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

:Chromosome number: ''x''= 12;''S. capsicoides'': 2''n''= 24,''S. erianthum'': 2''n''= 24,''S. mammosum'':''n''= 11, 12,''S. nigrum'': 2''n''= 72,''S. trilobatum'': 2''n''= 24

*Solanum, nightshade (En). *Solanum, morelle (Fr).

''Solanum'' shows insecticidal and fungicidal properties. The leaves and stems of many species are often cooked or steamed and eaten as a vegetable. The unripe fruits are eaten in curries, whereas the ripe ones of some ''Solanum'' species are edible either cooked or raw. Caution must be taken when eating ''Solanum'' , as several species are poisonous.

The steroidal alkaloids of the ''Solanaceae'' occur as glycosides (hence glycoalkaloids). The known steroidal alkaloids are based on a C₂₇cholestane skeleton and can be divided into 5 groups: solanidanes, spirosolanes, 22,26-epiminocholestane, α-epiminocyclohemiketal and 3-aminospirostane. The first 2 groups have attracted the most research. The solanidanes, with important alkaloids such as solanidine, leptidine and demissidine, are characterized by an indolizidine moiety. Important spirosolane alkaloids include solasodine, tomatidine and tomatidenol. The spirosolanes are structurally similar to saponins of the diosgenin type, except that the oxygen in the spiro-alketal pattern has been replaced by nitrogen.

Solanidine is present in ''S. capsicoides'' , whereas solasodine is found in ''S. erianthum'' , ''S. nigrum'' and ''S. trilobatum'' . The total alkaloid content of air-dried leaves and fruits is respectively 0.26% and 0.14% for ''S. capsicoides'' , 0.37% and 0.39% for ''S. erianthum'' , 0.43% and 0.10% for ''S. nigrum'' and 0.36% and 0.96% for ''S. trilobatum'' . The solasodine content in ''Solanum'' fruits from Indian samples is 0.01-0.70% in ''S. erianthum'' and 0-0.28% in ''S. nigrum,'' whereas the total glycoalkaloid content in fruits of ''S. trilobatum'' has been found to be 3.5%. Leaf samples of ''S. erianthum'' from Vietnam contained 0.26% solasodine, 0.05% tomatidine and 0.01% solaverbascine. ''S. erianthum'' also has steroidal saponins and free genins. As well as solasodine, ''S. nigrum'' contains the sapogenins diosgenin and tigogenin. The unripe berries have 0.68% solasodine, 0.19% diosgenin and 0.15% tigogenin, whereas leaves contain 1.28% tigogenin.

A large number of fungi are inhibited in growth and development by steroidal alkaloids such as tomatine, solanine, and chaconine. An alcoholic extract of leaves of ''S. nigrum'' is active against ''Staphylococcus aureus'' and ''Escherichia coli'' . Leaf extracts of ''S. nigrum'' inhibited lesion production in leaves in response to the tobacco mosaic virus. The flavonoid-rich extract of ''S. erianthum'' possesses antibacterial and antifungal activity. Gram-positive bacteria are inhibited, but gram-negative ones are not, whereas the flavonoids have been found to be toxic to the fungi ''Aspergillus flavus'' and ''Candida albicans'' . Some other pharmacological activities of ''Solanum'' include antispasmodic, hypotensive, hypocholesterolaemic and anti-HIV-1 activity induced by ''S. nigrum'' in mammals, and insecticidal and molluscicidal activity of ''S. nigrum'' and of ''S. mammosum'' L.

*Annual or perennial, erect or ascending, unarmed or spiny herbs, shrubs or rarely small trees, with simple, branched, stellate or glandular hairs. *Leaves alternate or rarely subopposite, simple and entire to lobed, pinnatisect or imparipinnate, petiolate, exstipulate. *Inflorescence a terminal cyme but usually appearing lateral by growth of a lateral bud and extra-axillary cyme, appearing racemose, umbellate or paniculate or rarely reduced to a solitary flower. *Flowers regular, bisexual or rarely andromonoecious; calyx campanulate, rotate or cupular, (4-)5(-10)-lobed; corolla stellate, rotate or campanulate, (4-)5(-10)-lobed, white, violet, purple or blue; stamens (4-)5, inserted on the corolla throat, alternating with the corolla lobes, anthers often connivent, opening by terminal pores or slits; ovary superior, 2(-4)-locular with many ovules in each cell, style simple, stigma capitate or bifid. *Fruit a usually globose berry, with a persistent and sometimes enlarged calyx, few to many-seeded. *Seeds orbicular to subreniform, compressed, often minutely pitted or reticulate. *Seedling with epigeal germination; cotyledons emergent, ovate to linear-lanceolate; first leaves usually entire.

''Solanum'' has been subdivided into 7 subgenera and numerous sections and series. ''S. nigrum'' , being the type-species of the genus, belongs to subgenus ''Solanum'' , ''S. erianthum'' to subgenus ''Brevantherum'' and the other four species treated below to subgenus ''Leptostemon'' which also includes ''S. melongena'' L. and ''S. mammosum'' L., species well-known for their fruits. It is in South-East Asia that the taxonomy of ''Solanum'' is least known: a thorough taxonomic revision is urgently needed. Adding to the taxonomic confusion is the fact that ''S. erianthum'' has been extensively referred to as ''S. verbascifolium'' L., which actually proved to be identical with a South American species. Moreover, in South-East Asian literature, ''S. capsicoides'' has often been misinterpreted as ''S. aculeatissimum'' Jacq. Furthermore, ''S. nigrum'' belongs to a complex of very similar species (including e.g. ''S. americanum'' Miller and ''S. villosum'' Miller), which are sometimes regarded as mere forms of a single variable species. ''S. nigrum'' arose from hybridization of the diploid ''S. americanum'' and the tetraploid ''S. villosum'' . ''S. villosum'' is distinguished by its yellow, orange or red berries. ''S. americanum'' and ''S. nigrum'' are much more difficult to distinguish. The former has usually umbellate inflorescences, anthers 1.0-2.0 mm long, a glossy, purplish-black berry with generally 50-80 seeds and an enlarged calyx with reflexed lobes in fruit. For the latter, see below. ''S. mammosum'' , originally from Central and South America but introduced in the Malesian region for its decorative fruits, has poisonous fruits which are occasionally used as an insecticide against cockroaches and caterpillars. ''S. procumbens'' Lour., ''S. spirale'' Roxb. and ''S. surattense'' Burm.f. (synonym: ''S. xanthocarpum'' Schrad. & J.C. Wendl.) are used in folk medicine in Indo-China. ''S. aviculare'' J.G. Forster, ''S. laciniatum'' Aiton and ''S. khasianum'' C.B. Clarke are a reputed rich source of solasodine. Originating from outside the Malesian region, they have received special attention in breeding programmes for cultivation at higher elevation in Java. In particular ''S. khasianum'' merrits further research.

Diosgenin and solasodine have been isolated from 6-month-old callus of ''S. erianthum'' ; the undifferentiated callus tissue was established from sterilized seeds on Murashige and Skoog's revised medium. Blue light stimulated solasodine synthesis and green light stimulated diosgenin synthesis in the callus. Optimal growth was reached after 6 weeks when the dry weight of the tissue had increased 6.6-fold. After 6 weeks only about 147 μg diosgenin and 47 μg solasodine had been produced per g of dry-weight tissue; this is very little.

*M.M. Blomqvist & Nguyen Tien Ban