44, 46, 48, 50, 52, 84, 88), 90,
C. diffusa: 2n= (18), 20, 28, 30,(42, 45, 56, 58), 60, (72), 90

Major species

Commelina benghalensis L., C. communis L.

Vernacular names

  • Spiderwort, dayflower, widow‚Äôs tears (En). Indonesia, Malaysia: gewor, tali (also used for other Commelinaceae)
  • Thailand: phak plaap
  • Vietnam: th√†i l√†i.

Origin and geographic distribution

Commelina consists of about (50-)100-150 species from the tropical and warm regions of the world.

Uses

The aerial parts of Commelina are very mucilaginous, and are therefore generally used for poulticing wounds and skin infections such as boils and ulcers, and also as a maturative. Internally, the fresh juice from the plants is taken for diarrhoea. In Peninsular Malaysia, the Philippines and India, C. benghalensis is considered refrigerant and astringent, and is used for strangury. In China, Indo-China and Taiwan, C. communis is more commonly used for these purposes. In Vietnam, C. communis is applied externally for arthritis. In Indo-China, the sap of the crushed plant is also put on inflamed eyes, while in Africa the sap of C. benghalensis or C. diffusa is used for this purpose. In India and China, C. communis is also used to combat vertigo, fever and bilious disorders, and in Vietnam, India and China as an antidote for snake poisons. In Korea and China, C. communis is considered to have hypoglycaemic effects and is therefore applied in diabetes. In East Africa, the sap of C. benghalensis is applied for sore throat and burns, and also for thrush in children.

In Indonesia, the crushed leaves and stems of C. diffusa are taken in decoction for irregular menstruation, for abortion and to help expel the placenta after birth. In Thailand, C. benghalensis and C. diffusa are applied for abscesses and fever. In Vietnam, the plant is used for colds, a sore throat and nosebleed. In Nigeria and the West Indies, the leaves are taken as an aperient and a decoction is used in fever or for severe menstruation. In Jamaica, they are also taken in decoction to relieve urinary burning and leucorrhoea.

In Papua New Guinea, a cold water infusion of the crushed leaves of C. paleata Hassk. is taken for malaria and fevers.

In Indonesia and Indo-China, the young tops of C. benghalensis and C. diffusa are steamed and eaten as a vegetable, while in China and India, mainly C. communis is eaten. The leaves and starchy roots of C. benghalensis are considered a famine food in India and Africa. A blue dye is obtained from the sap of the flowers of C. benghalensis in China and India. In Japan, the blue dye from the flowers of C. communis var. hortensis Makino is used to produce blue "Awobana" paper. Commelina is considered a good fodder for cattle and poultry in Africa and India, also because it provides an important part of the daily water requirements. In humid climates, the fodder quality is thought to be rather poor.

Production and international trade

C. benghalensis , and sometimes C. diffusa , is widely sold in Chinese herbalist shops in South-East Asia.

Properties

The flowers of many Commelina containblue coloured anthocyanins, such as delphinidin-3-p-cumaroylglucosido-5-glucoside, stabilized by copigments, such as commelinin. The latter compound, which is also an anthocyanin, found for instance in C. communis , yields delphinin (= delphinidin-3,5-diglucoside), glucose and p-hydroxycinnamic acid upon hydrolysis. From the methanolic extract of C. communis , the pyrrolidine alkaloid 2,5-dihydroxymethyl-3,4-dihydroxypyrrolidine, and 4 piperidine alkaloids, i.e. 1-deoxymannojirimycin, 1-deoxynojirimycin,α-homonojirimycin and 7-O-β-D-glucopyranosyl-α-homonojirimycin were isolated. As a whole, the methanolic extract showed a potent inhibitory activity on the enzymeα-glucosidase. In a general phytochemical screen, the compounds n-triacontanol, p-hydroxycinnamic acid, daucosteril and D-mannitol were isolated from the aerial parts of C. communis . Pharmacological evaluation subsequently revealed p-hydroxycinnamic acid to have some antibacterial activity, and D-mannitol showed an antitussive effect. The hypoglycaemic effects of C. communis from Korea were tested in male Sprague-Dawley streptozotocin-induced diabetic rats, by feeding them a diet containing 10% of the aerial parts. Plasma cholesterol and blood sugar were estimated and urinary glucose monitored, and showed a decrease in blood sugar, while urinary glucose was negative in the 4th week, and plasma cholesterol did not change. In another test, benzene extracts of entire plants exhibited cytotoxic activity against Leuk HL 60 and Leuk L 1210.

The whole plant of C. benghalensis , including the flowers, yields hydrocyanic acid. The plant is known to cause contact allergy in dogs. An aqueous extract of the aerial parts of C. benghalensis showed allelopathic effects by reducing seedling vigour of soya beans and maize.

