L-Aspartic 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-Aspartic acid (L-aspartate) |
|---|---|
| Chemical class | Non-essential acidic α-amino acid — two carboxyl groups |
| CAS | 56-84-8 (L-aspartic acid) · 1783-96-6 (D-aspartic acid) · 617-45-8 (DL-) |
| Molecular weight | 133.10 g/mol · isoelectric point approx. 2.8 |
| Not to be confused with | D-aspartic acid — a distinct compound with separate claims |
| Key applications | Urea cycle, malate-aspartate shuttle, purine and pyrimidine synthesis, mineral aspartate salts |
| Claim strength | High for the metabolic biochemistry; no supplementation evidence for the L-form |
| Buy from Herbuno | L-Aspartic Acid 99% Powder · D-Aspartic 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: From Asparagus, via asparagine, which Vauquelin and Robiquet isolated from asparagus juice in 1806 — the first amino acid ever isolated. Aspartic acid was obtained by Plisson in 1827 by hydrolysing asparagine, which is simply the amide of aspartic acid. The two carboxyl groups make aspartate one of the two acidic amino acids, with an isoelectric point near pH 2.8.
Biochemical position: Aspartate is a metabolic hub rather than a structural amino acid. It donates a nitrogen to the urea cycle via argininosuccinate synthetase, which is how the second nitrogen of urea is supplied; it contributes nitrogen and carbon skeletons to both purine and pyrimidine synthesis; and it is the carrier in the malate-aspartate shuttle, which transports reducing equivalents from cytosolic NADH into the mitochondrion, since NADH itself cannot cross the inner membrane. Few amino acids appear in so many core pathways.
Industrial position: Aspartic acid's largest commercial use is not nutritional. Aspartame is the methyl ester of the aspartyl-phenylalanine dipeptide, and its manufacture consumes a substantial share of world aspartic acid production. Aspartate is also the feedstock for enzymatic L-alanine manufacture via aspartate 4-decarboxylase, and for polyaspartic acid, a biodegradable polymer used as a scale inhibitor and superabsorbent.
Commercial source: L-aspartic acid is produced industrially by enzymatic addition of ammonia to fumaric acid using aspartase, a high-yield and well-established route, and also by fermentation. The enzymatic route is stereospecific and gives the L-form. DL-aspartic acid from chemical synthesis and D-aspartic acid obtained by resolution are separate articles traded for different purposes.
Evidence for L-Aspartic Acid Applications
L-aspartic acid is not D-aspartic acid, and conflating them is the commonest error in this category. D-aspartic acid is a distinct compound with its own CAS number, occurring endogenously in neuroendocrine tissue, and it is the subject of the testosterone-related supplement claims. L-aspartic acid is the proteinogenic form and carries none of those claims. The two are routinely confused in enquiries, and a specification that says only "aspartic acid" is ambiguous. State the isomer explicitly and by CAS number. Claim strength: High.
The D-aspartic acid evidence itself is weak and contradictory, which is worth knowing even when supplying the L-form. Early work reported increases in luteinising hormone and testosterone in men after short-term D-aspartic acid supplementation. Subsequent controlled trials in resistance-trained men have generally failed to replicate this, with some reporting no change and at least one reporting reduced testosterone at higher doses. The current position is that the claim is not supported. A customer asking for L-aspartic acid on the basis of that literature has the wrong isomer and an overstated expectation. Claim strength: Emerging, trending negative.
The urea cycle and nucleotide synthesis roles are settled biochemistry. Argininosuccinate synthetase condenses aspartate with citrulline, which is how the second nitrogen destined for urea enters the cycle; the aspartate carbon skeleton is then released as fumarate, linking the urea cycle to the tricarboxylic acid cycle. Aspartate also supplies nitrogen to purine synthesis and both nitrogen and carbon to the pyrimidine ring. These are core pathways and the dependence on aspartate is absolute, though not usually substrate-limited. Claim strength: High.
The malate-aspartate shuttle is aspartate's most distinctive function and is genuinely interesting mechanistically. Cytosolic NADH cannot cross the inner mitochondrial membrane, so its reducing equivalents are transferred via oxaloacetate reduction to malate, transport, and reoxidation, with aspartate and glutamate carrying the amino groups back across to complete the cycle. This is the principal route for cytosolic NADH oxidation in heart, liver and kidney, and it is why aspartate appears in cardiac and metabolic formulations. Whether a supplemental dose affects shuttle flux is unestablished. Claim strength: High for the biochemistry, Emerging for any supplementation inference.
Mineral aspartate salts are a legitimate delivery format with thinner evidence than their marketing suggests. Magnesium, potassium and zinc aspartates are traded on the argument that the amino acid counter-ion improves absorption relative to inorganic salts. The organic-acid salts of magnesium are generally better absorbed than magnesium oxide, which is a low bar, but head-to-head evidence establishing aspartate as superior to citrate, glycinate or malate is limited. The aspartate also contributes a measurable amino acid load that should be counted in the formula. Claim strength: Emerging.
Safety is unproblematic for the L-form at dietary and supplemental levels, with a caveat worth stating accurately. Aspartate is an excitatory amino acid and an NMDA receptor agonist in the central nervous system, which has prompted periodic concern about dietary aspartate and excitotoxicity. In practice dietary aspartate is extensively metabolised by the intestine and liver and does not meaningfully raise brain aspartate, and the same applies to aspartame-derived aspartate. The excitotoxicity concern is pharmacologically real and dietarily not. Claim strength: Moderate.
