Rehmannia glutinosa, commonly referred to as Chinese foxglove or “shu di huang” in Traditional Chinese Medicine (TCM), is a hardy, herbaceous plant cherished for its thick, starchy roots, known to be highly versatile in traditional herbal remedies. This perennial species, native to China, has earned acclaim for its purported benefits in supporting kidney and liver health, promoting vitality, and strengthening the immune system. Its historical use spans thousands of years, making it a cornerstone in TCM formulations and folklore. The roots are typically harvested after two to three years of growth, undergoing specific drying and processing methods to enhance their therapeutic potency.

Botanical Classification

• Kingdom: Plantae
• Clade: Tracheophytes
• Class: Magnoliopsida
• Order: Lamiales
• Family: Orobanchaceae
• Genus: Rehmannia
• Species: Rehmannia glutinosa

Plant Characteristics

Rehmannia glutinosa is a resilient plant that grows up to 30 centimeters (12 inches) tall, bearing dark green, ovate to lanceolate leaves arranged in a rosette pattern close to the ground. The leaves, with scalloped edges, have a slightly rough texture. The plant produces slender, erect flowering stems, each adorned with bell-shaped flowers that exhibit hues of pink to purple, blooming in late spring and early summer. Its roots are thick, cylindrical, and slightly twisted, covered in a dark, wrinkled skin that turns purplish-brown upon drying.

This robust morphology allows it to survive various climates, but it thrives best in temperate regions with moderate rainfall and well-drained soil, where it can develop its rich root system fully.

Chemical Composition and Structure

The biochemical composition of Rehmannia glutinosa is complex, containing a broad spectrum of active compounds responsible for its medicinal efficacy. Key constituents include:

• Iridoid Glycosides: Catalpol, rehmannioside A, D, and C. These compounds are pivotal to the plant’s anti-inflammatory and neuroprotective actions. Catalpol, in particular, is valued for its role in protecting nerve cells and modulating immune responses.

• Phenethyl Alcohol Glycosides: Acteoside and isoacteoside, known for potent antioxidant and anti-inflammatory properties, contribute to its role in cell protection and rejuvenation.

• Polysaccharides: Long-chain sugars found in Rehmannia root polysaccharides enhance its immune-modulating and liver-protective functions. These molecules are believed to support general health and immune responses.

• Amino Acids: The plant contains amino acids such as arginine and asparagine, which are thought to provide nourishing and restorative qualities, especially for muscle tissue and nervous health.

• Stachyose: A unique tetrasaccharide found in Rehmannia that has prebiotic effects, supporting gut health by fostering beneficial intestinal bacteria.

How to Cultivate Rehmannia glutinosa

Rehmannia glutinosa is cultivated widely for its roots. Below are the cultivation conditions and steps to ensure optimal growth:

1. Climate: Ideal in temperate zones with cool winters and warm, moist summers. High altitudes or excessively wet environments should be avoided.

2. Soil Requirements: Prefers loamy or sandy, well-drained soil, with a high organic content and pH ranging from 6.0 to 7.5. Soil should be free from compact layers to facilitate root expansion.

3. Propagation: Primarily grown from root cuttings, though it can also be propagated by seeds. Seed propagation should be done indoors in early spring, with transplantation when seedlings reach 5–7 cm in height.

4. Watering and Maintenance: Water consistently, ensuring the soil remains moist but not waterlogged. Regular mulching helps retain moisture and maintain soil temperature, while weeding prevents nutrient competition.

5. Harvesting: Roots are usually harvested in autumn after 2–3 years when they achieve full maturity. Harvesting involves carefully uprooting the plant to preserve the fleshy roots, which are then dried for medicinal use.

Uses and Benefits

In TCM and other traditional systems, Rehmannia glutinosa is highly valued for its multifaceted benefits:

• Kidney and Adrenal Support: Often used to bolster kidney function and address “kidney yin deficiency,” as described in TCM. It is believed to have a restorative effect on adrenal function, potentially aiding in energy regulation and stress management.

