Cyclohexanecarboxylic Acid

Cyclohexanecarboxylic Acid at a Glance

Cyclohexanecarboxylic acid — hexahydrobenzoic acid, or CHCA — is a simple saturated alicyclic carboxylic acid: a cyclohexane ring bearing a single –COOH group. Structurally it is benzoic acid with its aromatic ring fully reduced (hexahydro-), and by the same logic it is the fully dearomatised end-member of the shikimate-pathway acids — the ring that quinic acid and shikimic acid carry, stripped of its hydroxyls and its double bonds.

On this site its relevance is deliberately narrow. Cyclohexanecarboxylic acid earns a page because it is the reductive colonic-microbial metabolite of quinic acid — the branch that runs opposite to the oxidative route toward protocatechuic acid. When gut bacteria ferment quinic acid (and the shikimic acid and benzoic acid in the same pool), one fork aromatises the ring toward phenolic and benzoic acids, while the other dehydroxylates and reduces it all the way to cyclohexanecarboxylic acid ^{1Reference 1Naranjo Pinta M et al. · 2018In vitroIn vitro gut metabolism of [U-¹³C]-quinic acid, the other hydrolysis product of chlorogenic acidView study →}. Completing that degradation map is the whole reason this molecule appears here.

The honest framing, up front: this is a metabolite, not a bioactive. Cyclohexanecarboxylic acid has essentially no standalone pharmacology — no therapeutic literature, no efficacy claims, no receptor story. Its interest is entirely as a fate: where quinic-acid carbon goes on the reductive branch, and what the body then does with the CHCA it receives. (It is also a bulk industrial chemical, a nylon-precursor intermediate, but that is chemistry, not biology.)

The Reductive Branch of Quinic-Acid Metabolism

The single fact that places this molecule on the site is its role at the reductive end of quinic-acid breakdown. Quinic acid reaches the colon largely intact — poorly absorbed in the small intestine, and mostly delivered bound into the chlorogenic acids — and there the microbiota do the chemistry, along two divergent routes ^{1Reference 1Naranjo Pinta M et al. · 2018In vitroIn vitro gut metabolism of [U-¹³C]-quinic acid, the other hydrolysis product of chlorogenic acidView study →}:

• Oxidative / aromatising branch → the ring aromatises and dehydrates toward protocatechuic acid and related phenolic and benzoic acids, which are ultimately conjugated to hippuric acid and excreted.
• Reductive / dehydroxylating branch → the ring is stripped of its hydroxyls and reduced to cyclohexanecarboxylic acid — this molecule — the saturated, aromatic-ring-free product ^{1Reference 1Naranjo Pinta M et al. · 2018In vitroIn vitro gut metabolism of [U-¹³C]-quinic acid, the other hydrolysis product of chlorogenic acidView study →}.

In the Naranjo Pinta et al. (2018) study that traced [U-¹³C]-quinic acid through in vitro human faecal fermentation, cyclohexanecarboxylic acid was identified as one of the labelled products, confirming it as a genuine microbial degradation product of the quinic-acid skeleton rather than a background contaminant ^{1Reference 1Naranjo Pinta M et al. · 2018In vitroIn vitro gut metabolism of [U-¹³C]-quinic acid, the other hydrolysis product of chlorogenic acidView study →}. The quinic acid page names it as exactly this — the reductive-route counterpart to protocatechuic acid — and this is the other half of that cross-reference.

The same reductive fate applies to the closely related acids. Shikimic acid and benzoic acid feed overlapping colonic pools, and cyclohexanecarboxylic acid sits at the reduced floor of all of them: whatever aromatic or partly-oxygenated ring goes in, full ring reduction gives the same saturated carboxylic acid out.

Metabolic Fate

Once formed, cyclohexanecarboxylic acid is not an endpoint — the body processes it further, and this is where the older, better-characterised literature sits. Two routes dominate, and both are detoxification/excretion routes rather than anything pharmacological.

