Herb Rhizome (根茎 gēn jīng)

Hu Zhang

Giant Knotweed Rhizome · 虎杖

Polygonum cuspidatum Sieb. et Zucc. · Rhizoma Polygoni Cuspidati

Also known as: Hua Ban Zhu (花斑竹), Japanese Knotweed

Hu Zhang (Giant Knotweed Rhizome) plant

Images shown are for educational purposes only

Hu Zhang (Japanese knotweed rhizome) is a versatile herb best known for clearing Dampness-Heat from the Liver and Gallbladder, making it widely used for jaundice and liver complaints. It also moves stagnant Blood to relieve pain from injuries or menstrual problems, and calms coughs caused by Lung Heat. Rich in resveratrol and emodin, it has attracted modern research interest for its anti-inflammatory, liver-protective, and cardiovascular benefits.

Category Blood-invigorating and stasis-dispelling herbs (活血化瘀药) Herbs that clear Heat and dry Dampness (清热燥湿药)
Therapeutic focus Liver Health Joint and Muscle Health Menstrual Health Respiratory Health Skin Health

TCM Properties

Temperature

Slightly Cool

Taste

Bitter (苦 kǔ)

Channels entered

Liver, Gallbladder, Lungs

Parts used

Rhizome (根茎 gēn jīng)

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What This Herb Does

Every herb has a specific set of actions — here's what Hu Zhang does in the body, explained in both everyday and TCM terms

Therapeutic focus

In practical terms, Hu Zhang is primarily used to support these areas of health:

Liver Health Joint and Muscle Health Menstrual Health Respiratory Health Skin Health

TCM Actions

In TCM terminology, these are the specific therapeutic actions that Hu Zhang performs to restore balance in the body:

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

How these actions work

'Clears Dampness-Heat and reduces jaundice' refers to Hu Zhang's ability to drain accumulated Dampness and Heat from the Liver and Gallbladder, which makes it a go-to herb for conditions involving yellowing of the skin and eyes (jaundice). It promotes the normal flow of bile and helps the body eliminate excess fluid and heat through urination. This is its primary listed action in the Chinese Pharmacopoeia, and it is often combined with Yin Chen Hao (Artemisia) for this purpose.

'Clears Heat and resolves toxins' means Hu Zhang can combat infections and inflammatory conditions caused by Heat-toxin. This covers skin abscesses, boils, sore throat, and even burns and scalds. Applied externally as a paste or wash, it promotes wound healing. Pharmacological research has shown it contains emodin and resveratrol, which demonstrate antimicrobial and anti-inflammatory properties.

'Invigorates Blood and dispels stasis' describes how Hu Zhang gets stuck Blood moving again. This is especially relevant for women with absent or painful periods caused by Blood stasis, as well as for traumatic injuries with bruising and swelling. Classical texts from the Ming Bie Lu onward have noted its power to break up stagnant Blood and open the menstrual flow.

'Transforms Phlegm and stops coughing' refers to Hu Zhang's action on the Lungs. Because it enters the Lung channel and has a bitter, slightly cold nature, it can descend Lung Qi and clear Lung Heat, making it useful for coughs with thick yellow phlegm.

'Unblocks the bowels' is related to Hu Zhang's content of anthraquinone compounds (similar to Da Huang / Rhubarb). At sufficient doses, it has a gentle laxative effect, helpful for constipation caused by Heat accumulation in the intestines.

Patterns Addressed

In TCM, symptoms cluster into recognizable patterns of disharmony. Hu Zhang is used to help correct these specific patterns.

Why Hu Zhang addresses this pattern

Hu Zhang's bitter taste drains Dampness and its slightly cold nature clears Heat. Because it enters the Liver and Gallbladder channels directly, it targets the root pathomechanism of this pattern: Dampness and Heat steaming in the Liver-Gallbladder system, obstructing bile flow and producing jaundice. Its ability to promote urination helps drain the Dampness downward and out of the body, while its Heat-clearing action addresses the inflammatory component that drives the yellowing, dark urine, and hypochondriac fullness typical of this pattern.

