How to Qualify an Ergothioneine Supplier: CAS 497-30-3, Assay and COA Review

Quick Answer

Buying ergothioneine in bulk is not a matter of choosing the highest percentage in a product title. A 99% L-ergothioneine powder and a 1% mushroom extract may both be marketed as ergothioneine, but they are different raw-material decisions. They can differ in source, matrix, assay basis, analytical method, application, cost-in-use and documentation requirements. Treating them as interchangeable creates problems during formulation, quality review, labeling and repeat purchasing.

For most B2B buyers the correct sourcing sequence is: confirm identity, define the material type, review the assay method, check batch documentation, qualify the supplier, and only then compare commercial terms. This guide sits alongside the supplier screening checklist for ergothioneine and the COA review guide, which cover supplier scoring and document parsing in more detail.

Start with identity, not the purity headline

Ergothioneine is a sulfur-containing derivative of histidine. The commonly referenced material is L-(+)-ergothioneine, also known as 2-mercaptohistidine trimethylbetaine. Its CAS Registry Number is 497-30-3, with a molecular formula of C₉H₁₅N₃O₂S and a molecular weight of approximately 229.30 g/mol.[1] These details should appear consistently across the supplier's product title, specification sheet, Certificate of Analysis, Safety Data Sheet, quotation, packaging label, and export or customs documents where applicable.

A listing that shows "ergothioneine" but uses a different CAS number, a broad mushroom-extract description, or an unclear chemical identity should not automatically be treated as a high-purity L-ergothioneine supply.

The first question is not "is it 99%?" but: what exactly is the material being assayed?

Separate defined L-ergothioneine from mushroom extract

The supplier market generally contains at least two procurement routes.

Defined high-purity L-ergothioneine

This type is normally sold as a white or off-white crystalline powder and marketed around a high assay, often 98–99% or higher. The buyer usually expects:

• a clearly stated CAS number;
• a defined chemical identity;
• an assay method such as HPLC;
• controlled appearance and moisture-related specifications;
• a consistent lot number; and
• documentation suitable for formulation or further qualification.

This format is easier to dose when the formula is controlled around the active ingredient itself, and easier to compare across suppliers when the assay method and calculation basis are aligned. However, "99%" still does not answer every quality question. Confirm whether the value is a minimum specification or an actual batch result, whether it is reported on an as-is or dried basis, which method was used, whether the reference standard is identified, and whether the result belongs to the exact batch being offered.

Low-content mushroom extract

A 0.5–1% mushroom extract is a different material. It may be derived from species such as Pleurotus or other fungi and may contain polysaccharides, proteins, minerals, pigments and other extractable components in addition to ergothioneine.

For this type of material, confirm:

• mushroom species;
• fruiting body, mycelium, or mixed source;
• extraction ratio or extract method;
• carrier or excipient content;
• ergothioneine assay method;
• whether the percentage refers to ergothioneine itself or a broader extract marker; and
• microbiological, heavy-metal and pesticide requirements where relevant.

The biological literature supports the connection between fungi and ergothioneine production,[2,3] but the presence of a mushroom source does not by itself establish the final concentration or identity of the supplied powder. The commercial implication is that a 1% extract is not automatically a cheaper version of 99% L-ergothioneine.

Normalize active content before comparing price

Suppose one supplier quotes a 99% powder at $550/kg and another quotes a 1% extract at $80/kg. The second offer looks cheaper per raw kilogram, but the active-content comparison is very different:

A simple active-equivalent calculation is:

Active-equivalent cost = quoted price per kg ÷ assay fraction

Using the illustrative prices above, the 99% material is about $556 per kg of active-equivalent, while the 1% extract is about $8,000 per kg of active-equivalent. This does not mean the 1% extract is a poor purchase. It may be appropriate when the product concept requires a mushroom-derived ingredient, a broader botanical matrix or a lower-intensity positioning. It should not be evaluated as a direct substitute for a defined 99% raw material.

What to review on the COA

A useful COA review goes beyond a company logo and a large purity number. The COA review walkthrough covers document-level parsing; the checklist below is the qualification-critical subset.

Product identity

The COA should identify the product consistently with the quotation and packaging. At minimum, check the product name, CAS number, batch or lot number, manufacturing date, retest or expiry date, appearance, test date, and supplier or manufacturer name. A mismatch between "L-Ergothioneine", "mushroom extract" and a generic "antioxidant powder" should be clarified before the sample is approved.

