Diospyros (PROSEA Medicinal plants)

Plant Resources of South-East Asia
Introduction

Protologue: Sp. pl. 2: 1057 (1753); Gen. pl. ed. 5: 478 (1754).

Family: Ebenaceae

Chromosome number: x= 15; D. montana: 2n= 30

Origin and geographic distribution

Diospyros consists of over 300 species and occurs throughout the tropics. Some 170 species have been recognized within the Malesian region; 70 species occur within Peninsular Malaysia and about 100 in Indonesia.

Uses

In South-East Asia various parts of numerous Diospyros species are used medicinally; especially unripe fruits are used in traditional medicine. The fruit juice is applied to wounds and ulcers and is drunk in cases of dysentery and fever; it possesses antibacterial and anthelmintic activities. Bark extracts are also widely administered, e.g. a decoction of D. pilosanthera Blanco bark as a bechic in the Philippines. Fruits are used as a source of fish poison, e.g. fruits of D. montana and D. wallichii , as are those of D. ehretioides Wallich ex G. Don, D. lanceifolia Roxb., D. maritima Blume, D. rufa King & Gamble and D. toposia Buch.-Ham. Pounded bark is sometimes employed for the same purpose.

In Indo-China the fruits of D. decandra Lour. are prescribed to treat restlessness, insomnia, and diarrhoea. Fruit pulp is used as a vermifuge for children, and ashes of the rind are applied to wounds and inflammation of the skin. Finely cut, roasted leaves are used as cataplasms on ulcers and sores. In Thailand the bark and wood of D. rhodocalyx Kurz is applied as a general tonic and in the treatment of impotence and leucorrhoea. The fruit is used as an antinauseant, antidiarrhoeal, anthelmintic and anti-inflammatory; externally it is applied to abscesses and infected wounds. The roasted fruit rind is taken as a diuretic and to treat leucorrhoea. In Taiwan the stems of D. maritima are used as a traditional remedy for rheumatism.

The fruits of many Diospyros species are edible; the most important fruit trees are D. blancoi A.DC., D. digyna Jacq. and D. kaki L.f. Some of these species are also well known medicinally. In Malaysia the dried calyces and peduncles of D. kaki are used for treating coughs and difficult breathing. The fruit is considered stomachic, astringent and pectoral. The juice from unripe fruits reduces blood pressure, stops haemorrhages and acts as a laxative. The peduncle is considered stomachic, anti-emetic and bechic. The bark and wood are applied as a styptic on wounds and ulcers. A leaf decoction is used as a bechic and antifebrile, and in Japan as a traditional remedy for hypertensive diseases. Various preparations of bark and leaves of D. digyna are used to treat fever and skin diseases.

The unripe fruits of a few species (D. malabarica (Desr.) Kostel. and D. mollis Griffith) are used to dye cloth black and for tanning nets and sometimes hides. They are also applied medicinally. The unripe fruits of D. malabarica are used to treat diarrhoea, dysentery and leucorrhoea. Fruit juice is applied to wounds and sores. The fresh fruit or a fruit extract of D. mollis is used as an anthelmintic, being effective against hookworm and tapeworm but not ascarids.

The fancy wood of large-diameter Diospyros is in great demand for high quality sculptures and carving. It is also valued for furniture, cabinet work, household utensils, and toys, sometimes also for boxes and construction.

Properties

Diospyros fruits used as a fish poison are generally poor in tannin content. D. decandra fruits contain a glucosidic tannin yielding a pyrocatechic derivative, or phlobaphene, credited with anthelmintic properties. D. mollis fruits contain diospyrol diglycoside as the active principle responsible for the anthelmintic activity. Decomposition of the active compound to diospyrol causes systemic toxicity to visual nerves and the retina. This may result in temporary or permanent blindness depending on the dose.

Tannin from the leaves of D. kaki increases the lifespan and decreases haemorrhage and infarction in stroke-prone spontaneously hypertensive rats. A methanol extract from the leaves showed hypotensive activity in urethane anaesthetized rats. Flavonoids isolated from the leaves inhibited angiotensin-converting enzyme activity in a dose-dependent manner. In a screening programme for AcylCoA:cholesterol acyltransferase (ACAT) inhibitors, using ACAT extracted from rat liver microsomes, D. kaki extract inhibited more than 90% of ACAT activity. ACAT is a key enzyme responsible for cholesteryl ester formation in atherogenesis and in cholesterol absorption from the intestines. Under pathological conditions, formation and accumulation of cholesteryl ester constitute a characteristic feature of early lesions of atherosclerotic plaques. ACAT inhibitors are expected to be effective in the treatment of atherosclerosis and hypercholesterolaemia.

