Guan Zhong
StarDryopteris crassirhizoma Nakai
Traditionally used for
- Nose & throat
- Colds & fever
- Bowel health
- Menstrual & women's health
Cautions & contraindications
- Pregnancy
- Young children
- Liver conditions
- Seizure disorders
- Toxic — professional use only
☯ TCM Properties
Expels Parasites; Clears Heat and Resolves Toxicity; Cools the Blood and Stops Bleeding
Traditional Chinese Uses
Guan Zhong (dryopteris rhizome, shield fern rhizome) is a bitter, cool herb used in Chinese medicine to clear Heat toxin, stop bleeding, and expel intestinal parasites. It is applied for internal Heat with bleeding conditions such as uterine bleeding, nosebleeds, and bloody dysentery from Blood Heat. Its antiparasitic action addresses tapeworms and roundworms, and it is also used for febrile illnesses where the Heat has entered the blood level. It is toxic in excess and requires professional guidance for internal use.
Relationships
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Botanical Description
Dryopteris crassirhizoma is a robust terrestrial fern in the Dryopteridaceae, native to cool temperate forests of northeastern China, Korea, the Russian Far East, and Japan. It forms a stout, ascending to nearly erect rhizome densely covered in persistent, broad, brown, lustrous scales and the swollen scaly bases of old stipes. The crown bears a vase-like cluster of fronds 60-120 cm long; the lance-shaped, bipinnate to bipinnate-pinnatifid blades taper at both ends, with the lower pinnae shortened. Pinnules are oblong with serrate margins. Round sori with kidney-shaped indusia are arranged in two rows on the underside of fertile pinnules. The dried rhizome together with the persistent stipe bases is the medicinal Guan Zhong.
Active Constituents
Dryocrassin ABBA
Tetrameric acylphloroglucinolConcentration: the index (marker) constituent used to authenticate Dryopteris crassirhizoma; it is absent from Osmunda japonica, the other fern sold as Guan Zhong
The characteristic tetrameric phloroglucinol of this species, credited with its anthelmintic action. It inhibits influenza H5N1 neuraminidase in vitro with an IC50 of about 18.6 microM at low cytotoxicity, and it is one of two phloroglucinols reported to inhibit the SARS-CoV-2 main protease.
Filixic acid ABA
Trimeric acylphloroglucinolConcentration: one of the principal phloroglucinols of the dried rhizome
A trimeric member of the filicin group, the fraction responsible for both the anthelmintic effect and the systemic toxicity of Dryopteris rhizomes. It inhibits influenza H5N1 neuraminidase in vitro with an IC50 of about 29.6 microM and, with dryocrassin ABBA, binds the SARS-CoV-2 main protease.
Flavaspidic acid AP
Dimeric acylphloroglucinolThe most potent xanthine oxidase inhibitor isolated from the rhizome, with an IC50 of 6.3 microM, close to that of allopurinol (5.7 microM) in the same assay. This is the basis of interest in the herb for hyperuricaemia.
Flavaspidic acid AB
Dimeric acylphloroglucinolIsolated together with flavaspidic acid PB as the antibacterial principle of the rhizome in a bioassay-guided study. Flavaspidic acids are also reported to be antiviral and antioxidant.
Albaspidin AA
Dimeric acylphloroglucinolOne of the albaspidin series (AA, AP, PP) found alongside the filixic and flavaspidic acids. It belongs to the same lipophilic phloroglucinol pool that carries both the anthelmintic activity and the toxicity of the drug.
Butyryl-3-methylphloroglucinol
Monomeric acylphloroglucinolConcentration: the most abundant acylphloroglucinol quantified by HPLC in the dichloromethane fraction studied by Yim and colleagues
Strongly inhibits platelet aggregation in vitro, by 92% against collagen and 90% against arachidonic acid, without cytotoxicity. This is the pharmacological basis for treating the herb as an antiplatelet agent when combining it with anticoagulants.
Kaempferitrin
Flavonol glycoside (kaempferol dirhamnoside)A non-phloroglucinol anthelmintic principle: it killed the monogenean Dactylogyrus intermedius in goldfish with an EC50 of 2.71 mg/L and caused visible shrinkage and folding of the parasite tegument on electron microscopy.
Sutchuenoside A
Flavonol glycosideIsolated with kaempferitrin from the ethyl acetate fraction and comparably anthelmintic in the goldfish model (EC50 3.01 mg/L), with a 48-hour lethal concentration to the fish roughly twelve-fold above the effective dose.
⚠ Drug Interactions
Dietary fat, and oil-based purgatives such as castor oil
The filicin phloroglucinols are highly lipophilic and are absorbed only slightly from the gut, which is precisely what makes anthelmintic dosing survivable. Fat in the meal, and above all an oily purgative such as castor oil, dissolves them and drives systemic absorption. This is documented in the classical Western pharmacology of the closely related male fern, Dryopteris filix-mas, whose oleoresin caused serious and occasionally fatal poisoning by exactly this route, with optic neuropathy also reported in cattle that grazed the fern. Chinese sources give the same rule for D. crassirhizoma as an instruction to avoid greasy food while taking the herb, and Chinese pharmacology attributes the blindness to retinal vasospasm and direct injury to the optic nerve, with tremor, convulsion and medullary depression at high dose. In 2015 Health Canada suspended the licences of homeopathic male fern products, citing liver damage, blindness and death.
