Cooked rehmannia root, also called Shu Di Huang in Pinyin, is produced throughout China. However, when it comes to medicinal uses, the herb from Huaiqing region in Henan province is thought to be the most “authentic” species. Thanks to its wide ranging medicinal properties, it has long been known as one of the 4 most famous Huai-medicines. Compared to raw or fresh rehmannia root, its tonic properties have been greatly enhanced by processing. By the way, the commercial rehmannia is ungraded and all items are usually sold at a single price. Medicinally the preferred one is bigger in size, heavier in weight, softer and oilier, and with blacker cross section and sweeter taste. So, what is rehmannia used for and how to get the most health benefits from it? Here are some useful tips for you.
What is prepared rehmannia root?
It refers to the processed rehmannia glutinosa libosch root. The processing method is to steam along with auxiliary materials of wine, Amomum, and orange peel, dry them in the sun, repeat the above-mentioned steps until they become totally black, oily, soft and sticky. Medicinally it is used sliced or charred. Other common names of this herb include Chinese Foxglove Root, dihuang, Rehmannia glutinosa steamed root, Rehmanniae radix, Digitalis glutinosa, Rhizoma rehmanniae, Rehmannia chinensis, cooked or cured rehmannia, and so on.
The rehmannia plant is a perennial herb, 10 to 40cm in height. The whole plant is covered with off-white villus and glandular hairs. Thick root is succulent, in shapes of bulk, cylinder, or spindle. Erect stems are single or with a few branches at the base. Basal leaves are in clumps. Blade is obovate-lanceolate, 3 to 10cm long, 1.5 to 4cm wide, and with obtuse apex, narrow base, wrinkled surface, and irregular jagged edges. Stem leaves are much smaller. The floral axis is erect, hairy, and in racemes in upper stem; bracts are leafy, developed or degraded; calyx is in bell-shaped, 5-lobed apex, and with triangular lobes, multicellular villous and white long-hair, and 10 veins; tubular corolla is wide, slightly curved, 3 to 4cm long, dark purple outside and mixed with yellow inside, and with clear purple stripes, and 5-lobed apex. Stamens are 4, didynamous, and anther with fork base; superior ovary is ovoid, 2-roomed but 1-roomed after flowering, 1 style, and enlarged stigma. Capsule is ovate or ovate and with acute apex, persistent style, and wrapped with the persistent calyx outside. Seeds are many. Flowering time is from April to May and fruiting time is from May to June.
Rehmannia (cooked) root contains smaller amounts of iridoids and the isolated ingredients include leonuride, aucubin, catalpol, rehmannioside A, B, C, D, melittoside, tehmaglutin A, D, gluti-noside, etc. It also contains monoterpenes like jioglutin A, B, C, jioglutolide, jiolutin A, B, C, jioglutolide, jiofuran, rehmapicrogenin, and so on. It contains amino acids too, which don’t include lysine and have less content compared with dried rehmannia root. It contains more monosaccharide. In addition, it contains trihydroxy-β-ionone, 5-c-hydroxyaeginetic acid, suscinic acid, 5-oxoproline, 5-hydroxymethylfuroic acid, uracil, uridine, and the like.
Rehmannia root benefits
It was first appeared in Shen Nong Ben Cao Jing (Shen Nong’s Herbal Classic). Today there are there kinds of rehmannia available – prepared, fresh, and raw rehmannia root. All of them are capable of treating all diseases caused by deficiency of yin and body fluid since they can nourish Yin and produce saliva.
However, clinically they are not the same thing and with different healing properties. The fresh one is sweet-bitter in taste and extremely cold in nature. It is with weak yin-nourishing ability but a better performance on removing heat to cool blood, purging the pathogenic fire, and relieving restlessness. So, it is often used in patterns of blood heat due to exuberant pathogens and deficiency of yin and fluid; the dried one is of sweet taste and cold-moist nature. It is with less blood-cooling properties but a better ability on nourishing the yin of heart and kidney. Hence, it is the perfect option in the treatment of impaired yin caused by blood heat and fever due to yin deficiency; the cooked one is an important liver-kidney tonic that not only nourishes blood and yin, but also reinforces essence and marrow. Tradition Chinese medicine believes that essence and blood are the most fundamental material basis of the body. That’s to say, adequate blood and essence is precondition of normal function of liver and kidney and healthy body. On the contrary, deficiency of blood and essence will result in light-headedness, sore aching low back and knees, deafness, tinnitus, premature graying, premature aging, sexual dysfunction, and so on. In recent years, Liu Wei Di Huang Wan, a famous rehmannia-based Chinese patent medicine, has been found with promising effect on combating age-related diseases and anti-aging.
