Introduction of Di Huang:Rehmannia Root or Radix Rehmanniae.
✵The article gives records of the herb Rehmannia Root, its English name, Latin name, property and flavor, its botanical source two plant species, ①.Rehmannia glutinosa Libosch., ②.Rehmannia glutinosa Libosch.f.hueichingensis Hsiao., with a detailed introduction to the botanical features of this two plant species, the growth characteristics, and ecological environment of this two plant species, the features of the herb Rehmannia Root, its pharmacological actions, medicinal efficacy, and administration guide.
Radix Rehmanniae(Rehmannia Root).
Pin Yin Name: Dì Huánɡ, Xiān Dì Huánɡ.
English Name: Rehmannia Root.
Latin Name: Radix Rehmanniae.
Property and flavor: cold, sweet, bitter.
Brief introduction: The herb Radix Rehmanniae is the fresh or dried tuberous root of Rehmannia glutinosa Libosch, used to clear heat, cool blood, nourish Yin and promote fluid production for the treatment of febrile diseases at the nutrient and blood stages, bleeding due to blood heat, and thirst in cases of diabetes. The herb is commonly known as Radix Rehmanniae, Rehmannia Root, Dì Huánɡ.
Botanical source: The herb Radix Rehmanniae (Rehmannia Root) is the fresh or dried tuberous root of (1). Rehmannia glutinosa Libosch., or (2). Rehmannia glutinosa Libosch. f. hueichingensis Hsiao., they are plants of the Rehmannia genus, the Scrophulariaceae family (figwort family) of the Tubiflorae order. These two commonly used species are introduced:
The Rehmannia genus belongs to the Scrophulariaceae family and has 6~8 species, is distributed in eastern Asia, there are 6 species distributed in China, which grow in the northwest, southwest, central to the northern areas, some are planted for gardening viewing. A perennial herb, and has rhizomes. Globose and multicellular glandular hairs; leaves are alternate, obovate to oblong, coarsely serrate; flowers are large, short stipitate, grow in leaf axils or arranged in terminal racemes; calyx is clochee, 5-lobed apically, lobes are unequal in length, usually, the longest rear one, entire or re-split; corolla is bilabiate, slightly curved, tube side is swollen, lobes are deflexed; 4 stamens, sometimes 5, but one is smaller and contained; the base of the ovary rests with a ring or shallow cyathiform (cotyloid) disk, 2-loculed, or 2-loculed when young, 1 loculus in old age, 2-lobed at the top of the style; ovules are numerous; capsularfruit has chambers, room cracking; seeds are small, with meshes.
(1).Rehmannia glutinosa Libosch.
Botanical description: Rehmannia glutinosa Libosch is a plant of the Scrpophulariaceae family (figwort family) and Rehmannia genus, it is also known as Rehmannia glutinosa (Gaertn.) Libosch.ex Fisch.et Mey., or Digitalis glutinosa Gaertn., it is commonly known as Rehmannia glutinosa, Di Huang, or Dì Suǐ, etc. A perennial plant, the plant grows up to 10~40 cm high. The whole plant is densely covered with ash gray (grayish-white) pilose and glandular hairs. The root is hypertrophic, succulent, tuberous, cylindrical, or fusiform (spindle-shaped). The stem is upright, with single or several branches growing at the base. Basal leaves grow in a cluster, and the leaf blades are obovate-lanceolate, 3~10 cm long, 1.5~4 cm wide, the apex is obtuse, the base is gradually narrowing, decurrent to a long petiole, the leaf surface is mostly wrinkled, leaf edge is irregularly serrated; cauline leaves are smaller.
Scapes (flower stalks) are upright and pilous, and the upper stem is racemose; the flower bract is foliate (leaf-like), developed or degraded; Calyx is campanulate (bell-shaped), the apex is 5-lobed, lobes are triangular, covered with multicellular long pilose and while pilose, with 10 veins; corolla is wide fistuliform (tubulose), slightly curved, 3~4 cm long, out surface is dark purple, the inner surface is mixed with yellow, with conspicuous purple striae (striation), the apex is 5-lobed, slightly bilabiate; 4 stamens, didynamous, anther base is divaricated; the ovary is superior, oval (egg-shaped), 2-loculed, turns to 1-loculed after flowering, 1 style, stigma is enlarged.
Capsularfruit is oval (egg-shaped) or ovate-oblong, the apex is pointed, has a persistent style, and out surface is wrapped by a persistent calyx. Many seeds. Its flowering period is from April to May, and the fruiting period is from May to June.
Ecological environment: Rehmannia glutinosa Libosch is mainly cultivated, it also grows in the wild, on hillsides, roadsides and wastelands, in areas at altitudes of 50~1,000 meters above sea level. The plant is mainly distributed in the northern area, the middle and lower reaches of the Yellow River, and the reaches of the Yangtze River, in China.
