Ellagic acid

Ellagic acid (C₁₄H₆O₈, MW 302.19 g/mol) is a polyphenolic dilactone found naturally in various fruits and nuts. It is not a macronutrient or micronutrient source itself but rather a bioactive phytochemical. Key details: • Dietary sources and approximate concentrations: raspberries (150–300 mg/100g dry weight), strawberries (40–70 mg/100g dry weight), blackberries (150–200 mg/100g dry weight), pomegranates (50–100 mg/100g juice weight, with much higher concentrations in peel/husk at 2,000–5,000 mg/100g dry weight), walnuts (50–80 mg/100g), pecans (30–60 mg/100g). • Ellagic acid exists predominantly as ellagitannins (such as punicalagin in pomegranate and sanguiin H-6 in raspberries) which are hydrolyzed in the gut to release free ellagic acid. • Bioavailability is notably poor: oral absorption of free ellagic acid is limited (estimated <5% bioavailability) due to low aqueous solubility (~10 μg/mL at physiological pH), rapid first-pass metabolism, and binding to proteins/fiber in the food matrix. Peak plasma concentrations after dietary intake typically reach only 30–100 nM. • A critical metabolic pathway involves gut microbiota conversion of ellagic acid to urolithins (primarily urolithin A, urolithin B, and isourolithin A), which have substantially higher bioavailability and longer half-lives (plasma t½ ~24–48 hours vs. ~1–4 hours for ellagic acid). Urolithin production is highly variable between individuals, with approximately 40% classified as 'metabotype A' (producing primarily urolithin A), 25% as 'metabotype B' (producing urolithin B and isourolithin A), and ~10–15% as 'metabotype 0' (non-producers). • Contains no appreciable calories, protein, fat, carbohydrate, vitamins, or minerals at supplemental doses (typically 100–500 mg/day in clinical trials). • Supplemental forms include free ellagic acid powder, pomegranate extract standardized to 40–90% ellagitannins/ellagic acid, and raspberry seed extract. Nanoformulations and lipid-based delivery systems have shown 3–6 fold improvements in bioavailability in preclinical models. • Key bioactive properties include strong antioxidant capacity (ORAC value comparable to or exceeding many flavonoids), direct free radical scavenging of superoxide and hydroxyl radicals, metal chelation (particularly iron and copper), and inhibition of NF-κB signaling pathway and pro-inflammatory cytokine expression (TNF-α, IL-6, IL-1β).