L-Pyroglutamic Acid
Compiled from published pharmacological and botanical literature. Not independently verified by Herbuno. Spotted an error or have a correction? Flag it below →
| Compound | L-Pyroglutamic acid (5-oxo-L-proline, L-PCA) |
|---|---|
| Chemical class | Cyclic lactam of L-glutamic acid — an internal amide, not a free amino acid |
| CAS | 98-79-8 (L-pyroglutamic acid) · 28874-51-3 (sodium L-PCA) |
| Molecular weight | 129.11 g/mol |
| Primary application | Natural moisturising factor humectant, usually as sodium PCA |
| Metabolic position | Gamma-glutamyl cycle intermediate; recycled by 5-oxoprolinase |
| Claim strength | High for the humectant and cycle chemistry; Emerging for nootropic claims |
| Buy from Herbuno | L-Pyroglutamic Acid Powder · L-Glutamic Acid 99% Powder |
| Origin | Processed / Sourced from India |
| MOQ | R&D 100 g / 250 g (subject to stock) · Pilot batch 1–5 kg · Bulk 10 kg, 25 kg and above |
| Lead Time | Dispatch within 72 hrs from stock · fresh-batch production (typically 50 kg+): 10 working days |
| Documentation | CoA & MSDS standard with every lot |
Name origin: "Pyro-" records how it was first made — by heating glutamic acid, which cyclises as the side-chain carboxyl condenses with the α-amino group to form a five-membered lactam ring. The systematic name 5-oxo-L-proline reflects the ring's relationship to proline, and in cosmetic nomenclature it is almost always called PCA, for pyrrolidone carboxylic acid.
Why it is not a free amino acid: Pyroglutamic acid has no free amino group; the nitrogen is locked in the lactam. That changes its chemistry substantially: it is a weaker acid than glutamic acid, far more soluble, does not participate in Maillard reactions in the normal way, and behaves as a small hygroscopic organic acid rather than as an amino acid. Those properties are the basis of its commercial use.
Biochemical position: Pyroglutamate is a genuine intermediate of the gamma-glutamyl cycle, the pathway by which glutathione is synthesised and degraded. 5-Oxoprolinase converts pyroglutamate back to glutamate at ATP cost, closing the cycle. Where that enzyme is deficient, or where glutathione synthesis is disrupted, pyroglutamate accumulates — the basis of 5-oxoprolinuria, which also occurs as an acquired high anion gap metabolic acidosis in glutathione-depleted patients, classically associated with paracetamol and with flucloxacillin.
The cosmetic application: Sodium PCA is one of the principal components of the skin's natural moisturising factor, the mixture of small hygroscopic solutes in the stratum corneum that holds water in the outer skin layers. It is produced in skin from filaggrin breakdown. Topically applied sodium PCA is a well-established humectant, and this is the material's largest and best-founded commercial use.
Evidence for L-Pyroglutamic Acid Applications
The natural moisturising factor role is the best-founded application and is genuinely endogenous rather than an analogy. The stratum corneum contains a mixture of small hygroscopic solutes — free amino acids, urea, lactate and PCA among them — produced largely from filaggrin proteolysis, and this natural moisturising factor is what retains water in the outer skin layers. PCA is one of its major constituents, and reduced NMF content is a recognised feature of dry and atopic skin. Topical sodium PCA is therefore replacing a constituent the skin makes for itself. Claim strength: High.
Sodium PCA rather than the free acid is the practical cosmetic article. The free acid is strongly acidic in solution, which is unsuitable for most leave-on formulations at the concentrations needed for a humectant effect; the sodium salt is near-neutral, extremely hygroscopic and freely soluble, and is what cosmetic ingredient listings name. A formulator specifying the free acid for a leave-on product generally wants the salt, and the free acid is the article for pH adjustment, for in-situ neutralisation, or as a synthetic intermediate. Claim strength: High.
The gamma-glutamyl cycle position is settled biochemistry with a clinical corollary worth knowing. 5-Oxoprolinase recycles pyroglutamate to glutamate at ATP cost, completing the cycle by which glutathione is synthesised and broken down. When glutathione synthesis is disrupted or glutathione is depleted, gamma-glutamylcysteine synthetase loses its feedback inhibition, gamma-glutamyl cyclotransferase activity rises, and pyroglutamate accumulates — producing 5-oxoprolinuria and a high anion gap metabolic acidosis, classically described with paracetamol and with flucloxacillin. Pyroglutamate is a marker of that state, not a cause of it. Claim strength: High.
The piracetam structural resemblance proves nothing and is frequently used as though it did. Piracetam is 2-oxo-1-pyrrolidineacetamide, which shares the 2-oxopyrrolidine ring with pyroglutamic acid, and that resemblance is routinely cited to imply that pyroglutamate derivatives inherit racetam pharmacology. Structural similarity does not transfer evidence: the racetams have their own pharmacology and their own trial literature, and pyroglutamic acid has neither. Arginine pyroglutamate and other PCA salts have been marketed on this reasoning with very thin supporting data. Claim strength: Emerging at best; the structural argument is not evidence.
Oral pyroglutamate has no established application. There is no body of controlled human evidence for pyroglutamic acid or its common salts on cognitive, mood or any other endpoint; the few studies that exist are small, old and generally examine specific salts rather than the free acid. Given that pyroglutamate is endogenously produced and recycled by a dedicated enzyme, and that its accumulation is a marker of metabolic derangement rather than a desirable state, the mechanistic case for oral supplementation is weak as well as untested. Claim strength: Emerging, and effectively absent.
One analytical use is worth stating because it recurs across this catalogue. Pyroglutamate is the characteristic degradation product of glutamine and glutamic acid in solution, forming under heat and particularly in acidic concentrated conditions, so pyroglutamate determination is the standard indicator of thermal and storage history for those materials. That is why pyroglutamic acid is specified as a limit test on glutamine and glutamate certificates, and why the pure material is needed as a reference standard. Claim strength: High.
