Hu Zhang
StarPolygonum cuspidatum Sieb. et Zucc.
☯ TCM Properties
Clears Damp-Heat and Resolves Jaundice; Clears Heat and Resolves Toxicity; Invigorates Blood and Dispels Stasis; Alleviates Pain; Resolves Phlegm and Stops Cough; Promotes Bowel Movement
Traditional Chinese Uses
Hu Zhang (giant knotweed rhizome, Japanese knotweed) is a cool herb that invigorates Blood, clears Heat, promotes bile flow, and drains Dampness. It is used for Blood stagnation conditions including amenorrhea and traumatic injury, Damp-Heat patterns including jaundice and urinary infections, and Lung Heat cough with phlegm. Modern research has extensively studied its active compound resveratrol for cardiovascular and anti-inflammatory effects. Its broad Blood-moving and Heat-clearing profile gives it wide clinical applicability.
Western Herbalism Properties
Botanical Description
Reynoutria japonica (Polygonum cuspidatum, Fallopia japonica) is a large, vigorous rhizomatous perennial herb in the Polygonaceae, native to eastern Asia and notoriously invasive in much of Europe and North America. From a thick, deeply running, woody rhizome with bright orange-yellow interior, hollow stems rise 1-3 m tall, jointed and reddish-mottled like bamboo and conspicuously swollen at the nodes, each sheathed by a papery ochrea. The alternate leaves are broadly ovate with a truncate base and pointed tip, 5-15 cm long, glabrous. Small greenish-white to cream flowers are borne in slender, erect to nodding axillary panicles in late summer; plants are functionally dioecious. Fruits are small winged three-angled achenes. The dried rhizome and root, harvested in spring or autumn, are Hu Zhang.
Active Constituents
trans-Resveratrol
StilbeneConcentration: Documented; commercial extracts standardised to 8-20%+
A polyphenolic stilbene and one of the herb's signature actives. It has antioxidant, anti-inflammatory, cardioprotective and SIRT1-modulating activity, and Polygonum cuspidatum (Hu Zhang) is the richest botanical source of resveratrol used commercially.
Polydatin (piceid)
Stilbene glycoside (resveratrol-3-O-beta-D-glucoside)Concentration: Major stilbene, often exceeding free resveratrol
The glucoside of resveratrol and frequently the most abundant stilbene in the root. It is more water-soluble and chemically stable than resveratrol, showing antioxidant, anti-inflammatory, cardioprotective and lipid-lowering effects; it is partially hydrolysed to resveratrol in vivo.
Emodin
AnthraquinoneConcentration: Major anthraquinone marker compound
A hydroxyanthraquinone with anti-inflammatory, antimicrobial, hepatoprotective and mild purgative (laxative) activity. It contributes to the herb's traditional actions of clearing damp-heat, resolving jaundice and moving the bowels.
Emodin-8-O-beta-D-glucoside (polygonin)
Anthraquinone glycosideConcentration: Documented
The glucoside of emodin. It acts partly as a pro-drug hydrolysed to emodin in the gut and shares emodin's anti-inflammatory and gentle laxative properties.
Physcion (parietin)
AnthraquinoneConcentration: Minor anthraquinone
A methyl-ether anthraquinone with antioxidant, antimicrobial and anti-inflammatory activity that accompanies emodin in the root and contributes to the herb's heat-clearing profile.
(+)-Catechin
Flavan-3-ol (flavonoid)Concentration: Documented
A flavan-3-ol contributing antioxidant and vascular-protective activity, supporting the herb's traditional use for blood stasis and cardiovascular complaints.
Quercetin
Flavonol (flavonoid)Concentration: Minor flavonoid
A widely distributed flavonol with antioxidant, anti-inflammatory and antiplatelet activity, adding to the overall blood-invigorating and anti-inflammatory character of Hu Zhang.
⚠ Drug Interactions
Carbamazepine
In rats, a resveratrol-rich Polygonum cuspidatum extract significantly increased the AUC of carbamazepine and altered formation of its active metabolite, consistent with inhibition of CYP3A-mediated metabolism.
Clinical note: Use caution and consider monitoring drug levels when combining Hu Zhang or high-dose resveratrol with narrow-therapeutic-index CYP3A substrates such as carbamazepine.
Warfarin and antiplatelet/anticoagulant agents
Resveratrol and quercetin have antiplatelet activity and may inhibit platelet aggregation and CYP-mediated metabolism, which could theoretically potentiate anticoagulant and antiplatelet drugs.
Clinical note: Advise patients on warfarin or antiplatelet therapy to inform their clinician; monitor for signs of bleeding.
Methotrexate and BCRP substrates
Resveratrol and its glucuronides modulate the breast cancer resistance protein (BCRP/ABCG2) transporter; co-administration of Polygonum cuspidatum may alter the pharmacokinetics of BCRP substrates such as methotrexate in preclinical models.
Clinical note: Exercise caution when combining with methotrexate or other BCRP-transported drugs.
Dosage
| Form | Amount | Frequency | Duration | Population | Notes |
|---|---|---|---|---|---|
| decoction | 6-15g | Daily | — | — | — |
Preparation Methods
Water decoction (tang)
Parts: Dried root and rhizome
Typically 9-15 g of the sliced dried root and rhizome is decocted in water and taken to clear damp-heat, resolve jaundice, invigorate blood and relieve pain, cough or constipation.
Standardised extract / capsule
Parts: Dried root and rhizome
Ethanol or water-ethanol extracts are standardised to a defined resveratrol/polydatin content and taken as capsules or powders for cardiovascular and metabolic support.
Topical / external wash
Parts: Dried root and rhizome
Decoctions or powders are applied externally to burns, sores and traumatic injuries to clear heat, resolve toxicity and invigorate blood locally.
Clinical Studies
A Randomized Trial on Resveratrol Supplement Affecting Lipid Profile and Other Metabolic Markers in Subjects with Dyslipidemia
A randomized trial in subjects with dyslipidemia found that resveratrol supplementation, the principal active stilbene of Hu Zhang, favourably affected lipid profile and other metabolic markers relative to control, supporting a cardiometabolic benefit of resveratrol.
Historical Texts
Ming Yi Bie Lu (Miscellaneous Records of Famous Physicians)
Han-Wei period (c. 200-300 CE)Ben Cao Gang Mu (Compendium of Materia Medica), Li Shizhen
Ming dynasty (1578 CE)References
- Zhang H, Li C, Kwok ST, Zhang QW, Chan SW. A Review of the Pharmacological Effects of the Dried Root of Polygonum cuspidatum (Hu Zhang) and Its Constituents . Evidence-Based Complementary and Alternative Medicine 2013:208349 (2013) [DOI]
- Peng W, et al.. Advances for pharmacological activities of Polygonum cuspidatum - A review . Pharmaceutical Biology 60(1):2288-2300 (2022) [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.
📝 Notes
Public notes from the community and your own private notes on Hu Zhang.
No notes yet.