TCM: Listed under “Herbs that tonify” in “Herbs that tonify the Blood”, sweet, slightly warm Rehmannia glutinosa, prepared root enters the Heart, Kidney and Liver channels. It nourishes the Yin and Blood, generates Essence and promotes the production of body fluids.
General: for the treatment of dizziness, insomnia, irregular menstruation and palpitations from Blood deficiency; tinnitus, weak sore lower back, forgetfulness, night sweats with Yin deficiency, diabetes and gynaecological disorders.
History
The first extant text in which there is reference to Rehmannia glutinosa is the “Divine Husbandman’s Classic of the Materia Medica” (Shen Nong Ben Cao Jing) dating from the Eastern Han dynasty 25 – 220 CE. It was the first book that provided the theoretical framework for the practice of TCM.
”Gan Di Huang (dry Radix Rehmanniae) is sweet and cold. It mainlytreats broken [bonesl, severed sinews from falls, and damaged center. Itexpels blood impediment, replenishes the bone marrow, and promotesthe growth of muscles and flesh. When used in decoctions, it eliminatescold and heat, accumulations and gatherings, and impediment. Using theuncooked is better. Protracted taking may make the body light and prevent senility. Its other name is Di Sui (Earth Marrow). It grows in i.e., near rivers and swamps.” The Divine Farmer’s Materia Medica (Shen Nong Ben Cao Jing) trans: Yang Shorr-zhong. Blue Poppy Press. 7th Ed. 2008 p.18
This text includes Rehmannia (gan di huang) among the superior class herbs.
“There are 120 superior class medicinals which are used as sovereigns.They mainly nourish life and correspond to heaven. They are nontoxic and taking them in large amounts and for a long time will not harm people. If one intends to make one’s body light, boost the qi, prevent aging, and prolong life, one should base one’s efforts on the superior.” Ibid. Preface p.ix.
The earliest text to include Rehmannia in formulas, with explanations for their use, was the Shanghan Za bing Lun, 220 CE “Cold Injuries and Miscellaneous Diseases”.This treatise by Zhang Zhong Jing was later divided into two separate works, “Discussion of Cold Damage” (Shanghan Lun) and “Essentials from the Golden Cabinet’”(Jingui Yao Lue Fang Lun) Rehmannia was a relatively minor herb in these books.
Of the three Rehmannia formulas from the Jingui Yao Lue Fang Lun, still used today, one is widely used. Rehmannia Eight Formula, (fu gui ba wei wan), frequently prescribed for problems of urination. (See CM166 Rehmannia Eight Vitality Formula).
The earliest description of processed Rehmannia (shu di huang) is in Grandfather Lei’s Discussion of Processing of Materia Medica (Lei Gong Pao Zhi Lun) 420 – 479 CE, the earliest complete treatise on processing techniques such as various methods of cleaning, cutting, drying, stir-baking, boiling and calcination. These methods still guide current practice.
During the Song Dynasty (900–1100 CE.), a book of popular prescriptions was produced that had several Rehmannia formulas. This was the “Formulary of the Tai Ping Welfare Dispensary Bureau” (tai ping hui min he ji ju fang) 1151CE. In particular, this book listed Dang Gui Four Combination (si wu tang), in which Rehmannia represents one-quarter of the prescription. This formula remains the central Blood nourishing formula of modern Chinese medicine. (See CM186 Nourish the Blood Formula).
In 1119CE, a book of prescriptions for treating children, Craft of Medicinal Treatment for Childhood Disease Patterns (Xiaoer Yaozheng Zhijue), presented Rehmannia Six Formula (liu wei di huang Tang), a derivative of Rehmannia Eight Formula made by eliminating the two kidney-warming herbs cinnamon bark and aconite. The modified formula was designed originally to treat children who were slow to develop and lacked spirit (poor mental function, low energy). In the modern clinic, the formula is also used for adults with chronic and degenerative conditions stemming either from a hereditary weakness or the effects of ageing or burnout.
For an extensive history and analysis see Subhuti Dharmananda’s website ITM online, an oldie but a goodie: http://www.itmonline.org/arts/rehmann.htm
Botanical outline
Rehmannia is a genus of six species of flowering plants in the family Scrophulariaceae (Figwort) which includes Scrophularia ningpoensis (xuan shen), Euphrasia officinalis (eyebright) and Verbascum spp. (Mullein).
Rehmannia glutinosa is native to China, Japan and Korea. It has many cultivated varieties across China. A perennial herb growing to 30cms with a basal rosette of dentate margined, elliptical leaves growing on the stem. The plant bears reddish-purple, tubular, 5 lobed flowers that are cymose (an inflorescence wherein the main axis bears a solitary flower in the middle or at the terminal that blooms first). The buds are removed to increase root growth. Rehmannia has a large rhizome which is succulent and has a brownish-yellow color.
The roots of cultivated plants are harvested in the autumn or early winter, whilst wild plants are harvested in early spring. The best quality comes from Henan province.
Unprocessed Rehmannia root is slow roasted dry.Processed Rehmannia is made by mixing the dried roots with rice wine (30% by weight) and steaming until the roots are dark and moist throughout. They are then partially dried in the sun, sliced and the drying completed.
Medicinal properties
In TCM, processed Rehmannia is described as sweet and slightly warm, entering the Heart, Kidney and Liver channels.It is used to tonify Kidney Blood, Yin and Essence (jing). It is a primary longevity herb and a foundational herb in the maintenance of women’s health. It is frequently used in the treatment of menstrual disorders, gestational and postpartum disorders and infertility. It is also present in many male fertility and potency formulas.
Kidney Essence derives from one’s inherited energy (Pre-Heaven Essence) and is replenished by the energy that one derives from food (Post-Heaven Essence). It determines the basic constitutional strength governing growth, sexual maturation and reproduction. The Defensive (wei) Qi (immune system) also has its root in the Kidney Essence.
The Essence produces “marrow” which in turn produces bone marrow to support the production of Blood and fills the spinal cord and the brain. Thus weak Kidney Essence can lead to either poor bone development or poor concentration and memory.Kidney Essence is an aspect of Kidney Yin, replenished with difficulty, changing slowly over time. Signs of aging are signs of diminishing Essence.
Unprocessed Rehmannia is cold & bitter so can clear the heat in situations such as illnesses which involve Warm-Heat pathogens with fever, thirst and irritability, or clear heat in the Blood causing bleeding or skin disorders. It is also cold, sweet and generates fluids and can protect the Yin from damage both from the effects of exterior or deficient heat conditions or from the bitter, drying qualities of other heat clearing herbs. It also enters the channels of the Heart, Kidney & Liver.
In a number of formulas processed and unprocessed Rehmannia are used in combination. eg in treating chronic asthma, processed Rehmannia restores deficiency of Kidney Yin, while unprocessed Rehmannia will clear heat and generate fluids.
In Western herbal medicine, Rehmannia is looked upon as an adrenal tonic; and is believed to support the cells of the adrenal cortex and pituitary during times of prolonged stress.
Rehmannia has been shown to have hematinic, blood stimulant, analgesic, demulcent, laxative and hypotensive effects.
Components of Rehmannia root include iridoids and iridoid glycosides including catalpol being investigated for its anti-ageing potential.
Catalpol increases hippocampal neuroplasticity and up-regulates PKC and BDNF in the aged rats Jing Liu, Qiap-Jie Je, Wei Zou, Hong-xia Wang, Yong-ming Bao. Brain Research Vol 1123 Issue 1, 6 December 2006, Pages 68–79