A practitioner would look for one or more of these signs

Jaundice

Yellow discoloration of skin and eyes from Dampness-Heat

Dark Urine

Scanty dark yellow urine

Hypochondriac Pain

Distension and pain below the ribs

Thin Vaginal Discharge

Yellow, foul-smelling vaginal discharge from Dampness-Heat pouring downward

Commonly Used For

These are conditions where Hu Zhang is frequently used — but only when they arise from the specific patterns it addresses, not in all cases

Arises from: Damp-Heat in the Gallbladder

TCM Interpretation

In TCM, viral hepatitis is most commonly understood as Dampness-Heat lodging in the Liver and Gallbladder. The pathogenic factors of Dampness and Heat obstruct the normal coursing and draining functions of the Liver and impair the Gallbladder's role in secreting bile. This leads to jaundice (bile overflowing), fatigue (Dampness weighing down Qi), poor appetite and nausea (Dampness obstructing the Spleen and Stomach), and pain or distension in the rib area (Liver Qi stagnation worsened by Dampness-Heat). In chronic cases, prolonged Heat can damage Yin, and Blood stasis may develop from long-standing obstruction.

Why Hu Zhang Helps

Hu Zhang directly targets the Liver and Gallbladder channels, clearing the Dampness-Heat that drives hepatitis symptoms. Its primary Pharmacopoeia-listed action is 'clears Dampness-Heat and reduces jaundice,' making it one of the most commonly selected herbs for this condition. The herb also resolves toxins, which addresses the infectious component. Its Blood-invigorating properties help prevent the stasis that can develop in chronic liver disease. Modern pharmacological research confirms that Hu Zhang has hepatoprotective, anti-inflammatory, and antiviral effects, with its key compounds (resveratrol and emodin) showing activity against hepatitis B virus.

Also commonly used for

Jaundice

Especially from hepatitis or cholestasis with Dampness-Heat

Gallstones

Used with Yin Chen Hao and Jin Qian Cao

Painful Periods

With dark clotted menstrual blood

Skin Burns

Applied externally as paste or wash

Urinary Tract Infection

Painful urination from Dampness-Heat

Trauma

Bruising and blood stasis from falls or blows

Hypochondrial Pain That Is Worse On Coughing And Breathing

Lung Heat with yellow phlegm

Constipation

Heat-type constipation

Hyperlipidemia

Research supports lipid-lowering effects

Skin Abscess

Boils and carbuncles from Heat-toxin

Herb Properties

Every herb has an inherent temperature, taste, and affinity for specific channels — these properties determine how it interacts with the body

Temperature

Slightly Cool

Taste

Bitter (苦 kǔ)

Channels Entered

Liver Gallbladder Lungs

Parts Used

Rhizome (根茎 gēn jīng)

Dosage & Preparation

These are general dosage guidelines for Hu Zhang — always follow your practitioner's recommendation, as dosages vary based on the formula and your individual condition

Standard dosage

9-15g

Maximum dosage

Up to 30g in acute conditions such as severe Damp-Heat jaundice or painful obstruction, under practitioner supervision. Some historical formulas used larger amounts for Blood stasis obstruction (amenorrhea, abdominal masses), but modern clinical practice generally does not exceed 30g in decoction.

Dosage notes

Use lower doses (9 to 15g) for clearing Damp-Heat, resolving jaundice, and transforming phlegm to stop cough. Use moderate to higher doses (15 to 30g) for invigorating Blood, dispersing stasis, and treating amenorrhea, painful obstruction, or traumatic injury. For external use (burns, sores, skin infections), the herb can be ground into powder and applied as a paste, or a concentrated decoction can be used as a wash. A classical dosage study found that Hu Zhang's Heat-clearing and detoxifying effects are best expressed at smaller doses (up to 30g), while its Blood-moving effects require moderate doses. Excessive dosage may cause gastrointestinal irritation due to the emodin and tannin content.

Preparation

No special decoction handling required. Hu Zhang is simply decocted with other herbs in the standard manner. For external application, the dried root is ground to powder and mixed with tea water, egg white, vinegar, or sesame oil depending on the condition being treated.

Processing Methods

In TCM, the same herb can be prepared in different ways to change its effects — here's how processing alters what Hu Zhang does

Processing method

The raw sliced Hu Zhang is sprinkled with yellow rice wine (Huang Jiu), allowed to absorb the wine thoroughly, then stir-fried over gentle heat until dry.