Various extracts from the leaves of D. montana show broad-range antibacterial activity. Alcohol extracts from the bark exhibit central nervous system depressant activity in mice and rats, spasmolytic activity in rabbits and guinea-pigs, and hypotensive activity in anaesthetized dogs. An ethanol extract from the bark further showed potent anti-inflammatory and antipyretic activities in rats and analgesic activity in mice. The growth of Ehrlich ascites carcinoma in mice was also inhibited, diospyrin being the active principle. Diospyrin exhibits in-vitro anti-protozoal activity against Leishmania donovani. Diospyrin and some of its derivatives also show in-vitro antiplasmodial effects.

Alcohol extracts of D. malabarica have anti-amoebic, antiviral and hypoglycaemic activities, and an ether extract from the fruit displays antibacterial activity. An ethanol extract of aboveground parts showed activity on human epidermoid carcinoma of the nasopharynx in tissue culture, and diuretic activity. The extract significantly prevented rats from stress, gastric ulcers and hepatotoxicity.

Isodiospyrin isolated from D. maritima stems exhibited strong in-vitro cytotoxicity against hepatoma, colon carcinoma and cervical carcinoma.

Botany

Evergreen, usually dioecious or sometimes monoecious or polygamous shrubs or small to large trees up to 40(-50) m tall.
Leaves alternate, distichous, simple and entire, pinnately veined, without stipules.
Inflorescence axillary or cauliflorous on older branches or rarely on the trunk, cymose, 1-many-flowered, bracteate.
Flowers usually unisexual, regular, 3-5(-8)-merous; pedicel articulate; sepals united at base, sometimes free, the lobes valvate or imbricate, persistent in fruit; petals basally united into a tube, with patent lobes; stamens (3-)12-20(-100), often inserted at the base of the corolla tube, sometimes on the receptacle, rarely higher up on the corolla tube, often in 2 whorls, staminodes usually present in female flowers; ovary superior, 2-16-celled, rudimentary in male flowers, styles (1-)2-8.
Fruit a berry, with fibrous to fleshy pericarp, 1-16-seeded.
Seeds with a thin leathery testa, and thick, horny, smooth or ruminate endosperm; cotyledons leafy, flat.
Seedling usually with epigeal germination, sometimes hypogeal; first 2 leaves opposite or alternate, subsequent leaves alternate.

All Diospyros species are characterized by the architectural growth model of Massart, i.e. an orthotropic, monopodial trunk with rhythmic growth producing regular tiers of branches. The seeds are dispersed by birds, bats and monkeys.

Diospyros has been subdivided into 5 subgenera: Diospyros, Maba, Hierniodendron, Cargillia, and Mabacea. The first two are subdivided further into many sections. The distinction between the subgenera and sections is not always clear. Several cultivars of species producing edible fruits are known, including cultivars with seedless fruits.

Ecology

Diospyros usually occurs in primary lowland evergreen rain forest up to 900 m altitude. Some species occur in secondary forest, lower montane or montane forest up to 1700 m altitude, in peat-swamp forest, kerangas forest or on limestone hills and ultrabasic soils.

Management

Propagation of Diospyros is by seed or stumps. Species producing edible fruits may also be propagated by air layering, budding, grafting or separation of root suckers. Diospyros can be coppiced well.

Genetic resources

The Diospyros species treated here are not sought for their timber, are relatively widespread and occur in both primary and secondary forest; therefore the risk of genetic erosion seems to be limited. However, in general Diospyros prefers primary lowland rain forest as its habitat, which is under increasing pressure, and protection is needed for many species.

Prospects

Several Diospyros species tested showed interesting pharmacological properties, e.g. anthelmintic, hypotensive, antibacterial, anti-inflammatory, antipyretic, analgesic and anti-tumour activities, supporting many uses in traditional medicine. In most cases fruits and leaves constitute the medicinal plant parts, and this facilitates sustainable exploitation of the resources. Therefore, promotion of Diospyros as a medicinal plant seems desirable, but more pharmacological investigations are still needed.

Literature

479, 517, 541, 542, 594, 946, 967.

Selection of species

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Authors

Wardah