Mu Zei
StarEquisetum hiemale L.
Traditionally used for
- Eye health
- Urinary & fluids
☯ TCM Properties
Disperses Wind-Heat; Brightens the Eyes and Removes Visual Obstructions; Stops Bleeding
Traditional Chinese Uses
Mu Zei (scouring rush, horsetail herb) is a bitter, neutral herb used in Chinese medicine primarily for eye conditions — particularly those caused by Wind-Heat or Liver Heat affecting the eyes, including red, inflamed, excessively tearing eyes and visual cloudiness. Its mild hemostatic properties also address bleeding conditions, and its secondary action of clearing Wind-Heat from the exterior makes it appropriate for early-stage Wind-Heat exterior patterns. As an herb with both ophthalmic and hemostatic applications, it represents a distinct role in the Chinese materia medica.
Western Herbalism Properties
Relationships
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Botanical Description
Equisetum hyemale (Equisetaceae), the rough horsetail or scouring rush, is an evergreen, rhizomatous, perennial pteridophyte forming dense colonies of unbranched, hollow, jointed, dark-green stems 50-150 cm tall and 4-10 mm thick. The stems are deeply ridged (16-40 ridges) and impregnated with silica, giving them a sandpaper texture historically used for polishing wood and pewter. Tiny scale leaves are fused into blackish toothed sheaths at each node. Reproductive cones (strobili) 1-2 cm long, with a sharp apical point, develop atop fertile stems in summer and release spores. The species is circumboreal, growing in damp sandy soils along streams, ditches, and forest edges. The dried aerial stems are Mu Zei. (Sources: POWO; Wikipedia; PFAF)
Active Constituents
Amorphous hydrated silica
Inorganic biomineral (silicic acid polymer)Concentration: the knob tips of the stem surface reach up to about 33 wt% silicon as pure hydrated amorphous silica; Equisetaceae as a family accumulate silica up to roughly 25% of dry weight
The silica is deposited in and on the epidermal cell walls and is what makes the stem abrasive enough to have been used as a scouring rush and a wood polish. It is a structural mineral in close association with cell wall polymers, not a soluble drug constituent, and there is no evidence that decoction liberates it in a bioavailable form, so claims that Mu Zei supplies usable silicon are not supported by the chemistry.
Kaempferol and its glycosides
Flavonol and flavonol glycosidesConcentration: kaempferol, kaempferol-3-O-glucoside and other kaempferol glycosides identified in Equisetum hyemale extracts
Kaempferol is the flavonol the genus is most noted for and is an antiproliferative and antioxidant agent. Kaempferol glycosides are among the compounds that carry into aqueous and hydroalcoholic preparations.
Quercetin-3-O-rutinoside (rutin)
Flavonol glycosideConcentration: identified in the ethyl acetate extract alongside quercetin-3-O-glucoside and free quercetin
A widely distributed flavonol glycoside contributing to the antioxidant capacity of the extract; not specific to this species.
Luteolin-7-O-glucoside
Flavone glycosideConcentration: identified in the ethyl acetate extract with apigenin-5-O-glucoside
Part of the flavone fraction of the aerial part, with the usual antioxidant and anti-inflammatory activity of this class in cell models.
Caffeoylquinic acids
Hydroxycinnamic acid estersConcentration: identified with gallic acid and caffeic acid; total phenolic content of the ethyl acetate extract measured at 58.39 mg GAE/g and total flavonoids at 18.71 mg quercetin equivalents/g
The main water-soluble antioxidant fraction of the herb, responsible for the ABTS radical scavenging measured at IC50 2.57-2.68 micrograms/mL.
Campesterol
PhytosterolConcentration: a principal sterol of the hexane extract, reported with beta-sitosterol and ergost-5-en-3beta-ol
A lipophilic constituent of the non-polar fraction. It is not extracted to any degree by decoction in water.