• Blood Circulation and Hemoglobin Support: Used as a blood tonic, it is thought to nourish the blood and increase vitality, especially for individuals experiencing fatigue or anemia-related symptoms.

• Anti-inflammatory and Anti-Aging Properties: Bioactive compounds, particularly iridoid glycosides, are believed to inhibit pro-inflammatory cytokines, helping to mitigate inflammatory conditions. Additionally, the antioxidant content is thought to support cellular health and slow the aging process.

• Immune Modulation: Polysaccharides in Rehmannia may enhance immune function by promoting macrophage activity, aiding the body’s ability to fight infections.

• Hormonal and Endocrine Balance: Used traditionally to regulate hormones, particularly in women for menstrual and menopausal symptoms.

Applications

• Medical: In traditional formulations, Rehmannia glutinosa root extracts are used in treatments for kidney and liver ailments, blood sugar stabilization, chronic fatigue, and inflammatory conditions. It is a staple in TCM formulas targeting conditions that stem from deficiency syndromes (like “kidney yin deficiency”) and can be found in various supplement forms.

• Cosmetics: The root extracts are used in skincare products, capitalizing on their hydration, rejuvenation, and anti-aging potential. Antioxidants present in the extracts are thought to protect skin cells, improve hydration, and encourage collagen production.

• Other Applications: Used in wellness supplements focusing on adrenal health, vitality enhancement, and immunity. In prebiotic formulas, stachyose from Rehmannia can contribute to gut health by supporting beneficial bacteria.

Environmental and Safety Considerations

Rehmannia glutinosa is generally safe when used within recommended guidelines, though some people may experience mild digestive discomfort, especially with high doses or prolonged use.

Environmental considerations for cultivating Rehmannia include ensuring it is grown sustainably, avoiding pesticide-heavy cultivation, and preserving the integrity of soil conditions to prevent overharvesting. Users with allergies or hypersensitive skin should exercise caution, as certain bioactive compounds may cause sensitivity.

Bibliografia__________________________________________________________________________

Zhang RX, Li MX, Jia ZP. Rehmannia glutinosa: review of botany, chemistry and pharmacology. J Ethnopharmacol. 2008 May 8;117(2):199-214. doi: 10.1016/j.jep.2008.02.018. 

Abstract. Rehmannia glutinosa, a widely used traditional Chinese herb, belongs to the family of Scrophulariaceae, and is taken to nourish Yin and invigorate the kidney in traditional Chinese medicine (TCM) and has a very high medicinal value. In recent decades, a great number of chemical and pharmacological studies have been done on Rehmannia glutinosa. More than 70 compounds including iridoids, saccharides, amino acid, inorganic ions, as well as other trace elements have been found in the herb. Studies show that Rehmannia glutinosa and its active principles possess wide pharmacological actions on the blood system, immune system, endocrine system, cardiovascular system and the nervous system. Currently, the effective monomeric compounds or active parts have been screened for the pharmacological activity of Rehmannia glutinosa and the highest quality scientific data is delivered to support the further application and exploitation for new drug development.

Liu NA, Liu JQ, Liu Y, Zhu Q, Zheng D, Li F, Meng LZ, Qiu M. Rehmannia Glutinosa Polysaccharide Regulates Bone Marrow Microenvironment via HIF-1α/NF-κB Signaling Pathway in Aplastic Anemia Mice. An Acad Bras Cienc. 2023 Aug 4;95(3):e20220672. doi: 10.1590/0001-3765202320220672.

Abstract. Aplastic anemia (AA), a rare disorder, is associated with bone marrow microenvironment (BMM). Presently, AA treatment is of great difficulty. This study aimed to explore the mechanism of action of Rehmannia glutinosa polysaccharide (RGP) in AA. Busulfan was used to induce AA in BALB/c mice; blood cell count and Ray's Giemsa staining were used to assess the severity of hematopoietic failure; HE was performed to assess the pathological state of the marrow cavity; ELISA was performed to assess IL-4, IL-10, IL-6, IL-12, IL-1β, TNF-α, MCP-1, VEGF, and EPO; and WB was performed to evaluate the effects of RGP on the HIF-1α/NF-κB signaling. Significant downregulation of hemocyte levels in the blood and nucleated cells in the bone marrow was reversed by RGP and Cyclosporine A (CA). Compared with the AA group, dilating blood sinusoids, inflammation, hematopoiesis, decreased bone marrow cells and megakaryocytes were alleviated by RGP and CA, and the HIF-1α/NF-κB signaling was inhibited too. Notably, RGP was more effective when used in combination with CA. In this study, we established a relationship between BMM and the HIF-1α/NF-κB signaling pathway and found that RGP regulates BMM by suppressing the activation of the HIF-1α/NF-κB signaling. Thus, RGP exerts a pharmacological effect on AA.

