Rehmannia glutinosa, or known as Sheng Di Huang in Pinyin, is such a common medicine in TCM that it has been considered as one in 50 fundamental Chinese herbs these days. Usually it is the fresh or dried roots that are used clinically. But it is often used in the prepared form too, which is called Shu Di Huang. At this point it’s better to mention that these are two herbs with quite different medicinal uses, from the perspective of traditional Chinese medicine. Today rehmannia is a really versatile drug that can be compatible with a variety of other herbs for the treatment of many other diseases, such as idiopathic thrombocytopenic purpura, dysfunctional uterine bleeding, rheumatism and arthritis, Sheehan syndrome, eczema, neurodermatitis, urticaria, constipation, diabetes, infectious hepatitis, infertility, menopause, acne, hair loss, osteoporosis, tinnitus, and so on.
What is rehmannia glutinosa?
Medicinally it mainly refers to the fresh or dried root of Rehmannia glutinosa Libosch., which is one of medicinal plants in the family Scrophulariaceae. Other common names of it include Chinese foxglove, radix rehmanniae, radix rehmanniae glutinosae, and the like. In China it is primarily produced in provinces of Henan, Hebei, Inner Mongolia and the Northeast. And it is also cultivated in most parts of China. It is generally harvested in autumn. The following steps are to remove the residual part of stem, fibrous root, and soil. It is normally used fresh or dried.
The meaning of “Sheng” has a little subtle difference between ancient and modern backgrounds. In ancient time Sheng Di means the fresh herb since back then the prepared rehmannia didn’t invented yet, especially before the Tang and Song dynasties. Now the “Sheng”, meaning dried, is more an opposite concept of “Shu” (prepared). Hence, today when it is used in the fresh form, the prescription should give a clear indication of “Xian” (fresh).
Xian Di Huang (fresh form) is in the shape of spindle or strip, 8 to 24cm long, and in diameter of 24cm. Outer skin is thin, reddish yellow, and with curved longitudinal wrinkles, bud scars, long horizontal lenticels and irregular scars. It is succulent, easily broken, and with yellowish white cortex, visible orange oil spots, yellow-white xylem, and radially arranged xylem vessels in cross section. It is with slight odor and slightly sweet and bitter taste; Sheng Di Huang (dried raw form) is mostly in the shape of irregular lumps or oblong and with swollen middle and slightly small ends. Some are small, elongated, slightly flat and twisted, 6 to 12cm long, and 3 to 6cm in diameter. Surface is dark brown or brownish gray, very wrinkled, and with irregular horizontal curved lines. It is heavy, soft and tough, difficult to break, and with brown or black section that is shiny and sticky. And it is odorless and slightly sweet.
Main chemical constituents of rehmannia glutinosa tuber include β-sitosterol, mannitol, a small amount of stigmasterol and campesterol, iridoid, monoterpene and glycosides, organic acids, saccharides, amino acids, and more. And iridoid, monoterpene and glycosides include rehmannin, catalpol, dihydrocatalpol, acetyl catalpol, danmelittoside, melittoside, geniposide, ajugoside, daucosterol, 1-Ethyl-β-D-galactoside, rehmannioside A, B, C, D, etc. Organic acids include benzoic acid, caprylic acid, 3-Methoxy-4-hydroxybenzoic acid, cinnamic acid, oleic acid, linoleic acid, palmitic acid, stearic acid, octanoic acid, nonanoic acid, decanoic acid, lauric acid, tetradecanoic acid, pentadecanoic acid, heptadecanoic acid, nonadecanoic acid, eicosanoic acid, heneicosanoic acid, behenic acid, etc. Saccharides include stachyose, glucose, sucrose, fructose, raffinose, mannotriose, verbascose, galactose, and vitamin A substances. In addition, fresh rehmannia contains 20 kinds of amino acids, among which arginine has the highest content; dried rehmannia contains 15 kinds of amino acids, among which alanine has the highest level. And it also contains iron, zinc, manganese, chromium, and other 20 kinds of trace elements.
Rehmannia glutinosa benefits
Its main health benefits are mainly focused on two aspects – removing heat to cool blood and nourishing Yin and generating body fluid. Since it is of sweet-bitter taste and cold nature, it acts on blood aspect and can cool blood by clearing blood-aspect heat. As a result, it is ideal for warm disease and heat illness that is characterized as high fever, thirst, and deep red tongue. Besides, it can be used in treating a variety of hemorrhage too since it is able to stop heat-induced bleeding.
It can nourish Yin too thanks to its moist and juicy properties. And because of its sweet taste and cold nature it can also nourish Yin, moisten dryness, and promote the secretion of saliva or body fluid. Hence, it is the perfect remedy for those with body fluid impairment due to heat pathogen in late warm and heat disease. Also, its effect of nourishing yin and clearing heat is frequently used in the treatment of dry mouth, thirst, and dizziness due to fire excess from yin deficiency and xiaoke disease that belongs to the pattern of impairment of fluid by excessive heat.
