Urolithin A Analysis Service — Free, Conjugated and Total Urolithin A Quantification by LC-MS/MS

Urolithin A Analysis — Why Free vs Conjugated Quantification Matters

Urolithin A is not directly present in food. Gut bacteria produce it from ellagitannins — polyphenols in pomegranates, berries, and walnuts — but only 30-40% of individuals harbor the necessary microbes, a classic example of gut microbial metabolism determining systemic metabolite exposure. Once absorbed, urolithin A is rapidly conjugated by hepatic phase II enzymes. In human plasma, over 95% circulates as glucuronide or sulfate — less than 5% remains free.

This creates an analytical challenge that most methods do not address. A standard LC-MS/MS method without hydrolysis measures only free UA — missing over 95% of the circulating pool. A method with enzymatic deconjugation measures total UA — but cannot distinguish parent from metabolites.

The clinically relevant endpoint depends on your question: free UA for target engagement, total UA for bioavailability, and the free/total ratio as a marker of phase II conjugation capacity. Our method delivers all three from one sample.

Our method quantifies all three fractions — free, conjugated (by difference), and total — in a single workflow:

• Free urolithin A — measured directly in plasma or tissue extract without enzymatic treatment; represents the biologically active pool available for mitophagy activation and receptor binding.
• Total urolithin A — measured after β-glucuronidase/sulfatase hydrolysis; represents the sum of free + glucuronidated + sulfated UA; the relevant endpoint for bioavailability and PK studies.
• Conjugated fraction — calculated as total minus free; indicates the extent of phase II metabolism and can serve as a marker of hepatic conjugation capacity or inter-individual variability in UA pharmacokinetics.

What Problem Do We Solve?

Three analytical gaps make most urolithin A data unreliable — and each has a specific solution in our method:

• Measuring only free UA misses over 95% of the circulating pool. Without enzymatic hydrolysis, a standard LC-MS/MS method reports only the free fraction — which can be undetectable even after a 500 mg oral dose. Our β-glucuronidase/sulfatase step releases conjugated UA for total UA quantification that reflects actual systemic exposure.
• UA producer variability confounds study results. Only 30-40% of individuals harbor the gut bacteria needed to produce urolithin A from ellagitannins. Studies that do not screen for producer status at baseline risk diluting treatment effects with non-responders. Our panel confirms producer status before randomization.
• Urolithin B, urolithin C, and iso-urolithin A add metabolic context. The UA/UB/UC ratio reflects gut microbial consortium composition and ellagitannin conversion efficiency. These urolithins are available as add-on analytes using the same extraction and UHPLC method.

Urolithin A Detection Panel — Free, Conjugated and Total Quantification

Standard panel: free UA + total UA. Expanded panel: + urolithin B, urolithin C, iso-urolithin A. Contact us for custom configurations including tissue-specific protocols or high-throughput PK study support.

Instrumentation — UHPLC-MS/MS Platform and Method Performance

Urolithin A Analysis Workflow — From Sample to Free, Conjugated and Total UA Quantification

Why Choose Our Urolithin A Analysis?

• Free + Total UA from One Sample — The Distinction That Matters
  Over 95% of circulating urolithin A is conjugated. A standard LC-MS/MS method without hydrolysis measures only the free fraction — which can be undetectable even after a therapeutic dose. Our method splits your sample: one aliquot for direct free UA, one for enzymatic hydrolysis followed by total UA. One sample, two results, the complete PK picture.
• Clinical-Trial-Ready Sensitivity — LOD 0.05 ng/mL
  Plasma free urolithin A concentrations after oral dosing are in the low ng/mL range. A method with LOD of 1 ng/mL or higher will miss the free fraction entirely. Our UHPLC-MS/MS method achieves LOD 0.05 ng/mL and LOQ 0.1 ng/mL using urolithin A-d3 internal standard — validated per ICH M10 guidance for bioanalytical method validation.
• Multi-Matrix Validated — No Method Re-Development Per Study
  The same LC-MS/MS method has been validated across plasma, serum, urine, feces, and tissue homogenates. For PK studies requiring serial plasma sampling plus tissue distribution at terminal sacrifice, you use one method, one set of MRM transitions, one calibration range — not separate assays per matrix.
• UA Producer Status Confirmation at Baseline
  Because only 30-40% of individuals can convert ellagitannins to urolithin A, studies that do not confirm producer status at screening risk including non-responders. Our panel quantifies baseline UA in plasma and urine, enabling you to exclude non-producers before randomization — reducing variability and increasing statistical power.

Sample Requirements for Urolithin A Analysis — Plasma, Urine, Tissue and Feces

Critical Notes:

• UA producer status must be confirmed at baseline. Only 30-40% of individuals can produce urolithin A from dietary ellagitannins. For intervention studies, screen all participants for plasma UA after a standardized ellagitannin challenge and exclude non-producers before randomization.
• Enzymatic hydrolysis efficiency must be verified per batch. Include a hydrolysis control (UA-glucuronide standard) in each batch to confirm β-glucuronidase/sulfatase activity. Incomplete hydrolysis under-reports total UA.
• UA is light-sensitive. Protect samples from direct light during collection and processing. Use amber tubes or wrap in aluminum foil if clear tubes must be used.

Deliverables — Free UA, Total UA, and Conjugated UA Quantification

Applications of Urolithin A Quantification

Case Study: Urolithin A First-in-Human Trial Establishes Safety and Mitochondrial Health Benefits

The Mitophagy Activator Urolithin A Is Safe and Induces a Molecular Signature of Improved Mitochondrial and Cellular Health in Humans

Andreux, P. A., Blanco-Bose, W., Ryu, D., Burdet, F., Ibberson, M., Aebischer, P., Auwerx, J., Singh, A., and Rinsch, C. | Nature Metabolism, 2019, 1(6), 595–603

DOI: 10.1038/s42255-019-0073-4

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Background

Urolithin A had shown potent mitophagy-activating and anti-aging effects in preclinical models — extending lifespan in C. elegans and improving muscle function in aged mice — but had never been tested in humans. The key questions: is it safe at clinically relevant doses, is it bioavailable after oral administration, and does it produce the same mitochondrial health signature observed in preclinical models?

Challenge: Conduct the first-in-human clinical trial of urolithin A, establishing safety, pharmacokinetics, and pharmacodynamic biomarkers of mitochondrial health across a range of doses.

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Key Findings

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What This Means for Your Urolithin A Research

• Plasma UA quantification is the primary PK endpoint. This trial established LC-MS/MS-based UA quantification as the analytical method for determining systemic exposure. Our panel uses the same analytical approach — free UA and total UA by UHPLC-MS/MS with isotope-dilution — providing PK data directly comparable to the published literature.
• Dose-proportional PK enables formulation bridging studies. The trial demonstrated linear PK across the 250–2,000 mg range. For supplement companies developing new UA formulations, our panel provides the bioanalytical support to demonstrate bioequivalence or superiority to the reference formulation used in this trial.
• Acylcarnitines are the pharmacodynamic biomarker — and they are on a separate panel. The trial used plasma acylcarnitine modulation as the PD readout for mitochondrial health. Our UA panel quantifies the PK endpoint; acylcarnitine profiling for PD is available through our fatty acid analysis service.

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Conclusion

This first-in-human trial validated urolithin A as a safe, bioavailable mitophagy activator and established the PK/PD framework used by every subsequent UA clinical trial. Our UA analysis panel provides the same bioanalytical capability — free and total UA quantification by UHPLC-MS/MS — enabling you to generate PK data directly comparable to this landmark study.

Read the full paper: Andreux et al., Nature Metabolism, 2019