Herb Rhizome (根茎 gēn jīng)

Bi Xie

Fish-poison yam rhizome · 萆薢

Dioscorea hypoglauca Palibin · Rhizoma Dioscoreae Hypoglaucae

Also known as: Bì Jiè, Běi Xiè, Chuān Bì Xiè (川萆薢),

Bi Xie (Fish-poison yam rhizome) plant

Images shown are for educational purposes only

Bì Xiè is a bitter, mild-natured herb best known for clearing cloudy or turbid urine and restoring normal urinary function. It is also widely used for joint pain and stiffness caused by dampness, and for weeping skin conditions like eczema. Think of it as the body's 'water filter' herb, helping separate clean fluids from waste.

Category Dampness-draining herbs (利水渗湿药)
Therapeutic focus Urinary Health Joint and Muscle Pain Relief Skin Health Prostate Health

TCM Properties

Temperature

Neutral

Taste

Bitter (苦 kǔ)

Channels entered

Liver, Stomach, Urinary Bladder

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 Bi Xie does in the body, explained in both everyday and TCM terms

Therapeutic focus

In practical terms, Bi Xie is primarily used to support these areas of health:

Urinary Health Joint and Muscle Pain Relief Skin Health Prostate Health

TCM Actions

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

Separates the Clear from the Turbid Drains Dampness and Resolves Turbidity Dispels Wind-Dampness Relieves Painful Obstruction Clears Damp-Heat from the Skin

How these actions work

'Separates the clear from the turbid' is Bì Xiè's most distinctive action. In TCM, the body's water metabolism should separate clean fluids (which nourish the body) from turbid waste (which is excreted as urine). When this process breaks down, the urine becomes cloudy, milky, or greasy-looking (a condition called 'gāo lín' or 'fatty dysuria'). Bì Xiè helps restore the body's ability to sort clean from dirty, making the urine clear again. This is why it is considered an essential herb for cloudy or turbid urination.

'Drains Dampness and resolves turbidity' means Bì Xiè promotes the removal of excess moisture and metabolic waste from the lower body. It is particularly effective for conditions in the lower abdomen, urinary tract, and reproductive system where Dampness has accumulated, causing symptoms like vaginal discharge (leukorrhea), urinary frequency, or urinary tract discomfort.

'Dispels Wind-Dampness and relieves painful obstruction' means Bì Xiè can clear the combination of Wind and Dampness that lodges in muscles, joints, and channels, causing joint pain, stiffness, low back ache, and difficulty moving. It is especially useful when Dampness is the dominant factor, with heavy, aching sensations in the lower back and legs. Classical texts note it excels at treating Dampness, followed by Wind, and is less potent against Cold.

'Clears Damp-Heat from the skin' refers to its ability to treat skin conditions driven by Dampness and Heat, such as weeping eczema, sores, and ulcers on the lower limbs. By draining Dampness downward and out through urination, it helps reduce the swelling, oozing, and itching associated with these conditions.

Patterns Addressed

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

Why Bi Xie addresses this pattern

When Damp-Heat accumulates in the Lower Burner (the pelvic and urinary area), it disrupts the Bladder's ability to separate clean fluids from waste. This produces cloudy, turbid, or greasy urine, urinary discomfort, and sometimes vaginal discharge. Bì Xiè is bitter and neutral, entering the Bladder and Stomach channels. Its bitter nature drains and dries Dampness, while its core action of 'separating the clear from the turbid' directly addresses the Bladder's impaired sorting function. It clears the turbid Dampness downward and out, restoring normal urinary clarity. This is the pattern for which Bì Xiè is most frequently prescribed and considered an essential (要药) herb.

