Dioscorea

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Chapter: Pharmacognosy and Phytochemistry : Drugs Containing Glycosides

Dioscorea is the dried rhizome of several species of Dioscorea like D. villosa, D. prazeri Prain and Burk; D. composite; D. spiculiflora; D. deltoidea and D. floribunda, belonging to family Dioscoreaceae.


DIOSCOREA

 

 

Synonym

 

Yam.

 

Biological Source

 

Dioscorea is the dried rhizome of several species of Dioscorea like D. villosa, D. prazeri Prain and Burk; D. composite; D. spiculiflora; D. deltoidea and D. floribunda, belonging to family Dioscoreaceae.

 

Geographical Source

 

It is mainly found in North America, Mexico, India (Hima-layas from Kashmir and Punjab up to an altitude of 3,000 m), Nepal and China.

 

Cultivation and Collection

 

It is a perennial climber growing to 3 m. The plant prefers sandy, loamy and clay soils and requires well-drained soil. The plant prefers acid, neutral and basic (alkaline) soils. It can grow in semishade or no shade. It requires moist soil. It can be cultivated in three methods, by sowing seeds or stem cuttings or by tubercles. Seeds are sown in the month of March to April in a sunny position in a warm green house and only just covered. It germinates in one to three weeks at 20°C. The seedlings are taken out as soon as they are large enough to handle and grown on in a green house for their first year. Transplanted in late spring as the plant comes into new growth. Basal stem cuttings are done in the summer. Division is done in the dormant season, never when in growth. The plant will often produce a number of shoots, the top 5–10 cm of the root below each shoot can be potted up to form a new plant whilst the lower part of the root can possibly be eaten.

 

Tubercles (baby tubers) are formed in the leaf axils. These are harvested in late summer and early autumn when about the size of a pea and coming away easily from the plant. They should be potted up immediately in individual pots in a greenhouse or cold frame and transplanted out in early summer when in active growth.

 

Characteristics

 

The colour of the plant is slightly brown, odourless with bitter taste and vary in size.

 

Microscopy

 

The transverse section of the drug when observed under the microscope shows the absence of epidermis, the cork is made up of few layers and next to cork it has corical parenchymatous tissue with thin wall. The major part of the drug is occupied by stele and consists of collateral type of fibrovascular bundles. The drug has indistinguishable endodermis and pericycle.

 

Chemical Constituents

 

The roots contain diosgenin (4–6%) a steroidal sapogenin and its glycoside smilagenin, epismilagenin and beta isomer yammogenin. It also contains sapogenase (enzyme), phenolic compounds and starch (75%).

 


 

Uses

 

It is a main source of diosgenin. This is widely used in modern medicine in order to manufacture progesterone and other steroid drugs. These are used as contraceptives and in the treatment of various disorders of the genitary organs as well as in a host of other diseases such as asthma and arthritis.

 

Marketed Products

 

It is one of the ingredients of the preparations known as Explode (Herbotech Pharmaceuticals).

 

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