DL-Methionine
Compiled from published pharmacological and botanical literature. Not independently verified by Herbuno. Spotted an error or have a correction? Flag it below →
| Compound | DL-Methionine (racemic methionine) |
|---|---|
| Chemical class | Racemic mixture of D- and L-methionine — sulphur-containing amino acid |
| CAS | 59-51-8 (DL-methionine) · 63-68-3 (L-methionine) |
| Molecular weight | 149.21 g/mol |
| Nutritional basis | D-isomer converted to L- in liver and kidney — racemate is largely usable |
| Key applications | Poultry and swine feed, legume protein fortification, lipotropic formulations |
| Claim strength | High for the D-isomer conversion; low and cautioned for supplementation |
| Buy from Herbuno | DL-Methionine 99% Powder · L-Methionine 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: The racemate of methionine, named for its methyl- thioether side chain. John Howard Mueller isolated L-methionine from casein in 1922; the racemic form is a product of chemical synthesis rather than of biology, and arises because the industrial route produces both enantiomers in equal measure.
Production history: DL-methionine is the largest-volume amino acid after glutamate, and the great majority of world production goes to poultry feed, where methionine is the first limiting amino acid. The dominant route is chemical synthesis from acrolein and methyl mercaptan, via methional and the Strecker synthesis to the hydantoin, which is hydrolysed to the amino acid. That route is inherently non-stereoselective and yields the racemate, which is why DL-methionine is cheaper and more abundant than the L-form.
The unusual fact about this racemate: For most amino acids the D-isomer is nutritionally inert, so a racemate delivers roughly half the usable material. Methionine is a genuine exception. D-methionine is converted to L-methionine in liver and kidney via D-amino acid oxidase to the keto acid, followed by transamination, so the D-isomer has substantial nutritional value. This is why the racemate is accepted in feed and in several food applications where DL-arginine or DL-carnitine would be unacceptable.
Commercial source: DL-methionine is synthetic, produced at very large scale worldwide. Because feed demand dominates, a substantial proportion of available material is feed grade, and the specification gap against food or supplement grade is material rather than nominal — particularly on residual process impurities, heavy metals and microbiological limits. Methionine is also produced as the hydroxy analogue for feed use, which is a different article and not interchangeable with the amino acid.
Evidence for DL-Methionine Applications
D-methionine conversion is the central fact and it distinguishes this racemate from almost every other. D-amino acid oxidase in liver and kidney deaminates D-methionine to 2-oxo-4-methylthiobutyrate, which is then transaminated to L-methionine, so the D-isomer enters the normal metabolic pool. Efficiency is high though not complete and varies with species and with dose. The practical consequence is that DL-methionine has substantial nutritional value, which is why it is the standard article in feed and acceptable in many food applications, where a racemate of arginine, lysine or carnitine would not be. Claim strength: High.
The conversion is not instantaneous or unlimited, which qualifies the equivalence claim. The oxidase-transaminase route adds a metabolic step and has finite capacity, so at high single doses or in compromised hepatic or renal function the conversion may lag, and some D-methionine is excreted unchanged. Comparative feed trials generally find DL-methionine close to but marginally below L-methionine in bioefficacy on an equimolar basis, with the gap varying by species and study. The defensible statement is substantial rather than complete equivalence. Claim strength: Moderate.
The legume protein fortification application is the strongest food use and is unaffected by the isomer question. Methionine is the first limiting amino acid in soy, pea, chickpea and lentil proteins, so adding it raises the amino acid score of a legume-based protein substantially — the mirror image of lysine's role in cereals, and the biochemistry behind the traditional pairing of pulses with grains. Because the D-isomer converts, DL-methionine is a legitimate and more economical choice than L- for this purpose, subject to the regulatory position in the target market. Claim strength: High.
Homocysteine generation applies to the racemate exactly as to the L-form, and should be stated prominently rather than buried. Methionine catabolism via S-adenosylmethionine and S-adenosylhomocysteine yields homocysteine, and methionine loading raises plasma homocysteine sharply enough to be used as a clinical diagnostic challenge. Adequate folate, B12 and B6 are required to recycle it. A DL-methionine product at supplemental rather than protein-fortification doses should carry those cofactors; without them it raises a biomarker the rest of the category sells products to lower. Claim strength: High.
The feed-grade market structure is the dominant commercial risk in this category. Because poultry feed consumes the great majority of world DL-methionine production, feed-grade material is abundant and considerably cheaper than food or supplement grade. The specification differences are real: residual process impurities from the acrolein and methyl mercaptan route, heavy metals, and microbiological limits are all controlled more tightly for human-grade material. A price substantially below the prevailing food-grade range should prompt a specification question rather than an order. Claim strength: High.
Regulatory acceptability of the racemate differs by jurisdiction and by application, and should be confirmed before formulation. DL-methionine's acceptance in feed is universal; its acceptance in human food and supplements varies, with some jurisdictions and some product categories requiring the L-form specifically, and infant formula being the clearest case where the L-form is generally mandated. The conversion biochemistry does not settle the regulatory question. Resolve the most restrictive target market first rather than at registration. Claim strength: High.
Sourcing DL-methionine from Herbuno. We supply DL-methionine at 99% and L-methionine, so the choice can be made on application rather than availability.
