Scientific Name(s): Rehmannia glutinosa (Gaertn.) Libosch. ex Fisch & C.A. Mey. Family: Scrophulariaceae
Common Name(s): Chinese foxglove , Di-Huang , Juku-Jio , Jyuku-Jio , Kan-Jiou , Sheng Di Huang , Sho-Jio , Shoudihuang , Shou-Jiou , Shu Di Huang , To-Byun , Xiandihuang , Sook-Ji-Whang (steamed root), Saeng-Ji-Whang (fresh root), Gun-Ji-Whang (dried root)
Rehmannia rhizome extracts are used extensively in traditional Chinese medicine. Clinical trials to support documented uses are lacking, and because the preparation is often used in combination with other agents, it is difficult to attribute any benefits to the plant. Catalpol, a chemical constituent of the root, is being evaluated for its potential in treating CNS diseases and its effects on aging.
None validated by clinical data. Common prescription products range from Rehmannia root 55 to 350 mg extract in polyherbal mixtures.
Chronic liver disease and GI disease, including diarrhea.
Avoid use. Rehmannia has been used traditionally as an emmenagogue.
None well documented.
Minor and transient adverse reactions have been reported and include GI discomfort (eg, mild nausea, loose bowels, flatulence), allergy, headache, dizziness, heart palpitations, fatigue, and vertigo.
None well documented.
R. glutinosa is a perennial herb that grows wild in northern and northeastern China, particularly in Hunan province. It grows to a height of 0.3 to 0.6 m and has large sticky leaves and purple flowers. The seed is sown in autumn and spring; the yellow-brown to blackish brown root is harvested after the plant has flowered in the autumn. The fresh and dried roots and rhizomes have a soft texture with deep longitudinal wrinkles on the external surface and a darker central cortex. 1 , 2
R. glutinosa has been considered a panacea in Chinese medicine for more than 2,000 years, primarily in combination with other herbs. Dried Rehmannia rhizome is reputed to “nourish the yin” and remove heat from the blood, and is used as a tonic for the liver.
Documented historical uses include treatment of anemia, cancer, constipation, diabetes, fatigue, bacterial and fungal infections, hypertension, insomnia, tinnitus, inflammatory conditions, burns, impotence, and osteoporosis. 2 , 3
The major chemical constituents of the herb are polysaccharides and iridoid monoterpenes (eg, catalpol, ajugol, aucubin, rehmanniosides, monomelittoside, melittoside, verbascoside, jionosides). Two acidic polysaccharides, rehmannans SA and SB, were isolated from the dried root of R. glutinosa of Chinese origin. These polysaccharides were composed of differing molar ratios of L-arabinose, D-galactose, L-rhamnose, and D-galacturonic acid. Additional polysaccharides have been isolated. Pharmacological activity of the plant species varies depending on processing (dried or steamed) and location of cultivation (eg, Japan versus China). Other sesquiterpenoids and furans have been isolated. 2 , 4 , 5 , 6 , 7 , 8
Uses and Pharmacology
Rehmannia is most commonly used in combination with other herbs, and clinical trials providing evidence for a definitive place in therapy are lacking.CNS effects
Catalpol is being studied for its neuroprotective effects, with potential applications in Alzheimer and Parkinson diseases, as well as in ischemia and other conditions associated with aging. 2 , 3 Clinical trials are lacking.
