A quiet analytical research laboratory at night, racks of glass vials along a dim bench.

Urolithin A

Urolithin A is made by gut bacteria from ellagitannins in pomegranate, berries and walnuts, but many people produce little or none. Direct supplementation bypasses that microbial step. It has a US GRAS notice and small human trials on muscle endpoints; it is not an approved drug.

Biology and mechanism

Urolithin A (228 Da) is a dibenzopyranone formed from ellagic acid by specific gut microbes. In C. elegans and rodents it induced mitophagy, the selective removal of damaged mitochondria, and improved muscle function markers. Individuals fall into urolithin metabotypes: some produce urolithin A, some produce other urolithins, and some produce almost none, so dietary precursors give unpredictable exposure. That variability is a reason direct supplementation became the commercial route rather than ellagitannin-rich foods or extracts.

Human evidence and status

A first-in-human study showed oral urolithin A was bioavailable and modulated mitochondrial gene expression in muscle. Randomized trials in older adults and in middle-aged adults reported changes in some muscle endurance and strength measures and in plasma biomarkers, while other endpoints did not change. In the US, synthetic urolithin A is the subject of a GRAS notice to which FDA raised no questions. It is not an approved drug and not on the WADA Prohibited List.

The delivery problem

Urolithin A is poorly water-soluble and is extensively converted to glucuronide and sulfate conjugates after absorption, so circulating parent compound is a small share of total urolithin. Doses in trials were 500 to 1000 mg per day, large for a capsule and for a food matrix. Solubility, dose load and consistency between individuals are the formulation questions. A high powder load also affects capsule count, which influences how consistently people take a product.

Formulation routes in use

Commercial products use micronized powder in capsules and dispersions in food formats. Solubility-enhanced forms are an active area, but published comparative human pharmacokinetics are scarce. Because urolithin A crystallizes readily, amorphous dispersions must be protected from moisture and heat that trigger recrystallization during storage. Food formats such as drinks and bars add pH, water activity and processing heat to the stability question. Any product claim linked to muscle function also faces the regulatory limits on health claims in each market, independent of the delivery form chosen.

Key facts

Urolithin A induced mitophagy and extended lifespan in C. elegans and improved muscle function in rodents (Ryu et al. 2016, Nat Med 22:879)
Oral urolithin A was bioavailable in humans and modulated mitochondrial and cellular biomarkers in a first-in-human trial (Andreux et al. 2019, Nat Metab 1:595)
In a 4-month randomized trial in adults aged 65 to 90, urolithin A improved some muscle endurance measures but not the primary 6-minute walk endpoint (Liu et al. 2022, JAMA Netw Open 5:e2144279)
Urolithin A production from ellagitannins varies between individuals according to gut microbial metabotype (Tomás-Barberán et al. 2017, Mol Nutr Food Res 61:1500901)

How our delivery technology applies

The case for encapsulation is dose efficiency. Presenting urolithin A in an amorphous, solubilized core inside a biopolymer shell could raise the fraction that dissolves and is absorbed from each dose, which matters when current doses are 500 mg or more. A controlled-release outer layer spreads absorption over more of the small intestine. Conjugation after absorption is not changed by the shell. Any dose reduction must be proven in a comparative PK study before it is claimed.

Explore a lower-dose, solubilized urolithin A format in a feasibility study.