Rehmannia glutinosa - Chinese Foxglove

Common Names: Rehmannia glutinosa, Chinese Foxglove, Digitalis glutinosa, Rehmania chinensis, di huang, glutinous rehmannia, gan dihuang, Kan-jio, huaiquing dihuang, dihuang, juku-jio, Hachimijio-gan, Go-shajinki-gan, To-Byun, Sook-Ji-Whang, Rehmanniae, Go-shajinki-gan, To-Byun, Sook-Ji-Whang, Chinese RR, Di Huang, Kan-Jio, Juku-Jio, Jio, Sho-Jio, Saeng-Ji-Whang, Gun-Ji-Whang, Remannia, Rheumannia

Latin Name: Rehmannia glutinosa

Origin: Asia

Short Introduction

Rehmannia glutinosa thrives easily in its native habitats. In the temperate climate of the Czech Republic, it adapts well and can survive mild winters. The first successful attempts to cultivate it in Central Europe date back to 1995. The plant is adaptable to different soil types as long as key conditions are met; avoid waterlogged soils with excess nutrients. Rehmannia is propagated by sowing seeds or by taking cuttings from its fleshy root. Harvesting the root is challenging, as it breaks easily and grows deep in the substrate. After harvesting, roots should be carefully dried in well-ventilated spaces at temperatures above 40°C.

Detailed Description

Rehmannia glutinosa is traditionally valued for supporting longevity and is used to address ailments related to bones, blood, the vascular system, and more!

Botanical Information

Rehmannia glutinosa is a perennial herb reaching up to 30 cm in height with dense hairs along its reddish-pink stem. Its root, about 6 cm long, is fleshy and constitutes the most widely used part in traditional Chinese medicine and Ayurveda, most often applied fresh (when small and tender) or dried. The green, elliptic-oval leaves (2–13 cm long) are lighter on the underside and tinged red at the base, forming a basal rosette with toothed edges. The plant produces axillary flowers, ranging from yellow to purple, that appear from April to July. Its fruit is a capsule containing numerous tiny seeds.

Origin and Distribution

Rehmannia originates from the Chinese provinces of Henan, Shandong, Shanxi, Hebei, Liaoning, Jinan, Hubei, Sichuan, and central Asia, including parts of Mongolia. Today, it is most commonly cultivated throughout central Asia or found growing wild in uplands up to 1100 m in altitude, near coastal regions. In central Europe, it is predominantly seen among horticulturists and gardeners, where it can overwinter if winters are mild.

Usage / Dosage

Rehmannia glutinosa is a key ingredient in many traditional Chinese medicine and Ayurveda formulas, either on its own or in combination with herbs like ginseng, cinnamon, or astragalus (notably for respiratory remedy blends). Rehmannia's historical use in China spans centuries, with the earliest records dating to around 200 BCE during the Han dynasty. It is used traditionally to promote longevity and enhance quality of life by positively supporting a range of bodily systems.

An important application documented in the literature is the concurrent internal use of corticosteroids. Rehmannia may help mitigate adverse effects of these commonly prescribed medications at the level of soft tissue and bone, and supports protective and reparative effects for tissues during chronic chemotherapy administration.

In laboratory models of ischemia, Rehmannia's active compounds, along with those from three other traditional Chinese herbs, have shown significant neuroprotective effects in the context of inflammatory illnesses. In vitro studies confirmed a reduction of pro-inflammatory factors including IL-1beta, IL-6, and TNF-alpha, increased lactate dehydrogenase activity, and decreased phosphorylation of p65, several caspases, and other signaling pathways. The active substances in Rehmannia may therefore exhibit anti-inflammatory actions and could potentially help support therapies for ischemia. Similar results were observed in models focusing on ischemia in the cerebral vascular endothelial cells, specifically involving catalpol and puerarin (Liu Y., 2017).

Consequently, bioactive compounds in Rehmannia are being studied for their potential in supporting vascular health and function, with ongoing research investigating applications for ischemia models. The root has an official status as an herbal remedy with a beneficial effect on maintaining normal structure and function of blood vessel walls. This may explain its possible use in treating and regulating high blood pressure.

In rat models, ethanolic extract of Rehmannia root decreased fibrinolytic activity and erythrocyte deformability, increased total erythrocyte count, and boosted connective tissue volume in the thoracic artery in chronic inflammation models. The root’s constituents can improve hemorheological parameters by influencing the conversion of fibrinogen to fibrin and regulating plasminogen or plasmin activity. In vivo studies confirmed the anticoagulant effect of herbal blends where Rehmannia’s content made up about 24% of the mixture.