How it changes properties

Wine processing enhances Hu Zhang's Blood-invigorating and channel-opening actions, directing its effects more strongly to the sinews and collaterals. It also moderates the herb's cold nature slightly, making it less likely to upset digestion. The Blood-moving effect becomes stronger while the Dampness-clearing and Heat-clearing actions become secondary.

When to use this form

Preferred for Wind-Damp Bi syndrome with joint and muscle pain, traumatic injuries, Blood stasis amenorrhea, and conditions where the primary goal is moving Blood rather than clearing Dampness-Heat. Also gentler on the Stomach for patients with weak digestion.

Common Herb Pairs

These ingredients are traditionally combined with Hu Zhang for enhanced therapeutic effect

Yin Chen
Yin Chen 1:2 (Hu Zhang 10-15g : Yin Chen Hao 15-30g)

Hu Zhang and Yin Chen Hao together powerfully clear Dampness-Heat from the Liver and Gallbladder and reduce jaundice. Yin Chen Hao is the premier jaundice-resolving herb, while Hu Zhang adds Blood-invigorating and toxin-clearing actions, preventing the Blood stasis that often complicates prolonged jaundice.

When to use: Dampness-Heat jaundice, especially in hepatitis or cholecystitis where there is yellowing, dark urine, and rib-area discomfort.

Chi Shao
Chi Shao 3:2 (Hu Zhang 15g : Chi Shao 10g, following the classical ratio)

Hu Zhang and Chi Shao (Red Peony) are the two ingredients of the classical Hu Zhang San from the Sheng Ji Zong Lu. Both invigorate Blood and dispel stasis, but Chi Shao adds stronger Blood-cooling and pain-relieving properties. Together they break up blood stasis from traumatic injuries more effectively than either herb alone.

When to use: Traumatic injury with bruising, swelling, and blood stasis that does not disperse. Also applicable to Blood stasis pain conditions.

Dang Gui
Dang Gui 1:1 (Hu Zhang 15g : Dang Gui 15g)

Hu Zhang invigorates Blood and breaks stasis, while Dang Gui both nourishes and moves Blood. This pairing ensures that stasis is dispelled without depleting the Blood. Dang Gui's warming, tonifying nature complements Hu Zhang's cooler, more aggressive stasis-breaking action.

When to use: Blood stasis with underlying Blood Deficiency, such as amenorrhea, post-traumatic pain, or postpartum blood stasis with pain.

Huang Qin
Huang Qin 1:1 (Hu Zhang 10g : Huang Qin 10g)

Hu Zhang clears Heat from the Liver and Gallbladder while transforming Phlegm, and Huang Qin (Scutellaria) powerfully clears Lung Heat and dries Dampness. Together they clear Heat from both the Liver and Lung systems, with enhanced Phlegm-resolving and cough-stopping effects.

When to use: Lung Heat cough with thick yellow phlegm, especially when accompanied by signs of Liver-Gallbladder Dampness-Heat.

Comparable Ingredients

These ingredients have overlapping uses — here's how to tell them apart

Da Huang
Hu Zhang vs Da Huang

Both Hu Zhang and Da Huang (Rhubarb) belong to the Polygonaceae family, are bitter and cold, and share overlapping actions: clearing Heat, promoting bowel movements, invigorating Blood, and resolving toxins. However, Da Huang is far stronger as a purgative and is the primary herb for acute constipation with Heat accumulation. It also cools Blood to stop bleeding. Hu Zhang, by contrast, excels at clearing Dampness-Heat to reduce jaundice, is the better choice for Wind-Damp-Heat joint pain, and has Phlegm-transforming and cough-stopping actions that Da Huang lacks. Choose Da Huang when the priority is strong purgation or stopping bleeding from Blood Heat; choose Hu Zhang when the focus is jaundice, joint pain, or Lung Heat cough.

