Synonyms: Yam, Rheumatism root, Greater Yam, Asiatic Yam.
Biological source: It consist of dried tubers of the plants Dioscorea deltoidea, D. composita, D. floribunda.
Family: Dioscoreaceae
Geographical source: It is found in Africa, Asia, Europe, Mexico, South America, USA,
China and India. In India it is found in North Western Himalaya from Kashmir and Punjab to Nepal. It is also cultivated in Jammu and Kashmir, Himachal Pradesh, Tamilnadu, West Bengal, Maharashtra and Karnataka.
Cultivation and Collection:
The best yield is obtained in the medium loam and deep soils which should be rich in organic matter or humus. Red soil is best for D. floribunda and D. composita. The cultivation of D. floribunda and D. composita is more suited to the climate of tropical countries (tropics)
whereas D. deltoidea suitable climate is of temperate regions. The propagation is mainly done by seeds, rhizome and stem cuttings. In India commercial plantation are raised from tuber cuttings. Seed progeny is variable and takes a larger time to start yielding tubers compared to plants raised from tubers. There are three types of pieces from tuber pieces:
1. Crown (Stem ends)
2. Medians (Middle portion)
3. Tips (Distal end)
Macroscopic Character:
Colour: Slightly brown
Odour: Odourless or none
Taste: Bitter
Size: Variable (depending upon age of rhizomes)
Chemical Constituents:
Dioscorea have long been used for food as they are rich in starch. It contains about 75% starch but many species are non edible because they possess bitter taste. Diosgenin is the
chief active constituent of dioscorea which is the hydrolytic product of saponin dioscin. Other constituents are steroidal sapogenin (4-6 percent) and its glycosides, smilagenin,
epismilagenin and β-isomer yammogenin.
Uses:
Diosgenin, a steroidal sapogenin obtained from the drug is the major base chemical for the synthesis of several steroidal hormones, cortisone, corticosteroids and oral contraceptive pills. Dioscorea is used in the treatment of rheumatic arthritis.