Rehmannia

What Is Rehmannia?

In my opinion, rehmannia is one of the most useful herbs in the Western herbal dispensary.

It’s popular in Asia for conditions defined as “hot”, and is one of the most reliable adrenal tonics available. With so many people succumbing to chronic— often debilitating stress, this class of herbs is extremely valuable.

Hot” conditions— in the perspective of Western herbal medicine could define these conditions as metabolic disorders, involving the endocrine system.

It’s considered an adaptogen due to its high level of safety, and ability to modulate the HPA and HPG axis. This has been shown in a variety of animal studies focusing on the effects of rehmannia and its main active constituent catalpol on the hypothalamus, pituitary, and adrenal glands (and associated hormones). This same mechanism of action is responsible for the anti-diabetic and anti-Alzheimer’s activity of rehmannia as well.

What Is Rehmannia Used For?

Rehmannia is mainly used for endocrine-related conditions, including diabetes, adrenal fatigue, fevers, asthma, and the suppressive effects of corticosteroid treatment.

Traditional Uses

Traditional Chinese Medicine

In traditional Chinese medicine, cured rehmannia and uncured rehmannia is used differently. Uncured rehmannia is used to reduce fevers and heat conditions, as a haemostatic, to remove heat from the blood, for rashes, diabetes, low grade fevers and for bleeding. ^{1Reference 1Bone K · 2013Principles and Practice of Phytotherapy}. Cured rehmannia on the other hand, was used to regulate menstruation, promote blood production, correct anaemia, dizziness, weakness, tinnitus, amenorrhea, and metrorrhagia.

Fresh Rehmannia

Added to formulas to tonify yin in the liver, kidney and heart, and add cooling, anti-inflammatory actions. ^{4,6Reference 4Fu et al. · 2011A new carotenoid glycoside from Rehmannia glutinosaReference 6Teeguarden · 2000The ancient wisdom of the Chinese tonic herbs}.

Prepared Rehmannia

Prepared rehmannia is a fundamental kidney tonic in Chinese herbalism and is often associated with longevity. It’s a yin jing tonic, and frequently added to formulas designed to strengthen sexual function. ^{6Reference 6Teeguarden · 2000The ancient wisdom of the Chinese tonic herbs}.

Botanical Information

Rehmannia is currently listed under the family Orobanchaceae, but there has been a lot of confusion in this area. It has been included in the families Scrophulariaceae and Gesneriaceae in the past. Many of the Scrophulariaceae members were transferred to Plantaginaceae, but not rehmannia.

Rehmannia is a perennial herb growing up to 40 cm in height. The flowers are reddish-purple and tubular in shape. The root is a thick orange tuberous root. ^{1Reference 1Bone K · 2013Principles and Practice of Phytotherapy}.

Harvesting, Collection & Preparation

Curing rehmannia (prepared rehmannia) involves washing the fresh root in millet wine, before steaming, and drying several times each. ^{1Reference 1Bone K · 2013Principles and Practice of Phytotherapy}. In Chinese medicine, the prepared version is more highly regarded than fresh rehmannia.

Pharmacology & Medical Research

Adrenal Tonic

Not hypertensive like licorice but is toning to the adrenals and may be useful for preventing the suppressive effects of corticosteroid drugs. ^{1Reference 1Bone K · 2013Principles and Practice of Phytotherapy}.

It appears to antagonize the suppressive effect of glucocorticoids on the hypothalamic-pituitary-adrenal axis (uncured).

Catalpol from rehmannia was shown to increase hydrocortisone levels, and decrease CRH and ACTH in rats with Alzheimer’s disease after 7 days ^{16Reference 16Wang et al. · 2014AnimalCatalpol regulates function of hypothalamic-pituitary-adrenocortical-axis in an Alzheimer’s disease rat model}. This suggests modulating activity on the HPA axis in neuroendocrine dysregulated organisms.

Alzheimer’s Disease

Alzheimer’s disease is believed to have many causes and contributing factors. One of them being dysfunction of neuroendocrine function ^{12Reference 12Csernansky et al. · 2006Plasma cortisol and progression of dementia in subjects with Alzheimer-type dementia}. This is due to an increase in glucocorticoids in the blood, resulting in a reduction in corticotropin-releasing hormone (CRH), and neuronal loss in the hippocampus. This ultimately leads to reduced memory and cognitive capacity, promoting the progression of Alzheimer’s disease ^{13Reference 13Umegaki et al. · 2000ObservationalPlasma cortisol levels in elderly female subjects with Alzheimer’s disease: a cross-sectional and longitudinal study}.

