Merremia (PROSEA)
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Introduction |
Merremia Dennst. ex Endl.
- Protologue: Gen. Pl., Suppl. 1: 1403 (1841).
- Family: Convolvulaceae
- Chromosome number: x= 15; M. dissecta: 2n= 30, 32; M. emarginata: 2n= 28, 30; M. hederacea, M. peltata, M. tridentata, M. tuberosa, M. vitifolia: 2n= 30.
Major species
- Merremia hederacea (Burm.f.) Hallier f.,
- M. mammosa (Lour.) Hallier f.,
- M. peltata (L.) Merrill,
- M. umbellata (L.) Hallier f. subsp. orientalis (Hallier f.) Ooststr.,
- M. vitifolia (Burm.f.) Hallier f.
Vernacular names
- Malaysia: ulan.
Origin and geographic distribution
Merremia consists of about 80 species, widely distributed in the drier or humid tropics of both hemispheres. Approximately 23 species occur in South-East Asia.
Uses
The tubers, roots or stems of several Merremia species are used as a purgative. The tubers of M. tuberosa are known as a drastic purgative in India and Java, and this is their only use. The tubers of M. mammosa in Indonesia and Malaysia, M. peltata in the Philippines, M. umbellata in India, and M. tridentata subsp. hastata in Indo-China are mildly laxative and are widely taken for dysentery. The sap from the stems of M. peltata, the leaves of M. emarginata and the aerial parts of M. tridentata subsp. hastata are also applied as a laxative in Indo-China and India.
The leaves or stems of Merremia are a popular medicine for chest problems. In Indonesia, an infusion of the leaves of M. emarginata mixed with lumps of sugar is a remedy for cough, and in the Philippines, the sap from the stem of M. peltata is used for this purpose. In Africa, an infusion of the leaves of M. dissecta is taken as a sedative for chest complaints, and a poultice of fresh, crushed leaves is applied as a resolutive. In Indonesia and Malaysia, the sap of the fresh tubers of M. mammosa is widely drunk in affections of the throat and respiratory organs.
Merremia is also widely used against inflammations of various kinds. In the Philippines, the leaves of M. peltata are applied as maturative for inflammation of the breasts, and as a poultice on superficial wounds. In Fiji, a decoction of the leaves of M. peltata is used to treat boils, infections and appendicitis. A decoction of the roots is used to treat stomach muscular rigidity. A drink made from the juice of the leaves of M. peltata is reputed to be taken for the treatment of hernia, and the heated leaves are applied as a poultice. A decoction of the leaves together with the leaves of Colocasia esculenta (L.) Schott is used for the treatment of cysts. In Papua New Guinea, the leaf, part of the stem or the sap of M. peltata is put on wounds, sores and swellings. In the Philippines and India, a decoction of the roots of M. tridentata is used as a mouthwash for toothache. In India, a paste or powder made of the root of M. umbellata is applied to swellings. In Peninsular Malaysia and the Moluccas, pounded leaves of M. umbellata are used to poultice burns, sores and scalds. In India, the whole plant or the roots of M. tridentata are used for hemiplegia, piles, swellings and urinary disorders. The seeds of M. umbellata yield a mucilage used in India as an aperient and alterative in cutaneous diseases. The juice of the aerial parts of M. emarginata is dropped into the ear to cure sores. In Indonesia, Fiji and India, diluted sap from the young stems of M. peltata is used as eye or ear drops.
In Peninsular Malaysia and Thailand, a poultice of the leaves of M. hederacea, together with turmeric (Curcuma longa L.) and broken rice, is used to heal cracks in the hands and feet. In Indonesia, M. umbellata is used for this purpose.
In the Philippines and Thailand, a decoction of the leaves and tops of M. emarginata is sometimes used as a diuretic. In India, the decoction acts as a diuretic and alterative, and is used for rheumatism, neuralgia, and headache. The roasted seeds of M. tridentata are diuretic and antibilious. In the Philippines, a decoction of the roots of M. umbellata is drunk as a remedy for haematuria. In India, M. vitifolia is used for strangury and urethral discharges. The juice of the plant is considered cooling and diuretic. In the Philippines, the tubers of M. peltata are used to treat uterine haemorrhage.
In Peninsular Malaysia, a poultice of the leaves of M. tridentata is applied to the head for fever. In the Philippines, the roots of M. peltata are used in infusions to treat chills. The leaves of M. petaloidea (Choisy) Burkill from India, but sometimes planted in Peninsular Malaysia, are used for poulticing the head for fever. The sap of the fresh tubers of M. mammosa is widely drunk for fever or applied as a poultice on the head. In Peninsular Malaysia, an infusion of M. vitifolia is drunk for high fever. In Cambodia, an infusion of the stem is used internally and externally for malaria and small pox.