In vivo and in vitro studies indicate that Rehmannia root extract inhibits the growth of certain cancer cell lines in the respiratory system via effects on cell proliferation and differentiation. Several in vivo experiments have confirmed this anticancer effect for the root and its content when administered intraperitoneally or directly incubated in flasks. The anticancer benefits of Rehmannia polysaccharides were also visible via p53 gene regulation.

Clinical evidence supports the use of Rehmannia or its extracts for osteoporosis treatment. Traditional herbalists value its anti-osteoporotic effects, often linked to a positive impact on kidney and liver function. Rehmannia can therefore support management of postmenopausal, senile, and secondary osteoporosis by influencing bone mineral density. Of the more than 140 isolated compounds, catalpol, ajugol, and acetoside are showing the strongest effects.

Smaller studies suggest improvements in blood parameters and symptoms of aplastic anemia for those receiving Rehmannia monotherapy alongside stanozolol. Aqueous root extract has been shown, both in vivo and in vitro, to boost proliferation and differentiation of bone marrow cells and support erythropoiesis in progenitor cells. Glycoside D, isolated from the root, led to an increase in blood cell counts (including red and white blood cells) and promoted body weight gain in anemic rats. Numerous studies have described the immunostimulatory properties of Rehmannia root, by enhancing production and activity of lymphocytes, macrophages, and other immune system components.

A clinical trial using an oral decoction of Chinese herbs Rehmannia and Angelica in patients with chronic obstructive pulmonary disease (COPD) and hypoxemia found improved daytime and nighttime plasma oxygen saturation compared to standard oxygen therapy alone.

Research by Matsumoto et al. (2016) demonstrated in vivo the antihyperglycemic effect of Rehmannia glutinosa root extract. Another Chinese study in models of both type I and type II diabetes showed that Rehmannia extract lowered glucose levels, triglycerides, and cholesterol in diabetic animals. Researchers concluded that catalpol and other compounds may reduce hyperglycemia by increasing beta-endorphin secretion during the metabolic processing of nutrients. Leading health agencies acknowledge Rehmannia’s ability to stabilize glycemia and support normal blood glucose levels.

Traditional and Folk Medicine Uses

The root is the most used medicinal part of Rehmannia. In traditional practices, it is taken for constipation (modern medicine acknowledges its mild laxative effect), anemia, urinary tract issues, hair loss, infertility, senility, dizziness, fungal infections, menstrual irregularities, liver protection, bone-strengthening, and as a detoxifying agent. Ayurveda recommends it for similar purposes, and also as a blood tonic and diuretic.

Limitations and Safety

Although Rehmannia is considered very safe and generally well-tolerated, individuals with diabetes, pregnant women, transplant recipients, and children should avoid or limit its use, especially without first consulting their healthcare provider.

Active Compounds

The root contains about 70 biologically active compounds, but more than 140 have been identified in total. The most recognized glycoside is catalpol, followed by a group known as rehmanniosides. Other constituents include phytosterols (notably beta-sitosterol, campesterol, stigmasterol), arginine, polysaccharides (such as stachyose), oligosaccharides (mannitol, sucrose, raffinose, verbascose), iridoids (catalpol, dihydrocatalpol, danmelitoside, acetylcatalpol, leonurid, aucubin, rehmaglutin, rehmanniosides, rehmapicrosoides, echinacosides, jionosides, geniposides, ajugoside, ajugol), phenolic glycosides (ionone, acteoside, isoacteoside, forsythiaside, and others), flavonoids, 20 amino acids (most notably arginine), inorganic substances, organic acids (benzoic, caprylic, palmitic, and others), as well as minerals (iron, zinc, chromium, manganese).

Traditional Dosage

To prepare an extract: boil 5–10 grams of dried or fresh Rehmannia root in 500 ml of water for about 10 minutes. Drink the decoction twice daily, preferably on an empty stomach. For tincture: macerate 50–70 grams of root in 1000 ml of 40% alcohol for 2–3 months, then filter and take about 1 tablespoon 1–2 times daily on an empty stomach. Preclinical studies used extracts in doses of 0.15–0.5 mg per kg body weight (orally) or in different strengths intraperitoneally. Human use should follow traditional guidelines, as animal data is not directly transferable.