Growth characteristics: Rehmannia glutinosa prefers a warm climate, cold-resistant, it is appropriate to choose a field with sufficient sunlight, deep soil layers, and loose, fertile, neutral, or slightly alkaline sandy loam for cultivation, it can also be planted in mixed soil or fertile clay. Avoid continuous cropping. It is advisable to choose gramineous crops as the preceding crop, and better not to choose land that has been planted with cotton, sesame, legume, melons, etc., otherwise, diseases will be serious.
Characters of herbs: Fresh Rehmannia Root (Xiān Dì Huánɡ): the root is fusiform (spindle-shaped) or strip-shaped, 9~15 cm long, and 1~6 cm in diameter. The cortex is thin, and the surface is light red and yellow, with vertical straight curved wrinkles, bud marks, transverse long lenticels and irregular scars. The herb is succulent and easy to break, the cortex of the fracture surface is yellowish-white, orange oil spots are visible, the xylem (wood part) is yellowish white, and the tracheae are arranged radially. The herb has a slight smell, and it tastes slightly sweet and slightly bitter. The herb of a better grade has thick and long strips.
Dried Rehmannia Root (Gān Dì Huánɡ): the roots are irregular lumps or oblong, the middle part is enlarged, the two ends are slightly thin, 6~12 cm long, and 3~6 cm in diameter, some are thin and long strip-shaped, slightly flat and twisted. The surface is grayish black or brownish gray, extremely shriveled, with irregular transverse curved lines. The herb is heavy, the texture of the herb is soft and tough, and the fracture surface is grayish black, brownish-black, or corvinus (jet black), slightly glossy and sticky. The herb is odorless, it tastes slight sweet. The herb of a better grade has a big root lump, heavy, the fracture surface is corvinus and oleosus, and tastes slight sweet.
Pharmacological actions: ①.counteract the decrease of plasma corticosterone concentration after continuous dexamethasone administration; ②.antihypertensive effect; ③.hypoglycemia; ④.anti-inflammatory; ⑤.diuretic, etc.
Medicinal efficacy: Clear heat and cool blood, promote the secretion of saliva or body fluid and moistening dryness, indicated for acute fever, impairment of fluid and polydipsia, high fever and faintness, dizziness due to high heat, vomiting blood due to blood heat, hemafecia, epistaxis (bleeding from five aperture or subcutaneous tissue), sores of mouth and tongue, sore throat, consumptive fever and cough, macula, traumatic injury, carbuncle swelling.
Administration of Radix Rehmanniae (Dì Huánɡ):
Reference:
Administration Guide of Radix Rehmanniae (Dì Huánɡ)
TCM Books:
①.Internally:fresh rehmannia root, 12~30 grams, dry rehmannia root, 9~15 grams; ②.Internally:water decoction, 0.4~1 liang (about 12~30 grams), extract juice or prepare to paste. Externally:mashed and apply stick; ③.Internally:water decoction, 10~30 grams, extract juice or prepare to paste. Externally:proper amount, mashed and apply stick, or extract juice and smear.
(2).Rehmannia glutinosa Libosch. f. hueichingensis Hsiao.
Botanical description: The plant, Rehmannia glutinosa Libosch.f.hueichingensis Hsiao is a plant of the Scrpophulariaceae family (figwort family) and Rehmannia genus, it is also known as Rehmannia glutinosa Libosch f.huechingensis (Chao et Schih) Hsiao., it is commonly known as Rehmannia glutinosa hueichingensis, or Huái Dì Huánɡ, its shrubs grow similarly or the same as Rehmannia glutinosa Libosch. They are varietas of Rehmannia glutinosa Libosch., a perennial herb, the plant grows up to 25~40 cm high, and the whole plant is densely covered with gray villous hairs and glandular hairs. Rootstock is hypertrophic, lump, cylindrical or fusiform (spindle-shaped), 2.5~5 cm in diameter, single stem is upright, or a few branches grow from the base. Basal leaves are clustered, leaf blades are obovate or oblong, the apex is obtuse, the base attenuates and extended to the petiole; the edge has irregularly blunt teeth, and the leaf is wrinkled; the undersurface of some leaves is purple. Cauline leaves are not common.
Inflorescences are sparsely racemose; terminal corolla is broadly tubular slightly curved, about 4 cm, purple-red or light-purple, sometimes 5-lobed, pale yellow, with distinct purple lines, bilabiate (2-lipped); 4 stamens, didynamous, grow near the base of the corolla tube; 1 pistil, upper ovary. The pods are ovate or ovoid, wrapped by a persistent calyx, and many seeds. Its flowering period is from May to June.
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References:
1.Introduction of Di Huang:Rehmannia Root or Radix Rehmanniae.