Mallotus (PROSEA Medicinal plants)
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Introduction |
Mallotus Lour.
- Protologue: Fl. cochinch.: 635 (1790).
- Family: Euphorbiaceae
- Chromosome number: x= 11; M. philippensis, M. repandus: n= 11
Origin and geographic distribution
Mallotus comprises about 140 species. Only 2 of these occur in Africa and Madagascar, the others being found from India and Sri Lanka to Indo-China, China, Taiwan, Korea, Japan, Thailand, throughout the Malesian region, northern and eastern Australia and the Pacific (east to Fiji). Some 75 species occur within Malesia.
Uses
Bark, leaves, fruits and seeds of Mallotus are commonly used in traditional medicine in South-East Asia. The most common internal applications are for treating stomach complaints and intestinal problems. Externally they are used to treat boils, wounds, skin diseases and fever. The fruit granules of M. philippensis were previously important as an anthelmintic and purgative, but these uses have declined. The powder from the fruits is still used for the treatment of tapeworm infestation in livestock, particularly in poultry.
M. japonicus (Thunberg) Müll. Arg. is applied in Chinese traditional medicine, particularly to regulate the functions of the digestive system, e.g. to treat gastric and duodenal ulcers.
The red granules on the fruits of M. philippensis were formerly much used as a dye. The wood of several Mallotus species is used for small objects and as fuelwood.
Properties
The leaves of M. mollissimus showed activity against Staphylococcus aureus. The bark of M. philippensis is active against gram-positive as well as gram-negative bacteria. Kamala powder is a dull reddish-brown substance from M. philippensis fruits used for medicinal purposes, and formerly also for dyeing. Under the microscope it is seen to consist of very characteristic globular glands containing red resin and radiating groups of unicellular curved trichomes. In-vitro and in-vivo research showed that a fruit extract of M. philippensis displays activity against tapeworm. The resin caused a significant purgative effect after an oral dose (120 mg/kg) in rats, and killed 36% and 78% of tapeworms in the small intestine at doses of 60 mg/kg and 120 mg/kg, respectively. The anthelmintic activity is mainly attributed to the phloroglucinol derivatives rottlerin and isorottlerin. Rottlerin exhibited antifertility activity in rats and guinea-pigs, whereas isorottlerin was inactive. Rottlerin is a protein kinase inhibitor. Rottlerin and isorottlerin together constitute about 11% of the weight of the powder from ripe M. philippensis fruits. Leaf extracts showed antifilarial activity on Setaria cervi in vitro. The alcoholic extract of M. philippensis fruits exhibited in-vitro anticancer activity against human epidermoid carcinoma of the nasopharynx and sarcoma of mice.
Stem and root extracts of M. repandus showed radical scavenger activity. An aqueous extract of M. repandus stems exhibited anti-inflammatory activity against carrageenan-induced paw oedema. M. repandus showed significant antihepatotoxic activity in cultured hepatocytes. A methanol extract had anti-ulcer activity in stress-induced gastric ulcers and radio protective effect against bone marrow and skin injury.
Bergenin (an isocoumarin), the major constituent of M. japonicus, showed antihepatotoxic activity on carbon tetrachloride-intoxicated hepatocytes of rats. Bergenin has also been isolated from wood, bark and leaves of M. philippensis and from aerial parts of M. repandus. Several phloroglucinol derivatives isolated from M. japonicus (e.g. mallophenone, mallotojaponin (a major constituent of the fruit), isomallotolerin, isomallotochromene, mallotochroman and isomallotochroman) distinctly inhibited the replication of herpes simplex virus type 1. They also demonstrated cytotoxicity against human larynx and lung carcinoma cells as well as mouse melanoma and leukaemia cells, and caused a marked prolongation of the life-span of mice bearing L5178Y leukaemia. A methanol extract of M. japonicus stems showed significant inhibitory activity on human immunodeficiency virus type 1 (HIV-1) reverse transcriptase.
The presence of cardenolides has been demonstrated in the seeds of several Mallotus species. The seed-oil of M. philippensis is unstable; it polymerizes rapidly. Seeds contain up to 20% oil. The principle fatty acid is kamlolenic acid. The bark contains up to 10% tannin. Several hydrolyzable tannins have been isolated including colilagin, eugenin, furosin, geraniin, mallotinic acid, mallotinin and ropondusinic acids A and B.
Botany
- Dioecious, sometimes monoecious shrubs or small to medium sized trees up to 25(-35) m tall, sometimes lianas; indumentum often consisting of stellate hairs.
- Leaves arranged spirally or opposite, simple and entire, sometimes sinuate or dentate, rarely lobed, sometimes peltate, often whitish and with glandular granules below, venation pinnate or palmate; stipules small. Inflorescence a terminal or axillary raceme or spike, sometimes paniculate, generally unisexual.
- Flowers unisexual, calyx 2-4(-5)-lobed, petals absent; male flowers with numerous stamens, disk present or absent; female flowers with superior, 2-4-lobed ovary, styles simple to plumose, disk absent.
- Fruit a more or less distinctly lobed capsule, smooth to echinate, splitting into 2-valved, 1-seeded parts leaving a persistent central column.
- Seeds globose to ovoid, smooth, shiny black.
- Seedling with epigeal germination; cotyledons emergent, leafy; hypocotyl elongated; first few leaves arranged spirally, decussate higher up in species with opposite leaves.
Mallotus can grow quickly; a mean annual diameter increment of 1.4 cm has been recorded for M. philippensis, 1.7-3.6 cm for M. mollissimus. The seeds of many Mallotus species are dispersed by birds.
Mallotus is closely related to Macaranga, the latter differing by its 3-4-celled anthers and more conspicuously by its lateral inflorescences and absence of stellate hairs.
Ecology
Most Mallotus species occur in primary evergreen rain forest, but a few are abundant in secondary forest and in more open locations including savanna woodland, up to 2000 m altitude. They occur in dipterocarp, riverine and swamp forest. A few species (e.g. M. philippensis) are pioneers characteristic of secondary vegetation and may be gregarious elements in regenerated forest. They are among the first species to appear after fields are abandoned.
Management
Mallotus can be propagated by seed, but the germination rate may be poor, e.g. in M. philippensis. Trees may also reproduce from root suckers. Most species are light-demanding, but some need shade during establishment. In India, M. philippensis is resistant to drought, it coppices well and is capable of producing root suckers; it is not resistant to fire.
The red granules of M. philippensis fruits are usually separated by beating and shaking, or by stirring the fruits vigorously in water. The yield of the powder is only 1.5-4% of the fruit weight.
Genetic resources
The light-demanding Mallotus species exhibiting pioneer characteristics are at little risk of genetic erosion by deforestation. However, more research on taxonomy, geographic distribution and ecological requirements is needed to determine the risks for all the species of this large genus. Ex-situ germplasm collections are not known to exist.
Prospects
Many pharmacological properties demonstrated in Mallotus material outside South-East Asia deserve more attention in material from the region, especially the antitumour, antihepatotoxic, antibacterial and antiviral activities. The dye from M. philippensis is much too expensive to compete with synthetic dyes, but might have prospects in the food industry as an antioxidant.
Literature
49, 50, 476, 542, 627, 883.
Selection of species
Authors
- Ch.B. Lugt
