Naringin (Flavanone Glycoside)

Naringin (naringenin-7-O-neohesperidoside; C₂₇H₃₂O₁₄; MW 580.53 g/mol) is a flavanone glycoside, not a macronutrient source — it provides negligible calories, protein, fat, or fiber. Its significance is entirely as a bioactive polyphenolic compound. Key profile details: • Primary bioactive compound: Naringin itself, typically found at 100–600 mg per liter of grapefruit juice; whole grapefruit peel and albedo contain 2–10% naringin by dry weight. Pomelo peel can contain up to 15–20% by dry weight. • Aglycone (active metabolite): Naringenin (MW 272.26 g/mol), released by intestinal bacterial hydrolysis of the rhamnose-glucose disaccharide (neohesperidose) moiety. Naringenin is the principal absorbed form. • Bioavailability: Oral bioavailability of intact naringin is low (~5–8% in animal models). Absorption depends heavily on colonic microflora (e.g., Bacteroides spp.) cleaving the sugar moiety to yield naringenin, which is then absorbed and undergoes extensive phase II hepatic conjugation (glucuronidation and sulfation). Peak plasma concentrations of total naringenin metabolites after 500 mg oral naringin typically reach ~1–6 µmol/L (Tmax ~3–6 hours). Enteric recycling extends the elimination half-life to approximately 2–3 hours for naringenin conjugates. • Key micronutrient co-occurrence (when consumed via whole grapefruit): Vitamin C (~38 mg per fruit), potassium (~166 mg per 100 g), folate (~13 µg per 100 g), dietary fiber (~1.6 g per 100 g), and co-occurring flavonoids including hesperidin, narirutin, and furanocoumarins (bergamottin, 6',7'-dihydroxybergamottin — relevant to CYP3A4/CYP1A2 inhibition and drug interactions). • Other polyphenolic co-constituents in citrus matrix: Hydroxycinnamic acids (ferulic acid, p-coumaric acid), limonoids (limonin ~5–30 mg/L in juice), and carotenoids (β-cryptoxanthin, lycopene in pink/red grapefruit). • Supplemental dosing context: Human clinical trials (e.g., NCT01091077) have used 150–900 mg/day of purified naringin. Commercial supplements typically provide 500 mg per capsule of naringin extract (≥95% purity). • Solubility and formulation notes: Naringin has limited water solubility (~1 mg/mL at 25°C), contributing to its poor bioavailability. Naringin complexed with cyclodextrins or delivered as phospholipid complexes (phytosomes) can improve absorption 2–4 fold. Nanoformulations under investigation report up to 6-fold bioavailability enhancement in preclinical models. • Caloric/macronutrient contribution: Essentially zero at supplemental doses; when consumed via grapefruit (per 100 g raw): ~42 kcal, 0.77 g protein, 0.14 g fat, 10.7 g carbohydrate, 1.6 g fiber.