Sourcing L-aspartic acid from Herbuno. We supply L-aspartic acid and D-aspartic acid at 99%, as separate articles.
State the isomer by CAS number on the specification — "aspartic acid" alone is ambiguous and the two are routinely confused. If the enquiry is driven by the testosterone literature, that is D-aspartic acid, and the controlled trials have largely failed to replicate the original finding; we would rather say so than supply against an expectation that will not be met. All lots ship with CoA and MSDS; request a quotation for pilot or bulk volumes.
Dosage & Formulator Specification
L-aspartic acid is dosed as the free amino acid at 99%, with no salt conversion. There is no established requirement, since it is non-essential and readily synthesised by transamination of oxaloacetate, and no established supplemental dose for the L-form, since no outcome evidence supports one. In complete amino acid blends it is dosed against the target profile. In mineral aspartate salts the aspartate quantity follows from the salt stoichiometry and should be counted in the formula's total amino acid load rather than treated as an inert counter-ion.
Low solubility is the dominant formulation constraint and is frequently underestimated. L-aspartic acid dissolves at only around 0.5 grams per 100 millilitres in water at room temperature, which is among the lowest of the amino acids and makes liquid applications difficult at any meaningful concentration. Solubility rises sharply with pH as the carboxyl groups deprotonate, so a sodium or potassium aspartate salt is the practical route for liquids — which is the same logic that makes monosodium glutamate the soluble article for glutamate. A formulation requiring dissolved aspartate at concentration should specify a salt, not the free acid.
Acidity needs accounting for in any blend. With two carboxyl groups and an isoelectric point near pH 2.8, L-aspartic acid is a meaningful acid load, and in a reconstituted powder it contributes to the finished pH alongside any added acidulant. It has a sour, faintly umami taste rather than the bitterness typical of the neutral amino acids. In dry formats the acidity matters little; in anything reconstituted it should be deducted from the separately added acid rather than stacked on top.
Handling is otherwise straightforward. L-aspartic acid is a free-flowing crystalline powder, not notably hygroscopic, stable to heat and across a broad pH range, and compatible with common excipients and direct compression. It participates in Maillard reactions with reducing sugars. One practical note for thermally processed products: aspartame degrades on heating and in solution to aspartic acid, phenylalanine and methanol, so a product containing both aspartame and added aspartate will see the aspartate load rise over shelf life.
For analytical control, specify identity and assay by HPLC or ion-exchange chromatography with optical rotation confirming configuration, and specify the isomer by CAS number: L- at 56-84-8, D- at 1783-96-6, DL- at 617-45-8. This matters more than usual because D-aspartic acid commands a price premium driven by the supplement claims, so the substitution incentive runs toward supplying L- against a D- specification. Standard coverage includes heavy metals, residual solvents, microbiological limits, loss on drying and sulphated ash.
Production route should be named on the certificate. The dominant industrial route is enzymatic addition of ammonia to fumaric acid using aspartase, which is stereospecific for the L-form, high-yielding and well established; fermentation routes also exist. Where the enzymatic route is used, maleic acid is the relevant process-related impurity if the fumaric acid feedstock derives from maleic anhydride, and it should be specified as a limit test since an amino acid assay will not catch it. Name the enzyme source or fermentation organism and the substrate for vegan, non-GMO, kosher and halal documentation. Aspartic acid is synthetic or fermentation-derived rather than plant-extracted, so phytosanitary certification does not apply.
Frequently Asked Questions — L-Aspartic Acid
Is this the same as D-aspartic acid?
No. D-aspartic acid is a distinct compound, CAS 1783-96-6, occurring endogenously in neuroendocrine tissue, and it is the one carrying the testosterone-related supplement claims. L-aspartic acid, CAS 56-84-8, is the proteinogenic form and carries none of them. A specification saying only "aspartic acid" is ambiguous.
Does D-aspartic acid raise testosterone?
The evidence does not support it. Early work reported increases in luteinising hormone and testosterone after short-term supplementation, but subsequent controlled trials in resistance-trained men have largely failed to replicate it, with some finding no change and at least one reporting reduced testosterone at higher doses.
Can I use it in a liquid?
Not as the free acid at any meaningful concentration — it dissolves at only about 0.5 g per 100 ml at room temperature, among the lowest of the amino acids. Solubility rises sharply with pH as the carboxyls deprotonate, so specify a sodium or potassium aspartate salt for liquids. Same logic that makes MSG the soluble article for glutamate.
Are mineral aspartates better absorbed?
Better than magnesium oxide, which is a low bar. Head-to-head evidence establishing aspartate as superior to citrate, glycinate or malate is limited. The aspartate also contributes a measurable amino acid load that should be counted in the formula rather than treated as an inert counter-ion.
Is dietary aspartate excitotoxic?
Pharmacologically aspartate is an NMDA agonist; dietarily it is not a concern. Dietary aspartate is extensively metabolised by the intestine and liver and does not meaningfully raise brain aspartate, and the same applies to aspartame-derived aspartate. The mechanism is real and the dietary route to it is not.
What impurity should I specify?
Maleic acid, where the aspartase route starts from fumaric acid derived from maleic anhydride. It is a process-related impurity an amino acid assay will not catch. Also specify the isomer by CAS number with optical rotation — D- commands a premium, so the substitution incentive runs toward supplying L- against a D- specification.