Herbs (Global Traditional) · Traditional Chinese Medicine
Reynoutria japonica
Moderate Evidencebotanical
Hermetica Superfood Encyclopedia
Reynoutria japonica contains resveratrol and emodin as primary bioactive compounds that modulate inflammatory pathways. It demonstrates clinical efficacy in reducing respiratory infection recovery time and fever duration through anti-inflammatory mechanisms.
Reynoutria japonica (Japanese knotweed) is a perennial herb native to East Asia, now invasive across Europe and North America. The medicinal rhizome (underground stem) is extracted using ethanol (25-40%) or acetone solvents to concentrate bioactive compounds like resveratrol and procyanidins.
A 2022 systematic review analyzed 8 RCTs (n=1,123) using R. japonica in herbal mixtures for respiratory infections, finding significant symptom improvement without increased adverse events (PMC8911541). No standalone human trials exist; preclinical data shows anti-inflammatory effects in osteoarthritis models at 100-300 mg/kg doses.
No clinically validated dosages exist for standalone R. japonica. Human studies used it only in herbal mixtures for 3-45 days (typically 3-7 days) for respiratory infections. Preclinical studies used 100-300 mg/kg oral doses in animals. Consult a healthcare provider before starting any new supplement.
Reynoutria japonica (Japanese knotweed, known as Hu Zhang 虎杖 in TCM) is used medicinally rather than as a food source, so a conventional macronutrient profile is not the primary focus. Key bioactive compounds include: • **Resveratrol (trans-resveratrol):** Root/rhizome contains approximately 0.5–1.5 mg/g dry weight (among the richest natural plant sources); bioavailability is relatively low orally (~1–5% unchanged form) due to rapid glucuronidation and sulfation in the gut and liver, though metabolites may retain bioactivity. • **Polydatin (piceid/resveratrol-3-O-β-D-glucoside):** Present at approximately 1.5–6.0 mg/g dry weight in rhizomes; the glycosylated form has improved water solubility and may exhibit higher intestinal absorption via SGLT1-mediated active transport compared to free resveratrol. • **Emodin (1,3,8-trihydroxy-6-methylanthraquinone):** Approximately 0.3–2.0 mg/g dry weight in rhizome; exhibits anti-inflammatory and laxative properties; moderate oral bioavailability (~30–40% in animal models) with extensive hepatic metabolism. • **Physcion (1,8-dihydroxy-3-methoxy-6-methylanthraquinone):** Approximately 0.1–0.8 mg/g dry weight. • **Chrysophanol:** Approximately 0.1–0.5 mg/g dry weight; another anthraquinone derivative contributing to the laxative and antimicrobial profile. • **Catechins and proanthocyanidins:** Present in moderate concentrations (~5–15 mg/g dry weight total polyphenols in rhizome extracts), contributing to antioxidant capacity. • **Stilbene derivatives:** Additional minor stilbenes beyond resveratrol/polydatin at trace levels. • **Minerals:** Rhizome contains calcium (~2–5 mg/g), potassium (~4–8 mg/g), iron (~0.05–0.15 mg/g), and manganese (~0.02–0.06 mg/g) on a dry weight basis; however, concentrations vary significantly with soil and growing conditions. Note: R. japonica is known to hyperaccumulate certain heavy metals (particularly zinc, cadmium, and lead) from contaminated soils, so sourcing and quality control testing is critical. • **Dietary fiber:** Young shoots (consumed as a vegetable in parts of East Asia) contain approximately 2–4 g fiber per 100 g fresh weight, with modest vitamin C (~10–15 mg/100 g fresh shoot) and oxalic acid content (~0.5–1.0 g/100 g fresh weight, reducing mineral bioavailability). • **Total anthraquinone glycosides:** Chinese Pharmacopoeia (2020 edition) requires ≥0.60% combined emodin and polydatin content in crude Hu Zhang drug material. Overall, the rhizome is valued for its high concentration of resveratrol/polydatin and anthraquinones rather than macronutrient content. Bioavailability of key actives is enhanced by co-administration with piperine or lipid-based delivery systems in modern supplement formulations.
Reynoutria japonica's resveratrol inhibits nuclear factor-kappa B (NF-κB) signaling, reducing pro-inflammatory cytokine production including TNF-α and IL-6. The emodin component modulates cyclooxygenase (COX) pathways and enhances antioxidant enzyme activity. These combined actions support immune function and reduce inflammatory responses in respiratory tissues.
A systematic review of 8 randomized controlled trials involving 1,123 participants showed Reynoutria japonica in herbal mixtures improved respiratory infection recovery rates by 14% (RR 1.14, 95% CI [1.07, 1.21]). Three clinical trials with 396 participants demonstrated significant reduction in fever duration during acute respiratory tract infections. The evidence is moderate quality, though most studies used multi-herb formulations rather than isolated Reynoutria japonica. Additional research on standardized single-ingredient preparations is needed.
Reynoutria japonica is generally well-tolerated in clinical studies when used in traditional herbal formulations. Potential side effects may include gastrointestinal upset due to emodin content, particularly at higher doses. The resveratrol component may interact with anticoagulant medications by enhancing bleeding risk. Pregnancy and breastfeeding safety data is insufficient, requiring caution during these periods.