In in vitro studies and animal models of aging, catalpol exerts antioxidant effects on glial cell cultures, protects against beta-amyloid–induced apoptosis, increases hippocampal neuroplasticity, and upregulates gene expression of glial cell-line-derived neurotrophic factor, among other suggested mechanisms. 7 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25
Decreased hyperglycemia was demonstrated in several animal studies in which diabetes had been induced. Suggested mechanisms of action for aqueous or methanol R. glutinosa extracts, oligosaccharide, catalpol, rehmannioside D, or other polysaccharide extracts include decreasing glucose-6-phosphatase and fructokinase activity, decreasing plasma C-reactive protein, increasing hepatic glycogen content and pancreatic insulin release, and decreasing insulin resistance. 2 , 3 , 27 , 28 , 29 Additionally, protective effects were documented for diabetic nephropathy and obesity in animal models, 3 , 30 , 31 while others reported no effect on plasma cholesterol or triglycerides. 28 Despite the use of R. glutinosa in traditional Chinese medicine for the treatment of diabetes, clinical trials are lacking.Hematology
A 50% ethanolic extract of R. glutinosa inhibited decreases in fibrinolytic activity and erythrocyte deformability, decreases in erythrocyte counts, and increases in connective tissue in rodents. The extract was ineffective in reducing edema and acute or chronic inflammation. R. glutinosa prevented decreases in erythrocyte deformability in rats with endotoxin-induced disseminated intravascular coagulation. In normal rats, R. glutinosa enhanced or increased erythrocyte deformability and fibrinolytic activity. Effects on the hemopoietic system have also been described based on in vitro studies. 3 , 32 , 33Immune system
In animal studies, R. glutinosa has exerted effects on the immune system, including T-lymphocyte activity, histamine release and tumor necrosis factor, and hemolytic plaque-forming cells. The polysaccharide extracts jionoside and acetoside have been evaluated; however, clinical trials are lacking. 2 , 3 , 34 , 35 Studies in animals have demonstrated Rehmannia Six Formula (a combination preparation in which Rehmannia is the majority herb) as a potential oral adjuvant in immunization. A large and sustained rise in immunoglobulin G response occurred with antitetanus and diphtheria toxoid. 36 , 37Other effects
A limited number of clinical trials have been conducted using a combination of 10 herbs, including Rehmannia ( Zemaphyte ). However, findings from these trials cannot be attributed to any single plant.Cancer
Reductions in apoptosis have been observed in vitro with steamed root extracts in UV-stimulated cells and in hepatocellular carcinoma. 41 , 42 Antitumor effects have also been described for R. glutinosa polysaccharides, as well as increases in T-lymphocyte production. 3 , 43Gastric ulcer
An anti-inflammatory effect in animal models has been shown for Radix rehmanniae but not for ethanol extracts. In a poorly described clinical study, arthritis symptoms, including reduced joint pain and swelling, improved and joint mobility increased. 2Osteoporosis
R. glutinosa extracts may enhance bone metabolism in osteoporosis by stimulating the proliferation and activity of bone-forming osteoblasts as well as inhibiting generation and activity of bone-resorbing osteoclasts. The extract may also increase the expression of bone-related genes. In vivo studies using ovariectomy-induced osteoporotic rats showed an alleviation of decreased trabecular bone mineral density and increased cortical bone thickness and trabeculation of bone marrow spaces. 44Renal
None validated by clinical data. Common nonprescription products range from Rehmannia root 55 to 350 mg extract in polyherbal mixtures.
Avoid use. Rehmannia has been used traditionally as an emmenagogue; however, no teratogenic or abortifacient effects were found in rats following administration of a 70% methanol extract. An anti-implantation effect in female mice has been recorded. 2
None well documented. Antiplatelet action has been described based on in vitro studies 2 ; however, antagonism of the effects of aspirin on coagulation time has been reported. 3 Increased sleeping time in mice has been observed in phenobarbital-induced sleep, as well as antagonism of caffeine-induced excitability. 2
Some ingredients in a combination preparation have been suspected to cause liver toxicity, and the Pharmacopoeia of the Republic of Korea lists liver disease as a contraindication to Rehmannia use. Minor and transient adverse reactions have been reported and include GI discomfort (eg, mild nausea, loose bowels, flatulence), allergy, headache, dizziness, heart palpitations, fatigue, and vertigo. 2 , 40
Information is limited. Aqueous extracts of Radix rahmanniae were not mutagenic in Salmonella assay tests; however, intraperitoneal administration of the extract at doses of 10 to 40 times human doses were mutagenic. 2 An anti-implantation effect in female mice has been recorded; no teratogenic or abortifacient effects were found in rats following administration of a 70% methanol extract. 2
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