Hippuric Acid

Hippuric Acid at a Glance

Hippuric acid, or N-benzoylglycine, is the glycine conjugate of benzoic acid — a small aromatic acyl-glycine that the body makes to detoxify and excrete benzoate. It is one of the most abundant metabolites in human urine, and it matters here for an unusual reason: it is not a bioactive you take, but a downstream marker you measure ^{1Reference 1Brial F et al. · 2021Human and preclinical studies of the host–gut microbiome co-metabolite hippurate as a marker and mediator of metabolic healthView study →}. Almost every discussion of hippuric acid is really a discussion of what its concentration tells you — about diet, about the gut microbiome, about a chemical exposure, or about failing kidneys.

It sits at the terminal end of many metabolic funnels. Benzoic acid and benzoate preservatives, the polyphenols of coffee, tea, wine and fruit, chlorogenic acid and its quinic acid backbone, inhaled toluene, and the gut-microbial breakdown of aromatic amino acids all converge — via benzoic acid — on the same end-point: conjugation with glycine to hippurate, and excretion in urine ^{1,2,3Reference 1Brial F et al. · 2021Human and preclinical studies of the host–gut microbiome co-metabolite hippurate as a marker and mediator of metabolic healthView study →Reference 2Clifford MN et al. · 2020Bioavailability and metabolism of chlorogenic acids (acyl-quinic acids) in humansView study →Reference 3Pan Y et al. · 2025Gut microbiota may modify the association between dietary polyphenol intake and serum concentrations of hippuric acid: results from a 1-year longitudinal study in ChinaView study →}. Because so many inputs drain into this one molecule, its urinary level is a sensitive, integrative readout of aromatic-compound load.

The honest framing is therefore different from most compound entries. Hippuric acid’s “pharmacology” is mostly its diagnostic and physiological meaning: (1) a urinary biomarker of gut-microbiome activity and polyphenol intake; (2) an occupational biomarker of toluene exposure; and (3) a protein-bound uremic retention solute that accumulates in chronic kidney disease and is studied for its own vascular toxicity ^{1,6,7Reference 1Brial F et al. · 2021Human and preclinical studies of the host–gut microbiome co-metabolite hippurate as a marker and mediator of metabolic healthView study →Reference 6Daneshamouz S et al. · 2021Protein-bound uremic toxins (PBUTs) in chronic kidney disease (CKD) patients: production pathway, challenges and recent advances in renal PBUTs clearanceView study →Reference 7Shan X et al. · 2021Analytical techniques for monitoring of toluene and xylene exposure biomarkers hippuric acid and methylhippuric acid in human urine samplesView study →}. It is not a supplement, has no therapeutic dose, and its few “effects” are the effects of a retained waste product, not of a remedy.

How Hippuric Acid Is Made

The chemistry is a two-step, two-organ detoxification. First, a benzoate source — a dietary benzoic acid, a preservative, a microbial breakdown product, or oxidised toluene — is activated to benzoyl-CoA. Then the enzyme glycine N-acyltransferase (GLYAT) couples that benzoyl group to glycine, forming hippuric acid, which the kidney secretes into urine ^{1,6Reference 1Brial F et al. · 2021Human and preclinical studies of the host–gut microbiome co-metabolite hippurate as a marker and mediator of metabolic healthView study →Reference 6Daneshamouz S et al. · 2021Protein-bound uremic toxins (PBUTs) in chronic kidney disease (CKD) patients: production pathway, challenges and recent advances in renal PBUTs clearanceView study →}. This happens chiefly in the mitochondria of the liver and kidney, the tissues richest in the conjugating machinery.

