Introduction of Da Huang:Rhubarb or Radix et Rhizoma Rhei.

TCM Herbalism:Medicinals and Classifications. ✵The article gives records of the herb Rhubarb, its English name, Latin name, property and flavor, its botanical source three plant species, ①.Rheum palmatum L, ②.Rheum tanguticum Maxim. ex Balf, ③.Rheum officinale Baill., with a detailed introduction to the botanical features of these three plants, the growth characteristics, and ecological environment of these three plants, the features of the herb Rhubarb, its pharmacological actions, medicinal efficacy, and administration guide.

Radix et Rhizoma Rhei(Rhubarb).

Radix et Rhizoma Rhei:herb photo Pin Yin Name: Dà Huánɡ.
 English Name: Rhubarb.
 Latin Name: Radix et Rhizoma Rhei.
 Property and flavor: cold nature, tastes bitter.

 Brief introduction: The herb Radix et Rhizoma Rhei is the dried root and rhizome of Rheum palmatum L., Rheum tanguticum Maxim.ex Balf., or Rheum officinale Baill., used to induce catharsis, clear heat, purge fire, stop bleeding, counteract toxins and remove blood stasis, for treating (1).constipation with gastrointestinal accumulation, (2).warm diseases with high fever, delirium, and constipation, (3).postpartum abdominal pain, amenorrhea due to blood stasis, (4).hemoptysis, hematemesis and epistaxis associated with excessive heat in the blood, and, externally, (5).for burns, boils, and sores. The herb is commonly known as Radix et Rhizoma Rhei, Rhubarb, Dà Huánɡ.

 Botanical source: Common herbal classics and other famous herbal classics defined the herb Rhubarb Root(Da Huang) as the dry root and rhizome of the plant species (1). Rheum palmatum L, (2). Rheum tanguticum Maxim. ex Balf, or (3). Rheum officinale Baill. They are plant species of the Rheum L. genus, the Polygonaceae family (smartweed or buckwheat family) of the Polygonales suborder. These 3 commonly used species are introduced:

(1).Rheum palmatum L.

 Rheum palmatum L.:flowering plant Botanical description: The Rheum palmatum L., is a plant of the Polygonaceae family (smartweed or buckwheat family) and Rheum genus, it is commonly known as "Palmar leaf Rheum", or "Zhǎng Yè Dà Huánɡ" (literally it means Palm leaves Rheum), perennial, it grows up to 2 meters high. Roots and rhizomes are stout, hypertrophic, slightly woody, dark brown on the outside, dark yellow in cross-section, and arranged closely around the cross-section of rhizomes. Stems are upright, stout, glabrous.

 Rheum palmatum L.:flowering plant Basal leaves and lower leaves are with stout long petiole; leaf blade is broadly ovate or suborbicular, ca. 35 cm, palmately lobed to semi-fit, base is shallowly cordate, lobes are narrowly triangular, apex is pointed, both sparsely small nipples and short white bristles; cauline leaves are smaller. Inflorescences are conical, terminal, 10~20 cm long. Flowers are small, reddish-purple, several clustered; 6 tepals, arranged in 2 turns; 9 stamens, slightly exposed perianth; nutlet is oblong-elliptic, ca. 10 mm, width 7~8 mm, with 3 prisms, winged along the edge, tip is dimpled, base is subcordate, brown. Its flowering period is in June, fruiting from July to August.

 Rheum palmatum L.:drawing of plant parts Ecological environment: The Rheum palmatum L., grows in the forest, valley wetland, hillside, grassland of 1,500~4,400 meters above sea level, in the alpine mountains, soil moist grass slope, cultivated in north China. Geographical distribution: This species is mainly distributed in northwest, west, and southwest areas of China.

 Rheum palmatum L.:flowering plant Growth characteristics: The Rheum palmatum L., prefers a cool and humid climate, resistant to cold, avoid high temperatures. Usually it is planted at an altitude of 1,400 meters above sea level, the frost-free period of 120 to 150 days. The underground part can pass winter safely and begin to germinate when temperature reaches at 5 °C (Celsius, or 41 degrees Fahrenheit). The suitable temperature for growth is 15~22 °C (Celsius, or 59~71.6 degrees Fahrenheit). Roots are deeper and should be planted in loose, fertile sandy loam. Sticky, low-lying water planting easy roots.

