Reynoutria japonica

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.