L-Phenylalanine
Compiled from published pharmacological and botanical literature. Not independently verified by Herbuno. Spotted an error or have a correction? Flag it below →
| Compound | L-Phenylalanine |
|---|---|
| Chemical class | Essential aromatic α-amino acid — benzyl side chain |
| CAS | 63-91-2 (L-phenylalanine) · 150-30-1 (DL-phenylalanine) |
| Primary source | Microbial fermentation, typically engineered Escherichia coli |
| Key applications | Tyrosine and catecholamine precursor, protein synthesis, aspartame manufacture |
| Claim strength | High for essentiality and the PKU contraindication; Emerging for supplementation outcomes |
| Typical form | Crystalline L-phenylalanine, or DL- racemate (DLPA) at 99% |
| Buy from Herbuno | L-Phenylalanine 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 phenyl group on its side chain plus alanine — it is literally alanine carrying a benzene ring. Ernst Schulze and Johann Barbieri isolated it from lupin seedlings in 1879. The aromatic ring is what makes it the entry point to an entire branch of biochemistry: phenylalanine is hydroxylated to tyrosine, which becomes L-DOPA, dopamine, noradrenaline and adrenaline in sequence.
Discovery and production history: Phenylalanine's public profile comes almost entirely from phenylketonuria. PKU is an inherited deficiency of phenylalanine hydroxylase in which phenylalanine accumulates and causes severe, irreversible intellectual disability unless a restricted diet is begun in infancy. Newborn screening for PKU, introduced from the 1960s, was among the first mass genetic screening programmes anywhere. The second driver of phenylalanine's industrial scale is aspartame, which is a dipeptide of phenylalanine and aspartic acid, and which is why aspartame-sweetened products carry a phenylalanine warning.
Research trajectory: Direct supplementation research is limited. The main threads are the catecholamine precursor logic, which parallels tyrosine's and shares its limitations; DL-phenylalanine in pain management, on the proposed basis that the D- isomer inhibits enkephalin degradation; and vitiligo, where phenylalanine with UVA exposure has been trialled on the rationale that it is a melanin precursor. None has produced a robust evidence base.
Commercial source: L-phenylalanine is produced by fermentation, commonly using engineered Escherichia coli, at very large scale because aspartame manufacture consumes a substantial share of world production. DL-phenylalanine, the racemic mixture marketed as DLPA, is made by chemical synthesis. The two are different products with different rationales and should not be substituted for one another on price.
Evidence for L-Phenylalanine Applications
The PKU contraindication is absolute and must be declared, which makes this the most regulation-sensitive amino acid in the catalogue. Phenylketonuria affects roughly one in 10,000 to 15,000 births in most populations, is detected by newborn screening, and requires lifelong phenylalanine restriction. Any product containing phenylalanine, including as aspartame, carries a mandatory warning in most jurisdictions. This is not a precautionary statement but a legal requirement, and the consequence of ignoring it for an affected consumer is neurological harm. Claim strength: High.
The catecholamine precursor logic parallels tyrosine and carries the same limitation. Phenylalanine is hydroxylated to tyrosine, which is then converted through L-DOPA to dopamine and the catecholamines. Supplementing phenylalanine therefore supplies substrate two steps back. As with tyrosine, the synthesis is not substrate-limited in rested, well-nourished people, so the effect in that population is minimal. Phenylalanine also adds a conversion step that tyrosine does not require, so where the objective is catecholamine substrate, tyrosine is the more direct choice. Claim strength: Emerging.
DLPA is a different ingredient and should not inherit L-phenylalanine's profile. The rationale for the racemate is that D-phenylalanine inhibits carboxypeptidase A, slowing enkephalin degradation and theoretically prolonging endogenous opioid activity, which has generated use in chronic pain. The human trial evidence is sparse, old and methodologically weak, with several small studies producing inconsistent results. D-phenylalanine is not converted to the L- form in humans to any meaningful extent, unlike D-methionine, so DLPA delivers roughly half the nutritional phenylalanine of an equivalent weight of L-. Claim strength: Emerging.
The vitiligo work is interesting and preliminary. Phenylalanine is a precursor of tyrosine and therefore of melanin, and small studies have examined oral or topical phenylalanine combined with UVA exposure for repigmentation in vitiligo. Some have reported repigmentation in a proportion of patients. Trials are small, often uncontrolled, and the combination with UVA prevents attributing effects to phenylalanine alone. This is a clinical research direction rather than a supplement claim. Claim strength: Emerging.
Aromatic amino acid transport competition applies here as it does for tyrosine and has practical formulation consequences. Phenylalanine, tyrosine and tryptophan compete for the same large neutral amino acid transporter at the blood-brain barrier, and branched-chain amino acids compete with all three. A product combining high-dose BCAAs with phenylalanine or tyrosine for cognitive purposes is working against itself, and dosing either aromatic amino acid with a protein meal substantially reduces brain delivery. Claim strength: Moderate.
Safety in people without PKU is good at supplemental doses, with specific interaction cautions. Doses used in trials have generally been well tolerated. There are theoretical concerns about combining phenylalanine with MAO inhibitors given the catecholamine pathway, and caution is advised in people with existing hypertension. No tolerable upper intake level has been established. The overwhelming safety consideration remains PKU, where the issue is not dose-dependent toxicity but a metabolic inability to handle the amino acid at all. Claim strength: High.
Sourcing L-phenylalanine from Herbuno. We supply fermentation-derived L-phenylalanine as a crystalline powder.