(2).Rheum tanguticum Maxim. ex Balf.

 Rheum tanguticum Maxim. ex Balf.:growing plant Botanical description: The Rheum tanguticum Maxim. ex Balf., is a plant of the Polygonaceae family (smartweed or buckwheat family) and Rheum genus, it is commonly known as "Chicken toe Rheum", or "Táng Gū Tè Dà Huánɡ", or "Jī Zhǎo Dà Huánɡ" (literally it means chicken toe Rheum), tall herb, the plant grows up to 1.5~2 meters tall, with thick roots and rhizomes, yellow. Stems are coarse, hollow, striate, smooth, glabrous or with coarse short hairs at upper nodes.

 Rheum tanguticum Maxim. ex Balf.:drawing of plant parts Stem leaves are large, leaf blade is suborbicular or broadly ovate, 30~60 cm long, apically narrow and long pointed, base is slightly heart-shaped, usually palmately 5-parted, base-pair simple lobes, the lobes are mostly three-pinnatifid. The small lobes are long, narrowly lanceolate, with five basal veins. The masks on the leaves are papillary or rough, and the lower ones are short and dense. The petioles are nearly cylindrical and nearly equal in length to the leaves. Rough short hairs; cauline leaves are smaller, petiole is shorter, more lobes more narrow; stipules are large, more broken later, the outer mask is covered with rough short hair.

 Large panicles, branches are tightly clustered, flowers are small, reddish pale red; pedicels are filiform, 2~3 mm long, joints located at lower part; tepals are nearly elliptic, inner wheel is larger, ca. 1.5 mm; Most of the stamens are 9 and are not exposed; the disk is thin and connected to the base of the filaments to form a very shallow disk; the ovary is broadly ovate, with a short style, flat extension, and stigma is head shape. The fruit is round-oval to oblong, round or truncated at its tip and slightly heart-shaped at its base. It is 8~9.5 mm long, 7~7.5 mm wide, 2~2.5 mm wide, and the edge of the longitudinal veins are close to the wings. Seeds are ovate, dark brown. Its flowering period is in June, fruiting period is from July to August.

 Rheum tanguticum Maxim. ex Balf.:drawing of plant parts Ecological environment: The Rheum tanguticum Maxim. ex Balf., grows in an alpine valley at 1,600~3,000 meters above sea level, under the mountain shrubbery or forest margin, damp place. Geographical distribution: This species is mainly distributed in the north-west and west areas of China.

 The Rheum tanguticum Maxim. ex Balf., prefers cool, dry, and cold-resistant. It is easy to rot with high temperatures and humidity. This species should be planted in deep, well-drained sandy soil. Neutral and slightly alkaline soils are appropriate. The vitality of rhubarb is strong and the seed germination power can be maintained for 3-4 years. Only the leaf clusters were formed in the year or the second year after sowing. It returns to green in early April and blossoms in May and June in the third year and matures from June to October.

(3).Rheum officinale Baill.

 Rheum officinale Baill.:flowering plant Botanical description: The Rheum officinale Baill., is a plant of the Polygonaceae family (smartweed or buckwheat family) and Rheum genus, it is commonly known as "Rheum officinale", or "Dà Huánɡ", perennial herb, stems are upright, 2 meters high, hollow, smooth and glabrous. Basal leaves are large, long and stout fleshy, ca. as long as leaves; leaf blade is broadly cordate or suborbicular, ca. 40 cm in diameter, 3~7 deeply palmately lobed, often divided again on each lobe. Small papillae, pilose below; cauline leaves are smaller, shortly stipitate; stipules are sheathed, densely pubescent. Inflorescence is large cone-shaped, terminal; pedicel is slender, related to the lower middle section. Flowers are purplish-red or reddish-purple; 6 tepals, ca. 1.5 mm, in 2 turns; 9 stamens; 3 styles. Achenes have 3 edges, wings are ribbed, dimples slightly apex, base is nearly cordate, dark brown. Its flowering period is from June to July, fruiting from July to August.

 Rheum officinale Baill.:drawing of plant parts Ecological environment: The Rheum tanguticum Maxim. ex Balf., grows in mountain forest edge or grass slope, prefers damp environment, on mountains and grassy slopes and where the soil is thick and sunny, wild or cultivated. Geographical distribution: This species is mainly distributed in the southwest, the middle reaches area of the Yangtze River, the middle reaches area of the Yellow River, the area of the Hanjiang River, and other areas of China.

