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 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 commonly known "Common Yam", or "Shǔ Yù", or "Chinese yam", perennials winding plant. The tuber is thick, slightly cylindrical, vertical growth, up to 1 meter high, 2~7 cm in diameter, skin is brown, raw fibrous roots. Stems are slender, creeping, usually purplish, angular, smooth glabrous. Leaf is opposite or 3-leaf rotation, axillary leaf is often perennial (more than a child); leaf shape changes, triangular-ovate to triangular wide ovoid, 3.5~7 cm long, 2~4.5 cm wide, usually auriculate, central apex is acuminate, lobes on both sides of a round ear, the base of the halberd heart-shaped, both sides are smooth and glabrous; 7~9 veins; petiole is slender, 1.5~3.5 cm. Flowers are unisexual, dioecious; flowers are very small, yellowish-green, spikes; spadix; male inflorescence is upright, 2 to several polygamous in leaf axils, many of flower axils are zigzag-like; flowers are small, nearly sessile, triangular-ovate; 6 perianth, elliptic, apex is obtuse; 6 stamens, filaments are very short; female inflorescence is drooping, basal each flower with 2 unequal bracts, bracts are broadly ovate, apex is long gradually tip; 6 perianths; Ovary is inferior, oblong, 3-locule, stigma is 3-lobed. The capsularfruit has 3 wings, fruit wing length is equal to a few wide. Seeds are oval, there are broad-winged. Its flowering period is from July to August, fruiting from September to October.

 Dioscorea polystachya.:stem and leaves Ecological Environment: The Dioscorea opposita Thunb., grows in mountain sunny side, hillsides, valleys, streams, roadside shrubs or weeds; or for cultivation. Geographical distribution: This species is mainly distributed in the north, northwest, and central area, and cultivated in other areas of China. This species is native to China and now grows throughout East Asia, it was introduced to USA (the United States of America) as early as the 19th century for culinary and cultural uses, it was introduced to Europe in the 19th century during the European Potato Failure, the edible tubers, are cultivated largely in Asia and sometimes used in alternative herbs.

 Dioscorea is a herbaceous twining perennial common in China mainland, Mexico, the eastern and central USA (the United States of America). Twining 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 from 5~15 cm long and 3~12 cm wide, glabrous on top, and finely hairy underneath. 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 in drooping panicles, the female in drooping, spicate racemes.

 Growth characteristics: The Dioscorea opposita grows wildly in the mountainous area to the sun, prefers warm, cold resistance, in the north area covered a little then it can pass safely in winter. Because wild yam is a deep-rooted plant, the cultivation area should choose the sandy loam with a deep soil layer, good drainage, and fertile. The pH (pH scale:acidity-basicity) of soil better is neutral. If the soil is acidic, branch roots and nodule are easy to grow, which affects the yield and quality of roots. Much alkaline, the roots cannot grow down sufficiently.

 Common Yam Rhizome:herb photo Characters of herbs: Wild Yam: It is also known as Coarse Wild Yam or Máo Shān Yɑo. The herb is slightly cylindrical, slightly flat, and curved, with a length of 15~30 cm and a diameter of 1.5~6 cm. The surface is yellowish-white or light brown, with obvious longitudinal wrinkles and marks of incomplete cork bark, and a few fibrous root marks, with irregular ends. The texture of the herb is solid and firm, hard to break, the fracture surface is white, granular, and powdery, scattered with light brown spots. The herb has a slight odor, it tastes sweet and mild, slightly sour, sticky when chewed. The herb of better grade has thick strips, solid and firm texture, sufficient powder, and white.

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

 Wild Yam Slices: The herb is irregular thick slice, uneven shrinkage, the fracture surface is white or yellowish-white, the texture of the herb is firm, crisp, and 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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