Two features of this route explain the whole page. Because it consumes glycine and CoA, a large benzoate load (dietary or occupational) is drawn down through a finite conjugation capacity — the basis of both the historical liver-function test and toluene biomonitoring below. And because the immediate benzoate supply depends heavily on gut bacteria liberating and degrading dietary aromatics, urinary hippurate reflects microbiome activity as much as host metabolism ^{1,2Reference 1Brial F et al. · 2021Human and preclinical studies of the host–gut microbiome co-metabolite hippurate as a marker and mediator of metabolic healthView study →Reference 2Clifford MN et al. · 2020Bioavailability and metabolism of chlorogenic acids (acyl-quinic acids) in humansView study →}. The molecule is, quite literally, a host–microbe co-metabolite: the bacteria make the benzoate, the liver and kidney make the hippurate ^{1Reference 1Brial F et al. · 2021Human and preclinical studies of the host–gut microbiome co-metabolite hippurate as a marker and mediator of metabolic healthView study →}.

The Quinic-Acid & Polyphenol Connection

This site’s quinic acid page ends its gut-metabolism story here. Dietary chlorogenic acid — the dominant coffee polyphenol — is an ester of caffeic acid with quinic acid; colonic microbes hydrolyse it and ferment both halves down parallel aromatic-degradation routes, and the phenolic and benzoic acids that result are conjugated to hippuric acid and excreted ^{2,3Reference 2Clifford MN et al. · 2020Bioavailability and metabolism of chlorogenic acids (acyl-quinic acids) in humansView study →Reference 3Pan Y et al. · 2025Gut microbiota may modify the association between dietary polyphenol intake and serum concentrations of hippuric acid: results from a 1-year longitudinal study in ChinaView study →}. Quinic acid from cranberries, coffee and tea is a classic precursor of urinary hippurate for exactly this reason ^{2Reference 2Clifford MN et al. · 2020Bioavailability and metabolism of chlorogenic acids (acyl-quinic acids) in humansView study →}. Hippuric acid is, in other words, the terminal urinary metabolite of the quinic-acid / chlorogenic-acid gut cascade — the bucket those funnels empty into.

That makes urinary (and serum) hippurate a proxy for polyphenol-rich, plant-heavy eating. It rises with fruit, coffee, tea and wine intake and is associated with the Mediterranean-diet-type microbiome, which is why it recurs across nutritional-metabolomics studies as a marker of “how much plant polyphenol is passing through, and how actively the microbiome is processing it” ^{1,3,4Reference 1Brial F et al. · 2021Human and preclinical studies of the host–gut microbiome co-metabolite hippurate as a marker and mediator of metabolic healthView study →Reference 3Pan Y et al. · 2025Gut microbiota may modify the association between dietary polyphenol intake and serum concentrations of hippuric acid: results from a 1-year longitudinal study in ChinaView study →Reference 4Fernández-Cruz E et al. · 2025Urinary hippuric acid as a sex-dependent biomarker for fruit and nut intake raised from the EAT-Lancet index and nuclear magnetic resonance analysisView study →}.

What It's Used For

Read this section as biomarker validation and physiological consequence, not therapeutic efficacy. The “applications” below are the roles hippuric acid plays as a marker or a retained solute — diagnostic uses and pathophysiology, not benefits of ingesting it. There is nothing to ingest.

Evidence by IndicationStrength of support · Beta

Support here is an experimental score for how well-established each biomarker / physiological role is — weighted by study type and volume — not a therapeutic-efficacy score (hippuric acid is not a treatment). Read each row’s basis.

01Gut-Microbiome & Polyphenol-Intake BiomarkerPromising68%Multiple human cohorts + metabolomics; diet/diversity/metabolic-health associations ^{1,3,4,5Reference 1Brial F et al. · 2021Human and preclinical studies of the host–gut microbiome co-metabolite hippurate as a marker and mediator of metabolic healthView study →Reference 3Pan Y et al. · 2025Gut microbiota may modify the association between dietary polyphenol intake and serum concentrations of hippuric acid: results from a 1-year longitudinal study in ChinaView study →Reference 4Fernández-Cruz E et al. · 2025Urinary hippuric acid as a sex-dependent biomarker for fruit and nut intake raised from the EAT-Lancet index and nuclear magnetic resonance analysisView study →Reference 5Pallister T et al. · 2017Hippurate as a metabolomic marker of gut microbiome diversity: modulation by diet and relationship to metabolic syndromeView study →}