Jin Qian Cao
Hu Zhang vs Jin Qian Cao

Both herbs clear Dampness-Heat from the Liver and Gallbladder and are commonly used for jaundice, often combined together. However, Jin Qian Cao (Lysimachia) is the premier herb for dissolving and expelling stones (urinary and biliary), with stronger diuretic and stone-expelling actions. Hu Zhang has broader applications: it invigorates Blood for menstrual stasis, clears Heat-toxin for abscesses, and transforms Phlegm for coughs. Choose Jin Qian Cao when stones are the primary concern; choose Hu Zhang when Blood stasis or Lung Heat are also present.

Yi Mu Cao
Hu Zhang vs Yi Mu Cao

Both herbs invigorate Blood and are used for menstrual disorders. Yi Mu Cao (Leonurus / Motherwort) is specifically oriented toward gynecological Blood stasis and is the classic herb for postpartum blood stasis and irregular menstruation. It also promotes urination. Hu Zhang has a broader scope, addressing jaundice, joint pain, Lung Heat cough, and topical wound healing in addition to menstrual stasis. Choose Yi Mu Cao when the condition is purely gynecological; choose Hu Zhang when menstrual stasis coexists with Dampness-Heat, liver issues, or respiratory symptoms.

Identity & Adulterants

Related species and common adulterations to be aware of when sourcing Hu Zhang

The classical text Lei Gong Pao Zhi Lun warns against confusion with Tian Lan (天蓝) and Ban Xiu Gen (斑袖根), noting that these plants have similar root appearance and taste. In modern practice, Hu Zhang may be confused with roots from other related Polygonaceae family plants, such as Polygonum multiflorum (He Shou Wu), which contains similar anthraquinone and stilbene compounds but has very different therapeutic functions. Da Huang (Rhubarb, Rheum palmatum) root shares similar anthraquinone chemistry and may occasionally be mixed in. Sanguisorba officinalis (Di Yu) and Rumex japonicus (Yang Ti Gen) have also been documented as potential adulterants. Authentication can be confirmed by HPLC analysis for the characteristic marker compounds polydatin and emodin, as specified in the Chinese Pharmacopoeia.

Educational content — always consult a qualified healthcare provider or TCM practitioner before using any herb.

Toxicity Classification

Classical Chinese pharmacopoeia toxicity rating for Hu Zhang

Non-toxic

Hu Zhang is classified as non-toxic in the Chinese Pharmacopoeia at standard doses. However, it contains emodin and other anthraquinone derivatives, tannins, and multiple phenolic compounds. Excessive dosage may irritate the gastrointestinal mucosa, leading to nausea, vomiting, abdominal pain, or diarrhea. Animal toxicity studies on isolated polydatin (the glycoside form of resveratrol) showed that high intraperitoneal doses could cause liver cell necrosis, peritoneal inflammation, and bone marrow changes in rats, but these effects occurred at doses far exceeding normal therapeutic use. At standard oral doses in decoction (9 to 15g), Hu Zhang has a long track record of safe clinical use.

Contraindications

Situations where Hu Zhang should not be used or requires extra caution

Avoid

Pregnancy. Hu Zhang is a Blood-invigorating herb with a bitter, cold nature. Classical sources including the Ben Cao Gang Mu explicitly state that pregnant women should not take it, as its Blood-moving and downward-draining properties may disturb the fetus or cause uterine contractions.

Caution

Spleen and Stomach deficiency with cold. The bitter, slightly cold nature of Hu Zhang can further damage a weak digestive system, potentially worsening loose stools, poor appetite, or abdominal pain in patients with cold-deficiency patterns.

Caution

Absence of Blood stasis or Damp-Heat. Since Hu Zhang is strongly clearing and Blood-moving, it should not be used long-term or in high doses in patients without genuine Heat or stasis, as it may injure Qi and Blood.

Caution

Heavy menstrual bleeding or active hemorrhage without Blood stasis. Because Hu Zhang invigorates Blood and disperses stasis, it may worsen bleeding that is not caused by stasis obstruction.

Caution

Excessive dosage. Hu Zhang contains emodin, tannins, and other phenolic compounds. Overconsumption can irritate the stomach lining and cause nausea, vomiting, or diarrhea.

