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{{DISPLAYTITLE:''Morus'' (PROSEAMedicinal plants)}}

:Chromosome number: ''x''= 14;''M. alba'':''n''= 14,''M. australis'':''n''= 14,''M. nigra'': 2''n''= 89-106, 154, 308

*''Morus alba'' L., *''M. nigra'' L.

*Mulberry (En). *Mûrier (Fr). *Moral, morera (Sp)

''Morus'' comprises 10-15 species and is distributed in all tropical and temperate regions; in the tropics, mainly in montane habitats. Only one species ( ''M. macroura'' Miq.) is native to the Malesian region; several others have been introduced and have occasionally naturalized.

In most parts of South-East Asia it seems to be more important to cultivate mulberry trees (most often ''M. alba'' ) for their leaves, which are used to rear silkworms ( ''Bombyx mori'' ), than for their medicinal application. Trials have been done on the species discussed below and (in Sumatra and Java) on ''M. cathayana'' Hemsl. and ''M. latifolia'' Poir. to ascertain their suitability for raising silkworms. Furthermore, the tasty fruits are highly valued and made into juice, wine, jam, etc. In India the fruits are also used as a dye.

A series of flavone derivatives have been isolated from the root-bark of ''M. alba'' : mulberrin, mulberrochromene, cyclomulberrin, cyclomulberrochromene, mulbeeranol, and phenolic compounds albactalol, albanol A and albanol B. The flavone morin (2',3,4',5,7-pentahydroxyflavone, an isomer of quercetin) has been identified in the heartwood. Morin shows anti-angiotensin properties, with activity on blood pressure and isolated tissues of the rat. The latter effect of morin seems to be a direct action on the muscle-relaxing system. Morusinol, an isoprene-substituted flavone is found in the root-bark of ''M. alba'' together with a number of related compounds. In general these flavones are known to have some anti-tumour activity.

Eighteen N-containing sugars have been isolated from the roots of ''M. alba'' , including seven that were isolated from the leaves of ''M. bombycis'' Koidz. These N-containing sugars are: 1-deoxynojirimycin, N-methyl-1-deoxynojirimycin, fagomine, 3-epi-fagomine, 1,4-dideoxy-1,4-imino-D-arabinitol, 1,4-dideoxy-1,4-imino-D-ribitol, calystegin B₂(= 1α,2β,3α,4β-tetrahydroxy-nor-tropane), calystegin C₁(=1α,2β,3α,4β,6α-pentahydroxy-nor-tropane), 1,4-dideoxy-1,4-imino-(2-O-β-D-glucopyranosyl)-D-arabinitol, and nine glycosides of 1-deoxynojirimycin. These glycosides consist of 2-O- and 6-O-α-D-galactopyranosyl-1-deoxynojirimycins, 2-O-, 3-O- and 4-O-α-D-glucopyranosyl-1-deoxynojirimycins and 2-O-, 3-O-, 4-O- and 6-O-β-D-glucopyranosyl-1-deoxynojirimycins. Due to the presence of nitrogen in the molecules, some authors also refer to these compounds as alkaloids instead of N-containing sugars; this makes 3-epi-fagomine a new member of the polyhydroxylated piperidine alkaloids. Furthermore, the isolation of 1,4-dideoxy-1,4-imino-D-ribitol is the first report of its natural occurrence.

It has recently been found that the polyhydroxy-nor-tropane alkaloids possess potent glycosidase-inhibiting activities. Inhibition of glycosidases might be part of the mechanism involved in anti-hyperglycaemic effects. Calystegin A₃(from ''Calystegia sepium'' (L.) R. Br., Convolvulaceae) is an example of a trihydroxy-nor-tropane, and the calystegins B₁(from ''C. sepium'' ) and B₂(from ''C. sepium'' and ''M. alba'' ) are examples of tetrahydroxy-nor-tropanes. Calystegin C₁( ''M. alba'' ) is a new member of the calystegins, the first naturally occurring pentahydroxy-nor-tropane. The inhibitory activities of 3-epi-fagomine, calystegin B₂, calystegin C₁, and four glycosides of 1-deoxynojirimycin have been investigated against rat digestive glycosidases and various commercially available glycosidases. Calystegin C₁was found to be a particularly potent inhibitor of rat digestive glycosidase. The β-D-glucoside of 1,4-dideoxy-1,4-imino-D-arabinatol, which is known to be a potent inhibitor of yeast α-glucosidase and mouse intestinal isomaltase, completely lost inhibitory activity against rat glycosidases. When compared with the commercially available glycosidases, calystegin B₂performed better than calystegin C₁.