Thiaminase
Enzyme (thiamine-degrading)Concentration: demonstrated in fresh and dried Equisetum material; not quantified for Equisetum hiemale specifically in any source located
Thiaminase destroys thiamine (vitamin B1) in the gut before it can be absorbed. It is the established cause of equisetosis, the thiamine-deficiency syndrome seen in horses grazing horsetail, and both thiaminase types have been detected in Equisetum ramosissimum. The species-specific point matters here: the quantitative thiaminase and safety work in the literature is on Equisetum arvense and other congeners, and no published assay of Equisetum hiemale material was found, so the size of the risk for this particular drug is genuinely unquantified rather than known to be low.
Nicotine
Pyridine alkaloidConcentration: trace; reported for the genus Equisetum alongside palustrine, 3-methoxypyridine and equisetine, and not quantified for Equisetum hiemale specifically
Present in trace amounts only. It is listed here because genus-level toxicology repeatedly names it, not because any clinically relevant nicotine exposure from the drug has been demonstrated. Palustrine, the alkaloid most often cited in Equisetum toxicity, is characteristic of Equisetum palustre rather than of this species.
⚠ Drug Interactions
Thiamine (vitamin B1) status, and patients with alcohol use disorder, malnutrition or hyperemesis
Thiaminase in Equisetum degrades dietary thiamine in the gut. In horses this produces equisetosis, with ataxia, incoordination, loss of condition, weakness, muscle tremor and, untreated, convulsions and coma, reversible with parenteral thiamine. Human data are absent, but European assessments of horsetail flag thiamine depletion with long-term use on this basis. Patients who are already thiamine-marginal from alcohol, poor intake or persistent vomiting have the least reserve. Note that the thiaminase evidence is drawn from the genus and from Equisetum arvense and Equisetum ramosissimum; it has not been measured in Equisetum hiemale, which is the drug in this monograph.
Clinical note: Do not prescribe Mu Zei continuously for months. Keep courses short, and if extended use is unavoidable in a patient with any thiamine risk factor, supplement thiamine and review for neurological signs.
Equisetum arvense (Wen Jing) or Equisetum ramosissimum (Jie Jie Cao) supplied as Mu Zei
Three Equisetum species circulate as separate Chinese drugs: Mu Zei is Equisetum hiemale, Wen Jing is Equisetum arvense, and Jie Jie Cao is Equisetum ramosissimum, which is generally not used as Mu Zei. They are separable on inspection, since Jie Jie Cao has thin stems often branched below the middle, a loose leaf sheath, no black rings at the sheath base, and is soft and fibrous rather than rigid. The substitution matters beyond nomenclature because virtually all the published pharmacology, the diuretic clinical trial and the regulatory safety assessments concern Equisetum arvense, so a batch that is actually E. arvense has a different evidence base from the one prescribed.
Clinical note: Check that the material is rigid, unbranched or sparsely branched, and shows the dark rings at the sheath base. Treat any published claim about horsetail as belonging to E. arvense unless the paper names E. hiemale.
Diuretics (thiazides, loop diuretics) and lithium
The diuretic effect in this genus is real and has been quantified in humans, though for a different species: in a randomised double-blind crossover in 36 healthy men, 900 mg/day of standardised Equisetum arvense extract for four days produced a diuretic effect stronger than placebo and equivalent to hydrochlorothiazide 25 mg/day, without significantly increasing electrolyte elimination. Whether Equisetum hiemale shares this has not been tested. Any herb with meaningful diuretic activity has a theoretical effect on lithium clearance because lithium handling follows sodium and water.
Clinical note: Monitor fluid balance if Mu Zei is combined with a prescribed diuretic, and check lithium levels if a lithium-treated patient starts an Equisetum preparation long-term.
Chromium, nickel and other heavy metals in Equisetum harvested from contaminated ground
Equisetum species are efficient mineral accumulators, which is the same physiology that produces their silica content, and uptake of copper, chromium, nickel and iron by Equisetum arvense and Equisetum hyemale grown in mine tailings has been studied for that reason. This is a sourcing hazard rather than a pharmacological interaction, and it applies to wild-collected material from industrial or mining ground.
Clinical note: Buy Mu Zei from suppliers who test for heavy metals. Do not accept wild-collected material of unknown provenance.