02Toluene / Occupational-Exposure BiomarkerPromising70%Long-established biomonitoring; ~80% of toluene excreted as hippurate ^{7,8Reference 7Shan X et al. · 2021Analytical techniques for monitoring of toluene and xylene exposure biomarkers hippuric acid and methylhippuric acid in human urine samplesView study →Reference 8Oginawati K et al. · 2021Urinary hippuric acid level as a biological indicator of toluene exposure on batik workersView study →}

03CKD Uremic Solute & Vascular-Risk MarkerPromising52%Protein-bound uremic-toxin literature + mechanistic endothelial study ^{6,9Reference 6Daneshamouz S et al. · 2021Protein-bound uremic toxins (PBUTs) in chronic kidney disease (CKD) patients: production pathway, challenges and recent advances in renal PBUTs clearanceView study →Reference 9Huang M et al. · 2018The uremic toxin hippurate promotes endothelial dysfunction via the activation of Drp1-mediated mitochondrial fissionView study →}

04Historical Liver-Function & Urinary-Antiseptic UseShaky20%Superseded historical clinical use (benzoate → hippurate)

Physiology & Formation

Step / determinant	What happens	Relevant to
Benzoate supply (diet, preservatives, microbial degradation of polyphenols/aromatic amino acids, oxidised toluene)	provides the benzoic acid substrate	all biomarker roles
Benzoyl-CoA + glycine → hippurate (glycine N-acyltransferase, GLYAT), in liver/kidney mitochondria	glycine conjugation forms the molecule	formation; the benzoate–hippurate liver test
Gut microbiota	liberate and degrade dietary aromatics into benzoate — rate-setting for dietary hippurate	microbiome/polyphenol biomarker
Renal tubular secretion	primary clearance route; efficient when kidneys are healthy	why CKD causes retention
Albumin binding (>90%)	keeps hippurate in plasma and resists dialysis	uremic-solute accumulation
Endothelial Drp1 / mitochondrial ROS	activated by retained hippurate → endothelial dysfunction	CKD cardiovascular risk

The through-line: hippurate is a detoxification end-product whose concentration is set by three independent taps — how much aromatic substrate comes in, how actively the microbiome and liver conjugate it, and how well the kidney clears it. Which tap is “talking” is the whole interpretive question.

Pharmacokinetics

There is no “dosing” pharmacokinetics for hippuric acid because it is an endogenous end-metabolite, but its disposition is the point of the page. It is formed by hepatic and renal glycine conjugation of benzoate, distributes in plasma highly albumin-bound (>90%), and is cleared almost entirely by the kidney via active tubular secretion, appearing in urine within hours of a benzoate or toluene load ^{6,7Reference 6Daneshamouz S et al. · 2021Protein-bound uremic toxins (PBUTs) in chronic kidney disease (CKD) patients: production pathway, challenges and recent advances in renal PBUTs clearanceView study →Reference 7Shan X et al. · 2021Analytical techniques for monitoring of toluene and xylene exposure biomarkers hippuric acid and methylhippuric acid in human urine samplesView study →}. In health this clearance is fast and near-complete, so urine is where hippurate is measured. In kidney failure the protein binding that speeds tubular secretion becomes a liability — bound solute is poorly dialysed — so plasma hippurate climbs ^{6Reference 6Daneshamouz S et al. · 2021Protein-bound uremic toxins (PBUTs) in chronic kidney disease (CKD) patients: production pathway, challenges and recent advances in renal PBUTs clearanceView study →}. Baseline excretion also varies widely between people with diet and microbiome composition, which is exactly what makes it a useful nutritional-metabolomics marker but a noisy one that needs context ^{1,3Reference 1Brial F et al. · 2021Human and preclinical studies of the host–gut microbiome co-metabolite hippurate as a marker and mediator of metabolic healthView study →Reference 3Pan Y et al. · 2025Gut microbiota may modify the association between dietary polyphenol intake and serum concentrations of hippuric acid: results from a 1-year longitudinal study in ChinaView study →}.

