Source
The rhizome of Dioscorea opposita Thunb. (Fam. Dioscoreaceae).

Distribution
Mainly in Chinese provinces such as Henan, Hebei, Shaanxi, Hunan and Jiangxi. Cultivated.

Harvest & Processing
Dig out rhizomes in winter; cut off top part of roots; remove cork and fine roots; wash clean; dry under the sun to produce ' Mao shanyao'(Hairy Common Yam Rhizome). Alternatively, choose the plump and uncurved Mao shanyao and put into fresh water; soak thoroughly; knead on wooden boards until cylindrical; cut both ends cleanly; dry under the sun and polish to produce ' Guang shanyao'(Glabrous Common Yam Rhizome).

Description
Mao shanyao: Slightly cylindrical, curved and slightly flattened; 15-30 cm long, 1.5-6 cm in diameter; outer surface yellowishwhite or pale yellow, marked with longitudinal grooves, longitudinal wrinkles and scars of fine roots, and occasionally with remnants of light brown cork. Heavy; hard and solid, does not break easily; when broken, surface white and starchy. Taste: mild and slightly sour, sticky when chewed. Guang shanyao: Cylindrical, both ends even; 9-18 cm long, 1.5-3 cm in diameter; outer surface smooth, white or yellowish-white. Commonly seen in the form of angled-cut and length-wise cut slices.

Indications
1. Protracted diarrhoea, chronic enteritis
2. Cough and dyspnoea
3. Seminal emissions, leukorrhagia

Chemical Composition
Mainly contains dioscin, allantoin.

Photos