Bian Xu
StarPolygonum aviculare L.
Traditionally used for
- Bowel health
- Urinary & fluids
- Pain & joints
- Skin
☯ TCM Properties
Clears Heat and Promotes Urination to Relieve Stranguria; Expels Parasites; Relieves Itching
Traditional Chinese Uses
Bian Xu (knotgrass herb, polygonum aviculare) is a cool herb used in Chinese medicine to clear Damp-Heat from the Bladder, promote urination, and expel intestinal parasites. It is applied for urinary tract infections with burning and difficult urination from Damp-Heat, as well as for intestinal parasitic infections including roundworm and pinworm. Its anti-parasitic action differentiates it from many other diuretic herbs and gives it a dual role in Lower Burner Damp-Heat with concurrent parasite infestation.
Western Herbalism Properties
Traditional Uses
Polygonum aviculare is documented in the NAEB database with 20 medicinal (Drug) uses across Cherokee, Iroquois, Navajo (Ramah), Thompson, Choctaw, and Mendocino peoples. Recorded categories include pediatric aid, analgesic, antidiarrheal, dermatological aid, urinary aid, gynecological aid, orthopedic aid, and gastrointestinal aid applications, typically employing decoctions or infusions of the whole plant (NAEB).
Pharmacological Effects
- Diuretic: 20 g/kg produced diuresis in rats without tolerance on repeated dosing.
- Hypotensive: I.v. aqueous or ethanolic extract lowered blood pressure in cats, rabbits and dogs.
- Other: Inhibited Sonne bacillus and Trichophyton mentagrophytes; extracts accelerated blood coagulation and increased uterine tone.
Source: Zhu YP. Chinese Materia Medica: Chemistry, Pharmacology and Applications. Harwood Academic, 1998, p. 340.
Used In Formulas (6)
Relationships
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Botanical Description
Polygonum aviculare, common knotgrass or Bian Xu, is an annual herbaceous species in the Polygonaceae family with a near-cosmopolitan distribution on disturbed ground, paths, and field margins. Plants form prostrate to ascending mats 10-50 cm across, with slender, wiry, often reddish jointed stems bearing a characteristic silvery membranous ocrea at each node. Leaves are alternate, elliptic to lanceolate, 1-3 cm long, with entire margins. Tiny inconspicuous flowers 2-3 mm across, with greenish-white to pink-edged tepals, are borne singly or in small clusters in leaf axils from late spring to autumn, producing small triangular achenes.
Active Constituents
Avicularin (quercetin-3-O-arabinoside)
Flavonol glycosideConcentration: Approximately 0.2% of the dried herb
The characteristic flavonoid of knotgrass and the constituent that best matches its urinary use: after intravenous dosing in rats, tissue distribution measured by HPLC showed the highest concentrations of avicularin in kidney and bladder of the six tissues examined. That study used the intravenous route, so it establishes tissue tropism rather than oral bioavailability.
Total flavonoids
Flavonoid fractionConcentration: 0.1-1% of the dried herb, rarely 2.5-3%
Derivatives of quercetin, kaempferol and myricetin including juglanin, hyperoside, quercitrin, myricitrin, rutin, isoquercitrin, vitexin, isovitexin and desmanthin-1. This fraction is where the anti-inflammatory and antioxidant activity of the herb is generally located, and the tenfold to thirtyfold range in total content is a real quality problem for a drug dispensed by weight.
Tannins
Tannin (gallotannin and catechol tannin)Concentration: 3.5-4% of the dried herb, including rhatannin
The tannin content is the largest single constituent class by mass and accounts for the herb's astringency and its traditional oromucosal use. The EU herbal monograph for this drug covers mouth and throat rinsing as well as urinary flushing, and the tannins are the plausible basis of the former.
Water-soluble silicates (silicic acid)
Mineral acidConcentration: About 1% of the dried herb, together with tartaric and formic acids
Soluble silicic acid is the constituent most often invoked for knotgrass in European practice and is one of the reasons the herb is prepared as an infusion rather than a tincture. Its contribution to any clinical effect is unestablished.
Rhamnogalacturonan I pectin
PolysaccharideConcentration: PAPN1, an RG-I pectin with an alternating galacturonic acid and rhamnose backbone carrying arabinan and galactan side chains
The one constituent with a mechanistic account of the stranguria indication. Given orally at 10, 20 and 40 mg/kg/day in a rodent nephrolithiasis model it dose-dependently reduced renal calcium oxalate crystal deposition, apparently by reshaping the gut microbiota to raise taurine, which suppressed renal TNF-alpha and reduced crystal retention. Animal work only.
Phenolic acids
Phenolic carboxylic acidConcentration: Caffeic, chlorogenic, gallic and protocatechuic acids reported in the herb
A minor but consistently reported constituent class contributing to the antioxidant profile of the herb. No individual phenolic acid has been linked to a clinical effect of Bian Xu.
⚠ Drug Interactions
Loop and thiazide diuretics (furosemide, hydrochlorothiazide)
The accepted European traditional-use indication for this herb is to increase urine volume in order to flush the urinary tract, so additive fluid loss with a prescribed diuretic is the obvious concern. It is inference only: the HMPC assessment records no data on drug interactions for Polygoni avicularis herba, and no clinical pharmacokinetic or pharmacodynamic study of the herb exists.