Special Populations

Important considerations for pregnancy, breastfeeding, and pediatric use

Pregnancy

Contraindicated. Hu Zhang is a Blood-invigorating and stasis-dispersing herb with a slightly cold, bitter nature. Multiple classical sources explicitly warn against its use in pregnancy. The Ben Cao Gang Mu states: "Pregnant women must not take it" (有孕人勿服). The herb's active compounds, including emodin (an anthraquinone with laxative and uterine-stimulating properties) and resveratrol, may promote uterine contractions and disturb fetal development. Emodin has shown embryotoxic potential in animal studies. Hu Zhang should be strictly avoided throughout pregnancy.

Breastfeeding

Caution advised. Although no specific classical prohibitions exist for breastfeeding, Hu Zhang contains emodin and other anthraquinone compounds that are known to pass into breast milk (as demonstrated with related anthraquinone-containing herbs such as Da Huang). These compounds may cause loose stools or gastrointestinal irritation in the nursing infant. The slightly cold nature of the herb could also potentially affect lactation in women with underlying Spleen deficiency. Use only under practitioner guidance, and prefer alternative herbs when possible during breastfeeding.

Children

Not commonly used in paediatric formulas. If prescribed for children by a qualified practitioner, dosages should be proportionally reduced based on age and body weight (typically one-third to one-half of the adult dose for older children). The herb's bitter, cold nature and Blood-moving properties make it unsuitable for young children or infants. The anthraquinone content (emodin) may cause diarrhoea, so bowel function should be monitored closely. Avoid prolonged use in children.

Drug Interactions

If you are taking pharmaceutical medications, be aware of these potential interactions with Hu Zhang

Anticoagulant and antiplatelet medications (warfarin, heparin, aspirin, clopidogrel): Hu Zhang invigorates Blood and disperses stasis. Its active compound resveratrol has demonstrated antiplatelet aggregation effects in pharmacological studies. Concurrent use with anticoagulant or antiplatelet drugs may increase bleeding risk. Monitoring of coagulation parameters is advised.

Antidiabetic medications: Resveratrol from Hu Zhang has shown blood-glucose-lowering effects in animal studies. Concurrent use with insulin or oral hypoglycaemic agents could theoretically potentiate hypoglycaemia. Blood sugar should be monitored.

Hepatically metabolised drugs (CYP450 substrates): Emodin and resveratrol have been shown to modulate certain cytochrome P450 enzymes in laboratory studies. This could theoretically alter the metabolism of drugs processed through the liver, though clinical significance at standard herbal doses is not fully established.

Laxatives: The anthraquinone emodin in Hu Zhang has mild laxative properties similar to those of Da Huang (rhubarb). Combining it with other laxatives or cathartic medications may result in excessive purging or electrolyte imbalances.

Dietary Advice

Foods and dietary considerations when taking Hu Zhang

When taking Hu Zhang for Damp-Heat conditions (jaundice, urinary issues), avoid greasy, fried, and rich foods that generate Dampness and Heat. Avoid excessive alcohol. When using Hu Zhang for Blood stasis patterns, avoid cold and raw foods that could impede Blood circulation. Classical formulas for abdominal masses specifically warned against eating fresh fish and salt during treatment.

Botanical Description

Physical characteristics and morphology of the Hu Zhang source plant

Reynoutria japonica Houtt. (syn. Polygonum cuspidatum Sieb. et Zucc.) is a vigorous herbaceous perennial in the Polygonaceae (buckwheat) family. It has a stout, creeping rhizome and erect, hollow stems that can reach 1 to 3 metres tall. The stems are bamboo-like, with distinct raised nodes and characteristic red or purple speckles on the surface, which gave the herb its Chinese name ("tiger's walking stick" referring to the tiger-striped markings). Leaves are broadly ovate to heart-shaped, 5 to 12 cm long, arranged alternately in a zigzag pattern, with short petioles and membranous sheaths at the nodes.

The plant is dioecious (male and female flowers on separate plants). Small, greenish-white to creamy flowers appear in axillary panicle clusters in late summer (August to September), followed by shiny black-brown, three-angled achene fruits in autumn. It thrives in moist habitats such as hillside thickets, stream banks, roadsides, and field margins at elevations of 140 to 2000 metres. It prefers warm, humid conditions and loose, fertile soils but is remarkably hardy, tolerating cold, flooding, and poor soils. The medicinal parts are the dried rhizome and roots, which are thick, woody, and yellowish in cross-section with a dark brown outer bark.

