L-Ornithine
Compiled from published pharmacological and botanical literature. Not independently verified by Herbuno. Spotted an error or have a correction? Flag it below →
| Compound | L-Ornithine |
|---|---|
| Chemical class | Non-proteinogenic basic α-amino acid — diamino, one carbon shorter than lysine |
| CAS | 70-26-8 (L-ornithine) · 3184-13-2 (L-ornithine HCl) |
| Molecular weight | 132.16 g/mol |
| Metabolic role | Urea cycle carrier (regenerated, not consumed) · polyamine and proline precursor |
| Key property | Free base is strongly basic and very hygroscopic — traded as the HCl or aspartate |
| Claim strength | High for the urea cycle and polyamine biochemistry; Emerging for supplementation |
| Buy from Herbuno | L-Ornithine HCl Powder · L-Ornithine L-Aspartate 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 the Greek ornis, bird, because Max Jaffé isolated ornithuric acid — a dibenzoyl derivative of ornithine — from the excreta of hens fed benzoic acid in 1877. Structurally it is lysine minus one methylene group in the side chain, and that single-carbon difference is enough to exclude it from protein synthesis entirely.
Why it is not in proteins: Ornithine is non-proteinogenic. There is no codon for it and no transfer RNA that carries it, so it is never incorporated into a polypeptide. It exists purely as a metabolic intermediate, which is an unusual position for an amino acid in a commercial catalogue and worth stating plainly, because customers reasoning about ornithine as a protein building block are reasoning about the wrong thing.
Biochemical position: Ornithine's central role is as the carrier of the urea cycle. Ornithine transcarbamylase condenses it with carbamoyl phosphate to give citrulline, which proceeds through argininosuccinate to arginine, and arginase then cleaves arginine to urea and ornithine — regenerating the starting material. Ornithine is therefore catalytic in the cycle rather than consumed by it, which is a point most product copy gets wrong. Ornithine is also the committed precursor of the polyamines via ornithine decarboxylase, and feeds proline and glutamate via ornithine aminotransferase.
Commercial source: L-ornithine is produced by fermentation, typically using Corynebacterium glutamicum strains engineered to accumulate it, and by enzymatic conversion from arginine using arginase. It is traded almost exclusively as the hydrochloride or as the L-aspartate salt, because the free base is strongly basic and markedly hygroscopic. The free base itself is a specialty article rather than the commercial norm.
Evidence for L-Ornithine Applications
Ornithine is regenerated by the urea cycle, not consumed by it, and this correction matters for how a product is positioned. Arginase cleaves arginine into urea and ornithine, returning the ornithine to the start of the cycle, so under steady-state conditions the cycle does not deplete ornithine. The frequent claim that supplementing ornithine "fuels the urea cycle" to clear ammonia therefore needs qualification: what limits ammonia disposal is usually carbamoyl phosphate synthetase activity, N-acetylglutamate availability or hepatic capacity, not ornithine supply. Supplemental ornithine can raise cycle flux in compromised states, which is a narrower claim than the one usually made. Claim strength: High.
The polyamine pathway is ornithine's most distinctive function and is tightly regulated. Ornithine decarboxylase converts ornithine to putrescine, which is extended to spermidine and spermine, and these polyamines are essential for cell proliferation, chromatin organisation and translational control. Ornithine decarboxylase is the rate-limiting enzyme and has one of the shortest half-lives of any mammalian enzyme, reflecting how closely polyamine synthesis is controlled. That regulation means increased ornithine supply does not translate proportionally into increased polyamine synthesis. Claim strength: High.
The growth hormone claim derives from intravenous data and does not transfer cleanly to oral dosing. Intravenous ornithine, like intravenous arginine, raises growth hormone and has been used as a provocative test of pituitary function. Oral ornithine's effect on growth hormone is inconsistent and, where present, modest and transient, and no trial has linked it to a meaningful body composition or performance outcome. This parallels arginine's situation exactly and for related reasons. Claim strength: Emerging.
The fatigue and ammonia-clearance literature is small but is the most interesting supplementation thread. Trials of oral L-ornithine, generally in the range of 2 to 6 grams daily, have examined subjective fatigue, sleep quality and serum ammonia in healthy adults and reported modest benefits in some endpoints, with several of the better-known studies conducted in Japan at lower doses. Sample sizes are small, endpoints are subjective, and replication is limited. The mechanistic rationale through ammonia handling is coherent; the evidence is thin. Claim strength: Emerging.
Ornithine alpha-ketoglutarate has a separate and better-developed clinical literature in catabolic states, which should not be read across to free ornithine. OKG, a 2:1 salt, has been studied in burns, trauma and surgical recovery with reported effects on nitrogen balance and wound healing, and is used in clinical nutrition in some markets. The combination supplies both ornithine and a glutamine precursor, and the effects have been attributed to the pair rather than to ornithine alone. A free ornithine product cannot borrow that evidence. Claim strength: Moderate for OKG specifically.
Tolerability sets the practical dose ceiling and the free base sets the practical format. Oral ornithine causes dose-dependent gastrointestinal distress, with cramping and loose stools becoming common above roughly 10 grams in a single dose; divided dosing helps. Separately, the free base is strongly basic and very hygroscopic, deliquescing in ambient humidity, which is why commercial material is almost always the hydrochloride or the aspartate. A formulation specifying free-base ornithine for a dry format has a handling problem it may not have anticipated. Claim strength: High.