Clinical note: Never dispense Guan Zhong with an oily meal, a fat-soluble vitamin preparation, alcohol, or an oil-based purgative. Modern anthelmintics (praziquantel, niclosamide, albendazole) have superseded this drug for tapeworm and should be preferred; the Chinese Pharmacopoeia treats the herb as slightly toxic and cautions against use in pregnancy and in spleen-stomach deficiency cold. Stop immediately and refer for any visual disturbance, tremor or persistent vomiting.
Warfarin, direct oral anticoagulants, aspirin and other antiplatelet drugs
Acylphloroglucinols isolated from D. crassirhizoma inhibit collagen- and arachidonic acid-induced platelet aggregation in vitro, the most abundant of them, butyryl-3-methylphloroglucinol, by around 90%; the proposed mechanism is suppression of cyclooxygenase and reactive oxygen species through MAPK signalling. Antiplatelet activity is also listed among the established pharmacological actions of the herb in the 2024 review of its pharmacology. No human interaction study exists, so the risk is inferred from in vitro data.
Clinical note: Treat as an antiplatelet herb when combining. Note the paradox that the drug is simultaneously used to stop bleeding as charred Guan Zhong Tan; the antiplatelet data are from the raw drug. Stop before elective surgery and monitor patients on warfarin.
Other ferns substituted as Guan Zhong (Cyrtomium fortunei, Woodwardia japonica, Matteuccia struthiopteris, Osmunda japonica)
Guan Zhong is one of the worst substitution problems in the Chinese materia medica: rhizomes of many fern genera in several families are traded regionally under this one pinyin name. Chinese standards carry Mian Ma Guan Zhong (this species) and Zi Qi Guan Zhong (Osmunda japonica) as separate drugs with different chemistry, dryocrassin being the marker of D. crassirhizoma and osmundacetone that of O. japonica. Zhao and colleagues had to develop an rbcL chloroplast DNA test to separate D. crassirhizoma from its adulterants, and a plastid genome study confirmed the two official ferns differ in composition despite sharing the name. The practical consequence runs both ways: a prescription for the toxic Dryopteris drug may be filled with a milder fern, and a prescription written for a milder Guan Zhong may be filled with the toxic Dryopteris one.
Clinical note: Order by binomial, not by pinyin, and insist on material identified as Dryopteris crassirhizoma (Mian Ma Guan Zhong) with a TLC or DNA certificate. Do not assume the toxicity profile described here applies to a fern sold as Guan Zhong without identification.
Azathioprine, mercaptopurine and other xanthine oxidase substrates
Phloroglucinols from this rhizome are potent xanthine oxidase inhibitors in vitro, with flavaspidic acid AP reaching an IC50 of 6.3 microM against allopurinol's 5.7 microM in the same assay. Allopurinol's clinically dangerous interaction with azathioprine and mercaptopurine rests on exactly this enzyme. Whether oral dosing of the crude herb reaches inhibitory concentrations at hepatic xanthine oxidase has not been shown, so this is an inference from enzyme data only.
Clinical note: Avoid combining with azathioprine or mercaptopurine until human data exist. The same enzyme data are why the herb is being examined for hyperuricaemia.
Dosage
| Form | Amount | Frequency | Duration | Population | Notes |
|---|---|---|---|---|---|
| decoction | 4.5–9 g | Daily | — | — | 中国药典 2020 monograph 【绵马贯众】【用法与用量】4.5～9g。 【性味与归经】苦，微寒；有小毒。归肝、胃经。 — Matched by hand: Dryopteris crassirhizoma is exactly ChP 绵马贯众 (other 贯众 sources are separate monographs). Chinese Pharmacopoeia 2020, quoted verbatim. |
Evidence Tier
Moderate evidence · 8 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
8
2 verified · 6 unverified
Show 8 studies
- Phloroglucinol Derivatives from Dryopteris crassirhizoma as Potent Xanthine Oxidase Inhibitors
- Anti-Influenza Virus (H5N1) Activity Screening on the Phloroglucinols from Rhizomes of Dryopteris crassirhizoma
- Anticoronaviral Activity of the Natural Phloroglucinols, Dryocrassin ABBA and Filixic Acid ABA from the Rhizome of Dryopteris crassirhizoma by Targeting the Main Protease of SARS-CoV-2
- Antiplatelet Activity of Acylphloroglucinol Derivatives Isolated from Dryopteris crassirhizoma
- In vivo anthelmintic effect of flavonol rhamnosides from Dryopteris crassirhizoma against Dactylogyrus intermedius in goldfish (Carassius auratus)
- Antibacterial activity of two phloroglucinols, flavaspidic acids AB and PB, from Dryopteris crassirhizoma
- Identification of Dryopteris crassirhizoma and the Adulterant Species Based on cpDNA rbcL and Translated Amino Acid Sequences
- Plastid genome and composition analysis of two medical ferns: Dryopteris crassirhizoma Nakai and Osmunda japonica Thunb.