Sourcing & Harvesting

Where Hu Zhang is sourced, when it's harvested or collected, and how to assess quality

Harvesting season

Spring or autumn. Roots propagated by division are harvested from the second year onward; seed-propagated plants from the third year. The roots are dug up, cleaned of rootlets, washed, sliced into short segments or thick pieces while fresh, and sun-dried.

Primary growing regions

Hu Zhang is widely distributed across China, with key production areas in the southwest (Sichuan, Yunnan, Guizhou), south-central China (Hunan, Hubei), and eastern regions (Zhejiang, Jiangxi, Anhui, Jiangsu, Fujian). It also grows in Shaanxi (southern), Gansu (southern), Guangxi, Guangdong, and Hebei. Classical sources note it is found in Fenzhou (Shanxi), Yuezhou (Zhejiang), and Chuzhou (Anhui). It also occurs natively in Korea and Japan. The best quality material traditionally comes from the mountainous southwestern and south-central provinces where wild populations grow in moist hillside thickets.

Quality indicators

Good quality Hu Zhang root consists of thick, stout pieces that are firm and hard. The exterior bark should be brown to dark brown with longitudinal wrinkles and rootlet scars. In cross-section, the cortex is thin and the wood portion is broad and brownish-yellow with clearly visible radial ray lines. The cortex and wood layers should separate relatively easily. The rhizome pith should show visible partitions or hollow chambers. The material should feel heavy and solid. The aroma is faint, and the taste should be slightly bitter and astringent. The best material is described as thick, solid, and distinctly yellow in the cross-section. Avoid pieces that are overly thin, lightweight, darkened throughout, or show signs of mould or insect damage.

Classical Texts

Key passages from the classical Chinese medical texts that describe Hu Zhang and its therapeutic uses

Ming Yi Bie Lu (《名医别录》)

Original: 主通利月水，破留血癥结。

Translation: "Governs the free flow of menstruation, breaks up retained Blood and fixed abdominal masses."

Yao Xing Lun (《药性论》, Zhen Quan)

Original: 治大热烦躁，止渴，利小便，压一切热毒。

Translation: "Treats great Heat with agitation, stops thirst, promotes urination, and suppresses all Heat-Toxin."

Ri Hua Zi Ben Cao (《日华子本草》)

Original: 治产后恶血不下，心腹胀满。排脓，主疮疖痈毒，妇人血晕，扑损瘀血，破风毒结气。

Translation: "Treats postpartum retention of lochia with distension of the chest and abdomen. Expels pus. Governs sores, boils, and toxic swellings. Treats Blood-fainting in women, bruise-related Blood stasis, and breaks up Wind-Toxin with knotted Qi."

Ben Cao Gang Mu (《本草纲目》, Li Shizhen)

Original (释名): 杖言其茎，虎言其斑也。

Translation: "'Staff' (杖, zhang) refers to its stem; 'tiger' (虎, hu) refers to its spotted markings."

Ben Cao Gang Mu (《本草纲目》, Zhen Quan's commentary preserved therein)

Original: 暑月以根和甘草同煎为饮，色如琥珀可爱，甚甘美...时人呼为冷饮子，啜之且尊于茗，极解暑毒。

Translation: "In summer months, the root is decocted together with Gan Cao to make a drink. Its colour is lovely like amber and it tastes very sweet... People of the time called it a 'cold drink,' and it was considered superior to tea for its ability to resolve summer Heat-Toxin."

Historical Context

The history and evolution of Hu Zhang's use in Chinese medicine over the centuries

Hu Zhang has one of the longer documented histories among Chinese medicinal herbs. The plant first appears in the ancient dictionary Er Ya (《尔雅》) under the name "tú" (蒤), where it was noted for its resemblance to a coarse, prickly form of hong cao (red knotweed) that could be used as a red dye. Its first recorded medicinal use was in the Ming Yi Bie Lu (《名医别录》), where it was listed as a middle-grade herb under the name "Hu Zhang Gen" (虎杖根) and indicated for promoting menstrual flow and breaking up Blood stasis masses.