Studies on mice comparing the effects of catalpol purified from rehmannia and the common anti-Alzheimer’s drug donepezil found that catalpol was as effective for reducing biological markers for Alzheimer’s disease at a dose of 14mg/day as donepezil at 1.4mg/day. This mechanism of action was noted to be through mechanisms unrelated to antiacetylcholinesterase activity. ^{14Reference 14Xia et al. · 2012Memory defect induced by beta-amyloid plus glutamate receptor agonist is alleviated by catalpol and donepezil through different mechanisms}.

Another animal study investigated the role of rehmannias main active constituent, catalpol, on HPA axis function in an Alzheimer’s disease rat model. Researchers in this study reported a reduction in elevated hydrocortisone level as well as decreased CRH & ACTH. Structural changes associated with AD were also noted, including an increase in CRHR1 positive neurons. ^{16Reference 16Wang et al. · 2014AnimalCatalpol regulates function of hypothalamic-pituitary-adrenocortical-axis in an Alzheimer’s disease rat model}.

Adaptogenic Effects

The majority of studies on the interaction of rehmannia on glucocorticoids, HPA/HPG interaction, and adrenal function are in vitro or animal research only.

There are no randomized clinical trials available at the time of writing.

In vivo research has suggested HPA axis regulation as a mechanism of action for rehmannias effectiveness on Alzheimer’s disease ^{14Reference 14Xia et al. · 2012Memory defect induced by beta-amyloid plus glutamate receptor agonist is alleviated by catalpol and donepezil through different mechanisms}. This is based on earlier research that linked high cortisol levels with Alzheimer’s disease through a gradual dysregulation of CRH sensitivity in the hippocampus ^{13Reference 13Umegaki et al. · 2000ObservationalPlasma cortisol levels in elderly female subjects with Alzheimer’s disease: a cross-sectional and longitudinal study}. Other animal studies supported with results involving changes in essential HPA axis hormones in a neuroendocrine dysregulated rat model of Alzheimer’s disease after treatment of a rehmannia extract (catalpol) ^{16Reference 16Wang et al. · 2014AnimalCatalpol regulates function of hypothalamic-pituitary-adrenocortical-axis in an Alzheimer’s disease rat model}. Researchers in this study reported a reduction in elevated hydrocortisone (cortisol) levels as well as decreased CRH & ACTH. Structural changes associated with AD were also noted, including an increase in CRHR1 positive neurons. These findings suggest directly modulating activity of rehmannia constituents on the HPA axis.

Other animal studies suggesting HPA or HPG axis modulation in conditions traditionally classified as “yin deficiency” includes diabetes, immunosuppression ^{15Reference 15Huang et al. · 2010AnimalAntihyperglycemic effect of catalpol in streptozotocin-induced diabetic rats}, and bone catabolism ^{11Reference 11Kim et al. · 1998Effect of Rehmannia glutinosa on immediate type allergic reaction}.

Online sources have suggested inhibition of cortisone metabolism in the liver as a mechanism of action. However, no peer-reviewed research has been found to back up this claim.

Phytochemistry

Rehmannia’s defining chemistry is its iridoid glycosides — roughly 31 have been described, headed by the marker compound catalpol, alongside aucubin, ajugol and the rehmanniosides (A–D). Riding with them is a family of phenylethanoid glycosides, chiefly verbascoside (acteoside), plus ionone and terpenoid glycosides and root polysaccharides [1–4, 7–10].

Constituent Summary

Figures are % of dried root and fall hard during the traditional wine-steaming (“curing”) process, so prepared rehmannia is markedly lower in catalpol than the fresh root [17]. Treat the ranges as processing-dependent.

[caption id="" align=“alignnone” width=“270”] (Catalpol molecule) [/caption]

[caption id="" align=“alignnone” width=“270”] (Catalpol molecule) [/caption]

Clinical Applications

Rehmannia is useful for conditions involving the HPA and HPG axis.

This herb has a strong modulating activity on this system, useful for supporting a variety of endocrine-related conditions like hypothyroidism, diabetes, GAS, and adrenal fatigue. It’s also useful for dementia and Alzheimer’s disease through the same effect profile. Its effects on the HPG axis make it useful for low libido, poor fertility, menstrual irregularities, and erectile dysfunction.

It’s also useful as an anti-inflammatory and immunomodulator.

Cautions & Safety

Caution is advised in combination with corticosteroid use.