Clinical Use (Not Trials)

Hippuric acid is not trialled as a therapy; it is measured. Its established clinical/analytical roles are as a urinary biomarker — for toluene/solvent biomonitoring (occupational health), for diet and gut-microbiome status (nutritional metabolomics), and as a uremic retention solute tracked in CKD research ^{1,6,7Reference 1Brial F et al. · 2021Human and preclinical studies of the host–gut microbiome co-metabolite hippurate as a marker and mediator of metabolic healthView study →Reference 6Daneshamouz S et al. · 2021Protein-bound uremic toxins (PBUTs) in chronic kidney disease (CKD) patients: production pathway, challenges and recent advances in renal PBUTs clearanceView study →Reference 7Shan X et al. · 2021Analytical techniques for monitoring of toluene and xylene exposure biomarkers hippuric acid and methylhippuric acid in human urine samplesView study →}. There are no efficacy trials of hippuric acid as a treatment, because it is a waste product, not a drug.

Established as a biomarker	Investigational marker	Historical / obsolete	Not applicable
Toluene exposure (occupational); polyphenol intake / microbiome diversity	CKD uremic burden & cardiovascular-risk mediator	Benzoate–hippurate liver-function test; urinary antiseptic	Therapeutic dosing (none)

Last checked: July 2026.

Its Role in the Body

Hippuric acid is best understood as a disposal molecule. Benzoic acid — whether swallowed as a preservative, liberated by gut bacteria from dietary polyphenols, or generated by the liver from inhaled toluene — is mildly toxic and lipophilic; conjugating it with glycine makes it water-soluble, less reactive, and readily excreted ^{1,6Reference 1Brial F et al. · 2021Human and preclinical studies of the host–gut microbiome co-metabolite hippurate as a marker and mediator of metabolic healthView study →Reference 6Daneshamouz S et al. · 2021Protein-bound uremic toxins (PBUTs) in chronic kidney disease (CKD) patients: production pathway, challenges and recent advances in renal PBUTs clearanceView study →}. In that sense hippurate formation is a classic phase-II detoxification, comparable to glucuronidation or sulfation, and its steady presence in urine is a sign the pathway is working.

The twist is that this private housekeeping reaction turns out to be a window onto three systems at once — the diet and the microbiome that supply the substrate, the liver that conjugates it, and the kidney that excretes it. That is why a single, unglamorous end-metabolite ended up as one of the most-measured molecules in human metabolomics.

Prevalence in Nature

Unlike most compounds here, hippuric acid is not a plant constituent in any meaningful quantity — it is an animal (and human) urinary metabolite. Its name comes from horse urine (Greek hippos), from which it was first isolated in the 1820s, and it is abundant in the urine of humans and other mammals as the terminal product of benzoate metabolism ^{1Reference 1Brial F et al. · 2021Human and preclinical studies of the host–gut microbiome co-metabolite hippurate as a marker and mediator of metabolic healthView study →}. It occurs across mammalian urine broadly and rises with herbivorous, polyphenol-rich diets — grazing animals excrete large amounts — and in humans it scales with fruit, coffee, tea and wine intake and with the activity of the gut microbiome ^{1,3,4Reference 1Brial F et al. · 2021Human and preclinical studies of the host–gut microbiome co-metabolite hippurate as a marker and mediator of metabolic healthView study →Reference 3Pan Y et al. · 2025Gut microbiota may modify the association between dietary polyphenol intake and serum concentrations of hippuric acid: results from a 1-year longitudinal study in ChinaView study →Reference 4Fernández-Cruz E et al. · 2025Urinary hippuric acid as a sex-dependent biomarker for fruit and nut intake raised from the EAT-Lancet index and nuclear magnetic resonance analysisView study →}.