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
Phloroglucinol Derivatives from Dryopteris crassirhizoma as Potent Xanthine Oxidase Inhibitors
Bioassay-guided fractionation of the rhizome yielded four flavaspidic acids. Flavaspidic acid AP was the most potent xanthine oxidase inhibitor, with an IC50 of 6.3 microM, comparable to allopurinol at 5.7 microM in the same assay.
Anti-Influenza Virus (H5N1) Activity Screening on the Phloroglucinols from Rhizomes of Dryopteris crassirhizoma
Thirteen phloroglucinols were isolated from the rhizome and screened against influenza H5N1 neuraminidase. Dryocrassin ABBA and filixic acid ABA inhibited the enzyme with IC50 values of 18.59 and 29.57 microM respectively, dryocrassin ABBA showing low cytotoxicity (TC50 above 400 microM).
Anticoronaviral Activity of the Natural Phloroglucinols, Dryocrassin ABBA and Filixic Acid ABA from the Rhizome of Dryopteris crassirhizoma by Targeting the Main Protease of SARS-CoV-2
Two phloroglucinols from the rhizome inhibited SARS-CoV-2 replication in cell culture, with molecular and enzymatic evidence that they act on the viral main protease. The work is cell-based only and says nothing about oral dosing of the crude herb.
Antiplatelet Activity of Acylphloroglucinol Derivatives Isolated from Dryopteris crassirhizoma
The dichloromethane fraction of a water extract inhibited collagen-stimulated platelet aggregation concentration-dependently; five acylphloroglucinols and one flavonoid were isolated. Butyryl-3-methylphloroglucinol, the most abundant by HPLC, inhibited collagen- and arachidonic acid-induced aggregation by 92.4% and 89.5% without cytotoxicity.
In vivo anthelmintic effect of flavonol rhamnosides from Dryopteris crassirhizoma against Dactylogyrus intermedius in goldfish (Carassius auratus)
Protocatechuic acid, sutchuenoside A and kaempferitrin were purified from the ethyl acetate extract. Sutchuenoside A and kaempferitrin were anthelmintic against the fish monogenean with EC50 values of 3.01 and 2.71 mg/L, with tegument damage on electron microscopy and a 48-hour lethal concentration to the host fish about twelve-fold higher than the effective dose.
Antibacterial activity of two phloroglucinols, flavaspidic acids AB and PB, from Dryopteris crassirhizoma
Bioassay-guided isolation identified flavaspidic acids AB and PB as the antibacterial constituents of the rhizome.
Identification of Dryopteris crassirhizoma and the Adulterant Species Based on cpDNA rbcL and Translated Amino Acid Sequences
A chloroplast rbcL sequence method was developed to separate authentic D. crassirhizoma from the numerous fern species traded as Guan Zhong, because morphology alone does not reliably distinguish the processed rhizomes.
Plastid genome and composition analysis of two medical ferns: Dryopteris crassirhizoma Nakai and Osmunda japonica Thunb.
The two ferns sold in China under the name Guan Zhong were compared by plastid genome and chemical composition. Although both are used under the same name, their composition differs, dryocrassin being the index compound of D. crassirhizoma and osmundacetone that of O. japonica, so the authors argue identification is necessary before use.
⚠ Safety & Contraindications
- Pregnancy
- Young children
- Liver conditions
- Seizure disorders
- Toxic — professional use only
Contraindications
Contraindicated in pregnancy, in children, and in hepatic impairment.
Safety Warnings
- The optic toxicity is the reason the dose must not be exceeded — visual loss from filicin overdose can be irreversible.
- Not to be taken with fats or oils, which increase absorption of the toxic constituents.
- The name Guan Zhong covers several fern species with differing toxicity — confirm the botanical source.
⚠ Toxicity Information
Nausea, vomiting, headache and abdominal pain; in overdose, optic-nerve damage with visual impairment, which may be permanent, and hepatic injury.
Historical Texts
Shen Nong Ben Cao Jing
Han dynastyBen Cao Gang Mu
Ming dynasty (1596)Zhong Guo Yao Dian (Pharmacopoeia of the People's Republic of China)
Modern (2020 edition)References
- Qian-Xiang Bai, Zhao-Jiong Zhang, Hai-Peng Tang, Bing-You Yang, Hai-Xue Kuang, Meng Wang. Dryopteris crassirhizoma Nakai.: A review of its botany, traditional use, phytochemistry, pharmacological activity, toxicology and pharmacokinetics . Journal of Ethnopharmacology (2024) [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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