Clinical note: In a patient already on a diuretic, insist on adequate fluid intake and be alert to postural symptoms or a rising creatinine. Do not use the aquaretic action as a reason to reduce a prescribed diuretic.
Lithium
Lithium clearance tracks sodium and water handling, so any agent taken specifically to increase urine output raises a theoretical risk of altered serum lithium. There is no study of this herb with lithium, and no pharmacokinetic data on the herb at all; this is the standard caution applied to aquaretic herbs rather than a documented event.
Clinical note: Avoid combining, or if the patient insists, check serum lithium after one to two weeks and again after stopping the herb.
Dosage
| Form | Amount | Frequency | Duration | Population | Notes |
|---|---|---|---|---|---|
| decoction | 9–15 g | Daily | — | — | 中国药典 2020 【用法与用量】9～15g。外用适量，煎洗患处。 【性味与归经】苦，微寒。归膀胱经。 — Chinese Pharmacopoeia 2020, quoted verbatim; route and cautions preserved. Replaces a cleared category-filler value. |
Dui Yao — Herb Pairs
The classical two-herb combinations this herb appears in, each with an action neither herb has alone.
Clear damp-heat from the bladder and unblock painful urinary dribbling.
Heat and stone painful urinary dysfunction.
Core pair of a classical formula — Ba Zheng San, Taiping Huimin Hejiju Fang
Evidence Tier
Limited evidence · 2 studiesRecorded studies by study design, strongest design at the top. This is a study-design tier only, not a GRADE rating: it does not weigh risk of bias, consistency or precision.
Systematic review / meta-analysis
0
Randomized controlled trial
0
Other clinical trial
0
Observational / case report
0
In vitro / animal
2
1 verified · 1 unverified
Show 2 studies
- Multi-omics analyses reveal a rhamnogalacturonan I (RG-I) from Polygonum aviculare ameliorates nephrolithiasis through regulation of the gut-kidney axis
- Hydroethanolic Extract of Polygonum aviculare L. Mediates the Anti-Inflammatory Activity in RAW 264.7 Murine Macrophages Through Induction of Heme Oxygenase-1 and Inhibition of Inducible Nitric Oxide Synthase
Other / unclassified
0
Verified: design read from PubMed for a DOI that resolves to the cited paper Unverified: taken from the study's recorded description
Clinical Studies
Multi-omics analyses reveal a rhamnogalacturonan I (RG-I) from Polygonum aviculare ameliorates nephrolithiasis through regulation of the gut-kidney axis
Isolation and structural elucidation of PAPN1, an RG-I pectin from the herb, followed by oral dosing at 10, 20 and 40 mg/kg/day in a rodent nephrolithiasis model. Renal calcium oxalate crystal deposition fell dose-dependently and renal function improved. 16S rRNA sequencing and serum metabolomics showed reshaped gut microbiota with markedly increased taurine, and renal RNA sequencing showed suppressed TNF-alpha, giving a gut-kidney account of the traditional stranguria indication. Animal and multi-omics work with no human counterpart.
Hydroethanolic Extract of Polygonum aviculare L. Mediates the Anti-Inflammatory Activity in RAW 264.7 Murine Macrophages Through Induction of Heme Oxygenase-1 and Inhibition of Inducible Nitric Oxide Synthase
A hydroethanolic extract raised antioxidant response element activity and Nrf2-regulated heme oxygenase-1 in RAW264.7 macrophages, and reduced COX-2 and iNOS protein by inactivating NF-kappaB in LPS-stimulated cells. Blocking HO-1 with tin protoporphyrin restored iNOS expression and nitric oxide output, indicating HO-1 induction mediates the anti-inflammatory effect. A mechanistic cell study, not evidence of clinical anti-inflammatory activity.
⚠ Safety & Contraindications
Contraindications
Its use is cautious in patients with spleen deficiency.
Source: Xi S, Gong Y. Essentials of Chinese Materia Medica and Medical Formulas. Academic Press/Elsevier, 2017, pp. 146–150.
Historical Texts
Shen Nong Ben Cao Jing (Divine Husbandman's Classic of the Materia Medica)
Han dynasty, compiled c. 200 CEEuropean Union herbal monograph and HMPC assessment report on Polygonum aviculare L., herba
Adopted 5 April 2016, EMA/HMPC/143659/2015References
- Committee on Herbal Medicinal Products (HMPC), European Medicines Agency. Assessment report on Polygonum aviculare L., herba . European Medicines Agency, EMA/HMPC/143659/2015 (2016)
- Benrahou K, Driouech M, El Guourrami O, Mrabti HN, Cherrah Y, Faouzi MEA. Medicinal uses, phytochemistry, pharmacology, and taxonomy of Poygonum aviculare L.: a comprehensive review . Medicinal Chemistry Research (2023) [DOI]
- Chinese Pharmacopoeia Commission. Pharmacopoeia of the People's Republic of China, 2020 Edition, Volume I . China Medical Science Press, Beijing (2020)
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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