Dosage
| Form | Amount | Frequency | Duration | Population | Notes |
|---|---|---|---|---|---|
| decoction | 3–9 g | Daily | — | — | 中国药典 2020 【用法与用量】3～9g。 【性味与归经】甘、苦，平。归肺、肝经。 — Chinese Pharmacopoeia 2020, quoted verbatim; route and cautions preserved. Replaces a cleared category-filler value. |
Evidence Tier
Moderate evidence · 3 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
3
0 verified · 3 unverified
Show 3 studies
- Equisetum hyemale L. Extracts: Phytochemistry, Biological Performance, ADMET Profiling, and Toxicity Predictions
- Horsetail (Equisetum hyemale) Extract Accelerates Wound Healing in Diabetic Rats by Modulating IL-10 and MCP-1 Release and Collagen Synthesis
- New substances of Equisetum hyemale L. extracts and their in vivo antitumoral effect against oral squamous cell carcinoma
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
Equisetum hyemale L. Extracts: Phytochemistry, Biological Performance, ADMET Profiling, and Toxicity Predictions
Hexane, chloroform and ethyl acetate extracts of Equisetum hyemale were profiled and tested. The ethyl acetate extract carried the flavonoids and phenolic acids, with 58.39 mg GAE/g total phenolics and 18.71 mg quercetin equivalents/g flavonoids. Antioxidant activity was strong against ABTS (IC50 2.57-2.68 micrograms/mL) and weak against DPPH (IC50 303-1111 micrograms/mL). The extracts were ineffective against the bacteria tested. They were non-toxic to Artemia salina at 5-100 micrograms/mL but reduced Caenorhabditis elegans survival dose- and time-dependently.
Horsetail (Equisetum hyemale) Extract Accelerates Wound Healing in Diabetic Rats by Modulating IL-10 and MCP-1 Release and Collagen Synthesis
Equisetum hyemale extract accelerated wound closure in diabetic rats, with increased IL-10 and modulated MCP-1 release and enhanced fibroblast collagen synthesis. This is one of the few in vivo studies performed on this species rather than on Equisetum arvense.
New substances of Equisetum hyemale L. extracts and their in vivo antitumoral effect against oral squamous cell carcinoma
Phytochemical analysis of Equisetum hyemale identified kaempferol glycosides, cinnamic acid derivatives and six previously undescribed non-glycosylated flavonoids, and extracts reduced tumour growth in an in vivo model of oral squamous cell carcinoma. It is preclinical work and carries no implication for clinical use of the decocted herb.
⚠ Safety & Contraindications
Contraindications
It is used cautiously in patients with qi and blood deficiency.
Source: Xi S, Gong Y. Essentials of Chinese Materia Medica and Medical Formulas. Academic Press/Elsevier, 2017, pp. 26–31.
Historical Texts
Jia You Ben Cao
Song dynasty (1057-1060)References
- Sapei L, Gierlinger N, Hartmann J, Nöske R, Strauch P, Paris O. Structural and analytical studies of silica accumulations in Equisetum hyemale . Analytical and Bioanalytical Chemistry (2007) [DOI]
- Gierlinger N, Sapei L, Paris O. Insights into the chemical composition of Equisetum hyemale by high resolution Raman imaging . Planta (2007) [DOI]
- Boeing T, Tafarelo Moreno KG, Gasparotto Junior A, Mota da Silva L, de Souza P. Phytochemistry and Pharmacology of the Genus Equisetum (Equisetaceae): A Narrative Review of the Species with Therapeutic Potential for Kidney Diseases . Evidence-Based Complementary and Alternative Medicine (2021) [DOI]
- Carneiro DM, Freire RC, Honório TCD, Zoghaib I, Cardoso FFSS, Tresvenzol LMF, de Paula JR, Sousa ALL, Jardim PCBV, Cunha LC. Randomized, Double-Blind Clinical Trial to Assess the Acute Diuretic Effect of Equisetum arvense (Field Horsetail) in Healthy Volunteers . Evidence-Based Complementary and Alternative Medicine (2014) [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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