Where It Comes From

Origin	Basis	Note
Dietary benzoic acid / benzoate preservatives	direct substrate for glycine conjugation	E210–E213 preservatives, berries
Polyphenols (coffee, tea, wine, fruit) via gut microbes	chlorogenic acid/quinic acid → benzoate → hippurate	the diet/microbiome biomarker route 2,3Reference 2Clifford MN et al. · 2020Bioavailability and metabolism of chlorogenic acids (acyl-quinic acids) in humansView study →Reference 3Pan Y et al. · 2025Gut microbiota may modify the association between dietary polyphenol intake and serum concentrations of hippuric acid: results from a 1-year longitudinal study in ChinaView study →
Aromatic amino acids (phenylalanine) via gut microbes	microbial catabolism → benzoate	contributes microbiome-dependent baseline 1Reference 1Brial F et al. · 2021Human and preclinical studies of the host–gut microbiome co-metabolite hippurate as a marker and mediator of metabolic healthView study →
Inhaled toluene (occupational)	hepatic oxidation → benzoate → hippurate	~80% of absorbed toluene 7,8Reference 7Shan X et al. · 2021Analytical techniques for monitoring of toluene and xylene exposure biomarkers hippuric acid and methylhippuric acid in human urine samplesView study →Reference 8Oginawati K et al. · 2021Urinary hippuric acid level as a biological indicator of toluene exposure on batik workersView study →

Discovery & History

Hippuric acid has a long pedigree in the history of biochemistry. It was isolated from horse urine in the 1820s and named for that source, and it became an early proving ground for metabolic conjugation: nineteenth-century work (notably Wöhler and Keller) showed that feeding benzoic acid increases urinary hippuric acid, one of the first demonstrations that the body chemically transforms and detoxifies foreign compounds — an intellectual ancestor of modern drug metabolism. That same benzoate→hippurate relationship later became the benzoate–hippurate liver-function test. Today its history is mostly relevant as the origin of the analytical assays still used for toluene biomonitoring and nutritional metabolomics ^{7,8Reference 7Shan X et al. · 2021Analytical techniques for monitoring of toluene and xylene exposure biomarkers hippuric acid and methylhippuric acid in human urine samplesView study →Reference 8Oginawati K et al. · 2021Urinary hippuric acid level as a biological indicator of toluene exposure on batik workersView study →}.

Patents / industrial synthesis: not applicable — hippuric acid is measured as a metabolite, not manufactured as a product (reference-standard synthesis of benzoylglycine aside).

Toxicity & Safety

Hippuric acid carries a low flag, with important context. At the concentrations produced by a normal diet it is entirely benign — a rapidly excreted, water-soluble detoxification product that is present in everyone’s urine and that generally rises with healthier, plant-richer eating and a more diverse microbiome ^{1,5Reference 1Brial F et al. · 2021Human and preclinical studies of the host–gut microbiome co-metabolite hippurate as a marker and mediator of metabolic healthView study →Reference 5Pallister T et al. · 2017Hippurate as a metabolomic marker of gut microbiome diversity: modulation by diet and relationship to metabolic syndromeView study →}. It is not a supplement, is not ingested deliberately, and has no therapeutic dose to over-take.

The one setting where hippurate itself is implicated as harmful is kidney failure. As a protein-bound uremic retention solute, it accumulates when renal clearance fails, resists dialysis, and has been shown to promote endothelial dysfunction via mitochondrial-fission and ROS pathways — so in CKD it is studied as a contributor to cardiovascular risk, not merely a passive marker ^{6,9Reference 6Daneshamouz S et al. · 2021Protein-bound uremic toxins (PBUTs) in chronic kidney disease (CKD) patients: production pathway, challenges and recent advances in renal PBUTs clearanceView study →Reference 9Huang M et al. · 2018The uremic toxin hippurate promotes endothelial dysfunction via the activation of Drp1-mediated mitochondrial fissionView study →}. This is a consequence of retention in disease, not a risk of the molecule at ordinary levels.

Safety at a Glance

✅ Low / no toxicity

• A benign, universal detox metabolite at dietary levels. Present in everyone’s urine; its formation (glycine conjugation of benzoate) is a normal phase-II detoxification, and higher levels usually track a healthier plant-rich diet.
• Not a supplement — nothing to over-take. Hippuric acid is measured, not ingested; there is no therapeutic dose and no self-dosing scenario.
• A uremic toxin in kidney disease. Being >90% albumin-bound, it accumulates and is poorly dialysed in CKD, where it is linked to endothelial dysfunction and cardiovascular risk.
• Context decides its meaning. The same value can signal a polyphenol-rich diet, a solvent exposure, or a failing kidney — never interpret hippuric acid in isolation.