The first is re-aromatisation. Mammalian tissues can run the ring the other way — oxidising cyclohexanecarboxylic acid back through partially unsaturated intermediates to benzoic acid, which is then glycine-conjugated to hippuric acid and excreted in urine. Svardal and Scheline characterised this “aromatisation” system in detail: they mapped its substrate specificity and marked species differences ^{2Reference 2Svardal AM · 1985The aromatization of cyclohexanecarboxylic acid to hippuric acid: substrate specificity and species differencesView study →} and localised the responsible activity within liver tissue ^{3Reference 3Svardal AM · 1985Intracellular localization and some properties of the system in guinea pig liver responsible for the aromatization of cyclohexanecarboxylic acid to hippuric acidView study →}. So a fraction of the CHCA that microbes make by reducing the ring is re-oxidised by the host and leaves as ordinary hippurate — the two directions coexist. This is the same overall aromatising story Adamson and colleagues had described for quinic acid itself, whose conversion to hippuric acid in vivo depends heavily on gut bacteria and shows large species differences ^{4Reference 4Adamson RH et al. · 1970AnimalSpecies differences in the aromatization of quinic acid in vivo and the role of gut bacteriaView study →}.

The second route is direct glycine conjugation without aromatisation. Cyclohexanecarboxylic acid is a substrate for the glycine-conjugation machinery, giving cyclohexanoylglycine (hexahydrohippuric acid) — the saturated analogue of hippuric acid — which appears in urine as a recognised minor metabolite. (β-oxidation-type ring degradation is also plausible for a small alicyclic acid, but is not the load-bearing route here.)

The practical upshot: cyclohexanecarboxylic acid is a transient intermediate. It is made by microbial ring reduction, and it leaves either as hippuric acid (after host re-aromatisation) or as cyclohexanoylglycine (after glycine conjugation). Its own residence and any “activity” are incidental to that clearance.

What It's Used For

There is little to report, and the honest thing is to say so plainly. Cyclohexanecarboxylic acid has no meaningful standalone pharmacology in the therapeutic sense — no controlled efficacy studies, no established mechanism at any human target, no traditional or supplemental use. The literature that exists is metabolic: tracer and enzymology work on how the molecule is made and cleared ^{1,2,3,4Reference 1Naranjo Pinta M et al. · 2018In vitroIn vitro gut metabolism of [U-¹³C]-quinic acid, the other hydrolysis product of chlorogenic acidView study →Reference 2Svardal AM · 1985The aromatization of cyclohexanecarboxylic acid to hippuric acid: substrate specificity and species differencesView study →Reference 3Svardal AM · 1985Intracellular localization and some properties of the system in guinea pig liver responsible for the aromatization of cyclohexanecarboxylic acid to hippuric acidView study →Reference 4Adamson RH et al. · 1970AnimalSpecies differences in the aromatization of quinic acid in vivo and the role of gut bacteriaView study →}, not on what it does.

Pharmacokinetics

There is no conventional pharmacokinetic profile for cyclohexanecarboxylic acid as an ingested agent, because it is not ingested as one — it arises in situ in the colon from quinic/shikimic/benzoic-acid fermentation ^{1Reference 1Naranjo Pinta M et al. · 2018In vitroIn vitro gut metabolism of [U-¹³C]-quinic acid, the other hydrolysis product of chlorogenic acidView study →}. What is characterised is its disposition once formed: it is a substrate for hepatic aromatisation (→ benzoic → hippuric acid) and for glycine conjugation (→ cyclohexanoylglycine), both leading to urinary excretion, and the balance between them varies by species and dose ^{2,3,4Reference 2Svardal AM · 1985The aromatization of cyclohexanecarboxylic acid to hippuric acid: substrate specificity and species differencesView study →Reference 3Svardal AM · 1985Intracellular localization and some properties of the system in guinea pig liver responsible for the aromatization of cyclohexanecarboxylic acid to hippuric acidView study →Reference 4Adamson RH et al. · 1970AnimalSpecies differences in the aromatization of quinic acid in vivo and the role of gut bacteriaView study →}. Plasma exposure in humans is not tabulated here; as a small, moderately lipophilic carboxylic acid it is expected to be handled like other simple aliphatic acids and cleared renally after conjugation.

