Hesperetin

Hesperetin (molecular formula: C₁₆H₁₄O₆; MW: 302.28 g/mol) is a flavanone aglycone, not a food consumed for macronutrient value. It is the aglycone (sugar-free) form of hesperidin, released in the colon by bacterial β-glucosidases (primarily Bifidobacterium and Lactobacillus species) cleaving the rutinoside moiety. Key bioactive characteristics: • Classification: Flavanone subclass of flavonoids; 4'-methoxy-5,7-dihydroxyflavanone. • Natural concentrations in food sources: Found indirectly via hesperidin in sweet orange peel (~28–42 mg hesperidin/g dry weight), lemon peel (~15–25 mg/g dry weight), grapefruit juice (~1–5 mg/100 mL as hesperidin equivalents), and whole oranges (~20–40 mg hesperidin per fruit). Free hesperetin in intact fruit is negligible (<0.5 mg/100 g); it is generated almost entirely by gut microbial deglycosylation. • Bioavailability: Oral bioavailability of hesperetin from hesperidin is estimated at ~3–6% in humans (Tmax ~4–7 hours reflecting colonic liberation). When administered as hesperetin-7-O-glucoside (a more soluble precursor), absorption is faster (Tmax ~1–2 hours) and peak plasma concentrations are ~3–5× higher than from hesperidin. Plasma concentrations typically reach 0.1–2.2 µmol/L after single doses of 130–500 mg hesperidin equivalents. • Phase II metabolism: Extensively conjugated in intestinal epithelium and liver to hesperetin-7-O-glucuronide (major circulating metabolite, ~70–87% of plasma flavanone pool), hesperetin-3'-O-glucuronide, and hesperetin sulfates. Free (unconjugated) hesperetin in plasma is <5% of total. • Key functional groups: Two phenolic hydroxyl groups (C-5, C-7) and one methoxy group (C-4') contribute to antioxidant capacity (ORAC ~2.5–3.0 µmol Trolox equivalents/µmol). The 4'-OCH₃ reduces radical-scavenging potency relative to eriodictyol (the fully hydroxylated analog) but enhances lipophilicity (log P ~2.6) and membrane permeability. • Micronutrient/macronutrient content: Not applicable — hesperetin is a phytochemical, not a source of vitamins, minerals, protein, fiber, or caloric energy at physiologically relevant intake levels. • Solubility: Poorly water-soluble (~12–18 µg/mL at 25 °C, pH 7.0); solubility increases at alkaline pH due to phenolate formation. Lipid-based delivery systems, cyclodextrin complexation, and nanoformulations have been shown to improve solubility 5–20×. • Interactions with nutrients: In vitro evidence suggests hesperetin can chelate iron (Fe²⁺/Fe³⁺) and copper (Cu²⁺) at micromolar concentrations, potentially modulating metal-catalyzed oxidation but unlikely to affect mineral absorption at dietary intakes. May modulate P-glycoprotein and CYP3A4 activity at high concentrations (IC₅₀ ~10–50 µmol/L in vitro), with theoretical but clinically unconfirmed effects on drug/nutrient bioavailability.