Feng Wei Jiao Ye
StarCycas revoluta Thunb.
Synonyms: Cycas miquelii Warb.
Also known as: Fêng Wei Chiao Yeh · Wade–Giles
Safety at a glance
No rule in our tables for this herb: pregnancy, breastfeeding, incompatible pairs (十八反 / 十九畏), herb–drug, dose ceiling. This is not a safety clearance.
Not graded — No toxicity grade is recorded. Most herbs in the catalogue carry none.
Traditionally used for
- Cough & breathing
- Digestion
- Skin
Cautions & contraindications
- Pregnancy
- Young children
- Liver conditions
- Toxic — professional use only
☯ TCM Properties
Regulates Qi, invigorates the Blood, breaks up Blood Stasis, dispels Wind and eliminates toxins
Traditional Chinese Uses
Feng Wei Jiao Ye (also Tie Shu Ye, "iron-tree leaf") is the leaf of Cycas revoluta, the sago cycad (Folium Cycadis Revolutae). Warm in nature and entering the liver and stomach channels, it regulates qi and invigorates the blood, breaks up blood stasis and stops pain, disperses swelling, and resolves toxicity; in folk use it is also taken to stop bleeding (such as vomiting of blood) and to relieve cough. It is applied to blood-stasis pain, epigastric and abdominal discomfort, swellings and sores.
Safety: cycads contain cycasin, which gut bacteria convert to a carcinogenic, hepatotoxic and neurotoxic compound; the seeds are especially poisonous. This substance should be used only cautiously under qualified supervision.
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Botanical Description
Feng Wei Jiao Ye is the leaf (frond) of Cycas revoluta (Cycadaceae), the sago cycad, an evergreen gymnosperm of coastal southern Japan and south-east China. A stout, columnar, unbranched trunk is crowned by a spreading rosette of stiff, glossy dark-green pinnate leaves 0.5-2 m long; the numerous narrow, leathery leaflets have strongly revolute margins and sharp-pointed tips, giving the phoenix-tail appearance. The plant is dioecious, bearing a dense terminal cone (male) or a mass of woolly megasporophylls (female). The dried fronds are used in TCM to regulate qi, invigorate the blood, resolve stasis and stop pain, and reduce swelling and detoxify. Seeds and stem pith are toxic.
Coastal thickets and rocky slopes; very widely cultivated as an ornamental.
Active Constituents
Cycasin
Azoxyglycoside (methylazoxymethanol beta-D-glucoside)Concentration: highest in the seed, where reported levels reach roughly 0.2-0.3%; lower but present in leaves and roots, and no reliable figure for the leaf drug has been published
Cycasin itself is not the toxin: it is hydrolysed by bacterial beta-glucosidase in the gut to methylazoxymethanol (MAM), a spontaneously decomposing alkylating agent that methylates DNA guanine. MAM is hepatotoxic, neurotoxic, teratogenic and carcinogenic in rodents, and cycasin was shown to produce radiomimetic chromosome damage as early as 1965.
Methylazoxymethanol (MAM)
Azoxy aglycone / DNA-alkylating agentConcentration: not present as such in the plant; generated in vivo from cycasin by gut microbial beta-glucosidase
MAM produces the centrilobular hepatic necrosis and haemorrhage seen in cycad-poisoned dogs, and is a recognised experimental colon and liver carcinogen. Because activation depends on gut flora, germ-free animals are markedly less susceptible to orally administered cycasin than conventional ones.
beta-N-methylamino-L-alanine (BMAA)
Non-protein amino acid (neurotoxic)Concentration: 6.96 micrograms per gram of free BMAA measured in Cycas revoluta seeds by LC-MS/MS (Kruger et al., 2010); leaf content not established
BMAA is a glutamatergic excitotoxin that can be misincorporated into protein in place of L-serine, and it is the compound at the centre of the hypothesis linking cycad consumption to the amyotrophic lateral sclerosis-parkinsonism-dementia complex (ALS-PDC) of Guam. That epidemiology concerns Cycas micronesica seed and flying-fox consumption rather than Cycas revoluta leaf, and the causal link remains contested, but the genus association is real and is the reason this drug should not be taken chronically.
Sotetsuflavone
Biflavonoid (amentoflavone-type)Concentration: a leaf biflavonoid; no validated quantitative figure for the crude drug
Named after sotetsu, the Japanese name of this species, and isolated from its leaves. In cultured A549 non-small-cell lung cancer cells it raises intracellular reactive oxygen species, collapses mitochondrial membrane potential, arrests cells in G0/G1, reverses epithelial-mesenchymal transition and induces autophagy. All of this is cell-culture and xenograft work with no human data.
Amentoflavone
BiflavonoidConcentration: reported by HPLC as the most abundant biflavonoid of the leaves, ahead of hinokiflavone, sciadopitysin and podocarpusflavone A; absolute figures vary by source and season
A widely distributed biflavonoid with antioxidant and anti-inflammatory activity in vitro. Amentoflavone is a known in vitro inhibitor of several cytochrome P450 isoforms, which is the plausible basis for pharmacokinetic caution with this drug, though no clinical interaction study exists for Cycas revoluta leaf.
⚠ Drug Interactions
Hepatotoxic drugs (paracetamol/acetaminophen, methotrexate, isoniazid, azole antifungals)
Cycasin is hydrolysed in the gut to methylazoxymethanol, which alkylates hepatocyte macromolecules. In a retrospective series of 60 dogs poisoned by this species, 95% developed hepatic and gastrointestinal injury and 53.3% had neurological signs, and a later canine series identified marked ALT elevation and coagulopathy as predictors of death. There is no reason to assume a human liver handles the compound differently.