A practitioner would look for one or more of these signs

Cloudy Urine

Urine appears milky, greasy, or like rice water

Frequent Urination

Urinary frequency with turbid or incomplete voiding

Thin Vaginal Discharge

Excessive white or turbid vaginal discharge from Dampness

Urinary Tract Infection

Urinary discomfort with a sensation of heaviness in the lower abdomen

Commonly Used For

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

Arises from: Damp-Heat

TCM Interpretation

TCM understands gout as a form of painful obstruction (痹证) caused primarily by Damp-Heat accumulating in the joints, often in the lower limbs. The Spleen and Kidneys fail to properly transform and transport fluids, allowing turbid, damp waste material to pool in the joints, causing sudden hot, swollen, intensely painful attacks. The condition often involves both turbid urine and joint inflammation, reflecting a systemic failure to 'separate the clear from the turbid' at multiple levels.

Why Bi Xie Helps

Bì Xiè directly addresses gout's dual presentation. Its core action of separating the clear from the turbid helps the body clear metabolic waste (corresponding to uric acid in biomedical terms) through the urinary route, while its Wind-Dampness dispelling action relieves joint pain and swelling. Modern research on formulas containing Bì Xiè (such as modified Bì Xiè Fēn Qīng Yǐn) has shown it can lower serum uric acid levels with sustained effects even after discontinuation. Its neutral temperature makes it suitable for both hot and cold presentations of gouty arthritis.

Also commonly used for

Cloudy Urine

Chyluria, albuminuria, or milky urine (膏淋)

Urinary Tract Infection

Chronic urinary tract infections with turbid urine

Benign Prostatic Hypertrophy

Prostate enlargement with urinary frequency

Rheumatoid Arthritis

Rheumatoid and rheumatic arthritis with Dampness dominance

Thin Vaginal Discharge

Excessive leukorrhea due to Dampness

Lower Back Pain

Chronic low back pain due to Wind-Dampness

Moving Pain

Painful obstruction syndrome of the joints

Herb Properties

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

Temperature

Neutral

Taste

Bitter (苦 kǔ)

Channels Entered

Liver Stomach Urinary Bladder

Parts Used

Rhizome (根茎 gēn jīng)

Dosage & Preparation

These are general dosage guidelines for Bi Xie — 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 cases of severe Dampness or acute turbid urination, under practitioner supervision. Fresh herb has been traditionally used at doses up to 60g (approximately 2 liang) in folk medicine for urinary turbidity.

Dosage notes

Use the lower range (9-10g) for mild dampness or as a supporting herb in formulas. Use the higher range (12-15g) when Bi Xie is the principal herb for treating turbid urination (gao lin) or pronounced Wind-Dampness with joint pain. When addressing hyperuricemia or gout, modern practitioners sometimes use up to 30g. For urinary turbidity conditions, combining with a small amount of salt in the decoction (an ancient method from the Bi Xie Fen Qing Yin formula) is traditionally believed to guide the herb to the Kidneys and lower body. The Fen Bi Xie (powdery) type is preferred for urinary conditions, while Chuan Bi Xie or Mian Bi Xie is preferred for Wind-Dampness and joint pain.

Preparation

No special decoction handling is required. Bi Xie is simply added to the decoction pot and decocted normally with other herbs. It is used in its raw, unprocessed form (生用) for most indications. Dry-frying (炒) may be used to enhance its Stomach-entering and Dampness-transforming action. Salt-frying (盐炒) is sometimes used to direct the herb's action to the Kidneys for urinary conditions. Wine-frying (酒炒) is used when Wind-Dampness is the primary target.

Processing Methods

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

Processing method

Mix clean Bì Xiè slices with salt water (2kg salt per 100kg herb), let absorb, then stir-fry over gentle heat until dry.

How it changes properties

Salt processing guides the herb's action downward toward the Kidneys (salt has a descending, Kidney-directing nature in TCM). This enhances Bì Xiè's ability to consolidate the Lower Burner and strengthen its effect on urinary conditions. The thermal nature remains neutral.

When to use this form

Preferred when treating Bladder deficiency-cold with loss of urinary control (enuresis, incontinence), or when the primary goal is to direct the herb specifically to the Kidney and Bladder for urinary turbidity and frequency.

