Introduction of Di Huang:Rehmannia Root or Radix Rehmanniae.
✵The TCM herbalism is also known as pharmaceutics of Traditional Chinese Medicine, or Chinese pharmaceutics, is the branch of health science dealing with the preparation, dispensing, and proper utilization of Chinese herbs. It is majorly composed of Introduction of Chinese Medicinals, Classification of Chinese Herbs, Formulas, and Patent medicines.
Classifications of Herbs:Herbs Clearing Heat and Cooling the Blood.
Introduction:Herbs Clearing Heat and Cooling the Blood: an agent or substance herbs that has the effect of eliminating pathological heat from the nutrient and blood systems in cases of warm diseases marked by fever accompanied by delirium, eruptions and bleeding symptoms, and also in other diseases with bleeding due to heat in the blood.
✵Till the date Oct 10th,2019, there are totally  kinds of common TCM herbs,  kinds of related plant species, are recorded in this category. These Herbs Clearing Heat and Cooling the Blood. are briefly introduced separately:
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(family Scrophulariaceae), 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 of the Tubiflorae order.
The Rehmannia genus, belongs to the Scrophulariaceae family and has 6-8 species, distributed in eastern Asia, there are 6 species distributed in China, grows in the northwest, southwest, central to the north, some are planted for garden viewing. Perennial herbs, with rhizomes. Globose and glandular hairs multicellular; leaves alternate, obovate to oblong, coarsely toothed; flowers large, short-stalked, born in leaf axils or arranged in terminal racemes; Calyx clochee, 5-lobed apically, lobes unequal in length, usually the longest rear one, entire or re-split; corolla 2-lipped, slightly curved, tube side swollen, lobes deflexed; 4 stamens, sometimes 5, But one is smaller and contained; the base of the ovary rests with a ring or shallow cup-shaped disk, 2 chambers, or 2 chambers when young, 1 chamber in old age, 2 shallow at the top of the style; ovules numerous; capsules with lodgings, Room cracking; seeds small, with mesh.
(1).Rehmannia glutinosa Libosch.: Botanical description: The Rehmannia glutinosa Libosch., is a plant of the Scrpophulariaceae family and Rehmannia genus, it is commonly known as "Rehmannia glutinosa", or "Di Huang", perennial plant, height 10~30 cm, densely gray-white multicellular villous and glandular hairs. The rhizome meat is hypertrophic, fresh yellow, under the cultivation conditions, the diameter of up to 5.5 cm, purple stem. The leaves usually integrate into a rosette at the base of the stem, narrowing strongly upwards into bracts, or gradually narrowing to alternate at stems; leaves ovate to oblong, green above, purplish or purple below, long 2~13 cm, width 1~6 cm, margins irregularly crenate or bluntly serrate to teeth; base gradually narrowed into stalks, veins indented above, bulges underneath. The flowers have a 0.5~3 cm pedicel, the stems are thin, curved and then ascending, arranged slightly in racemes at the top of the stem, or almost entirely solitary and scattered on the stem; calyx campanulate, 1~1.5 cm. Closely covered with multicellular villous and white long hairs, with 10 uplifted veins; 5 carious teeth, oblate-lanceolate or ovate-lanceolate or ± triangular, 0.5~0.6 cm long, 0.2~0.3 cm wide, two in front of the dilute and each cracking again, the total number of caries is as many as seven; the corolla is 3~4.5 cm long; the corolla is tubular and curved, and the outside is purple-red (there is another variant, the flower is yellow, the back of the foliage is Green) is multicellular villous; corolla lobes, 5, apex obtuse or dimpled, inside yellow-purple, purple outside, both sides are multicellular villous, length 5~7 mm, width 4 mm; 4 stamens; the capsule is oblong, 2.5 mm long, 1.5 mm wide, and the base is divergent, so that the two drug chambers are often in a straight line. The ovary is 2 years old when young. Hairless; the top of the style expands into 2 sheet stigmas. Capsules fruit shape ovate to long ovate, 1~1.5 cm long. The flowering and fruiting period is from April to July.
Growth characteristics: The Rehmannia glutinosa prefers a warm climate, cold-resistant, cultivation is appropriate with sufficient sunlight, deep soil, loose, fertile neutral or slightly alkaline sandy loam, it can also be planted in mixed soil, fertile clay. Avoid continuous cropping. It is advisable to select gramineous crops before planting, and not to select land that has been planted with cotton, sesame, beans, melons, etc., otherwise, diseases will be serious.
Characters of herbs: The herb is spindle-shaped or striped, 9~15 cm long, 1~6 cm in diameter. The surface is pale red and yellow, with vertical and curved wrinkles, transverse lenticels, and irregular scars. Fleshy, easily broken, the fracture surface skin is yellowish-white, orange-red oil spots, yellowish-white in wood part, radial arrangement of conduits. It smells slightly, tastes slightly sweet, slightly bitter. It is better to use straight and thick stripes.
Pharmacological actions: The herb can counteract the decrease of plasma corticosterone concentration after continuous dexamethasone administration. Water extract had a significant antihypertensive effect on acute experimental hypertension. It can increase the number of T lymphocytes in peripheral blood and improve the phagocytosis of the reticuloendothelial system. It can also be anti-inflammatory, sedative, diuretic, hypoglycemia, and liver protection. Ethanol extract can also shorten the clotting time.
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):
Administration Guide of Radix Rehmanniae(Dì Huánɡ)
Internally:fresh rehmannia root,12~30 grams, dry rehmannia root,9~15 grams(CP), Internally:water decoction, 0.4~1 liang(about 12~30 grams), extract juice or prepare to paste. Externally:mashed and apply stick(DCTM), Internally:water decoction, 10~30 grams, extract juice or prepare to paste. Externally:proper amount, mashed and apply stick, or extract juice and smear(CHMM).
(2).Rehmannia glutinosa Libosch. f. hueichingensis Hsiao.: Botanical description: The Rehmannia glutinosa Libosch.f.hueichingensis Hsiao., is a plant of the Scrpophulariaceae family and Rehmannia genus, it is commonly known as "Rehmannia glutinosa hueichingensis", or "Huai Di Huang", its shrubs grows similarly or the same as the Rehmannia glutinosa Libosch. Actually, they are varietas of the Rehmannia glutinosa Libosch., perennial, plant height 25~40 cm, the whole plant densely gray villous and glandular hairs. Rootstock hypertrophy, blocky, cylindrical or spindle-shaped, 2.5~5 cm in diameter, single stem erected or a few branches from the base. Basal leaves clustered, leaf blade obovate or oblong, apex obtuse, base attenuates and prolonged growth petiole; edge irregularly blunt teeth, the page wrinkled; some leaves below the purple. Stem leaves are not common. Inflorescences sparsely inflorescences racemose; terminal corolla broadly tubular slightly curved, ca. 4 cm, purple-red or light-purple, sometimes 5-lobed, pale yellow, with distinct purple lines, 2-lipped; 4 stamens, 2 Strong, born near the base of the corolla tube; 1 pistil, upper ovary. The pods are ovate or ovoid, wrapped by persistent calyx, and the seeds are mostly. Its flowering period is from May to June.
1.Introduction of Di Huang:Rehmannia Root or Radix Rehmanniae.
2.TCM Books:DCTM(Dictionary of the Chinese Traditional Medicine),CHMM(Chinese Herbal Materia Medica).