Introduction of Shan Yao:Common Yam Rhizome, Wild Yam or Rhizoma Dioscoreae.

TCM Herbalism:Medicinals and Classifications. ✵The article gives records of the herb Common Yam Rhizome, its English name, Latin name, property and flavor, its botanical source one plant species, ①.Dioscorea opposita Thunb., with a detailed introduction to the botanical features of this plant species, the growth characteristics, and ecological environment of this plant species, the features of the herb Common Yam Rhizome, its pharmacological actions, medicinal efficacy, and administration guide.

Rhizoma Dioscoreae(Common Yam Rhizome).

Rhizoma Dioscoreae:fresh rhizome Pin Yin Name: Shān Yɑo.
 English Name: Common Yam Rhizome, Wild Yam.
 Latin Name: Rhizoma Dioscoreae.
 Property and flavor: neutral in nature, tastes sweet.

 Brief introduction: The herb Rhizoma Dioscoreae is the dried rhizome of Dioscorea opposita Thunb., used (1).to replenish Qi and Yin, tonify the spleen, lung, and kidney for the treatment of (1).weakness of the spleen and stomach with poor appetite and chronic diarrhea, (2).lung insufficiency with chronic cough, (3).insecurity of the kidney with nocturnal emission, polyuria and leukorrhagia, and (4).Yin deficiency in cases of diabetes. The herb is commonly known as Rhizoma Dioscoreae, Common Yam Rhizome, Shān Yɑo.

 Botanical source: Herbal classic book defined the herb Common Yam Rhizome (Shan Yao) as the tuber of the Dioscoreaceae family plant species (1).Dioscorea opposita Thunb. It is a plant of the Dioscorea L. genus, the Dioscoreaceae family (yam family) of the Liliflorae order. This commonly used species is introduced:

(1).Dioscorea opposita Thunb.

 Dioscorea polystachya.:growing plant Botanical description: The plant, Dioscorea opposita Thunb., is a plant of the Dioscoreaceae family (yam family) and Dioscorea genus, some latest classification systems identified the species as Dioscorea polystachya, it is also known as Dioscorea batatas Decne. (D.batatas Decne.), it is commonly known as Common Yam, Shǔ Yù, or Chinese yam. A perennial twisted herbal liana. The tuber is long cylindrical, grows vertically, up to 1 meter long, and 2~7 cm in diameter, the fracture surface is white when it is fresh, turns white flour when it is dried, and the cortex is brown, with raw fibrous roots. Stems are slender, creeping, usually with violet red, dextrorse, smooth, and glabrous. Simple leaves, alternate on the lower part of the stem, opposite above the middle part, rarely in whorls of three; the shape of leaves varies, ovate-triangular to broadly ovate-hastate, 3-9 cm long, 2-7 cm wide, the apex is acuminate, the base is deeply cordate, broadly cordate, or hastate to subtruncate, edge is often 3-lobed to deeply 3-parted, central lobes are ovate-elliptic to lanceolate, lateral lobes are auriform (ear-shaped), circular, subquadrate (nearly square) to oblong, the junction between ambilateral lobes and central lobes connected and form different arc lines, the variance of leaf shapes often occur even on the same plant. In the seedling stage, general leaf blades are broad-ovate (broadly ovate) or oval (egg-shaped), and the base is deeply cordate. There are bulbules (bulblet) often grow in leaf axils.

 The plant is dioecious, flowers are very small, yellowish-green; male inflorescence is a spike, 2-8 cm long, nearly upright, 2 to 8 flowers grow and insert in leaf axils, occasionally conical arranged; inflorescence axis is conspicuously zigzag-like; flower bracts and tapels (perianth lobes) are covered with puce (purple brown) dots; flower petals of male flower in outer whorl are broad-ovate, flower petals in inner whorl are oval (egg-shaped); 6 stamens. The female inflorescence is a spike, 1-3 grows and inserts in leaf axils.

 The capsularfruit is not reflexed, prismatic oblate, or prismatic circular, 1.2-2.0 cm long, 1.5-3.0 cm wide, and out surface has white powder. Seeds grow and are inserted in the middle of the axile of each cell, and have membranous wings. Its flowering period is from June to September, the fruiting period is from July to November.

 Dioscorea polystachya.:stem and leaves Ecological Environment: Dioscorea opposita Thunb., grows on sunny mountain slopes, hillsides, forests in valleys, streams, bushes on roadsides, or in weeds; or it is cultivated. Geographical distribution: This species is mainly distributed in the northern, northwest, and central areas, and cultivated in other areas of China. This species is native to China and now grows throughout East Asia, it was introduced to the USA (the United States of America) as early as the 19th century for culinary and cultural uses, and it was introduced to Europe in the 19th century during the European Potato Famine (Irish Potato Famine, or Famine of 1845–49, a famine that occurred in Ireland in 1845–49 when the potato crop failed in successive years.), the edible tubers, are cultivated largely in Asia and sometimes used in alternative herbs.

