Japanese knotweed
Reynoutria japonica Houtt.Polygonaceae // root · rhizome
Overview
Plant parts
root, rhizome
Known constituents
resveratrol, polydatin, emodin
Research corpus coverage
Chemistry notes
- CHEMISTRY: Relevant reported constituents include resveratrol; polydatin; emodin; constituent presence alone does not establish clinical efficacy.
Uses & Evidence
Traditional / historical use
Documented traditional use — not a claim of established efficacy.
TRADITIONAL: Japanese knotweed has been used for circulatory and inflammatory complaints; this records historical/traditional use and does not establish efficacy.
MODERATE · regulatory monograph · WHO Monographs on Selected Medicinal Plants
Modern evidence
EVIDENCE: For the major use set (circulatory and inflammatory complaints), the evidence assessment is insufficient: Insufficient clinical evidence for whole herb.
LOW · regulatory monograph and mixed scientific literature · WHO Monographs on Selected Medicinal Plants
Preparation
Forms used traditionally
A listed form does not imply it suits every plant part, or that one preparation is interchangeable with another — see the plant’s own notes below.
PREPARATION: The medicinal material is root; rhizome; traditional and modern forms include decoction, tincture, powder/capsule, standardized extract. No dose or potency is specified.
MODERATE · regulatory monograph · EMA European Union herbal monographs and list entries
Preparation-specific evidence should not be generalized across extracts, teas, oils, or whole herb.
Safety
Additional safety notes (general, unstructured)
Free-text safety notes carried from their source — not broken out by species, route, or hazard type, and not equivalent to the structured records above. Each note names the kind of source it came from.
SAFETY: Major issues include GI upset; anthraquinone laxation; possible liver effects. Contraindications/cautions include Bleeding disorders; pregnancy.
HIGH · observational/case series and expert review · LiverTox: Herbal and Dietary Supplements
SAFETY: Clinically relevant interaction concerns include Potential additive anticoagulant and CYP interactions.
MODERATE · observational/case series and expert review · LiverTox: Herbal and Dietary Supplements
Some interactions are theoretical or based on case reports/pharmacokinetics rather than outcome trials.
SAFETY: Pregnancy/lactation reference: Avoid medicinal use in pregnancy/lactation.
MODERATE · regulatory monograph or evidence synthesis · WHO Monographs on Selected Medicinal Plants
Absence of evidence is not evidence of safety.
Preparation × species risk matrix
Unknown means insufficient evidence was located — not that a form is safe.
Cats
- tinctureCaution
- concentrated extractUnknown
- essential oilUnknown
- glyceriteUnknown
- infused oilUnknown
- salveUnknown
- smoke/combustionUnknown
- tea/infusionUnknown
- whole herbUnknown
Dogs
- tinctureCaution
- concentrated extractUnknown
- essential oilUnknown
- glyceriteUnknown
- infused oilUnknown
- salveUnknown
- smoke/combustionUnknown
- tea/infusionUnknown
- whole herbUnknown
Identity
- Synonym
GBIF resolves Fallopia japonica (Houtt.) Ronse Decr. as a synonym of Reynoutria japonica. The older name still appears in herbal and taxonomic literature.
HIGH · GBIF Species Match API
- Synonym
GBIF resolves Polygonum cuspidatum Siebold & Zucc. as a synonym of Reynoutria japonica. The older name still appears in herbal and taxonomic literature.
HIGH · GBIF Species Match API
Botanical synonym
Fallopia japonica (Houtt.) Ronse Decr., Polygonum cuspidatum Siebold & Zucc.
Taxonomic identity note
- Japanese knotweed is treated here as Reynoutria japonica Houtt. in the family Polygonaceae; recorded older names include Fallopia japonica (Houtt.) Ronse Decr.; Polygonum cuspidatum Siebold & Zucc..
Sources
Research records are source-linked but may not yet be editorially reviewed.
WHO monograph
NIH LiverTox monograph
- Plants of the World Online1 claim
botanical taxonomy database
EMA monograph
- GBIF Species Match API1 claim
authoritative taxonomic database
- GBIF Species Match API1 claim
authoritative taxonomic database