Plant Comparison
Japanese knotweed vs Common coltsfoot
A side-by-side comparison of two medicinal plants — every documented constituent, action, use, safety note and cited source, assembled automatically from the Omnia Sana database.
At a glance
Japanese knotweed and Common coltsfoot: they share 3 indicated uses (arthritis / joint pain, inflammation (general), skin irritation); 1 pharmacological action in common.
Evidence face-off — shared uses
| Condition | Japanese knotweed | Common coltsfoot | Verdict |
|---|---|---|---|
| Arthritis / joint pain | 2/10 | 1/10 | Comparable evidence |
| Inflammation (general) | 7/10 | 2/10 | Stronger for Japanese knotweed |
| Skin irritation | 1/10 | 1/10 | Comparable evidence |
Evidence scores (1–10) are computed from the tier of each cited source. “Comparable” means the two scores are within one point. Follow a score to its detailed sources.
Key Constituents
Considered the principal bioactive constituents, responsible for much of the antioxidant, anti-inflammatory and cardioprotective activity attributed to this root.
Emodin has laxative and anti-inflammatory activity at typical concentrations but can cause gastrointestinal upset at high doses.
Hepatotoxic constituents that are the central safety concern for this plant; regulatory limits and PA-controlled/PA-reduced products exist specifically because of these compounds.
Demulcent polysaccharide contributing to the traditional soothing action on irritated airways.
Pharmacological Actions
Traditional & Indicated Uses
inferred from anti-inflammatory action
inferred from anticancer action
inferred from anti-inflammatory action
inferred from anti-inflammatory action
inferred from anti-inflammatory action
inferred from sedative action
Safety, Cautions & Contraindications
Japanese knotweed root contains resveratrol and emodin; high doses of emodin may cause GI discomfort and have laxative effects. Not recommended during pregnancy (emodin has potential teratogenic effects in animal studies). May interact with anticoagulants and antiplatelet medications. Quality control of commercial preparations is important as invasive weed extracts vary significantly.
Duke (2002) rates Japanese knotweed (listed as Hu-Zhang, Fallopia japonica) as +++ and highlights its rich content of resveratrol and emodin. Experimental evidence (score 1) supports COX-2 inhibitory, antioxidant, anti-inflammatory, hepatoprotective, and lipid-lowering activities — largely attributed to resveratrol. Duke notes its use in traditional Chinese medicine for fractures, burns, abscesses, and gynecological conditions. No significant clinical trials were available at time of publication, but resveratrol's biological activity is well-documented in vitro (Duke, 2002).
Safety notes (contraindications, interactions, pregnancy/lactation notes, adverse effects, dose-duration cautions) Important: Coltsfoot naturally contains pyrrolizidine alkaloids (PAs)—plant chemicals that can damage the liver and may increase cancer risk with enough exposure (EMA, 2021; Kopp et al., 2020).
Because of this, European regulators set very strict limits for PA exposure from herbal products (EMA, 2021).
Many safety-focused herbal references recommend avoiding homemade/internal coltsfoot use, unless the product is specifically made to be PA-controlled / PA-reduced (EMA, 2021).
Avoid internal use if you are pregnant or breastfeeding, have liver disease, or for children—these groups are treated as “sensitive” in PA risk guidance (EMA, 2021).
Medication caution: if you take medicines that stress the liver (some prescription drugs can), it’s extra important to avoid unregulated PA exposure (general PA risk logic; consult a clinician) (EMA, 2021).
Topical use may still carry PA considerations; EMA discusses limits and recommends use only on intact skin for PA-containing products (EMA, 2021).
Duke (2002) provides clinical support (score 2) for coltsfoot's anti-inflammatory and expectorant effects, explaining its traditional use in bronchitis and coughs. However, the plant contains hepatotoxic pyrrolizidine alkaloids (PAs), and Duke notes a carcinogenic score (1) — a critical safety concern. Commission E has placed restrictions on coltsfoot use, recommending maximum internal use of 4–6 weeks per year and avoiding use in pregnancy, lactation, and in children under 12. Duke rates its overall safety as low (+) and emphasizes that preparations free of PAs are preferred (Duke, 2002).