Clinical note: Do not combine this herb with any hepatotoxic medication, and do not use it at all in a patient with existing liver disease or raised transaminases. If it is used, monitor liver function and stop at the first enzyme rise.
Broad-spectrum oral antibiotics (e.g. neomycin, rifaximin, metronidazole)
Cycasin is a glycoside with no intrinsic alkylating activity; toxicity requires bacterial beta-glucosidase to release methylazoxymethanol, which is why germ-free rodents tolerate oral cycasin far better than conventionally reared ones. Suppressing colonic flora would be expected to blunt that activation, and conversely a patient recolonising after antibiotics has an unpredictable activating capacity.
Clinical note: Not a reason to co-prescribe antibiotics. It is a reason not to assume that a dose tolerated once will be tolerated again, since the toxic exposure depends on the patient's microbiome rather than on the dose alone.
Cytotoxic chemotherapy and other DNA-alkylating or genotoxic agents
Methylazoxymethanol derived from cycasin is a direct-acting DNA methylating agent, and cycasin was demonstrated to have radiomimetic chromosome-breaking effects in 1965. Superimposing it on alkylating chemotherapy or radiotherapy has no therapeutic rationale and adds a second genotoxic exposure.
Clinical note: Avoid entirely in oncology patients, and avoid in pregnancy and in children given the documented teratogenicity of methylazoxymethanol in animals.
Dosage Calculator
⚖ Dosage Calculator
A weight-based mathematical estimate for Feng Wei Jiao Ye. Not a prescription.
Evidence Tier
5 studies on recordRecorded 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
1
0 verified · 1 unverified
Show the study
In vitro / animal
4
1 verified · 3 unverified
Show 4 studies
- Survival and Prognostic Indicators for Cycad Intoxication in Dogs
- Sotetsuflavone inhibits proliferation and induces apoptosis of A549 cells through ROS-mediated mitochondrial-dependent pathway
- Sotetsuflavone suppresses invasion and metastasis in non-small-cell lung cancer A549 cells by reversing EMT via the TNF-α/NF-κB and PI3K/AKT signaling pathway
- Sotetsuflavone Induces Autophagy in Non-Small Cell Lung Cancer Through Blocking PI3K/Akt/mTOR Signaling Pathway in Vivo and in Vitro
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
Cycad palm toxicosis in dogs: 60 cases (1987-1997)
Retrospective review of 60 dogs exposed to cycad palms, predominantly Cycas revoluta. Gastrointestinal and hepatic signs occurred in 95% of cases and neurological abnormalities in 53.3%; 38.7% had eaten seeds. This remains the largest documented case series of Cycas revoluta poisoning in any species and is the practical basis for treating the plant as frankly hepatotoxic.
Survival and Prognostic Indicators for Cycad Intoxication in Dogs
Retrospective study of dogs with cycad ingestion identifying the clinicopathological features that predicted death, notably marked hepatocellular enzyme elevation and coagulation abnormalities. Confirms that acute liver failure, not the neurological signs, is the usual cause of death after Cycas ingestion.
Sotetsuflavone inhibits proliferation and induces apoptosis of A549 cells through ROS-mediated mitochondrial-dependent pathway
Sotetsuflavone, a biflavonoid isolated from Cycas revoluta, raised intracellular reactive oxygen species in A549 lung adenocarcinoma cells, collapsed mitochondrial membrane potential, produced G0/G1 arrest and triggered intrinsic apoptosis. Cell-culture work only; it says nothing about what a leaf decoction does in a patient.
Sotetsuflavone suppresses invasion and metastasis in non-small-cell lung cancer A549 cells by reversing EMT via the TNF-α/NF-κB and PI3K/AKT signaling pathway
Sotetsuflavone inhibited A549 migration and invasion, upregulating E-cadherin and downregulating N-cadherin, vimentin and Snail, with the anti-metastatic effect attributed to HIF-1α downregulation via PI3K/AKT and TNF-α/NF-κB inhibition.
Sotetsuflavone Induces Autophagy in Non-Small Cell Lung Cancer Through Blocking PI3K/Akt/mTOR Signaling Pathway in Vivo and in Vitro
In cultured cells and in a xenograft model, sotetsuflavone induced autophagy through blockade of PI3K/Akt/mTOR signalling. The only in vivo work on a Cycas revoluta constituent with a therapeutic rather than toxicological endpoint; it uses a purified biflavonoid, not the crude leaf.
References
- Kruger T, Monch B, Oppenhauser S, Luckas B. LC–MS/MS determination of the isomeric neurotoxins BMAA (β-N-methylamino-l-alanine) and DAB (2,4-diaminobutyric acid) in cyanobacteria and seeds of Cycas revoluta and Lathyrus latifolius . Toxicon (2010) [DOI]
- Du Q, Xing N, Guo S, Li R, Meng X, Wang S. Cycads: A comprehensive review of its botany, traditional uses, phytochemistry, pharmacology and toxicology . Phytochemistry (2024) [DOI]
- Teas HJ, Sax HJ, Sax K. Cycasin: Radiomimetic Effect . Science (1965) [DOI]
- Abdul K, Prakash PS, Nakshathra KV, Devika V. Ethnobotany, Phytochemistry, Pharmacology, and Toxicology of Cycas revoluta Thunb.: An Updated Review . Sciences of Phytochemistry (2026) [DOI]
- CITES Secretariat. Appendices I, II and III to the Convention on International Trade in Endangered Species of Wild Fauna and Flora — Cycadaceae spp. . CITES (2023)
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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