The racemate is a legitimate economic choice here rather than a compromise, because the D-isomer converts in vivo — but confirm two things first. Whether the racemate is permitted in your target markets and category, since that varies and the biochemistry does not settle it. And whether the specification is food grade, given that feed demand dominates this market. All lots ship with CoA and MSDS; request a quotation for pilot or bulk volumes.
Dosage & Formulator Specification
DL-methionine is dosed as the free amino acid at 99%, with no salt conversion to apply, which makes the arithmetic simpler than for the hydrochloride categories. Adult requirement for methionine plus cysteine combined is around 19 milligrams per kilogram daily, since cysteine is synthesised from methionine and spares it. For legume protein fortification, inclusion is calculated against the isolate's measured amino acid profile and typically falls in the range of 1 to 2% of protein weight for a pea or soy base. There is no consensus supplemental dose, reflecting the absence of a clear supplementation indication.
The isomer question is a regulatory and specification matter rather than a nutritional one. Because D-methionine converts in vivo, the racemate carries substantial nutritional value, so the decision between DL- and L- turns on whether the racemate is permitted in the target market and category, on whether the application is clinical, and on price. Specify the isomeric form explicitly, because L- and DL- cannot be distinguished by a standard assay and the price difference creates a substitution incentive running in the opposite direction from most categories — here the risk is DL- supplied against an L- specification.
Formulation handling is dominated by odour and is identical for both forms. Methionine carries a pronounced sulphurous, cabbage-like note that intensifies with heat and on oxidation and is difficult to mask at supplemental doses; capsules are the usual answer. It is moderately soluble in water, stable across a reasonable pH range, and not notably hygroscopic. It participates in Maillard reactions with reducing sugars, and in thermally processed sugar-containing products the combination of browning and sulphurous Strecker volatiles can be particularly objectionable, so compatibility testing in the finished matrix is advisable rather than optional.
For analytical control, specify the isomeric form explicitly with optical rotation or a chiral method to confirm it, since a standard assay will not distinguish L- from DL-. Require residual acrolein and methyl mercaptan derivatives as specified impurities for synthetic material — these are route-specific and are not captured by an amino acid assay. Standard coverage includes heavy metals, residual solvents, microbiological limits, loss on drying and sulphated ash. Methionine is synthetic rather than plant-extracted, so phytosanitary certification does not apply.
One article distinction is worth flagging because it causes real confusion in procurement. The feed industry also uses methionine hydroxy analogue — 2-hydroxy-4-methylthiobutanoic acid, sold as a liquid or calcium salt — which is a different compound from DL-methionine, is converted to methionine in vivo at a different and debated efficiency, and is priced differently. It is sometimes quoted against a methionine enquiry without the distinction being made explicit. Confirm that a quotation is for DL-methionine the amino acid rather than the hydroxy analogue, and that the stated assay basis is methionine rather than methionine activity.
On form selection, the honest position is that DL- is the correct default for feed and for permitted legume protein fortification on economic grounds, with the conversion biochemistry genuinely supporting it. L- is the specification where the regulatory position requires it, where the application is clinical or in infant nutrition, where the conversion step is undesirable in a compromised population, or where a customer's existing formula or monograph specifies it. Neither form addresses methionine's central supplementation problem, which is homocysteine generation, so a methionine product at supplemental doses needs folate, B12 and B6 regardless of which isomer is used.
Frequently Asked Questions — DL-Methionine
Is DL-methionine as good as L-methionine?
Substantially, though not completely. D-methionine is converted to L- in liver and kidney via D-amino acid oxidase and transamination, so the racemate carries real nutritional value — unlike DL-arginine or DL-carnitine. Comparative feed trials find DL- close to but marginally below L- on an equimolar basis. The conversion has finite capacity and adds a step.
Why is DL-carnitine unacceptable if DL-methionine is fine?
Because D-carnitine is not inert — it competes with L-carnitine for the OCTN2 transporter and for carnitine acyltransferases, so it actively opposes the L-form. D-methionine simply enters a conversion pathway and joins the normal metabolic pool. The two racemates are not analogous, and the distinction is worth making explicitly.
Can I use DL-methionine in a human supplement?
Depends on the market and category, and the biochemistry does not settle it. Acceptance in feed is universal; acceptance in human food and supplements varies, with some jurisdictions and categories requiring L- specifically and infant formula being the clearest case where L- is generally mandated. Resolve the most restrictive target market before formulating.
Why is it sometimes so cheap?
Because poultry feed consumes the great majority of world production, so feed-grade material is abundant and considerably cheaper than food grade. The specification differences are real: residual process impurities from the acrolein and methyl mercaptan route, heavy metals, microbiological limits. A price well below the food-grade range warrants a question.
Is methionine hydroxy analogue the same thing?
No, and this causes real procurement confusion. Methionine hydroxy analogue — 2-hydroxy-4-methylthiobutanoic acid, sold as liquid or calcium salt — is a different compound, converted to methionine in vivo at a different and debated efficiency, and priced differently. Confirm a quotation is for the amino acid, and that the assay basis is methionine rather than methionine activity.
Does the racemate avoid the homocysteine problem?
No. Methionine catabolism yields homocysteine regardless of which isomer was supplied, and methionine loading raises plasma homocysteine sharply enough to be used as a clinical diagnostic challenge. A methionine product at supplemental doses needs folate, B12 and B6 to recycle it, whichever isomer is used.