External Ids
Botanical Description
Vigorous, invasive rhizomatous perennial (Polygonaceae) with hollow, bamboo-like, jointed stems 1-3 m tall (occasionally taller), speckled reddish-purple. Leaves are broad, heart- to shovel-shaped with a flat base. Abundant sprays of small, creamy-white flowers appear in late summer, followed by small winged fruit.[6]
Low perennial herb notable for flowering before its leaves appear: solitary, bright yellow, dandelion-like flower heads emerge on scaly pinkish stalks in very early spring, followed later by large, hoof-shaped (heart-shaped with angular teeth), white-woolly-backed leaves arising directly from the creeping rhizome.[11]
Habitat
Native to East Asia (Japan, China, Korea), now a notorious invasive species across Europe and North America, growing in disturbed ground, riverbanks, roadsides and waste land, spreading aggressively via an extensive rhizome network.[6]
Grows on disturbed, damp or clay-rich waste ground, riverbanks, railway embankments and bare soil; native to Europe, North Africa and temperate Asia and naturalised in North America.[11]
Harvesting
The rhizome/root, the main medicinal part, is dug in autumn or winter when resveratrol content is highest; young spring shoots (stems) are also edible and used. Strict containment is required when harvesting, given the plant's severe invasiveness.[6]
Flowers are gathered in very early spring before the leaves appear; leaves are gathered later in the season once expanded. Given the plant's pyrrolizidine alkaloid content, harvesting from a positively confirmed patch (not a look-alike) and preferring PA-tested commercial material for internal use is strongly advised.[2]
Traditional Uses
Known as Hu Zhang in Traditional Chinese Medicine, Japanese knotweed root has a centuries-old use for inflammation, infections, jaundice and menstrual complaints. Modern interest centres on its resveratrol and emodin content, now studied (as Polygonum cuspidatum extract) for antioxidant, anti-inflammatory, cardioprotective and hepatoprotective activity, and more recently for supportive use in acute respiratory infections.[2, 3, 6]
Coltsfoot has an ancient European and Chinese tradition, reflected in its Latin name (tussis = cough), as an expectorant and demulcent remedy for coughs, bronchitis and irritated airways; because of its pyrrolizidine alkaloid content, contemporary use is restricted to short courses of PA-controlled preparations under regulatory limits (see contraindications).[1, 2, 12]
Preparations
Commercially prepared, pyrrolizidine-alkaloid-tested extract or syrup, the only form recommended for internal use given the plant's natural PA content.
Dried flower or leaf infused in hot water; traditional but subject to strict duration/PA-content limits under EU herbal regulation.
Dosage
Duke (2002) and general phytotherapy guidance treat this as an experimentally supported herb without a single agreed clinical dose; commercial resveratrol-standardised extracts should be dosed per product labelling. Educational reference only, not a prescription; avoid in pregnancy.
EU regulatory guidance restricts internal use to PA-controlled preparations. The EMA public statement on unsaturated pyrrolizidine alkaloids records a maximum daily intake for internal use of 1 microgram of PAs for at most 6 weeks per year, or 0.1 microgram per day with no duration limit; for cutaneous use the limits are 100 micrograms for at most 6 weeks per year, or 10 micrograms without a duration limit. Not for use in pregnancy, breastfeeding, or children. Note that these are limits on PA intake, not a herb dose — no EMA monograph exists for Tussilago farfara, so there is no official posology for the herb itself. Educational reference only, not a prescription — consult a qualified practitioner and prefer tested commercial products.
References
Lookalikes Review
Dangerous Lookalikes
Not documented
References & Sources
- Dong, X., Fu, J., Yin, X., Cao, S. and others (2016) 'Emodin: A Review of its Pharmacology, Toxicity and Pharmacokinetics', Phytotherapy Research, 30(8), pp. 1207-1218. doi:10.1002/ptr.5631 Traditional / reference
https://doi.org/10.1002/ptr.5631 - Wang, S., Yang, Y., Sun, L., Qiao, G. and others (2022) 'Reynoutria japonica Houtt for Acute Respiratory Tract Infections in Adults and Children: A Systematic Review', Frontiers in Pharmacology, 13, pp. 787032. doi:10.3389/fphar.2022.787032 Meta-analysis / review