In the Philippines, sap from the stem of M. peltata or the roasted seeds of M. tridentata are taken as an anthelminthic.
In Indonesia and Malaysia, the tubers of M. mammosa used to be widely used in the treatment of diabetes, but this use is no longer common, as it has been shown that the plant does not posses suitable properties.
Several Merremia species are planted as ornamentals, e.g. M. dissecta and M. vitifolia in India and M. tuberosa in Africa. In India, the leaves of M. emarginata are eaten as a pot-herb, and in India and Peninsular Malaysia, the young leaves of M. umbellata are eaten as a vegetable. In Malesia, the tubers of M. mammosa and M. peltata are eaten, although they tend to have a purgative effect. The leaves of M. dissecta smell like bitter almonds and are used in India for making liquor.
The stems of M. mammosa yield a fine, strong fibre, with a satin shine, which is made into cloth. The clothes made have to be dried in the shade after washing them, to prevent loss of this shine. In the Philippines, the stem of M. peltata is sometimes used for tying purposes.
M. dissecta is poisonous to cattle in India. The hairs on the leaves of M. vitifolia are irritating. M. hederacea however, is eaten readily by cattle, which thrive on it even if given nothing else to eat.
Production and international trade
Merremia species are mainly cultivated and traded on a local scale, for medicinal purposes.
Properties
The tubers of M. mammosa contain a resin, of which the greater part consists of glycosides of hydroxy fatty acids (sometimes referred to as glycoretins) e.g. jalapinolic acid, convolvulinolic acid, ipurolic acid and 3,11-dihydroxyhexadecanoic acid. The resin also contains the ether-insoluble jalapins woodrosin I and II, and the ionophoric resin glycosides, merremosides, and mammosides A-G, H1 and H2. In general, these glycosides are responsible for the laxative effects of the resin.
An ethanol extract of the tubers of M. mammosa inhibited the growth of the tumour Crown gall in potato disks, inoculated with Agrobacterium tumefaciens, in vitro. Tuber extracts also significantly decreased the blood glucose levels in male white rats.
The roots of M. tuberosa contain 12-25% resin of which 5-6% is soluble in ether. The resins show, as do the resins of the roots of M. dissecta, allelopathic activity on the radicle growth of Amaranthus sp., wheat and oats, but had no antibacterial activity against Bacillus subtilis and Escherichia coli.
The leaves of M. dissecta contain cyanogenic glycosides, which on hydrolysis yield hydrocyanic acid (with a characteristic odour of bitter almonds). In addition, the seeds contain amygdalin acyl derivatives (cyanogenic glycosides), prunasin and prunasin-6'-malonate, and the roots tropane alkaloids (known as merresectines). The leaves of M. vitifolia also contain a glycoside, which on hydrolysis yields hydrocyanic acid and benzaldehyde.
The seeds of M. emarginata contain caffeic acid, p-coumaric acid, ferulic acid and sinapic acid. The extract exhibits antibacterial activity against Bacillus sp., Pseudomonas sp. and Typhimurium sp.
In a general screening, the leaves of M. peltata showed antimicrobial activity, and gave a positive reaction for alkaloids. An MeOH extract of M. peltata showed anti-HIV activity, inhibiting HIV-1 reverse transcriptase and gp120-CD4 binding, in vitro.
The flavonoids diosmetin, luteolin, diosmetin-7-O-β-D-glucoside and luteolin-7-O-β-D-glucoside have been isolated from the aerial parts of M. tridentata. The ethanol extract of the aerial parts of M. tridentata subsp. hastata also showed significant larvicidal activity on the larvae of the tick Boophilus microplus.
Adulterations and substitutes
In India, the root of Ipomoea purga (Wender.) Hayne is used as an adulterant of M. tuberosa root.
Description
- Annual or perennial herbs or shrubs, usually twining, but also prostrate and rooting at the nodes, erect herbs or low, erect shrubs; sometimes with tuberous roots.
- Leaves alternate, variable in size and shape, entire, dentate, lobed or palmately or dentately partite or compound; petiole present; stipules absent.
- Inflorescence axillary, few- to many-flowered, variously ramified, large to small; peduncle present to almost absent; bracts usually small.