Modern pharmacological actions of rehmannia glutinosa root
1) It can fight against the decline of plasma corticosterone concentration after continuous administration of dexamethasone. In addition, it can prevent adrenal cortical atrophy;
2) The gavage of rehmannia root decoction to rat can significantly reduce the amount of vitamin C in the adrenal gland, which shows that it can resist the pituitary – adrenal cortex system inhibition caused by dexamethasone. And it can promote the synthesis of adrenal hormones;
3) Liu Wei Di Huang Tang can significantly lower blood pressure on experimental renal hypertension in rat, improve kidney function, and reduces the risk of disease mortality;
4) Liu Wei Di Huang Tang can significantly fight against the roventriculus squamous carcinoma cells induced by N-nitroso acid ethyl ester in mice.
Sample rehmannia cured root tuber recipes on herbal remedies
The Chinese Materia Medica considers that it is sweet in flavor and warm in nature. And it covers meridians of liver and kidney. Essential functions include enriching the blood, moistening, invigorating the essence, and filling the marrow. Primary rehmannia root uses and indications are sallow complexion due to deficient blood, dizziness, palpitations, irregular menstruation, profuse uterine bleeding, Yin-deficiency in liver and kidney, hot flashes and night sweats, nocturnal emission, impotence, infertility, soreness and weakness of waist and knees, tinnitus and deafness, dim eyesight, premature graying, diabetes, constipation, and breathlessness caused by deficient kidney. And today it is also used for infertility, acne, thyroid, hair loss, and the like. Recommended rehmannia root dosage is from 10 to 30 grams in decoction. And you can choose other related products too, such as rehmannia root combo tea extract, tea, capsules, extract, powder, pills, and more.
1) Si Wu Tang from Tai Ping Hui Min He Ji Ju Fang (Formulas of the Peaceful Benevolent Dispensary). It is formulated with Dang Gui (Dong Quai), Bai Shao (White Peony Root), and Chuan Xiong (lovage) to treat blood-deficiency induced sallow complexion, dizziness, palpitations, insomnia, irregular menstruation, metrorrhagia and metrostaxis, and more.
2) Jiao Ai Tang from Jin Gui Yao Lue (Essential Prescriptions of the Golden Coffer). It works with E Jiao (Donkey-Hide Gelatin), Ai Ye (Mugwort Herb), etc. to cure blood deficiency, cold in blood, and cold pain in lower abdomen because of metrorrhagia and metrostaxis.
3) Liu Wei Di Huang Wan from Xiao Er Yao Zheng Zhi Jue (Key to the Therapeutics of Children’s Diseases). It joins with Shan Yao (Chinese Yam), Shan Zhu Yu (Cornelian Cherry), etc. to heal yin deficiency in liver and kidney, sore aching low back and knees, nocturnal emission, night sweating, tinnitus, deafness, and diabetes.
4) Da Bu Yin Wan from Dan Xi Xin Fa (Dan Xi’s Experiential Methods). It cooperates with Zhi Mu (Anemarrhena Rhizome), Huang Bai (Amur Cork Tree Bark), Gui Jia (Reeves’ Turtle Shell), etc. to treat yin deficiency induced bone steaming and hot flashes.
5) Qi Bao Mei Ran Dan from Yi Fang Ji Jie (Wang Ang and his Variorum of medical recipes). It matches with He Shou Wu (Polygonum Multiflorum), Niu Xi (Achyranthes), Tu Si Zi (Cuscuta), etc. to heal premature graying due to essence-blood deficiency.
Root of rehmannia clinical research
a) When used to treat hypertension, prepared rehmannia decoction can lower high blood pressure, serum cholesterol and triglycerides at the same time. In addition, the cerebral blood flow and ECG were also improved.
b) The total effective rate of treating male infertility by oral administration of Fu Fang Wu Zi Di Huang Kou Fu Ye was 84%.
Rehmannia root side effects and contraindications
Although cooked rehmannia root is a tonic and one of the best herbs for gynecological diseases. But misuse of it may still cause a lot of trouble since it is with some toxicity. In addition, it may cause allergic reaction in individual cases since it is prepared with wine and it contains a variety of carbohydrates. The adverse reactions include diarrhea, abdominal pain, fatigue, heart palpitations, facial itching, round wheals spreading from neck to the trunk and limbs, and scattered rash that is above the skin surface. And the symptomatic treatment is taking anti-allergic medicines. TCM wise, it shouldn’t be used in the cases of deficiency of spleen and stomach, Qi stagnation and excessive phlegm, and abdominal bloating and loose stools.
a) The Expertise Report of Scientific Research on Whether or not Adding Wine When Cooking Rehmannia, 1980.6;
b) Zhong Xi Yi Jie He Za Zhi (Chinese Journal of Modern Developments in Traditional Medicine), 1995;15(4):209.