# Reynoutria japonica

**Canonical URL:** https://ingredients.hermeticasuperfoods.com/ingredients/reynoutria-japonica
**Data Source:** Hermetica Superfoods Ingredient Encyclopedia
**Updated:** 2026-03-19
**Evidence Score:** 6 / 10
**Category:** Traditional Chinese Medicine
**Also Known As:** Fallopia japonica, Polygonum cuspidatum, Japanese knotweed, Hu Zhang, Tiger Cane, Mexican bamboo, Crimson beauty, Polygonum reynoutria

## Overview

Reynoutria japonica contains resveratrol and emodin as primary bioactive compounds that modulate [inflammatory pathway](/ingredients/condition/inflammation)s. It demonstrates clinical efficacy in reducing respiratory infection recovery time and fever duration through anti-inflammatory mechanisms.

## Health Benefits

• Respiratory infection recovery: Systematic review of 8 RCTs (n=1,123) showed improved symptom recovery rates (RR 1.14, 95% CI [1.07, 1.21]) when used in herbal mixtures
• Fever reduction: Clinical trials demonstrated shortened fever duration in acute respiratory tract infections (3 trials, n=396)
• [Anti-inflammatory](/ingredients/condition/inflammation) effects: Preclinical studies show dose-dependent reduction of IL-1β, IL-6, and TNF-α in osteoarthritis models
• Wound healing support: In vitro studies found 25% ethanol extracts enhanced fibroblast proliferation and collagen III synthesis
• Cartilage protection: Animal models demonstrated reduced cartilage breakdown markers, though human evidence lacking

## Mechanism of Action

Reynoutria japonica's resveratrol inhibits nuclear factor-kappa B (NF-κB) signaling, reducing [pro-inflammatory cytokine](/ingredients/condition/inflammation) production including TNF-α and IL-6. The emodin component modulates cyclooxygenase (COX) pathways and enhances [antioxidant](/ingredients/condition/antioxidant) enzyme activity. These combined actions support [immune function](/ingredients/condition/immune-support) and reduce inflammatory responses in respiratory tissues.

## Clinical Summary

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.

## Nutritional Profile

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](/ingredients/condition/inflammation) and laxative properties; moderate oral bioavailability (~30–40% in animal models) with extensive hepatic [metabolism](/ingredients/condition/weight-management). • **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](/ingredients/condition/immune-support) profile. • **Catechins and proanthocyanidins:** Present in moderate concentrations (~5–15 mg/g dry weight total polyphenols in rhizome extracts), contributing to [antioxidant](/ingredients/condition/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.

## Dosage & Preparation

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.

## Safety & Drug Interactions

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.

## Scientific Research

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](/ingredients/condition/inflammation) effects in osteoarthritis models at 100-300 mg/kg doses.

## Historical & Cultural Context

In Traditional Chinese Medicine, R. japonica rhizome (Hu Zhang) has been used for centuries to invigorate blood, cool heat, and resolve toxicity, treating conditions like jaundice, scalds, and constipation. Modern interest leverages its invasive status as a sustainable medicinal source.

## Synergistic Combinations

Elderberry, Echinacea, Andrographis, Vitamin C, Zinc

## Frequently Asked Questions

### What is the active ingredient in Reynoutria japonica?

The primary active compounds are resveratrol and emodin. Resveratrol provides anti-inflammatory effects while emodin contributes antioxidant properties.

### How much Reynoutria japonica should I take for respiratory infections?

Clinical studies used herbal formulations containing 3-9g of dried Reynoutria japonica root daily. Standardized extracts typically provide 50-100mg of resveratrol per dose.

### How long does Reynoutria japonica take to work for fever?

Clinical trials showed fever duration reduction within 2-3 days of treatment initiation. Symptom improvement typically begins within 24-48 hours of consistent use.

### Can Reynoutria japonica be taken with blood thinners?

Caution is advised as resveratrol may enhance anticoagulant effects of warfarin and other blood thinners. Consult healthcare providers before combining with anticoagulant medications.

### Is Reynoutria japonica the same as Japanese knotweed?

Yes, Reynoutria japonica is the scientific name for Japanese knotweed. It's also known as Fallopia japonica and Polygonum cuspidatum in traditional medicine systems.

### What does clinical research show about Reynoutria japonica for respiratory infections?

A systematic review of 8 randomized controlled trials involving 1,123 participants found that Reynoutria japonica in herbal mixtures improved symptom recovery rates by 14% compared to control groups (RR 1.14, 95% CI [1.07, 1.21]). Additional clinical trials demonstrated that it shortened fever duration in acute respiratory tract infections across 3 trials with 396 participants. While these results are promising, most research involves Reynoutria japonica as part of multi-ingredient formulas rather than as a standalone supplement.

### Is Reynoutria japonica safe for children or elderly individuals?

Safety data specifically evaluating Reynoutria japonica use in pediatric or geriatric populations is limited, and most clinical trials have enrolled adults of working age. While the ingredient has a long history in traditional medicine systems, dosing recommendations for children or elderly individuals have not been established through rigorous clinical research. Consultation with a healthcare provider is recommended before giving Reynoutria japonica to children or using it in elderly patients, particularly those with multiple comorbidities.

### What forms of Reynoutria japonica are most effective—extract, powder, or whole root?

Clinical trials demonstrating efficacy for respiratory infections have primarily used standardized extracts or herbal mixtures rather than whole powdered root, suggesting that extraction methods may concentrate bioactive compounds. Reynoutria japonica contains resveratrol and other polyphenols that show dose-dependent anti-inflammatory effects in preclinical studies, with extract formulations allowing for more consistent active compound levels. However, direct comparative studies between different forms of Reynoutria japonica are limited, making it difficult to definitively recommend one format over another.

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*Source: Hermetica Superfoods Ingredient Encyclopedia — https://ingredients.hermeticasuperfoods.com*
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