- Flowers bisexual, regular, small to large, pedicel present; sepals 5, usually subequal, often somewhat enlarged in fruit; corolla funnel-shaped or campanulate, slightly 5-lobed, mid-petaline bands well-defined, white, yellow to orange; stamens 5, inserted near the base of corolla tube, included, filaments often unequal in length, anthers often contorted, pollen glabrous; ovary 2-4-celled, with 4 ovules, style 1, simple, filiform, included, stigma 2-globular.
- Fruit a globose or ovoid capsule, 4-valved, 4-seeded.
- Seed glabrous, pubescent or villose, especially at the margins.
- Seedling with epigeal germination; cotyledons often deeply divided into lobes or slips.
Growth and development
In Java, most Merremia species can be found flowering throughout the year. M. hederacea is found flowering from April to November, and M. vitifolia from May to November. The flowers of M. dissecta open in the evening and remain open till the following afternoon; of many other Merremia species the flowers open well after dawn.
The tubers of M. mammosa are bunched, and on sandy soil long and thin; on clayish soil however, they can become as large as coconuts.
Other botanical information
Merremia and Ipomoea are taxonomically closely related. The main differences are the spiralled anthers and the smooth pollen in Merremia, as well as campanulate corollas, which are commonly yellow, while yellow is rare in Ipomoea.
Ecology
Merremia grows on disturbed sites, such as roadsides, grasslands, cultivated areas, and along forest borders, sometimes covering entire shrubs and trees. Several Merremia species are serious weeds in tree plantations, and can be reduced by burning or cattle grazing.
Propagation and planting
Merremia is mainly propagated by seed, sometimes from stem cuttings. M. mammosa and M. vitifolia are propagated by stem cuttings. They are fast growing, and suitable for covering walls, trellis and pergolas. The seeds of M. dissecta germinate within one week.
Husbandry
Tubers of M. mammosa will grow bigger when planted in fertile soil. Before planting, the soil is well tilled, and raised beds are made, 50-60 cm high, to prevent waterlogging. Fertilization with potassium is especially beneficial for tuber growth.
Diseases and pests
M. dissecta and M. emarginata are highly susceptible to the fungus Albugo ipomoeae, resulting in irregular growth. The Coleoptera Mylabris pustulata and the Chrysomelid Aspidomorpha furcata feed on flower buds of M. tuberosa.
Harvesting
In Java, the tubers of M. mammosa are harvested when the plant has dried out, more than 1 year after planting.
Handling after harvest
In Ambon, the tubers of M. mammosa are cooked whole, in Bali they are first peeled thickly before cooking and afterwards they can be mashed. In India, the root of M. tuberosa is cut into slices of 5-8 cm in diameter and 0.5-1 cm thick before drying.
Genetic resources and breeding
As many Merremia species are widespread and have a weedy habit, there seems to be little risk of genetic erosion. A small ex situ collection of M. mammosa, originating from Indo-China, is present in the Bogor Botanical Gardens in Indonesia.
Prospects
The use of Convolvulaceae resins as a laxative, e.g. from Ipomoea, is quite well established due to the presence of glycosides of hydroxy fatty acids. Some of the resins found in several Merremia species are of similar composition and may therefore be of local importance. In general, more information on the pharmacology and phytochemistry is needed to fully evaluate other potential uses of the species.
Literature
- Burkill, H.M., 1985. The useful plants of West tropical Africa. 2nd Edition. Vol. 2. Royal Botanic Gardens, Kew, United Kingdom. pp. 1455-1457.
- Fanoka, 1990. Studies of anti-tumour effects of six plant ethanol extracts on potato disks inoculated by the bacteria Agrobacterium tumefaciens. In: Research on medicinal plants at the University of Indonesia. Proceedings V. Department of Health, Jakarta, Indonesia. pp. 49-50. (in Indonesian)
- Perez-Amador, M.C., Garcia-Argaez, A., Contreras, C., Herrera, J. & Rios, M., 1998. Resins of four species of Convolvulaceae and their allelopathic potential. Phyton Buenos Aires 62(1-2): 195-198.
- Quisumbing, E., 1978. Medicinal plants of the Philippines. Katha Publishing Co., Quezon City, the Philippines. pp. 763-765.
- van Ooststroom, S.J., 1953. Merremia. In: van Steenis, C.G.G.J. (Editor): Flora Malesiana. Series 1, Vol. 4. Noordhoff-Kolff, Djakarta, Indonesia. pp. 439-454.
- Yamamoto, T., Takahashi, H., Sakai, K., Kowithayakorn, T. & Koyano, T., 1997. Screening of Thai plants for anti-HIV-1 activity. Natural Medicines 51(6): 541-546.
Selection of species
Authors
- Muhammad Mansur