 Dioscorea opposita is a herbaceous twining perennial common in China mainland, Mexico, and the eastern and central USA. It grows and twines in hedges, and over bushes and fences, the thin, woolly, reddish-brown stem grows up to 6 meters long.

 The slender, tuberous rootstock is crooked and laterally branched. Broadly ovate and cordate, the leaves are 5~15 cm long and 3~12 cm wide, glabrous on the upper surface, and the under surface is finely hairy. They are usually alternate, but the lower leaves sometimes grow in twos and fours. The small, greenish-yellow flowers bloom during June and July, the male flowers are pendulous panicles, and the female flowers are pendulous spicate racemes.

 Growth characteristics: Dioscorea opposita grows wildly in the sunny mountainous areas, it prefers warm, is tolerant to coldness, slightly gets covered then can pass safely in winter in the northern area. Because Dioscorea opposita is a deep-rooted plant, it is appropriate to choose fields with deep soil layers, and loose and fertile sandy loam with good drainage for cultivation. The pH (pH scale:acidity-basicity) of soil is better neutral. If the soil is acidic, rootlets and root nodules (root tubercles) grow easily, which affects the yield and quality of roots. If the soil is peralkaline, the roots cannot grow downward sufficiently.

 Common Yam Rhizome:herb photo Characters of herbs: Wild Yam: It is also known as Coarse Wild Yam or Máo Shān Yɑo (means hairy wild yam). The herb is slightly cylindrical, slightly flat, and curved, its length is 15~30 cm, and 1.5~6 cm in diameter. The surface is yellowish-white or light yellowish brown, has conspicuous vertical wrinkles and marks of incompletely removed cork bark, and a few marks of fibrous root, the two ends are irregular. The texture of the herb is solid and firm, uneasy to break, the fracture surface is white, granular, and has mealiness (powdery), with light brown spots scattered on it. The herb has a slight odor, it tastes sweet and mild, slightly sour, and sticky when it is chewed. The herb of a better grade has thick strips, the texture is solid and firm, sufficient mealiness, and spotlessly white.

 Smooth Wild Yam: The herb is cylindrical, both ends are regular and flat, the length is 7~16 cm, and 1.5~3 cm in diameter, uniform in thickness, straight and upright. The surface is smooth, spotlessly white or yellowish-white, with sufficient mealiness. The herb of a better grade has thick strips, the texture is solid and firm, sufficient mealiness, and spotlessly white.

 Wild Yam Slices: The herb is irregular thick slices, has uneven shrinkage, the fracture surface is white or yellowish-white, the texture of the herb is firm, and crisp, and has mealiness (powdery). The herb has a slight odor, it tastes mild and slightly sour.

 Pharmacological actions: ①.lowering blood sugar; ②.regulating the body's response to non-specific stimulation, improving immune function; ③.nourishing effect; ④.relieving diarrhea; ⑤.removing phlegm; ⑥.affecting the digestive system to stimulate intestinal movement, enhancing the absorption function of the small intestine, helping digestion, inhibiting the secretion of serum amylase and so on.

 Medicinal efficacy: Replenish the spleen and nourish the stomach, generate body fluid and invigorate the lung, nourishing lung, reinforce the kidney, replenish the vital essence, reinforcing the kidney and controlling noctural emission. It is indicated for spleen deficiency and poor appetite, poor appetite and edema, splenasthenic diarrhea, unstoppable chronic diarrhea, chronic dysentery, lung deficiency and dyspnea with cough, emission with renal asthenia, spermatorrhea, morbid leukorrhea, frequent micturition, kidney deficiency and frequent urination, consumptive disease with cough, asthenic fever and wasting thirst (deficient heat and consumptive thirst), carbuncle swelling, scrofula (lymphoid tuberculosis), etc. Fried wild yam invigorate the spleen and strengthening the stomach, it is indicated for spleen deficiency and poor appetite, diarrhea and loose stool, leukorrhagia, etc.

 Administration of Rhizoma Dioscoreae (Shān Yɑo): 
Reference: Administration Guide of Rhizoma Dioscoreae (Shān Yɑo)
TCM Books: ①.Internally: 3~9 grams; ②.Internally:water decoction, 3~6 qian (about 9~18 grams), or prepare to pill, powder. Externally:mashed and apply stick; ③.Internally:water decoction, 15~30 grams, big dosage could be 60~250 grams;or prepared to pill, powder. Externally:proper amount, mashed and apply stick. To nourish Yin, better use raw herb;to replenish spleen and relieve diarrhea, better use fried herb.
 Contraindications,Precautions and Adverse Reactions:the herb Rhizoma Dioscoreae should not be combined with Radix Kansui.

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