https://doi.org/10.3389/fphar.2022.787032 - Ke, Y., Zhan, L., Lu, T., Zhou, C. and others (2023) 'Advances for pharmacological activities of Polygonum cuspidatum (Reynoutria japonica) - A review', Pharmaceutical Biology, 61(1), pp. 177-188. doi:10.1080/13880209.2022.2158349 Traditional / reference
https://doi.org/10.1080/13880209.2022.2158349 - Zhang, Q., Zhao, Y., Zhang, M., Zhang, Y. and others (2021) 'Bioactive amides from Reynoutria japonica', Journal of Asian Natural Products Research, 23(3), pp. 228-234. doi:10.1080/10286020.2021.1873298 Preclinical
https://doi.org/10.1080/10286020.2021.1873298 - Lai, Y., Zhou, C., Huang, P., Dong, Z. and others (2024) 'Polygonum cuspidatum polysaccharide: A review of its extraction and purification, structure analysis, and biological activity', Journal of Ethnopharmacology, 331, pp. 118079. doi:10.1016/j.jep.2024.118079 Traditional / reference
https://doi.org/10.1016/j.jep.2024.118079 - Peng, W., Qin, R., Li, X. and Zhou, H (2013) 'Botany, phytochemistry, pharmacology, and potential application of Polygonum cuspidatum Sieb. et Zucc.: a review', Journal of Ethnopharmacology, 148(3), pp. 729-745. doi:10.1016/j.jep.2013.05.007 Traditional / reference
https://doi.org/10.1016/j.jep.2013.05.007 - Wang, X., Liang, L., Yan, J., Li, Z. and others (2023) 'Citri Reticulatae Pericarpium-Reynoutria japonica Houtt. herb pair suppresses breast cancer liver metastasis by targeting ECM1-mediated cholesterol biosynthesis pathway', Phytomedicine, 116, pp. 154896. doi:10.1016/j.phymed.2023.154896 Preclinical
https://doi.org/10.1016/j.phymed.2023.154896 - Jiang, Y., Liu, Y., Zhang, X. and others (2020) 'New phenolic glycosides from Reynoutria japonica', Journal of Asian Natural Products Research, 22(1), pp. 17-23. doi:10.1080/10286020.2019.1646730 Preclinical
https://doi.org/10.1080/10286020.2019.1646730 - Liu, Y., Wang, J., Li, Q. and others (2024) 'The Possibility of Polygonum cuspidatum against Osteoarthritis based on Network Pharmacology', Current Computer-Aided Drug Design, 20(2), pp. 121-133. doi:10.2174/1573409919666230403114131 Preclinical
https://doi.org/10.2174/1573409919666230403114131 - Espinosa-Andrews, H., Morales-Hernandez, N., Garcia-Marquez, E. and others (2025) 'Physicochemical and rheological characteristics of commercial Greek-style yogurt enriched with Polygonum cuspidatum roots or the P. cuspidatum beta-cyclodextrin inclusion complex', Food Research International, 203, pp. 115854. doi:10.1016/j.foodres.2025.115854 Preclinical
https://doi.org/10.1016/j.foodres.2025.115854 - Burns, J., Yokota, T., Ashihara, H., Lean, M.E.J. and Crozier, A (2002) 'Plant foods and herbal sources of resveratrol', 50(11), pp. 3337--3340. doi:10.1021/jf0112973 Traditional / reference
https://doi.org/10.1021/jf0112973 - Royal Botanic Gardens, Kew (n.d.). Available at: https://powo.science.kew.org Traditional / reference
https://powo.science.kew.org - World Health Organization (2007) 'WHO Monographs on Selected Medicinal Plants'. Traditional / reference
https://scholar.google.com/scholar?q=WHO%20Monographs%20on%20Selected%20Medicinal%20Plants - Duke, J.A (2002) 'Handbook of Medicinal Herbs, Second Edition'. Traditional / reference
https://scholar.google.com/scholar?q=Handbook%20of%20Medicinal%20Herbs%2C%20Second%20Edition
- Ahmad, I., Kudaibergenova, B., Ahmad, M. and others (2025) 'Coltsfoot (Tussilago farfara L.; Asteraceae): modern methods of extraction, phytochemistry, nanoparticles synthesis, ethnopharmacology, and biological activities', Natural Product Research, pp. 1-20. doi:10.1080/14786419.2025.2548616 Traditional / reference
https://doi.org/10.1080/14786419.2025.2548616 - Chen, S., Dong, L., Quan, H., Zhou, X. and others (2020) 'A review of the ethnobotanical value, phytochemistry, pharmacology, toxicity and quality control of Tussilago farfara L. (coltsfoot)', Journal of Ethnopharmacology, 267, pp. 113478. doi:10.1016/j.jep.2020.113478 Traditional / reference
https://doi.org/10.1016/j.jep.2020.113478 - Feng, J., Zhang, Y., Qin, X., Gao, T. and others (2022) 'Novel Quinic Acid Glycerates from Tussilago farfara Inhibit Polypeptide GalNAc-Transferase', ChemBioChem, 23(3), pp. e202100539. doi:10.1002/cbic.202100539 Preclinical