Description

Annual or perennial, procumbent and ascending herbs, stems fleshy, up to 1.5 m long, mat-forming, rooting at the nodes. Leaves spirally arranged, simple, veins parallel; petiole short; basal sheath closed. Inflorescence axillary or terminal, composed of a scorpioid cyme with 2 racemes (cincinni), upper raceme with male or sterile flowers, lower raceme bisexual, cincinni more or less enclosed by a funnel-shaped, folded, keeled bract (spathe), green. Flowers ephemerous, zygomorphic; sepals 3, free, unequal, the lower one hooded; petals 3, free, the upper 2 clawed, the lower reduced, white, yellow, pink, lilac or blue; fertile stamens 3, anterior, often dimorphic, anthers hastate, staminodes 2-–3, posterior, anthers X-shaped, all filaments glabrous; ovary superior, 3-loculed, ovules 1-2 per locule. Fruit normally a dry, dehiscent capsule, with few seeds. Seed with mealy endosperm, hilum linear. Seedling with epigeal germination; hypocotyl absent; cotyledon 1, sheath-like, glabrous, transparent; first leaf with closed sheath, parallel-veined, apex rounded.

Growth and development

Commelina is fast growing and starts flowering and fruiting early in the season. Many Commelina species are self-incompatible, but C. benghalensis is preferably autogamous.

Other botanical information

The large variation in chromosome numbers found in several Commelina species suggests that they are in the process of differentiation. Polyploids and aneuploids are often found in cultivation, e.g. C. communis f. albiflora has 2 n = 48 (4 x + 4) or 88 (8 x ), var. hortensis has 2 n = 46 (4 x + 2) and f. caeruleopurpurascens has 2 n = 44 (4 x ). There has been considerable confusion in older literature about the name C. nudiflora L. (synonym Aneilema nudiflorum (L.) Sweet) which is now a synonym of Murdannia nudiflora (L.) Brenan. It is a perennial herb, with long, linear leaves, and flowers in a long raceme without spathe. C. nudiflora in South-East Asian literature is often a wrongly applied name for C. diffusa Burm.f., a perennial herb with ovate-lanceolate leaves, and flowers in 2 short racemes in a spathe.

Ecology

Commelina occurs under moist, swampy and even waterlogged conditions, along irrigation ditches or roadsides, in gardens, in sunny or lightly shaded areas, and also as a weed in arable land. It is often perennial when the dry period is not too long, but becomes annual after an extended dry season.

Propagation and planting

Commelina is propagated by seed and stolons. The seeds are hydrochorous. One well-developed plant of C. benghalensis is able to produce up to 1600 seeds, but normally fewer are produced. Seeds were found to germinate readily between 25-30°C, but not at 10°C. Light did not influence germination, and flowering occurs regardless of photoperiod.

Diseases and pests

Commelina is a common host for several agriculturally important plant viruses, e.g. cucumber mosaic cucumovirus, U2-tobacco mosaic virus, and groundnut rosette virus, but also for specific viruses attacking Commelina, such as Commelina yellow mottle badnavirus and Commelina diffusa virus, both from C. diffusa. Commelina is also a host for the fungi Alternaria alternata and Pseudomonas solanacearum, which cause leaf spot diseases on important crops. C. benghalensis is furthermore a host for the taro planthopper (Tarophagus proserpina) and for the caterpillar of the moth Diacrisia obliqua. In China, C. communis is attacked by the monophagous insect Lema scutellaris, which could offer some perspective for biological control. Commelina is also a host for nematodes.

Several Commelina are troublesome weeds of annual and perennial crops as they resist desiccation, and are thus difficult to eradicate. C. benghalensis is a weed of 25 crops in about 30 countries, while C. diffusa has been recorded as a weed of 17 crops in about 25 countries. Many herbicides have been tried for the eradication of Commelina , and are best applied as pre- or early post-emergence herbicides. Photosynthesis-inhibiting herbicides are not effective. At later growth stages, removal by hand is often the only effective method of control.

Harvesting

Commelina is harvested from the wild, whenever needed.

Handling after harvest

Commelina is normally used fresh.

Genetic resources and breeding

The Commelina species treated here are widespread and common throughout South-East Asia, and therefore not endangered. There are no known breeding programmes of Commelina for medicinal purposes. Several Commelina are cultivated for ornamental purposes. Of C. benghalensis the cultivar "Variegata" has variegated creamy white leaves, and of C. communis the cultivar "Aureostriata" has striped creamy white leaves. In Japan, var. hortensis Makino "Awobana" is cultivated as an ornamental and for the production of a blue dye.

Prospects

The recorded anti-diabetic activities of some Commelina seem to justify more research, especially in the field of safe application. The plants might also be of interest as a local source of blue dye, which could have some application as colourants in foods.

Literature

  • Backer, C.A. & Bakhuizen van den Brink Jr, R.C., 1968. Flora of Java. Vol. 3. Noordhoff, Groningen, the Netherlands. pp. 20-22.
  • Faden, R.B., 1993. The misconstrued and rare species of Commelina (Commelinaceae) in the eastern United States. Annals of the Missouri Botanical Garden 80(1): 208-218.
  • Nguyen Van Duong, 1993. Medicinal plants of Vietnam, Cambodia and Laos. Mekong Printing, Santa Ana, California, United States. pp. 115-116.
  • Quisumbing, E., 1978. Medicinal plants of the Philippines. Katha Publishing Co., Quezon City, the Philippines. pp. 149-150.
  • Tang, X.Y., Zhou, M.H., Zhang, Z.H. & Zhang, Y.B., 1994. Active constituents of Commelina communis L. Journal of Chinese Materia Medica 19(5): 297-298. (in Chinese)
  • Wilson, A.K., 1981. Commelinaceae - a review of the distribution, biology and control of the important weeds belonging to this family. Tropical Pest Management 27(3): 405‚Äì-418.

Authors

Isa Ipor