Sourcing L-ornithine from Herbuno. We supply ornithine as the hydrochloride and as the L-aspartate salt, both of which genuinely deliver ornithine; free base is availability on request.
The salt is not a refinement here. Free-base ornithine is strongly basic and markedly hygroscopic, so for any dry format the hydrochloride at 78.4% ornithine is the practical article. The aspartate is the specification where chloride is unwanted or where the aspartate itself is part of the rationale. All lots ship with CoA and MSDS; request a quotation for pilot or bulk volumes.
Dosage & Formulator Specification
Because ornithine is traded as a salt, dose on ornithine content. The hydrochloride is approximately 78.4% ornithine and the 1:1 L-aspartate approximately 49.8%, so a 2 gram ornithine target requires about 2.55 grams of the hydrochloride or about 4.02 grams of the aspartate. Doses in the fatigue and sleep literature run from a few hundred milligrams to around 6 grams of ornithine daily; the OKG clinical nutrition literature has used higher intakes. There is no established requirement, since ornithine is endogenously generated by the urea cycle.
Positioning should reflect that ornithine is non-proteinogenic and catalytic. It is not a protein building block and has no codon, so claims framed around muscle protein substrate are simply wrong for this molecule. Nor is it consumed by the urea cycle under steady-state conditions, so the "fuels the urea cycle" framing needs qualifying: ammonia disposal is usually limited elsewhere. The defensible statements are the polyamine precursor role, the proline and glutamate route via ornithine aminotransferase, and the modest fatigue and ammonia findings presented at their actual strength.
Hygroscopicity determines the format and should be settled before development. Free-base ornithine deliquesces in ambient humidity, cakes and liquefies in the container, and will cause weight-variation and flow problems in capsule filling and tableting. The hydrochloride is only mildly hygroscopic and behaves as a normal crystalline powder; the aspartate is similarly manageable. If a specification calls for free base in a dry format, raise it, because the handling cost usually outweighs the density advantage.
Co-formulation follows the pathway rather than the marketing. Ornithine with arginine is common and biochemically redundant in one direction, since arginase converts arginine to ornithine anyway, though the pair does load the cycle at two points. Ornithine with citrulline is more coherent for arginine elevation, since citrulline bypasses intestinal arginase. Where the objective is ammonia handling, the aspartate salt has a stronger rationale than free ornithine, because aspartate supports muscle glutamine synthetase. Where the objective is polyamine synthesis, nothing in a formula will overcome ornithine decarboxylase regulation.
For analytical control, specify identity and assay by HPLC or ion-exchange chromatography with optical rotation confirming L-configuration, counter-ion content confirming salt stoichiometry, and water content given the hygroscopicity of the series. L-arginine and L-citrulline are the relevant process-related impurities where the enzymatic arginase route is used, and L-lysine is worth specifying as a limit given the structural similarity. Standard coverage includes heavy metals, residual solvents, microbiological limits, loss on drying and sulphated ash, with the fermentation organism and substrate named for certification.
One point of clinical awareness worth carrying in technical documentation. Ornithine transcarbamylase deficiency is the most common urea cycle disorder, and ornithine aminotransferase deficiency causes gyrate atrophy of the choroid and retina with hyperornithinaemia. In both, ornithine handling is abnormal, and in the latter the therapeutic direction is ornithine restriction rather than supplementation. These are rare conditions and not a general contraindication, but a high-dose ornithine product should not be positioned as universally benign, and anyone with a known urea cycle disorder is a population to exclude explicitly rather than by omission.
Frequently Asked Questions — L-Ornithine
Is ornithine a protein building block?
No. Ornithine is non-proteinogenic — there is no codon for it and no tRNA carries it, so it is never incorporated into a polypeptide. It exists purely as a metabolic intermediate. Claims framed around muscle protein substrate are wrong for this molecule, which is worth correcting with customers who reason about it as a lysine analogue.
Does supplementing ornithine fuel the urea cycle?
Needs qualifying. Arginase cleaves arginine into urea and ornithine, regenerating the ornithine, so the cycle is catalytic in ornithine rather than consuming it. What usually limits ammonia disposal is carbamoyl phosphate synthetase activity, N-acetylglutamate availability or hepatic capacity. Supplemental ornithine can raise flux in compromised states — a narrower claim.
Why is it always sold as a salt?
The free base is strongly basic and markedly hygroscopic — it deliquesces in ambient humidity, caking and liquefying in the container, which causes weight-variation and flow problems in capsule filling and tableting. The hydrochloride at 78.4% ornithine is the practical article for dry formats; the aspartate where chloride is unwanted.
How strong is the fatigue and sleep evidence?
Thin. Trials at roughly 2 to 6 grams daily, several of the better-known ones from Japan at lower doses, report modest benefits on subjective fatigue, sleep quality and serum ammonia in healthy adults. Small samples, subjective endpoints, limited replication. The ammonia mechanism is coherent; the outcome data are not strong.
Can I use the OKG clinical evidence?
No. Ornithine alpha-ketoglutarate is a separate 2:1 salt with its own literature in burns, trauma and surgical recovery, and the effects have been attributed to the pair — ornithine plus a glutamine precursor — rather than to ornithine alone. A free ornithine product cannot borrow it.
Who should avoid it?
Anyone with a known urea cycle disorder, ornithine transcarbamylase deficiency being the most common. Separately, ornithine aminotransferase deficiency causes gyrate atrophy with hyperornithinaemia, where the therapeutic direction is ornithine restriction. Rare, but a high-dose product should exclude them explicitly rather than by omission.