Urolithin A

Urolithin A (3,8-dihydroxy-6H-dibenzo[b,d]pyran-6-one) is a dibenzopyranone metabolite produced by the human gut microbiota through sequential dehydroxylation of ellagic acid, itself the hydrolysis product of dietary ellagitannins found in pomegranates, walnuts, raspberries, and strawberries. The compound was first characterized as a bioactive ellagitannin metabolite in human plasma and urine by the Tomas-Barberan and Espin laboratories at CEBAS-CSIC (Murcia, Spain) in the early 2000s and was subsequently identified by the Auwerx laboratory at the Ecole Polytechnique Federale de Lausanne (EPFL) as a potent, first-in-class inducer of mitophagy in Caenorhabditis elegans and in mammalian systems through the PINK1/Parkin-dependent mitochondrial quality control pathway. The seminal Ryu et al. (2016) report in Nature Medicine demonstrated that urolithin A extends lifespan in C. elegans, improves exercise capacity in aged rodents, and induces a molecular signature of mitophagy in skeletal muscle, establishing the compound as the first dietary metabolite with demonstrated mitophagy-inducing activity at physiologically achievable concentrations [1]. Amazentis SA (Lausanne, Switzerland) subsequently developed a synthetic, pharmaceutical-grade form of urolithin A (marketed as Mitopure) and advanced the compound through a series of randomized, placebo-controlled clinical trials in human subjects. The first-in-human trial (Andreux et al. 2019, Nature Metabolism) demonstrated safety, oral bioavailability, and upregulation of mitochondrial gene expression in skeletal muscle of 60 healthy elderly subjects at doses of 250 to 2000 mg administered over 28 days [2]. A subsequent four-month randomized trial in 88 middle-aged adults (Singh et al. 2022, Cell Reports Medicine) demonstrated significant improvement in muscle strength (approximately 12 percent increase in hamstring muscle strength) and exercise performance at 500 mg and 1000 mg daily doses, with concurrent improvement in plasma biomarkers of mitochondrial health [3]. A parallel randomized trial (Liu et al. 2022, JAMA Network Open) in 66 older adults confirmed improvement in muscle endurance at 1000 mg daily over four months [4]. Most recently, a 2025 randomized trial (Singh et al. 2025, Nature Aging) in 50 healthy middle-aged adults demonstrated that 1000 mg daily urolithin A for four weeks expanded peripheral naive-like CD8+ T cell populations, reduced markers of T cell exhaustion, and increased CD8+ fatty acid oxidation capacity, establishing the first clinical evidence of urolithin A activity on immune senescence [5]. The molecular pharmacology of urolithin A extends beyond mitophagy induction to include activation of AMP-activated protein kinase (AMPK), inhibition of mechanistic target of rapamycin (mTOR), activation of sirtuin 1 (SIRT1) with consequent deacetylation of peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1alpha) to promote mitochondrial biogenesis, suppression of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-kappaB) signaling with reduction of proinflammatory cytokines, and inhibition of dual-specificity tyrosine phosphorylation-regulated kinase 1A (DYRK1A) relevant to Alzheimer’s disease pathology. Pharmacokinetics in humans are characterized by intestinal absorption followed by extensive hepatic phase II conjugation (glucuronidation and sulfation), producing circulating glucuronide and sulfate conjugates with peak plasma concentrations at approximately 6 to 8 hours and elimination half-lives of 17 to 24 hours for the predominant glucuronide species. The compound received Generally Recognized as Safe (GRAS) status from the United States Food and Drug Administration in 2018 (GRN 000791) at dietary intake levels up to 1000 mg per serving. Preclinical safety assessment established a no-observed-adverse-effect level (NOAEL) of 3451 mg/kg/day in male rats and 3826 mg/kg/day in female rats in a 90-day oral toxicity study, with no evidence of genotoxicity or mutagenicity. This monograph reviews the chemistry, endogenous biosynthesis, and chemical synthesis of urolithin A; the multi-target molecular pharmacology encompassing mitophagy, mitochondrial biogenesis, anti-inflammatory, and neuroprotective mechanisms; the human pharmacokinetic profile including interindividual variability driven by gut microbiome metabotype; the clinical evidence base across muscle function, immune health, and emerging neurodegenerative and cardiometabolic indications; sourcing and quality verification for research applications; reconstitution and handling; stack interaction considerations; adverse-event profile; and a structured comparative assessment of five mitochondrial-targeted compounds against urolithin A on five competency standards.