 Rhubarb Root:herb photo Characters of herbs: The herb is a cylindrical, conical, oval, or irregular block, with a length of 3~17 cm and a diameter of 3~10 cm. Except for the bark, the surface is yellow-brown to reddish-brown, and some of them can see the white-like reticular texture and scattered stars (heteromorphous vascular bundles), and the remaining cortex is brown, with many rope holes and coarse wrinkles. The texture of the herb is firm and solid, some are slightly soft in the center, the fracture surface is light reddish-brown or yellowish-brown, showing granularity; The pith is broad, with stars in a ring or scattered; The root wood part is well-developed, with radial texture, cambium ring is obvious and no stars. The herb has a delicate fragrance, it tastes bitter and slightly puckery, sticky to teeth when chewed, and a sense of sands.

 Pharmacological actions: ①.purgative effect; ②.inhibit both Gram-positive and Gram-negative bacteria, Staphylococcus aureus, Streptococcus, Diphtheria bacillus, Bacillus subtilis, Bacillus anthracis, Typhoid bacillus, Paratyphoid bacillus, and Dysentery bacillus; ③.inhibit melanoma, breast cancer, and ascites cancer in mice.

 Medicinal efficacy: Inducing purgation and attack accumulation, break stagnation and stasis, clear heat and purging fire, clear dampness and heat, purging pyretic toxicity(toxic heat), purging the pathogenic fire, cooling the blood and detoxification, remove stasis and restoring menstrual flow, activate blood stasis, remove dampness through diuresis and removing jaundice, dispel phlegm, detoxification. It is indicated for excessive heat indigestion and constipation, dyspepsia and distention fullness (food retention, distention fullness), blood heat and hematemesis or epistaxis, hematemesis (spitting blood), epistaxis (nose bleeding or bleeding from five aperture or subcutaneous tissue), red eye (hot eye), swelling and pain in throat, sore of mouth and tongue, emesia of stomach heat (stomach heat and vomiting), swelling ophthalmalgia, abdominalgia with intestinal abscess (abdominal pain, intestinal abscess), blood stasis and menostasis (stagnation of blood and menostasis), postpartum stasis blocking, abdominal mass and lumps, injuries from falls, dampness-heat dysentery,onset of dysentery, rectal tenesmus, jaundice and red urine, stranguria, edema, edema and abdominal fullness, stranguria with turbid discharge, difficulty in urination, delirium (delirious speech, wild talks), seasonal epidemic heat, yang jaundice, erysipelas (inflammatory disease with redness of skin), large carbuncle and pyogenic infections, carbuncle swelling, malignant boil;Externally for scald and burn injury. The wine prepared Rhubarb is good at clearing pyretic toxin in the upper energizer, indicated for red eye and pharyngeal swelling, gingival atrophy. The prepared Rhubarb is smooth in purgation, clearing fire and detoxification, indicated for virulent fire carbuncle ulcer. The charred Rhubarb functions in cooling blood, remove stasis and stanch bleeding, indicated for blood heat stasis and bleeding syndrome, etc.

 Administration of Radix et Rhizoma Rhei (Dà Huánɡ): 
Reference: Administration Guide of Radix et Rhizoma Rhei (Dà Huánɡ)
TCM Books: ①.Internally:3~15 grams, better not decoct long time for the purpose of purgation. Externally:proper amount, prepare to finely ground herb powder, apply stick at affected area; ②.Internally:water decoction, better not decoct long time for the purpose of purgation,1~4 qian (about 3~12 grams);or prepare to pill, powder. Externally:prepare to finely ground herb powder, mixed with water or vinegar and apply stick at affected area; ③.Internally:water decoction,3~12 grams, better not decoct long time for the purpose of purgation;or brewing with boiling water and extract juice;prepare to finely ground herb powder,0.5~2 grams;or prepare to pill, powder. Externally:proper amount, prepare to finely ground herb powder, apply stick or wash with water decoction, smear apply.
 Contraindications,Precautions and Adverse Reactions:the herb Radix et Rhizoma Rhei should be used cautiously during pregnancy, menstruation, lactation period, before and after childbirth. The herb should not be combined with Resina Toxicodendri.

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