Nguyen HD, Ho Thi L, Ho XB, Cao VA, Le Hoang DM. Effect of Rehmannia glutinosa Libosch extract on proliferation and cardiogenic pre-differentiation of human mesenchymal stem cells. Biomedicine (Taipei). 2022 Mar 1;12(1):39-52. doi: 10.37796/2211-8039.1243. 

Abstract. Background: Vietnamese medicine tried and tested certain bioactive compounds from plants to increase the rate of tissue immunomodulation, regeneration, and differentiation. Although there are many research papers discovered about phytochemicals of Rehmannia glutinosa Libosch and differentiation induction potential of some substances purified from this herbal, it finds difficult to seek research that investigated the effect of hot water-extracted R. glutinosa Libosch (RGE) on proliferation and cardiogenic differentiation of mesenchymal stem cells, even though it has commonly been used for a long time because of its function as a restorative and as a critical role in cardiovascular treatment in traditional. ....Conclusion: The RGE could either stimulate proliferation-migration of MSCs or induce the cardiac pre-differentiation process. This extract can be classified as non-toxic to the UC-MSCs.

Zhang RX, Jia ZP, Kong LY, Ma HP, Ren J, Li MX, Ge X. Stachyose extract from Rehmannia glutinosa Libosch. to lower plasma glucose in normal and diabetic rats by oral administration. Pharmazie. 2004 Jul;59(7):552-6.

Abstract. The hypoglycemic effects of water extract and stachyose extract (Part III) from Rehmannia glutinosa Libosch. were investigated in this paper by oral administration to normal, glucose- and adrenaline-induced hyperglycemic and alloxan-induced diabetic rats. The results showed that Part III had the effect of lowering fasted plasma glucose level and partially preventing hyperglycemia induced by glucose (2.5 g x kg(-1), i.p.) and adrenaline (300 microg x kg(-1), i.p.), respectively, but no obvious dose-dependent effect was found when it was administered at the doses of 100, 200 and 400 mg x kg(-1) for 6 days, i.g. In alloxan-induced diabetic rats, Part III (200 mg x kg(-1) for 15 days, i.g.) gave a significant decrease in blood glucose level. The results suggested that Part III, which is mainly composed of stachyose from Rehmannia glutinosa Libosch., had a significant hypoglycemic effect in glucose- and adrenaline-induced hyperglycemic and alloxan-induced diabetic rats.

Yang Y, Yu L, Zhu T, Xu S, He J, Mao N, Liu Z, Wang D. Neuroprotective effects of Rehmannia glutinosa polysaccharide on chronic constant light (CCL)-induced oxidative stress and autophagic cell death via the AKT/mTOR pathway in mouse hippocampus and HT-22 cells. Int J Biol Macromol. 2024 Mar;261(Pt 2):129813. doi: 10.1016/j.ijbiomac.2024.129813. Epub 2024 Jan 28. PMID: 38286367.

Liang L, Yue Y, Zhong L, Liang Y, Shi R, Luo R, Zhao M, Cao X, Yang M, Du J, Shen X, Wang Y, Shu Z. Anti-aging activities of Rehmannia glutinosa Libosch. crude polysaccharide in Caenorhabditis elegans based on gut microbiota and metabonomic analysis. Int J Biol Macromol. 2023 Dec 31;253(Pt 8):127647. doi: 10.1016/j.ijbiomac.2023.127647. Epub 2023 Oct 24. PMID: 37884235.