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MEDICINAL YAMS Dioscorea spp.

Dioscoreaceae

The growing need for steroidal drugs and the high cost of obtaining them from animal
sources led to a widespread search for plant sources of steroidal sapogenins, which
ultimately led to the most promising one. It is the largest genus of the family constituted by
600 species of predominantly twining herbs. Among the twining species, some species twine
clockwise while others anti-clockwise (Miege, 1958). All the species are dioceous and
rhizomatous. According to Coursey (1967), this genus is named in honour of the Greek
physician Pedenios Dioscorides, the author of the classical Materia Medica Libri Quinque.
Some of the species like D. alata and D. esculenta have been under cultivation for a long
time for their edible tubers. There are about 15 species of this genus containing diosgenin.
Some of them are the following (Chopra et al, 1980).

D. floribunda Mart. & Gal.

D. composita Hemsl; syn. D. macrostachya Benth.

D. deltoidea Wall. ex Griseb; syn. D. nepalensis Sweet ex Bernardi.

D. aculeata Linn. syn. D. esculenta

D. alata Linn. syn. D. atropurpurea Roxb.

D. Globosa Roxb; D. purpurea Roxb; D. rubella Roxb.

D. bulbifera Linn. syn. D. crispata Roxb.

D. pulchella Roxb.; D. sativa Thunb. Non Linn.

D. versicolor Buch. Ham. Ex Wall.

D. daemona Roxb. syn. D. hispida Dennst.

D. oppositifolia Linn.

D. pentaphylla Linn. syn. D. jacquemontii Hook. f.

D. triphylla Linn.

D. prazeri Prain & Burkil syn. D. clarkei Prain & Burkill

D. deltoidea Wall. var. sikkimensis Prain

D. sikkimensis Prain & Burkill

Among the above said species, D. floribunda, D. composita and D. deltoidea are widely
grown for diosgenin production.

1. D. floribunda Mart. & Gal

D. floribunda Mart. & Gal. is an introduction from central America and had wide
adaptation as it is successfully grown in Karnataka, Assam, Meghalaya, Andaman and Goa.
The vines are glabrous and left twining. The alternate leaves are borne on slender stems and
have broadly ovate or triangular ovate, shallowly cordate, coriaceous lamina with 9 nerves.
The petioles are 5-7cm long, thick and firm. Variegation in leaves occurs in varying degrees.
The male flowers are solitary and rarely in pairs. Female flowers have divericate stigma
which is bifid at apex. The capsule is obovate and seed is winged all round. The tubers are
thick with yellow coloured flesh, branched and growing upto a depth of 30cm (Chadha et al,
1995).

2. D. composita Hemsl.

D. composita Hemsl. according to Knuth (1965) has the valid botanical name as D.
macrostachya Benth. However, D. composita is widely used in published literature. It is a
Central American introduction into Goa, Jammu, Bangalore, Anaimalai Hills of Tami Nadu
and Darjeeling in W. Bengal. The vines are right twinning and nearly glabrous. The
alternate leaves have long petioles, membraneous or coriaceous lamina measuring upto
20x18cm, abruptly acute or cuspidate-acuminate, shallowly or deeply cordate, 7-9 nerved.
The fasciculate-glomerate inflorescence is single or branched with 2 or 3 sessile male