Common Herb Pairs

These ingredients are traditionally combined with Bi Xie for enhanced therapeutic effect

Yi Zhi Ren
Yi Zhi Ren 1:1 (equal parts, as in the original Bì Xiè Fēn Qīng Sàn)

Bì Xiè drains Dampness and separates the clear from the turbid, while Yì Zhì Rén warms the Kidneys, consolidates essence, and astringes urine. One drains and the other consolidates, creating a balanced approach that clears turbidity without causing excessive fluid loss and warms without trapping Dampness.

When to use: Kidney deficiency with Dampness causing cloudy, turbid urine, urinary frequency, or vaginal discharge. This is the core pairing in Bì Xiè Fēn Qīng Yǐn.

Shi Chang Pu
Shi Chang Pu 1:1

Bì Xiè drains Dampness and separates turbid from clear fluids, while Shí Chāng Pú is aromatic and penetrating, transforming Dampness and opening the waterways. Together, their Dampness-resolving and turbidity-clearing effects are significantly strengthened.

When to use: Dampness obstructing the Lower Burner with cloudy urine, urinary frequency, or a sense of incomplete voiding. Also present together in Bì Xiè Fēn Qīng Yǐn.

Niu Xi
Niu Xi 2:1 (Bì Xiè 10-15g : Niú Xī 6-10g)

Bì Xiè dispels Wind-Dampness and relieves painful obstruction, while Niú Xī (Huái Niú Xī) tonifies the Liver and Kidneys, strengthens sinews and bones, and guides other herbs downward to the lower body. The pair combines pathogen-expelling with body-strengthening actions.

When to use: Wind-Damp painful obstruction (Bi Syndrome) of the lower back and legs, with heavy aching pain, stiffness, and weakness of the knees and lumbar region.

Wei Ling Xian
Wei Ling Xian 1:1 (Bì Xiè 10g : Wēi Líng Xiān 10g)

Both herbs dispel Wind-Dampness, but through complementary mechanisms. Bì Xiè focuses on draining Dampness, while Wēi Líng Xiān excels at unblocking channels and relieving pain. Together, they offer stronger Wind-Dampness expulsion and pain relief for joint conditions.

When to use: Wind-Damp Bi Syndrome with joint swelling, pain, and difficulty bending or straightening the limbs, especially for 'moving' (行痹) or 'fixed' (着痹) painful obstruction.

Key Formulas

These well-known formulas feature Bi Xie in a prominent role

Bi Xie Fen Qing Yin 萆薢分清飲 King

This is the definitive formula showcasing Bì Xiè's signature action of separating the clear from the turbid. Originally named Bì Xiè Fēn Qīng Sàn from the Yáng Shì Jiā Cáng Fāng, it pairs Bì Xiè with Yì Zhì Rén, Shí Chāng Pú, and Wū Yào to treat cloudy, turbid urine due to Lower Burner deficiency-cold with Dampness. Bì Xiè serves as King herb, and the formula's very name ('Bì Xiè Decoction to Separate the Clear') emphasizes the herb's core identity.

Bi Xie Shen Shi Tang 萆薢渗湿汤 King

From Gāo Bǐng Jūn's Yáng Kē Xīn Dé Jí, this formula showcases Bì Xiè's skin-directed Dampness-draining action. As King herb, Bì Xiè works alongside Huáng Bǎi, Yì Yǐ Rén, Zé Xiè, and others to clear Damp-Heat from the lower body, treating weeping eczema, lower-leg ulcers (臁疮), erysipelas, and skin infections. It demonstrates that Bì Xiè's Dampness-draining action extends beyond the urinary system to the skin.

Comparable Ingredients

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

Tu Fu Ling
Bi Xie vs Tu Fu Ling

Both Bì Xiè and Tǔ Fú Líng drain Dampness, enter the Liver and Stomach channels, and treat damp skin conditions and painful obstruction. However, Bì Xiè excels at separating the clear from the turbid, making it the superior choice for cloudy urine (膏淋) and vaginal discharge. Tǔ Fú Líng has stronger toxin-resolving ability and is the primary herb for syphilis (梅毒) and mercury poisoning. Choose Bì Xiè for urinary turbidity; choose Tǔ Fú Líng for toxic sores and infections.