Pregnancy/lactation is not adjudicated here: hippuric acid is an endogenous metabolite, not an administered agent, so no isolate-specific reproductive verdict applies.

Dosage

Not applicable. Hippuric acid is an endogenous urinary metabolite and biomarker, not a supplement or drug — there is no recommended or therapeutic dose, and it is not taken deliberately. The only numbers attached to it are diagnostic: urinary hippuric acid reference/action levels for toluene biomonitoring in occupational health, and research measurements of serum/urinary hippurate as a diet, microbiome or CKD marker ^{1,6,7Reference 1Brial F et al. · 2021Human and preclinical studies of the host–gut microbiome co-metabolite hippurate as a marker and mediator of metabolic healthView study →Reference 6Daneshamouz S et al. · 2021Protein-bound uremic toxins (PBUTs) in chronic kidney disease (CKD) patients: production pathway, challenges and recent advances in renal PBUTs clearanceView study →Reference 7Shan X et al. · 2021Analytical techniques for monitoring of toluene and xylene exposure biomarkers hippuric acid and methylhippuric acid in human urine samplesView study →}. Those are values to interpret, not doses to take.

References

1. Brial F, Chilloux J, Nielsen T, et al. (2021). Human and preclinical studies of the host–gut microbiome co-metabolite hippurate as a marker and mediator of metabolic health. Gut. https://pubmed.ncbi.nlm.nih.gov/33975870/
2. Clifford MN, Kerimi A, Williamson G (2020). Bioavailability and metabolism of chlorogenic acids (acyl-quinic acids) in humans. Comprehensive Reviews in Food Science and Food Safety. https://pubmed.ncbi.nlm.nih.gov/33337099/
3. Pan Y, Yang Y, Peng Q, et al. (2025). Gut microbiota may modify the association between dietary polyphenol intake and serum concentrations of hippuric acid: results from a 1-year longitudinal study in China. American Journal of Clinical Nutrition. https://pubmed.ncbi.nlm.nih.gov/39837385/
4. Fernández-Cruz E, de la O V, Fernández-Diaz CM, et al. (2025). Urinary hippuric acid as a sex-dependent biomarker for fruit and nut intake raised from the EAT-Lancet index and nuclear magnetic resonance analysis. Metabolites. https://pubmed.ncbi.nlm.nih.gov/40559371/
5. Pallister T, Jackson MA, Martin TC, et al. (2017). Hippurate as a metabolomic marker of gut microbiome diversity: modulation by diet and relationship to metabolic syndrome. Scientific Reports. https://pubmed.ncbi.nlm.nih.gov/29057986/
6. Daneshamouz S, Eduok U, Abdelrasoul A, Shoker A (2021). Protein-bound uremic toxins (PBUTs) in chronic kidney disease (CKD) patients: production pathway, challenges and recent advances in renal PBUTs clearance. NanoImpact. https://pubmed.ncbi.nlm.nih.gov/35559786/
7. Shan X, Zhang L, Ye H, et al. (2021). Analytical techniques for monitoring of toluene and xylene exposure biomarkers hippuric acid and methylhippuric acid in human urine samples. Bioanalysis. https://pubmed.ncbi.nlm.nih.gov/34696600/
8. Oginawati K, Anka AAH, Susetyo SH, et al. (2021). Urinary hippuric acid level as a biological indicator of toluene exposure on batik workers. Heliyon. https://pubmed.ncbi.nlm.nih.gov/34430750/
9. Huang M, Wei R, Wang Y, Su T, Li P, Chen X (2018). The uremic toxin hippurate promotes endothelial dysfunction via the activation of Drp1-mediated mitochondrial fission. Redox Biology. https://pubmed.ncbi.nlm.nih.gov/29573704/
10. Li W, Dong H, Niu K, et al. (2024). Analyzing urinary hippuric acid as a metabolic health biomarker through a supramolecular architecture. Talanta. https://pubmed.ncbi.nlm.nih.gov/38972275/

View all 10 references▾