Di Huang
StarRehmannia glutinosa (Gaertn.) DC.
☯ TCM Properties
Clears Heat and Cools the Blood; Nourishes Yin and Generates Fluids; Cools the Nutritive Level; Cools the Blood and Stops Bleeding; Moistens the Intestines and Unblocks the Bowels
Traditional Chinese Uses
Di Huang refers to both the raw (Sheng Di Huang) and processed (Shu Di Huang) forms of rehmannia root. Raw rehmannia is cool to cold, nourishing Yin, clearing Heat, and cooling the Blood — useful for febrile illness, thirst, and bleeding from Heat. Processed rehmannia is warm, deeply tonifying the Liver and Kidney Blood and Yin — used for menstrual disorders, dizziness, tinnitus, and chronic weakness from Blood and Yin deficiency. Both are fundamental in TCM tonic and heat-clearing formulas.
Botanical Description
Rehmannia glutinosa is a sticky-glandular herbaceous perennial in the Orobanchaceae (formerly placed in Scrophulariaceae), native to northern and central China and adjacent parts of Korea and Japan, where it grows on dry, sunny slopes, roadsides and field margins on loose sandy or loamy soils. Plants grow 15-40 cm tall from clusters of fleshy, fusiform, orange-red taproots that ooze a sticky juice when cut. The whole plant is covered in long, soft, sticky, glandular hairs that give it a velvety, slightly clammy feel. The basal rosette leaves are obovate to oblong, 3-12 cm long, with shallowly toothed to crenate margins and a coarsely reticulate, deeply impressed venation on the wrinkled upper surface. The flowering stems bear loose racemes of showy, drooping, tubular-bell-shaped flowers about 4 cm long, reddish-purple to dull pink-brown outside and yellow to violet with darker veining inside.
Active Constituents
Catalpol
Iridoid glycosideConcentration: Approximately 0.2-2% of dried root; the principal marker compound used for quality control in the Chinese Pharmacopoeia
Catalpol is the most-studied active constituent of Rehmannia. Preclinical studies report antioxidant, hypoglycemic, neuroprotective and anti-inflammatory activity, including reduction of plasma glucose and enhancement of antioxidative enzymes (SOD, GSH-Px, CAT) in diabetic rat models.
Acteoside (verbascoside)
Phenylethanoid glycosideConcentration: Minor to moderate constituent of the root; content increases in some processed preparations
A phenylethanoid glycoside with documented antioxidant, anti-inflammatory and free-radical-scavenging activity that contributes to the herb's yin-nourishing and blood-cooling reputation.
Stachyose
Raffinose-family oligosaccharideConcentration: Major carbohydrate of the fresh root (often the most abundant sugar)
The dominant oligosaccharide of Rehmannia. It has immunomodulating and prebiotic properties; steam-processing (to make Shu Di Huang) reduces oligosaccharide content, lessening flatulence and altering the herb's energetics.
Rehmannioside D
Iridoid glycosideConcentration: One of several rehmanniosides (A-D) present in the root
An iridoid glycoside characteristic of the genus, contributing to the antioxidant and reno-protective activity attributed to the total iridoid fraction.
5-Hydroxymethylfurfural (5-HMF)
Furan aldehyde (Maillard/processing product)Concentration: Low in raw root; increases substantially with repeated steaming to produce prepared Rehmannia (Shu Di Huang)
Formed during heat-processing of the root and used as a marker distinguishing prepared from raw Rehmannia. Reported antioxidant activity; its rise on steaming parallels the traditional shift toward blood-tonifying properties.
Geniposidic acid
Iridoid glycosideConcentration: Minor iridoid constituent of the root
An iridoid acid contributing to the anti-inflammatory and mild laxative activity of the herb.
⚠ Drug Interactions
Antidiabetic agents (insulin, sulfonylureas, metformin)
Rehmannia oligosaccharides and catalpol lower fasting blood glucose and improve glucose tolerance in animal models. Concurrent use with conventional hypoglycemic drugs could produce additive effects and increase the risk of hypoglycemia.
Clinical note: Monitor blood glucose when combined with antidiabetic therapy and adjust doses under professional supervision.
Anticoagulant / antiplatelet drugs (warfarin, aspirin, clopidogrel)
Rehmannia has been reported to influence platelet aggregation and blood coagulation in traditional and preliminary reports. A theoretical additive effect on bleeding risk exists when combined with anticoagulant or antiplatelet drugs.
Clinical note: Caution and monitoring advised in patients on anticoagulants; robust human interaction data are lacking.
Dosage
| Form | Amount | Frequency | Duration | Population | Notes |
|---|---|---|---|---|---|
| decoction | 6-15g | Daily | — | — | — |
Preparation Methods
Raw/dried decoction (Sheng Di Huang)
Parts: root tuber
The dried unprocessed root is sliced and decocted (typically 9-30 g) to clear heat, cool the blood and nourish yin. Usually added to the pot with the other herbs and simmered.
Wine-steamed prepared root (Shu Di Huang)
Parts: root tuber
The root is repeatedly steamed (classically with yellow rice wine, sometimes with Sha Ren/Amomum) until black and glossy, then dried. This warms the nature of the herb and shifts it toward tonifying blood and kidney essence; decocted 9-30 g.
Fresh root / fresh juice (Xian Di Huang)
Parts: fresh root tuber
The fresh root is expressed for juice or decocted; regarded as the most strongly cooling and fluid-generating form, used for severe heat in the blood and thirst.
Clinical Studies
Antidiabetic and antioxidant effects of catalpol extracted from Rehmannia glutinosa (Di Huang) on rat diabetes induced by streptozotocin and high-fat, high-sugar feed
In streptozotocin plus high-fat/high-sugar-induced diabetic rats, catalpol reduced the rise in plasma glucose, increased the activity of antioxidative enzymes (SOD, GSH-Px, CAT) and lowered malondialdehyde, indicating combined antidiabetic and antioxidant effects.
Hypoglycemic effect of Rehmannia glutinosa oligosaccharide in hyperglycemic and alloxan-induced diabetic rats and its mechanism
Rehmannia glutinosa oligosaccharide produced a significant hypoglycemic effect in normal, hyperglycemic and alloxan-induced diabetic rats, lowering blood glucose and modifying hepatic glucose metabolism, supporting the antidiabetic use of the root.
Historical Texts
Shennong Bencao Jing (Divine Farmer's Materia Medica)
Han dynasty (c. 1st-2nd century CE)Ben Cao Gang Mu (Compendium of Materia Medica), Li Shizhen
Ming dynasty (1578)References
- Zhu H, Wang Y, Liu Z, Wang J, Wan D, Feng S, Yang X, Wang T. Antidiabetic and antioxidant effects of catalpol extracted from Rehmannia glutinosa (Di Huang) on rat diabetes induced by streptozotocin and high-fat, high-sugar feed . Chinese Medicine (2016) [DOI]
- Zhang R, Zhou J, Jia Z, Zhang Y, Gu G. Hypoglycemic effect of Rehmannia glutinosa oligosaccharide in hyperglycemic and alloxan-induced diabetic rats and its mechanism . Journal of Ethnopharmacology (2004) [DOI]
This information is for educational purposes only and is not intended to replace professional medical advice. Always consult a qualified healthcare provider before using any herbal remedy, especially if you are pregnant, nursing, or taking medications.
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