Plan the PKU declaration into the label from the outset — it is a legal requirement in most markets, not a precautionary note, and it applies to any phenylalanine-containing product. If your objective is catecholamine substrate, tyrosine is the more direct route and avoids a conversion step. All lots ship with CoA and MSDS as standard; request a quotation for pilot or bulk volumes.
Dosage & Formulator Specification
L-phenylalanine is dosed as the free amino acid at 99%. Adult requirement for phenylalanine plus tyrosine combined is around 25 milligrams per kilogram daily, since tyrosine is synthesised from phenylalanine and spares it. Supplemental doses in the sparse literature run 500 milligrams to 1.5 grams daily. DLPA is dosed similarly by weight, but delivers roughly half the nutritional phenylalanine, since the D- isomer is not meaningfully converted in humans — a point of difference from DL-methionine that is often missed.
The labelling requirement should be settled before anything else. Most jurisdictions mandate a phenylalanine declaration on products containing it, and the wording and placement are specified rather than discretionary. Confirm the requirement for each target market at the formulation stage. This also affects co-formulation decisions: a product already carrying aspartame as a sweetener has a phenylalanine source and a declaration regardless of whether phenylalanine is added as an active.
Handling is unremarkable with one notable property. Phenylalanine is poorly soluble in water at around 2.7 grams per 100 millilitres at room temperature, which constrains liquid applications though less severely than leucine or tyrosine. It is stable to heat and across a wide pH range, not notably hygroscopic, and carries a mildly bitter taste. It participates in Maillard reactions and, in thermally processed products, phenylalanine-derived Strecker degradation products contribute characteristic baked and floral notes, which may be desirable or not depending on the format.
For analytical control, specify identity and assay by HPLC with optical rotation confirming L-configuration, and state explicitly whether the specification is for L- or DL-, since DLPA is a different product at a different price and the substitution would not be caught by a standard assay. Standard amino acid specifications cover heavy metals, residual solvents, microbiological limits and loss on drying. For fermentation-derived material, specify residual host-cell protein and endotoxin, and name the organism and substrate on the certificate.
The regulatory workload around phenylalanine is heavier than its formulation workload, and should be scoped before development rather than during registration. Beyond the PKU declaration itself, which varies in required wording and placement by market, phenylalanine's position as a catecholamine precursor brings it into the scope of monoamine oxidase inhibitor interaction warnings in several jurisdictions, and some markets treat aromatic amino acids at supplemental doses differently from the same material used as a protein fortificant. Where a product is intended for multiple markets, resolve the most restrictive requirement first and design the label to it, because retrofitting a declaration into a finished artwork is more expensive than designing around it. This is the single most common avoidable cost in phenylalanine formulation.
On application selection, the honest guidance is that phenylalanine has fewer good uses than its catalogue presence suggests. For catecholamine substrate, tyrosine is more direct. For protein fortification, phenylalanine is rarely limiting in common protein sources, so the fortification case that exists for lysine in cereals or methionine in legumes does not apply here. For pain applications, the DLPA evidence is sparse and the racemate is a different material. What remains is phenylalanine as one of nine essentials in a complete amino acid blend, where it is dosed against a target profile and the PKU declaration is handled as a matter of course, and phenylalanine as an industrial intermediate. Both are legitimate; neither supports a standalone consumer positioning, and a customer proposing one is worth redirecting.
Frequently Asked Questions — L-Phenylalanine
What is the PKU warning and do I have to carry it?
Yes, in most markets it is a legal requirement rather than a precaution. Phenylketonuria is an inherited inability to metabolise phenylalanine, affecting roughly one in 10,000 to 15,000 births, and accumulation causes irreversible neurological harm. Any phenylalanine-containing product must declare it — which is also why aspartame-sweetened products carry the same warning. Settle the wording per market before the label is finalised.
Is DLPA the same as L-phenylalanine?
No. DLPA is the racemate, and unlike DL-methionine the D- isomer is not meaningfully converted to the L- form in humans, so DLPA delivers roughly half the nutritional phenylalanine per gram. Its rationale is separate — D-phenylalanine is proposed to slow enkephalin degradation, used in chronic pain — and that evidence is sparse, old and inconsistent.
Should I use phenylalanine or tyrosine for cognitive products?
Tyrosine, if catecholamine substrate is the objective. Phenylalanine is one conversion step further back and offers no advantage for that purpose. Both share the same core limitation: catecholamine synthesis is not substrate-limited in rested, well-nourished people, so the effect at baseline is minimal. Tyrosine at least has the acute-stressor evidence.
Does it interact with BCAAs?
Yes, and against you. Phenylalanine, tyrosine and tryptophan compete for the same blood-brain barrier transporter, and branched-chains compete with all three. A product combining high-dose BCAAs with phenylalanine for cognitive purposes works against itself. Dosing with a protein meal has the same effect.
What should the certificate state?
Whether the material is L- or DL-, explicitly, with optical rotation confirming it — a standard assay will not distinguish them and the price difference creates a substitution incentive. For fermentation material, also specify residual host-cell protein and endotoxin and name the production organism.
Why source phenylalanine from India?
Around 80% of raw nutraceutical ingredients originate in China and amino acids are among the most concentrated categories, so a second qualified origin is a continuity measure. Phenylalanine is produced at very large scale globally because aspartame manufacture consumes much of it, and India has established fermentation capacity with supplement-grade specification.