References

1. Bone K, Mills S. (2013). Principles and Practice of Phytotherapy. Elsevier health. China. (Pg. 799-803).
2. Liu, Y. F., Liang, D., Luo, H., Hao, Z. Y., Wang, Y., Zhang, C. L., … & Yu, D. Q. (2012). Hepatoprotective iridoid glycosides from the roots of Rehmannia glutinosa. Journal of natural products, 75(9), 1625-1631.
3. Liu, Y. F., Liang, D., Luo, H., Hao, Z. Y., Wang, Y., Zhang, C. L., … & Yu, D. Q. (2014). Ionone glycosides from the roots of Rehmannia glutinosa. Journal of Asian natural products research, 16(1), 11-19.
4. Fu, G. M., Shi, S. P., Ip, F. C., Pang, H. H., & Ip, N. Y. (2011). A new carotenoid glycoside from Rehmannia glutinosa. Natural product research, 25(13), 1213-1218.
5. Bone, K. (2003). A clinical guide to blending liquid herbs: Herbal formulations for the individual patient. Edinburgh [u.a., MO: Churchill Livingstone.
6. Teeguarden, R. (2000). The ancient wisdom of the Chinese tonic herbs. New York, NY: Warner Books. (Pg. 179-180).
7. Morota, T., Nishimura, H., Sasaki, H., Chin, M., Sugama, K., Katsuhara, T., & Mitsuhashi, H. (1989). Five cyclopentanoid monoterpenes from Rehmannia glutinosa. Phytochemistry, 28(9), 2385-2391.
8. Yoshikawa, M., Fukuda, Y., Taniyama, T., Cha, B. C., & Kitagawa, I. (1986). Absolute configurations of rehmaionosides A, B, and C and rehmapicroside three new ionone glucosides and a new monoterpene glucoside from Rehmanniae radix. Chemical and pharmaceutical bulletin, 34(5), 2294-2297.
9. Sasaki, H., Nishimura, H., Chin, M., & Mitsuhashi, H. (1989). Hydroxycinnamic acid esters of phenethylalcohol glycosides from Rehmannia glutinosa var. purpurea. Phytochemistry, 28(3), 875-879.
10. Morota, T., Sasaki, H., Nishamura, H., Sugama, K., Masao, C.C.Z., & Mitsuhashi, H. (1989). Chemical and biological studies on Rehmanniae radix. Part 4. Two iridoid glycosides from Rehmannia glutinosa. Phytochemistry, 28, 2149–2153
11. Kim, H., Lee, E., Lee, S., Shin, T., Kim, Y., & Kim, J. (1998). Effect of Rehmannia glutinosa on immediate type allergic reaction. International journal of immunopharmacology, 20(4-5), 231-240.
12. Csernansky, J. G., Dong, H., Fagan, A. M., Wang, L., Xiong, C., Holtzman, D. M., & Morris, J. C. (2006). Plasma cortisol and progression of dementia in subjects with Alzheimer-type dementia. American Journal of Psychiatry, 163(12), 2164-2169.
13. Umegaki, H., Ikari, H., Nakahata, H., Endo, H., Suzuki, Y., Ogawa, O., … & Iguchi, A. (2000). Plasma cortisol levels in elderly female subjects with Alzheimer’s disease: a cross-sectional and longitudinal study. Brain research, 881(2), 241-243.
14. Xia, Z., Zhang, R., Wu, P., Xia, Z., & Hu, Y. (2012). Memory defect induced by beta-amyloid plus glutamate receptor agonist is alleviated by catalpol and donepezil through different mechanisms. Brain research, 1441, 27-37.
15. Huang, W. J., Niu, H. S., Lin, M. H., Cheng, J. T., & Hsu, F. L. (2010). Antihyperglycemic effect of catalpol in streptozotocin-induced diabetic rats. Journal of natural products, 73(6), 1170-1172.
16. Wang, J. H., Li, W. T., Yu, S. T., Xie, H., & Han, H. R. (2014). Catalpol regulates function of hypothalamic-pituitary-adrenocortical-axis in an Alzheimer’s disease rat model. Die Pharmazie-An International Journal of Pharmaceutical Sciences, 69(9), 688-693.
17. Lee, S. J., Jang, M. G., Lee, J. Y., et al. (2023). Standardization of Rehmannia glutinosa (Gaertn.) DC. steam processing and evaluation of its chemical, anti-oxidant, and anti-inflammatory properties. Applied Biological Chemistry, 66, 47.