Bian Xu
Bi Xie vs Bian Xu

Both are Dampness-draining herbs used for urinary conditions and skin issues. However, Biǎn Xù (Polygonum aviculare) is better at clearing Bladder Damp-Heat, treating painful, burning urination with blood (hot-type or blood-type dysuria), and killing parasites. Bì Xiè is better at resolving turbidity in the urine without strong Heat-clearing action, making it more appropriate for cloudy urine where Dampness predominates over Heat. Bì Xiè also has the additional benefit of treating Wind-Damp joint pain, which Biǎn Xù does not.

Yi Yi Ren
Bi Xie vs Yi Yi Ren

Both drain Dampness and treat Bi Syndrome. Yì Yǐ Rén (Coix seed) is cool and also clears Heat, strengthens the Spleen, and expels pus, making it broadly useful for Damp-Heat conditions and skin abscesses. Bì Xiè has the unique ability to separate clean from turbid urine, which Yì Yǐ Rén cannot do. For cloudy urination, Bì Xiè is irreplaceable; for general Dampness with Spleen weakness or skin abscesses, Yì Yǐ Rén is preferred.

Common Substitutes & Adulterants

Related species and common adulterations to be aware of when sourcing Bi Xie

Bi Xie has a long history of confusion with related herbs: 1. Tu Fu Ling (土茯苓, Smilax glabra rhizome): The most common confusion, noted by Li Shizhen himself. Tu Fu Ling has a mildly sweet taste with no bitterness, a slightly finer cross-section with no coarse fibrous tissue, and becomes sticky and slippery when wet or boiled. Bi Xie is slightly bitter, has a rougher cross-section, and does not become sticky when wet. 2. Ba Qia (菝葜, Smilax china rhizome): Historically mixed with Bi Xie. Ba Qia rhizomes tend to be more nodular with prominent joint-like structures, and are reddish in color. 3. Red-colored Bi Xie: A reddish-colored product mainly from Sichuan, derived from Smilax family plants rather than Dioscorea, has sometimes been sold as Bi Xie. It has a bitter, astringent taste and is not considered authentic. 4. Vendors have historically used cheaper Smilax species rhizomes (from Liliaceae) to adulterate or substitute for genuine Dioscorea-sourced Bi Xie.

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

Toxicity Classification

Classical Chinese pharmacopoeia toxicity rating for Bi Xie

Non-toxic

Bi Xie is classified as non-toxic in the classical literature. The Ming Yi Bie Lu specifically states it is "gan, wu du" (sweet, non-toxic). Its primary active constituents are steroidal saponins (including dioscin and diosgenin), which are generally well tolerated at standard dosages. At excessive doses, gastrointestinal discomfort may occur due to the saponin content. No specific toxic components requiring special processing have been identified, and the herb is used in its raw, unprocessed form.

Contraindications

Situations where Bi Xie should not be used or requires extra caution

Caution

Kidney Yin deficiency with deficiency Heat. When there is no actual Dampness in the lower body but symptoms like dribbling urination or urethral pain arise from Yin deficiency and flaring Fire, Bi Xie's drying and draining nature will worsen the condition.

Caution

Seminal loss due to Kidney deficiency (Yin deficiency with spermatorrhea). When the underlying cause is Kidney weakness unable to secure essence rather than Dampness, using this herb can aggravate the leakage.

Caution

Sinking Qi unable to hold essence, with frequent urination and urgency of bowel movements. The Ben Jing Feng Yuan warns that mistaken use in this pattern will make the disease dramatically worse.

Caution

Spleen deficiency with loose stools or diarrhea. Bi Xie's dampness-draining action can further weaken digestive function in those with Spleen Qi deficiency.