An aqueous methanol extract of the root of ''M. alba'' showed a hypoglycaemic effect on intraperitoneal administration in normal mice. The active component was found to be a glycoprotein called moran A. A dose-dependent activity for the purified compound was furthermore established on intraperitoneal injection in both normal and alloxan-induced diabetic mice, 7 and 24 hours after administration. The hypoglycaemic activity is also found in an ethanol extract of the leaves of ''M. alba'' . The aqueous extract of the leaves of ''M. alba'' also exhibited uterine stimulant and estrogenic activity. Clinical study of aqueous extracts of the fruits showed laxative, central nervous sytem depressant and cholecystokinin receptor binding activities. Hypoglycaemic activity in humans is not only for ''M. alba'' but also for orally administered ''M. nigra'' leaf extracts.

*Dioecious or monoecious shrubs or trees up to 35 m tall; bark surface fissured, exuding white or yellowish-white latex. *Leaves alternate, simple or 3-5-lobed, dentate, palmately 3-5-veined; stipules lateral, caducous. *Inflorescence axillary, spicate. *Flowers unisexual, small, with 4, free or basally united, imbricate tepals; male flowers in long catkin-like inflorescences, with 4 exserted stamens and top-shaped pistillode; female flowers in short to capitate inflorescences, tepals accrescent and succulent in fruit, ovary included, 1(-2)-locular with a single ovule, style 2-partite, staminodes absent. *Fruit a juicy syncarp, composed of many achenes enclosed in the succulent tepals; endocarp woody. *Seed subglobose, with endosperm. *Seedling with epigeal germination; cotyledons emergent; hypocotyl elongated; first leaves often palmately or pinnately lobed.

Growth of ''M. alba'' is initially rapid but slows down abruptly after about 10 years. Pollination is probably by wind. ''Morus'' fruits may be set without pollination and are eaten by birds, the seeds defecated and thus dispersed; dispersal by water is also known. Vesicular-arbuscular mycorrhizae are present in ''M. alba'' , ''M. australis'' and ''M. nigra'' but the degree of colonization varies.

The number of ''Morus'' species is often greatly over-estimated because many cultivated forms that have arisen through hybridization have been described as species. ''M. bombycis'' Koidz. is sometimes thought to be conspecific with ''M. australis'' .

Most mulberry species occur in warm temperate to subtropical regions, and in tropical highland areas. In temperate regions white mulberry is the most frost-hardy ''Morus'' , though some clones are damaged at 6°C whereas others can stand temperatures of -40°C. In India, white mulberry has invaded irrigated plains very rapidly. Although black mulberry seems to be much less cold-tolerant, this may vary among clones, with absolute minimum temperatures between -18°C and -12°C. In general, ''Morus'' prefers well-drained, loamy soils, but white mulberry, for example, is quite tolerant of drought and poor soils.

The major diseases of ''Morus'' as observed in India are: powdery mildew ( ''Phyllactinia corylea'' , also found in Indonesia), leaf spot ( ''Cercospora moricola'' , ''Pseudocercospora mori'' ) and leaf rust ( ''Cerotelium fici'' ). The stem borer ''Batocera rufomaculata'' is an important pest. In Thailand, the nematode ''Hoplolaimus seinhorsti'' is often found in ''M. alba'' plantations and probably associated with a root-rot disease which is widespread in the north-eastern part of the country.

An annual yield of 25 t fresh leaves per ha is considered acceptable for ''M. alba'' .

There are over 1000 races of ''M. alba'' , mainly to produce fodder for silkworms. In India, the techniques to induce tetraploidy in ''M. alba'' have recently been standardized and diploids, autotriploids and tetraploids are being studied, to assess their relative advantages.

The hypoglycaemic properties of ''Morus'' deserve further attention for their possible application in diabetes. Furthermore, the anti-inflammatory properties and the wide range of traditional clinical applications warrant continuing interest in ''Morus'' .

*D.S. Alonzo