Dioscorea Biological Source
The dried rhizome of Dioscorea species is the main source of Dioscorea. These plants are found at altitudes of 3000m in India, Nepal, China, etc. Common species are,
- Dioscorea villosa
- D. prazeri Prain and Burk
- D. composite
- D. spiculiflora
- D. deltoidea
- D. floribunda
Characteristics
The Dioscorea plant appears in varying sizes, slightly brown, has a bitter taste, but is odorless.
- It is a perennial climber of 3 m, preferring moist but well-drained sandy, loamy, and clay soils.
- Prefers acid, neutral, and basic (alkaline) soils.
- It can grow in semishade or no shade.
- It can be cultivated by sowing seeds, stem cuttings, or by tubercles.
- Seeds are sown between March and April and germinate in one to three weeks at 20°C. The seedlings are taken out and grown in a greenhouse for their first year.
- Transplantation happens in late spring, and basal stem cuttings are done in summer.
- Tubercles (baby tubers) are formed in the leaf axils.
- Its microscopy reveals the absence of epidermis.
- The cross-section of the drug shows a cork followed by thin-walled parenchymatous tissue.
- Stele has a collateral type of fibrovascular bundle occupying a major portion of the drug.
- The endodermis and pericycle are indistinguishable.
Chemical Constituents
The root of Dioscorea contains
- Diosgenin, a steroidal sapogenin
- Glycoside smilagenin
- Epismilagenin
- Beta isomer yamogenin
- Sapogenase phenolic compounds
- Starch
Uses of Dioscorea
Dioscorea is the main source of diosgenin, which is used to make progesterone and other steroids. It is used in contraceptives and for treating genital organs. Moreover, it is used to treat asthma and arthritis.
Diosgenin is a huge source of steroid hormone synthesis.
Isolation of Diosgenin
Diosgenin is obtained from the dried tubers of Dioscorea deltoidea Wallich and other species of Dioscorea. Several methods are used for its extraction.
Alcoholic extraction method
- The tubers are chopped, dried in the sun, and powdered.
- Extraction is done with ethanol or methanol twice for 6–8 hours.
- It is filtered and concentrated to a syrupy liquid.
- The concentrated liquid is hydrolysed using an acid, hydrochloric acid or sulphuric acid for 2–12h.
- During which, almost 85% of the crude diosgenin is precipitated, which is filtered, washed with water, and purified using alcohol.
Acid hydrolysis method
- The dried tubers are powdered and then refluxed or heated in an autoclave with 2–4 N mineral acid for 2–6 h.
- It is filtered, and the crude hydrolyte is washed with water to neutralize.
- It is again dried and extracted for 6 h using a hydrocarbon solvent.
- The liquid is concentrated to 25 ml and allowed to stand for an hour in a refrigerator.
- The crystals of diosgenin are filtered out, and then it’s washed with acetone.
Fermentation cum acid hydrolysis method
- The fresh roots are smashed in a hammer mill.
- The mesh is allowed to ferment in the fermentation bin for two days.
- The fermented mesh is dried under the sun to reduce the moisture content to 7–8%.
- It is then hydrolysed with a mineral acid at reduced temperature.
- The resulting solution is extracted with heptane to obtain diosgenin.
Incubation cum acid hydrolysis method
- The fresh plant material is incubated in water at 37°C for a few days and subjected to acid hydrolysis.
- The hydrolysed liquid is concentrated and extracted with hydrocarbon solvent to get diosgenin.
- The fresh roots are homogenized with an equal amount of water.
- Concentrated acid is added to it until the required strength is obtained.
- It is extracted with hydrocarbon solvent to obtain diosgenin.
Melting point of diosgenin: 204–207°C
Thin Layer Chromatography of Diosgenin
- TLC of diogenin is developed in Toluene: ethyl acetate (7:3).
- The sample is dissolved in methanol and spotted on silica gel plates.
- When the plate is sprayed with anisaldehyde-sulphuric acid reagent, the dark green spot (Rf – 0.37) of diosgenin appears.
References
- Shah, Biren N, Avinash Seth. (2010). Textbook of Pharmacognosy and Phytochemistry. Elsevier.
- Rudresh A, Chandrashekar K S, Vasudev P, Richard L, Aswatharam H N, Vamshi
- K T, Ullas P D’S, Rajesh K S. A Comprehensive Review on the Pharmacological Potential of Dioscorea bulbifera and its Potential Hepatotoxicity. Pharmacogn J. 2025;17(4): 520-530
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