Assay and method

The assay line should state both the result and the test method. A report that says only "Purity: 99%" gives the buyer limited information. Ask whether the result was measured by HPLC, whether the reference standard is identified, whether the value is a minimum specification or an actual result, whether moisture correction is applied, and whether the method quantifies ergothioneine specifically.[4]

Optical rotation and stereochemistry

For buyers specifying L-(+)-ergothioneine, optical rotation can be a useful supporting parameter when it appears in the supplier's specification and the test conditions are clear. A rotation result cannot be interpreted without the solvent, concentration, temperature, wavelength and method. One supplier's rotation range should not be rewritten as a universal industry standard. The specific rotation guide covers the test conditions to request.

Moisture, residual solvents and contaminants

Relevance depends on the production route and intended application. A buyer may need loss on drying or moisture, residual solvents, heavy metals, microbiological limits, pesticide residues for mushroom or botanical extracts, foreign matter, particle size and bulk density where relevant.

Supplier age is a useful signal, not proof of quality

Sample approval does not equal commercial qualification

A sample answers a limited question: whether the tested material appears suitable under the conditions examined. It does not by itself prove repeat-batch consistency, long-term supply capacity, an unchanged manufacturing route, stable packaging, consistent assay, change-control discipline or complaint handling.

Before moving from sample to purchase order, request:

1. the sample's batch number;
2. the corresponding COA;
3. a current specification sheet;
4. the planned commercial batch format;
5. packaging details;
6. storage and transport conditions;
7. retest policy; and
8. change-notification expectations.

For a low-content mushroom extract, also request the botanical source and the method used to quantify ergothioneine. A generic botanical extract COA is not enough when ergothioneine is the commercial marker being purchased.

Supplier history matters because repeat purchasing requires commercial continuity. A long operating history may indicate that the company has maintained a business presence, export activity and a customer base over time. It does not prove that the exact ergothioneine product has been supplied for the same period, that the company manufactures the material itself, or that every listed specification is current.

Supplier age is therefore one part of a broader review. The buyer should still establish whether the supplier is the manufacturer, a distributor, an exporter or a trading company. A distributor can be acceptable when the supply chain and documentation are transparent.

Current commercial examples

The two listings below represent different sourcing roles rather than a ranking of best suppliers. Marketplace data is dynamic and should be refreshed before a purchase decision.

For the high-purity role, the marketplace record shows a well-established supplier with a substantial catalogue history; treat that as a screening signal that shortens the first call, not as a reason to skip the identity and assay review. For the alternative role, confirm mushroom species, extraction description, carrier information, assay method and the exact documentation package before approval.

A practical RFQ checklist

Before requesting a final quote, send the supplier a specification request that separates identity from commercial terms.

Product identity

• product name;
• CAS 497-30-3, where applicable;
• L-(+)-ergothioneine or standardized mushroom extract;
• source organism or production route; and
• intended application.

Analytical package

• current specification sheet;
• lot-specific COA;
• assay method;
• identity method;
• optical rotation and test conditions, if claimed;
• moisture or loss on drying;
• residual solvents;
• heavy metals;
• microbiology; and
• pesticide testing for botanical material.

Commercial details

• MOQ;
• sample quantity and cost;
• price tiers;
• packaging;
• lead time;
• Incoterm;
• payment terms;
• shelf life;
• storage conditions; and
• available annual or monthly capacity.

Final decision rule

A suitable ergothioneine supplier is not necessarily the one offering the highest assay or the lowest price. For a defined high-purity ingredient, prioritize identity consistency, assay method, batch documentation, stereochemical or identity support, repeat-supply capability and commercial terms. For a mushroom extract, prioritize species and material source, extraction and standardization details, ergothioneine assay, contaminant and microbiological controls, active-equivalent cost and supply continuity.

The final procurement decision should be based on the material that best fits the formulation and quality system, not on a purity number copied from a marketplace title.

References

1. Chemical Abstracts Service. Ergothioneine, CAS 497-30-3. https://commonchemistry.cas.org/detail?cas_rn=497-30-3
2. Borodina I, Kenny LC, McCarthy CM, et al. The biology of ergothioneine, an antioxidant nutraceutical. Nutrients. 2020. https://pmc.ncbi.nlm.nih.gov/articles/PMC7653990/
3. Paul BD, Snyder SH. A Stress Vitamin with Antiaging, Vascular, and Neuroprotective Effects. Antioxidants and Redox Signaling. 2022. https://pmc.ncbi.nlm.nih.gov/articles/PMC9221166/
4. Liu L, et al. Determination of L-Ergothioneine in Cosmetics Based on UPLC-MS/MS. Journal of Analytical Methods in Chemistry. 2022. https://pmc.ncbi.nlm.nih.gov/articles/PMC9532160/