https://doi.org/10.1002/cbic.202100539 - Zhao, J., Evangelopoulos, D., Bhakta, S., Gray, A.I. and Seidel, V (2014) 'Antitubercular activity of Arctium lappa and Tussilago farfara extracts and constituents', Journal of Ethnopharmacology, 155(1), pp. 796-800. doi:10.1016/j.jep.2014.06.034 Preclinical
https://doi.org/10.1016/j.jep.2014.06.034 - Avila, C., Breakspear, I., Hawrelak, J., Salmond, S. and Evans, S (2020) 'A systematic review and quality assessment of case reports of adverse events for borage (Borago officinalis), coltsfoot (Tussilago farfara) and comfrey (Symphytum officinale)', Fitoterapia, 142, pp. 104519. doi:10.1016/j.fitote.2020.104519 Meta-analysis / review
https://doi.org/10.1016/j.fitote.2020.104519 - Lee, J., Park, S., Kim, M.J., Kwon, S.J. and others (2019) 'Sesquiterpenoids from Tussilago farfara Flower Bud Extract for the Eco-Friendly Synthesis of Silver and Gold Nanoparticles Possessing Antibacterial and Anticancer Activities', Nanomaterials (Basel), 9(6), pp. 819. doi:10.3390/nano9060819 Preclinical
https://doi.org/10.3390/nano9060819 - Bota, V.B., Neamtu, A.A., Olah, N.K., Chiselita, O. and others (2022) 'A Comparative Analysis of the Anatomy, Phenolic Profile, and Antioxidant Capacity of Tussilago farfara L. Vegetative Organs', Plants (Basel), 11(13), pp. 1663. doi:10.3390/plants11131663 Preclinical
https://doi.org/10.3390/plants11131663 - Boucher, M.A., Cote, H., Pichette, A., Ripoll, L. and Legault, J (2020) 'Chemical composition and antibacterial activity of Tussilago farfara (L.) essential oil from Quebec, Canada', Natural Product Research, 34(4), pp. 545-548. doi:10.1080/14786419.2018.1489384 Preclinical
https://doi.org/10.1080/14786419.2018.1489384 - Li, Z.Y., Zhang, J., Zhang, Y.B., Yang, X.W. and others (2022) 'Polyhydroxylated eudesmane sesquiterpenoids and sesquiterpenoid glucoside from the flower buds of Tussilago farfara', Chinese Journal of Natural Medicines, 20(4), pp. 301-308. doi:10.1016/S1875-5364(21)60120-6 Preclinical
https://doi.org/10.1016/S1875-5364(21)60120-6 - Jang, H., Lee, J.W., Lee, C., Jin, Q. and others (2016) 'Sesquiterpenoids from Tussilago farfara inhibit LPS-induced nitric oxide production in macrophage RAW 264.7 cells', Archives of Pharmacal Research, 39(1), pp. 127-132. doi:10.1007/s12272-015-0667-7 Preclinical
https://doi.org/10.1007/s12272-015-0667-7 - Royal Botanic Gardens, Kew (n.d.). Available at: https://powo.science.kew.org Traditional / reference
https://powo.science.kew.org - Westendorf, J., Czok, G., Marquardt, R., Nausner, M., Krauer, B. and Paul, H.L (1988) 'Pyrrolizidine alkaloid content of Tussilago farfara plants from different regions and preparations', pp. 903--909. Traditional / reference
https://scholar.google.com/scholar?q=Pyrrolizidine%20alkaloid%20content%20of%20Tussilago%20farfara%20plants%20from%20different%20regions%20and%20preparations - European Medicines Agency (HMPC) (2021) 'Public statement on the use of herbal medicinal products containing toxic, unsaturated pyrrolizidine alkaloids (PAs), including recommendations regarding contamination of herbal medicinal products with PAs, Revision 1'. Available at: https://www.ema.europa.eu/en/documents/public-statement/public-statement-use-herbal-medicinal-products-containing-toxic-unsaturated-pyrrolizidine-alkaloids-pas-including-recommendations-regarding-contamination-herbal-medicinal-products-pyrrolizidine_en.pdf Traditional / reference
https://www.ema.europa.eu/en/documents/public-statement/public-statement-use-herbal-medicinal-products-containing-toxic-unsaturated-pyrrolizidine-alkaloids-pas-including-recommendations-regarding-contamination-herbal-medicinal-products-pyrrolizidine_en.pdf - Duke, J.A (2002) 'Handbook of Medicinal Herbs, Second Edition'. Traditional / reference
https://scholar.google.com/scholar?q=Handbook%20of%20Medicinal%20Herbs%2C%20Second%20Edition - Sperl, W. and Stuppner, H. and Gassner, I. and Judmaier, W. and Dietze, O. and Vogel, W (1995) 'Reversible hepatic veno-occlusive disease in an infant after consumption of pyrrolizidine-containing herbal tea', European Journal of Pediatrics, 154(2), pp. 112-6. doi:10.1007/BF01991912 Clinical study
https://doi.org/10.1007/BF01991912
Generated automatically from the Omnia Sana plant database and its cited sources. For educational purposes only — not medical advice. Always consult a qualified practitioner before using medicinal plants.