Classical Incompatibilities

Traditional Chinese pharmacological incompatibilities — herbs or substances to avoid combining with Bi Xie

Bi Xie does not appear on the Eighteen Incompatibilities (十八反) or Nineteen Mutual Fears (十九畏) lists. However, the Ben Cao Jing Ji Zhu (Tao Hongjing) records that Yi Yi Ren (Coix seed) serves as its envoy herb (使), and that Bi Xie "fears" (畏) Kui Gen (mallow root), Da Huang (rhubarb), Chai Hu, Mu Li (oyster shell), and Qian Hu. The Ben Cao Bei Yao additionally notes it is incompatible with tea (茗).

Special Populations

Important considerations for pregnancy, breastfeeding, and pediatric use

Pregnancy

No specific pregnancy contraindication is recorded in the classical literature. However, Bi Xie's primary action is to drain Dampness and promote urination, which can deplete fluids. Pregnant women, who need adequate fluid retention for fetal development, should use this herb with caution and only under practitioner supervision. There is no documented uterine-stimulating effect, but the lack of specific safety data warrants conservative use.

Breastfeeding

No specific classical or modern data addresses Bi Xie during breastfeeding. Its steroidal saponin content (including diosgenin, which is structurally related to steroid hormones) theoretically warrants caution regarding potential transfer through breast milk, though no adverse effects have been documented. Use during breastfeeding should be limited to situations where a clear clinical indication exists, at standard dosages and under practitioner guidance.

Children

No specific classical pediatric dosage guidelines exist for Bi Xie. In children, dosage should be reduced proportionally based on age and body weight, generally to one-third to one-half of the adult dose. As a dampness-draining herb with a bitter taste, it may be poorly tolerated by young children. Use in children should be limited to clear clinical indications of Dampness and under practitioner supervision.

Drug Interactions

If you are taking pharmaceutical medications, be aware of these potential interactions with Bi Xie

No well-documented drug interactions have been established through clinical studies. However, based on the pharmacological profile of its active constituents (steroidal saponins, particularly dioscin and diosgenin), the following theoretical interactions should be considered:

  • Urate-lowering drugs (allopurinol, febuxostat, probenecid): Bi Xie's saponins promote uric acid excretion through URAT1 inhibition and ABCG2 activation. Concurrent use with pharmaceutical urate-lowering agents could theoretically produce additive effects, potentially lowering uric acid excessively. Monitor uric acid levels if combining.
  • Diuretic medications: As Bi Xie promotes urination and fluid drainage, combining it with pharmaceutical diuretics could enhance fluid loss and increase the risk of dehydration or electrolyte imbalance.
  • Hypoglycemic agents: Related Dioscorea saponins have been shown to influence blood glucose levels in animal studies. People taking diabetes medications should monitor blood sugar if also taking Bi Xie.

Dietary Advice

Foods and dietary considerations when taking Bi Xie

While taking Bi Xie, avoid greasy, heavy, or overly rich foods that generate internal Dampness, as these counteract the herb's dampness-draining purpose. Cold and raw foods should be minimized, particularly in cases of lower body Dampness with cold signs. Reduce intake of high-purine foods (organ meats, shellfish, beer) if using Bi Xie for hyperuricemia or gout. The classical text Ben Cao Bei Yao advises avoiding tea (茗) while taking Bi Xie. An early formula reference (Li An Wan) also notes to "avoid beef" (禁吃牛肉) when taking Bi Xie for lower back and leg conditions.

Botanical Description

Physical characteristics and morphology of the Bi Xie source plant

Bi Xie comes from perennial climbing herbaceous vines of the Dioscorea genus (yam family, Dioscoreaceae). The two main source species recognized in the Chinese Pharmacopoeia are Dioscorea hypoglauca Palibin (Fen Bi Xie, 粉萆薢) and Dioscorea spongiosa / D. futschauensis (Mian Bi Xie, 绵萆薢).