Sourcing L-pyroglutamic acid from Herbuno. We supply L-pyroglutamic acid and L-glutamic acid.
For a leave-on cosmetic humectant, most enquiries actually want sodium PCA rather than the free acid, which is strongly acidic in solution — the free acid is the article for pH adjustment, in-situ neutralisation, synthesis or as an analytical reference standard. We will not support a nootropic claim on the piracetam structural resemblance: sharing a 2-oxopyrrolidine ring does not transfer racetam trial evidence. All lots ship with CoA and MSDS; request a quotation for pilot or bulk volumes.
Dosage & Formulator Specification
Inclusion depends entirely on the application and the two main ones differ by orders of magnitude. In topical cosmetic formulations sodium PCA is typically used in the range of roughly 0.2 to 4% depending on the format and the humectant load wanted, and is often paired with glycerin, urea and other NMF constituents rather than used alone. As an analytical reference standard the quantity follows the method. There is no established oral dose, because there is no established oral application.
Free acid or sodium salt is the first decision and is usually settled by pH. L-pyroglutamic acid is a moderately strong organic acid and gives acidic solutions, so at humectant concentrations in a leave-on product it will pull the formulation pH down further than most systems tolerate; sodium PCA is near-neutral and is what cosmetic ingredient declarations name. Where the free acid is specified deliberately, it is generally for pH adjustment, for neutralisation in situ with another base, or as a synthetic or analytical article.
Hygroscopicity is extreme and is the defining handling property. Both the free acid and particularly the sodium salt are strongly hygroscopic — sodium PCA is used as a humectant precisely because it holds water avidly — so the material will absorb atmospheric moisture, cake and deliquesce under ordinary storage. Sealed packaging with desiccant, humidity-controlled weighing and handling, and short open-container times are all necessary. Sodium PCA is commonly supplied as a 50% aqueous solution for exactly this reason, and for most cosmetic work the solution is the more practical article.
Solubility and stability are both favourable. Pyroglutamic acid is freely soluble in water, far more so than glutamic acid, because the lactam removes the zwitterionic character that limits the parent compound; it is stable to heat and across a broad pH range, though strongly alkaline conditions will hydrolyse the lactam back to glutamate. Having no free amino group, it does not participate in Maillard browning in the way amino acids do, which is an advantage in thermally processed formats.
For analytical control, specify identity and assay with optical rotation confirming L-configuration, since the D-form and the racemate exist and the ring carries the chiral centre. Specify L-glutamic acid as a limit test: it is both the starting material and the hydrolysis product, making it the direct indicator of material purity and storage history, and the relationship runs both ways since pyroglutamate is itself the degradation marker specified on glutamate and glutamine certificates. Water content matters given the hygroscopicity. Standard coverage includes heavy metals, residual solvents, microbiological limits, loss on drying and sulphated ash.
On claim construction, the position is clear in both directions and worth documenting for customers. Defensible: PCA is a major constituent of the skin's natural moisturising factor, produced endogenously from filaggrin breakdown, and topical sodium PCA is a well-established humectant replacing a constituent the skin makes for itself. Also defensible: pyroglutamate is a gamma-glutamyl cycle intermediate recycled by 5-oxoprolinase, and the standard degradation marker for glutamine and glutamate. Not defensible: cognitive or nootropic claims resting on the shared 2-oxopyrrolidine ring with piracetam, since structural similarity transfers no evidence and pyroglutamic acid has no controlled human trial literature of its own. A customer proposing an oral PCA nootropic is building on an analogy rather than a finding.
Frequently Asked Questions — L-Pyroglutamic Acid
What is PCA actually used for?
Topical humectancy, principally. PCA is one of the major constituents of the skin's natural moisturising factor — the mixture of small hygroscopic solutes in the stratum corneum, produced largely from filaggrin breakdown — and reduced NMF content is a recognised feature of dry and atopic skin. Topical sodium PCA replaces a constituent the skin makes itself.
Free acid or sodium salt?
Sodium salt for leave-on cosmetics. The free acid is a moderately strong organic acid and at humectant concentrations will pull formulation pH further down than most systems tolerate; sodium PCA is near-neutral and is what cosmetic declarations name. The free acid is for pH adjustment, in-situ neutralisation, synthesis or analytical reference.
Is the piracetam connection meaningful?
No. Piracetam is 2-oxo-1-pyrrolidineacetamide and shares the 2-oxopyrrolidine ring, and that resemblance is routinely cited to imply inherited racetam pharmacology. Structural similarity transfers no evidence — the racetams have their own trial literature and pyroglutamic acid has none. Arginine pyroglutamate and similar salts have been marketed on exactly this reasoning.
Any handling warning?
Extreme hygroscopicity, especially the sodium salt — which is used as a humectant precisely because it holds water avidly. Expect caking and deliquescence under ordinary storage. Sealed packaging with desiccant, humidity-controlled weighing, short open-container times. Sodium PCA is commonly supplied as a 50% aqueous solution, which is the more practical article for most cosmetic work.
Why does pyroglutamate appear on my glutamine certificates?
Because it is the characteristic degradation product. Glutamine and glutamic acid cyclise to pyroglutamate under heat and particularly in acidic concentrated conditions, so pyroglutamate determination is the standard indicator of thermal and storage history for those materials. The pure compound is needed as the reference standard.
What should I specify beyond assay?
L-glutamic acid as a limit test — it is both the starting material and the hydrolysis product, making it the direct indicator of purity and storage history. Also optical rotation, since the D-form and racemate exist and the ring carries the chiral centre, and water content given the hygroscopicity.