Dihydroquercetin (Taxifolin)

Dihydroquercetin (taxifolin) is a flavanonol (dihydroflavonol) polyphenolic compound with the molecular formula C₁₅H₁₂O₇ and molecular weight of 304.25 g/mol. It is not a food per se and therefore lacks a conventional macronutrient or micronutrient profile (no significant protein, fat, carbohydrate, fiber, vitamins, or minerals). Key bioactive characteristics: • Structurally it is (2R,3R)-2-(3,4-dihydroxyphenyl)-3,5,7-trihydroxy-2,3-dihydrochromen-4-one, featuring five hydroxyl groups responsible for its antioxidant electron-donating capacity. • In vitro radical-scavenging activity (DPPH, ABTS) is comparable to or modestly lower than quercetin, largely because the C2–C3 single bond (saturated) reduces π-conjugation relative to quercetin. • Natural concentrations: found in moderate amounts in the heartwood of Siberian larch (Larix sibirica/gmelinii), ~1–4% dry weight of heartwood extract; trace amounts in Douglas fir bark; minor constituent in milk thistle (Silybum marianum) seeds alongside silibinin; small amounts in onions, grapes, and citrus fruits (typically <5 mg/kg fresh weight). • Commercial purified supplement forms typically provide 50–500 mg per dose as taxifolin dihydrate (≥90–98% purity). • Bioavailability notes: Oral bioavailability in animal models is low-to-moderate, estimated at roughly 10–30% in rats. Taxifolin undergoes extensive Phase II metabolism (glucuronidation and sulfation) in the intestinal wall and liver, yielding taxifolin-glucuronides and taxifolin-sulfates as major circulating metabolites. Peak plasma concentrations (Cmax) after a single 50 mg/kg oral dose in rats are approximately 2–8 µg/mL, with Tmax ~0.5–2 hours and an elimination half-life of ~2–4 hours. Colonic microbiota can further metabolize unabsorbed taxifolin via C-ring cleavage to produce 3,4-dihydroxyphenylacetic acid and phloroglucinol. Water solubility is relatively low (~0.5–1 mg/mL at 25 °C, pH 7), which limits absorption; complexation with cyclodextrins or formulation as nanoparticles has been explored to enhance solubility and bioavailability in preclinical studies. • Other notable bioactive properties (in vitro/animal only): acts as an iron chelator (catechol B-ring), inhibits lipid peroxidation (IC₅₀ ~1–10 µM in membrane model systems), and serves as a substrate/intermediate in flavonoid biosynthesis (converted to leucocyanidin by dihydroflavonol 4-reductase, or to quercetin by flavonol synthase in plants). No established Dietary Reference Intake (DRI), Adequate Intake (AI), or Tolerable Upper Intake Level (UL) exists for taxifolin in any regulatory jurisdiction.