These are twining vines that can reach 2 to 3 meters in length, with slender stems bearing longitudinal grooves. The leaves are alternate, heart-shaped to triangularly cordate with pointed tips, and display 7 to 9 basal veins. The plants are dioecious (male and female flowers on separate plants). Male flowers appear in racemes or panicles, while female flowers form spicate or panicle-like inflorescences. The fruit is a winged capsule that turns chestnut-brown when ripe, containing flat, oval seeds. Flowering occurs from June to August, with fruit maturing from August to October.

These wild yams grow in lowland thickets, ravines, and bamboo forests in moist, partially shaded environments throughout southern China. The medicinal part is the thick, irregularly branched, roughly cylindrical rhizome, which is harvested, washed, sliced, and sun-dried.

Sourcing & Harvesting

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

Harvesting season

Autumn and winter. The rhizomes are dug up, cleaned of fibrous roots, washed, sliced, and sun-dried.

Primary growing regions

Bi Xie is primarily produced in regions south of the Yangtze River. Fen Bi Xie (from D. hypoglauca) is mainly produced in Zhejiang, Anhui, and Hunan provinces. Mian Bi Xie (from D. spongiosa/D. futschauensis) is mainly produced in Zhejiang and Fujian provinces. Other producing regions include Guangdong, Guangxi, Sichuan, and Jiangxi. Historically, the herb from Zhejiang has been considered of high quality. All commercial Bi Xie is wild-harvested rather than cultivated.

Quality indicators

Two commercial types exist with different quality markers: Fen Bi Xie (粉萆薢): Irregular thin slices with yellowish-white to pale gray-brown cut surfaces. The texture is firm yet elastic, easy to snap. Good quality pieces are dry, yellowish-white in color, large and thin, with visible powdery character and elasticity, uniform and unbroken. Slight smell, slightly pungent and bitter taste. Mian Bi Xie (绵萆薢): Irregular oblique slices 2-5mm thick. The outer skin is yellowish-brown, with scattered yellow-brown vascular bundle dots on the cut surface. Texture is loose and slightly spongy (cotton-like). Good quality is white, soft and cotton-like, neat and unbroken. Slight smell, slightly bitter taste. For both types, avoid pieces that are dark-colored, broken, or musty. The cross-section should not feel sticky or slippery when wetted (this distinguishes it from Tu Fu Ling, which does become slippery).

Classical Texts

Key passages from the classical Chinese medical texts that describe Bi Xie and its therapeutic uses

Shen Nong Ben Cao Jing (《神农本草经》, middle grade)

Original: 萆薢，味苦，平。主腰背痛强，骨节风寒湿周痹，恶疮不瘳，热气。

Translation: Bi Xie is bitter in taste and neutral in nature. It mainly treats rigidity and pain of the lower back, Wind-Cold-Damp painful obstruction of the bones and joints, stubborn sores that do not heal, and Heat conditions.

Ming Yi Bie Lu (《名医别录》)

Original: 伤中恚怒，阴痿失溺，老人五缓，关节老血。甘，无毒。

Translation: [It also treats] internal injury from anger, impotence with urinary incontinence, the five types of laxity in the elderly, and old Blood in the joints. Sweet [in addition to bitter], non-toxic.

Ben Cao Gang Mu (《本草纲目》, Li Shizhen)

Original: 萆薢之功，长于袪风湿，所以能治缓弱顽痹、遗浊、恶疮诸病之属风湿者。

Translation: The strength of Bi Xie lies in its ability to dispel Wind-Dampness. This is why it can treat laxity and weakness, stubborn painful obstruction, turbid discharge, and obstinate sores that all belong to the category of Wind-Dampness diseases.

Yao Xing Lun (《药性论》)

Original: 治冷风顽痹，腰脚不遂，手足惊掣，主男子臂腰痛久冷，是肾间有膀胱宿水。

Translation: It treats stubborn painful obstruction from Cold-Wind, inability to use the waist and legs, spasms of the hands and feet, and in men, long-standing cold pain of the arms and lower back due to retained water between the Kidneys and Bladder.

