Herbal Exhibition
Rhizoma Dioscoreae
Common Yam Rhizome


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

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).

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.

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

Chemical Composition
Mainly contains dioscin, allantoin.


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The information and images in this Online Herbal Exhibition is form the book, "An Illustrated Chinese Materia Medica in Hong Kong", edited by Professor Zhao Zhongzhen, School of Chinese Medicine, Hong Kong Baptist University. For the complete collection of Chinese Materia Medica compiled by Professor Zhao, please go to this website: http://www.bucmm.org.

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