Prevalence in Nature

Cyclohexanecarboxylic acid is not a notable plant constituent and does not accumulate in the herbs here. Its biological occurrence is as a trace metabolite — the reductive-branch product of colonic quinic/shikimic/benzoic-acid fermentation ^{1Reference 1Naranjo Pinta M et al. · 2018In vitroIn vitro gut metabolism of [U-¹³C]-quinic acid, the other hydrolysis product of chlorogenic acidView study →} and a minor endogenous/dietary metabolite that is re-aromatised or glycine-conjugated for excretion ^{2,3Reference 2Svardal AM · 1985The aromatization of cyclohexanecarboxylic acid to hippuric acid: substrate specificity and species differencesView study →Reference 3Svardal AM · 1985Intracellular localization and some properties of the system in guinea pig liver responsible for the aromatization of cyclohexanecarboxylic acid to hippuric acidView study →}. Outside biology it is a bulk industrial chemical (a caprolactam / nylon-6 intermediate and an intermediate in various syntheses), which is where most of the world’s cyclohexanecarboxylic acid actually is — but that is manufacturing, not natural abundance. No source-level table is given because there is no meaningful plant source to tabulate.

Toxicity & Safety

Cyclohexanecarboxylic acid carries a low flag in the context that matters here — as a transient endogenous/microbial metabolite present at trace levels, on a well-trodden clearance path to hippuric acid and cyclohexanoylglycine ^{2,3Reference 2Svardal AM · 1985The aromatization of cyclohexanecarboxylic acid to hippuric acid: substrate specificity and species differencesView study →Reference 3Svardal AM · 1985Intracellular localization and some properties of the system in guinea pig liver responsible for the aromatization of cyclohexanecarboxylic acid to hippuric acidView study →}. At the amounts formed from ordinary dietary quinic acid there is no toxicological concern; it is simply part of the aromatic-acid excretion economy.

The honest limits are those of any minor metabolite: as an industrial chemical the pure acid is a skin/eye irritant and is handled with normal laboratory precautions, and there is no human safety dossier for it as a deliberately-taken substance because it is not one. It is preclinical-only in the strict sense that everything known about it is tracer, enzymology or occupational data — none of it a human ingestion study.

Safety at a Glance

✅ Low / no toxicity

• A trace, transient metabolite. Formed in the colon from quinic/shikimic/benzoic-acid fermentation and cleared to hippuric acid or cyclohexanoylglycine — not something that accumulates ^{1,2,3Reference 1Naranjo Pinta M et al. · 2018In vitroIn vitro gut metabolism of [U-¹³C]-quinic acid, the other hydrolysis product of chlorogenic acidView study →Reference 2Svardal AM · 1985The aromatization of cyclohexanecarboxylic acid to hippuric acid: substrate specificity and species differencesView study →Reference 3Svardal AM · 1985Intracellular localization and some properties of the system in guinea pig liver responsible for the aromatization of cyclohexanecarboxylic acid to hippuric acidView study →}.
• No dietary-level concern. At the amounts arising from ordinary quinic-acid intake it is part of normal aromatic-acid excretion, with no characteristic toxicity.
• Not a supplement, no human dose. There is no ingestion, dosing or interaction data — it is a metabolic intermediate, and any figures in the literature are experimental, not recommendations.
• Industrial handling differs. As a bulk chemical the pure acid is an irritant handled with lab precautions; that context is separate from its trace biological role.

References

1. Naranjo Pinta M, Montoliu I, Aura AM, Seppänen-Laakso T, Barron D, Moco S (2018). In vitro gut metabolism of [U-¹³C]-quinic acid, the other hydrolysis product of chlorogenic acid. Molecular Nutrition & Food Research. https://pubmed.ncbi.nlm.nih.gov/30113130/
2. Svardal AM, Scheline RR (1985). The aromatization of cyclohexanecarboxylic acid to hippuric acid: substrate specificity and species differences. Molecular and Cellular Biochemistry. https://pubmed.ncbi.nlm.nih.gov/4047028/
3. Svardal AM, Scheline RR (1985). Intracellular localization and some properties of the system in guinea pig liver responsible for the aromatization of cyclohexanecarboxylic acid to hippuric acid. Molecular and Cellular Biochemistry. https://pubmed.ncbi.nlm.nih.gov/3982394/
4. Adamson RH, Bridges JW, Evans ME, Williams RT (1970). Species differences in the aromatization of quinic acid in vivo and the role of gut bacteria. The Biochemical Journal. https://pubmed.ncbi.nlm.nih.gov/4985157/