Historical Context

The history and evolution of Bi Xie's use in Chinese medicine over the centuries

Bi Xie was first recorded in the Shen Nong Ben Cao Jing (dating to the Han dynasty), where it was classified as a middle-grade (中品) herb. Its classical alternate names include Bai Zhi (百枝), Zhu Mu (竹木), and Chi Jie (赤节). Throughout history, the identity of Bi Xie has been complex and sometimes confused with related plants.

Li Shizhen addressed this confusion directly in the Ben Cao Gang Mu (16th century), noting that Bi Xie is a climbing vine with leaves resembling those of Ba Qia (Smilax) but larger, and a hard, long root. He criticized the common error of his day in which people used Tu Fu Ling (Smilax glabra rhizome) as a substitute for Bi Xie, emphasizing that the stems, leaves, roots, and seedlings of the two plants are entirely different. Li Shizhen also observed that Bi Xie, Ba Qia, and Tu Fu Ling, while morphologically distinct, share overlapping therapeutic functions in dispelling Dampness. A 2025 scholarly article confirmed that from antiquity through the mid-20th century, rhizomes from both Dioscorea and Smilax species were mixed in use as Bi Xie, but since the Tang dynasty the Dioscorea species have been considered superior.

The herb's name in formulas often carries a geographical prefix: "Chuan Bi Xie" (川萆薢, Sichuan origin) is traditionally considered better for dispelling Wind-Dampness and unblocking channels, while "Fen Bi Xie" (粉萆薢, powdery type) is considered superior for separating the clear from the turbid and treating urinary turbidity. This distinction reflects the longstanding Chinese pharmaceutical concept that processing method and regional origin affect a herb's clinical action.

Modern Research

3 published studies investigating the pharmacological effects or clinical outcomes of Bi Xie

1

Preclinical study: Effect and mechanism of dioscin from Dioscorea spongiosa on uric acid excretion in animal model of hyperuricemia (2018)

Zhang Y, Jin L, Liu J, Wang W, Yu H, Li J, Chen Q, Wang T. Journal of Ethnopharmacology, 2018, 214, 29-36.

This animal study investigated dioscin, the key saponin from Bi Xie, in rats and mice with induced hyperuricemia. Both 25 and 50 mg/kg oral doses of dioscin reduced serum uric acid levels. Two weeks of treatment also lowered serum creatinine, increased uric acid clearance, and reduced kidney damage. The study identified tigogenin (a dioscin metabolite) as the active substance, which inhibited uric acid reabsorption through the URAT1 transporter and promoted uric acid excretion via the ABCG2 transporter.

PubMed
2

Preclinical study: Total saponins from Dioscorea septemloba Thunb reduce serum uric acid levels in rats with hyperuricemia through OATP1A1 up-regulation (2016)

Chen Y, Chen XL, Xiang T, Sun BG, Luo HX, Liu MT, et al. Journal of Huazhong University of Science and Technology [Medical Sciences], 2016, 36(2), 237-242.

This study evaluated total saponins extracted from Dioscorea septemloba (Bi Xie) in a rat model of hyperuricemia. The extract effectively reduced serum uric acid levels, and the mechanism was found to involve upregulation of the organic anion transporting polypeptide 1A1 (OATP1A1), which facilitates uric acid excretion. This provides a pharmacological basis for the traditional use of Bi Xie in treating conditions associated with turbid urine and gout.

PubMed
3

Preclinical study: Polysaccharide isolated from Dioscorea septemloba improves hyperuricemia and alleviates renal fibrosis through gut-kidney axis in mice (2024)

Wang Z, Wu G, Niu T, Guo Y, Wang C, Wang X, Yu J. International Journal of Biological Macromolecules, 2024.

This study isolated and purified a polysaccharide (BXP) from Dioscorea septemloba and tested it in hyperuricemic mice. The polysaccharide reduced uric acid levels and alleviated kidney fibrosis. Using metabolomics and gut microbiome sequencing, the researchers found that BXP worked through the gut-kidney axis, modifying gut bacteria composition and improving renal function. This suggests that beyond saponins, polysaccharides from Bi Xie also contribute to its anti-hyperuricemic effects.

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.