Li Shizhen, in the Ben Cao Gang Mu, explained the etymology of the name: "zhang" (杖, staff or cane) describes its bamboo-like upright stem, while "hu" (虎, tiger) refers to the distinctive reddish-purple spots on the stem, reminiscent of tiger stripes. Because "tiger" was also euphemistically called "da chong" (大虫, great creature), the herb was also known as Da Chong Zhang. Other folk names such as Suan Zhang (酸杖, sour staff) and Ku Zhang (苦杖, bitter staff) reflect the sour or bitter taste of the stem when chewed. A charming cultural note: the Tang dynasty physician Zhen Quan recorded that people in summer would decoct the root with Gan Cao (licorice) to make an amber-coloured beverage, prized as a "cold drink" that was considered finer than tea for clearing summer Heat.

Over the centuries, understanding of the herb broadened considerably. Early sources emphasized its gynaecological uses (amenorrhea, lochia retention, abdominal masses). Later texts expanded its applications to include Wind-Damp joint pain, Damp-Heat jaundice, urinary stones, burns, and toxic sores. In the modern era, Hu Zhang gained significant scientific attention as one of the richest natural sources of resveratrol, a polyphenolic compound extensively studied for cardiovascular, anti-inflammatory, and antioxidant properties. This has made the humble "tiger staff" one of the most commercially important medicinal plants for both traditional and modern pharmaceutical applications worldwide.

Modern Research

4 published studies investigating the pharmacological effects or clinical outcomes of Hu Zhang

1

An Anti-inflammatory and Reactive Oxygen Species Suppressive Effects of an Extract of Polygonum cuspidatum Containing Resveratrol (RCT, 2010)

Ghanim H, Sia CL, Abuaysheh S, et al. Journal of Clinical Endocrinology and Metabolism, 2010, 95(9): E1-E8.

This randomized controlled trial in 20 healthy human subjects found that a 6-week course of Polygonum cuspidatum extract (containing 40mg resveratrol) significantly suppressed NF-kB binding activity in blood immune cells, and reduced circulating levels of inflammatory markers TNF-alpha and IL-6, along with reactive oxygen species generation, compared to placebo.

Link
2

A Review of the Pharmacological Effects of the Dried Root of Polygonum cuspidatum (Hu Zhang) and Its Constituents (Review, 2013)

Peng W, Qin R, Li X, Zhou H. Evidence-Based Complementary and Alternative Medicine, 2013, vol. 2013, Article ID 208349, 13 pages.

This comprehensive review summarized the major chemical components of Hu Zhang (resveratrol, polydatin, emodin, quercetin, physcion) and their demonstrated pharmacological activities including hepatoprotection, lipid-lowering, anti-inflammatory, antimicrobial, antiviral, and antitumor effects in both experimental and clinical settings.

Link
3

Advances for Pharmacological Activities of Polygonum cuspidatum - A Review (Review, 2023)

Multiple authors. Pharmaceutical Biology, 2023, 61(1): 177-188.

A recent comprehensive review published in Pharmaceutical Biology that systematically evaluated the therapeutic effects of Polygonum cuspidatum across multiple disease models. It confirmed that the major active compounds (resveratrol, polydatin, emodin, quercetin) demonstrate anti-inflammatory, antioxidant, antiviral, antimicrobial, neuroprotective, and anticancer activities through mechanisms including NF-kB suppression, JAK/STAT pathway modulation, and apoptotic pathway regulation.

Link
4

Root Extract of Polygonum cuspidatum Ameliorates DSS-Induced Ulcerative Colitis by Affecting NF-kappaB Signaling Pathway in a Mouse Model (Preclinical, 2018)

Liu B, Li S, Sui X, et al. Frontiers in Pharmacology, 2018, 9: 347.

This preclinical mouse study demonstrated that Polygonum cuspidatum root extract significantly ameliorated dextran sulfate sodium-induced ulcerative colitis symptoms through synergistic effects of polydatin, resveratrol, and emodin. The mechanism involved suppression of the NF-kB signaling pathway and reduction of inflammatory cytokine levels in colon tissue.

Link

Research on individual TCM herbs is growing but still limited by Western clinical trial standards. These studies provide emerging evidence and should be considered alongside practitioner expertise.