Modern pharmacology of rehmannia
1) Its water extract has antihypertensive, sedative, anti-inflammatory, and anti-allergic effects;
2) Its liquid extract has cardiotonic and diuretic effects;
3) Its ethanol extract can shorten the clotting time;
4) Rehmannia-based Liu Wei Di Huang Wan can lower blood pressure, improve kidney function, and reduce tumor;
5) It resists the declined concentration of plasma corticosterone after continuous administration of dexamethasone;
6) It prevents the atrophy of adrenal cortex;
7) It promotes the conversion of lymphoblasts of the body and increases the number of T lymphocytes;
8) It enhances the phagocytosis of reticuloendothelial cells, which is especially obvious for immunocompromised persons.
Sample rehmannia recipes on herbal remedies
The fresh rehmannia is sweet and bitter in flavor, cold in nature, with functions of clearing heat, promoting fluid production, cooling blood, and stopping bleeding, which makes it an excellent herb for impairment of Yin in heat disease, purple tongue, polydipsia, rash, spitting blood, epistaxis, and sore throat. In comparison, the raw rehmannia is sweet in flavor and cold in nature, with clearing heat, cooling blood, nourishing Yin, and induce the production of body fluid, which is perfect for the treatment of purple tongue, fidget, and thirst due to fever, internal heat due to yin deficiency, hectic fever due to yin deficiency, consumptive fever, consumptive thirst caused by internal heat, vomiting blood, nosebleed, and eruption. Both of them go to meridians of heart, liver, and kidney. And recommended rehmannia glutinosa dosage is from 12 to 30 grams in fresh form and 9 to 15 grams in raw form in decoction. Besides, you can choose rehmannia glutinosa supplement, rehmannia complex, compound pills, rhizome extract, and more.
1) Qing Ying Tang from Wen Bing Tiao Bian (Detailed Analysis of Warm Diseases). It is formulated with Xuan Shen (Scrophularia), Lian Qiao (Forsythia), Dan Shen (Salvia Miltiorrhiza), etc. to treat heat entering nutrient-blood in warm-heat disease that manifest as high fever, polydipsia, coma, and purple tongue.
2) Da Huang San from the Shang Han Zong Bing Lun (General Treatise on Cold Damage). It is coupled with Da Huang (rhubarb) to cure vomiting blood and nosebleed.
3) Liang Di Dan from Shi Shi Mi Lu (Secret Records of the Stone Chamber). It is matched with Di Yu (Sanguisorba Officinalis) to heal blood in the stool and in the urine due to blood heat.
4) Di Huang Gao from Gu Jin Yi Tong (Ancient and Modern Medical Book). It is joined with Zhi Mu (Anemarrhena Rhizome) and Di Gu Pi (Lycium Barbarum Root Bark) to treat Yin asthenia generating intrinsic heat, hot flash, and steaming bone.
5) Yi Wei Tang from “Detailed Analysis of Warm Diseases”. It is equipped with Mai Men Dong (Mondo Grass), Sha Shen (Glehnia), Yu Zhu (Solomon’s Seal), etc. to cure impairment of yin and polydipsia in heat illness.
Clinical research of rehmannia
a) 20 cases of lupus erythematosus acrodynia have been treated with the decoction of 120g rehmannia, 60g Huang Qin (Scutellaria), and 30g Ku Shen (Sophora Flavescens Root). And all of them were cured.
b) 51 cases of female idiopathic sexual precocity have been treated with concentrated oral mixture, which consists of rehmannia, Huang Bai (Amur Cork Tree), Zhi Mu (Anemarrhena Rhizome), Scrophularia, etc. And the effect was really significant.
c) 30 cases of viral myocarditis have been treated with decoction of rehmannia, Huang Qi (Astragalus Root), Tai Zi Shen (pseudostellaria heterophylla), Mondo Grass, Mu Dan Pi (Tree Peony), and Fu Ling (Poria). And the total efficiency was 70%.
Rehmannia glutinosa side effects and contraindications
After taking rehmannia glutinosa root, a few patients may have diarrhea, abdominal pain, dizziness, fatigue, heart palpitations and other adverse reactions. But they will go away on their own within a few days. Else, it was ever reported that it resulted in shock 20 minutes after eating 100g rehmannia and the patient restored normal later by receiving the anti-shock treatment. TCM wise, it should be used with caution in the cases of diarrhea due to spleen deficiency, reduced appetite caused by stomach deficiency, and excessive phlegm in chest.
a) Shan Dong Zhong Yi Za Zhi (Shandong Journal of Chinese Medicine), 1981;2:93;
b) Zhong Xi Yi Jie He Za Zhi (Chinese journal of modern developments in traditional medicine), 2001; 10:732;
c) Shang Hai Zhong Yi Yao Za Zhi (Shanghai Journal of Traditional Chinese Medicine), 2001;3:19.