Alpha-lipoic acid
Alpha-lipoic acid suppliers and sourcing guide
Alpha-lipoic acid is a sulfur-containing fatty acid (1,2-dithiolane-3-pentanoic acid) with one chiral center. Ingredient supply is made by chemical synthesis: the standard grade is racemic DL-alpha-lipoic acid, a pale yellow crystalline powder, while the R-form is made by resolution or asymmetric synthesis. Because R-lipoic acid tends to polymerize when warmed, it is often sold as a sodium salt or a stabilized grade.
- Category
- Specialty nutrients
- Also known as
- Thioctic acid · ALA · 1,2-Dithiolane-3-pentanoic acid · R-lipoic acid
- Facts checked
- November 2026
Forms and grades of alpha-lipoic acid
Suppliers sell different products under the same name. Specify the one you need.
DL-alpha-lipoic acid
The racemic 50:50 mix of R and S forms, the most common and lowest-cost grade, sold as crystalline powder or granules.
R-alpha-lipoic acid
The single R enantiomer, sold at a higher price; it has a low melting point and can polymerize, so handling and storage matter more.
Sodium R-lipoate
The sodium salt of R-lipoic acid, more stable in storage than the free acid and more soluble in water.
Granulated and direct-compression grades
Grades with larger, denser particles for tableting, sometimes with a flow agent declared on the specification.
What to check on the COA
Compare each result with your own specification when the lot arrives.
- Assay
- Lipoic acid content by HPLC or titration, as named on the specification.
- Optical rotation
- Separates racemic from R-form material; this is the test that confirms you received R-lipoic acid if that is what you paid for.
- Melting range
- Confirms identity and purity; a low or broad melting range can point to impurities or polymer.
- Related substances and polymer
- Impurities and polymerized lipoic acid by HPLC or GPC, especially relevant for R-lipoic acid.
- Residual solvents
- Solvents from synthesis and crystallization, against USP <467> or the buyer's limits.
- Heavy metals and microbiology
- Lead, arsenic, cadmium and mercury by ICP-MS, plus total plate count, yeast and mold, and pathogens.
Storage, lots and expiry
Storage and shelf life
Store alpha-lipoic acid sealed in a cool, dry place away from light; R-lipoic acid in particular should be kept below the supplier's stated temperature limit because warm storage leads to melting and polymerization. The powder has a sulfur odor and can pick up moisture once opened. Shelf life is set by the supplier's specification, with assay and appearance checked at retest.
Lots and expiry dates
Record assay and optical rotation for each lot so racemic and R-form stock are never mixed up. Check older R-lipoic acid lots for clumping or color change before use.
Regulatory status
Facts from regulators and standards bodies, each linked to its source.
Health Canada's natural health product monograph for DL-alpha-lipoic acid and R-alpha-lipoic acid lists both as synthetic medicinal ingredients, including sodium R-(+)-lipoate as a source ingredient for the R-form.
Source: webprod.hc-sc.gc.ca (opens in a new tab)
This is general information, not regulatory advice. Status differs by country and by how the ingredient is used, so check the rules for your product and market.
Alpha-lipoic acid suppliers
Manufacturers and distributors whose own websites say they sell it.
We are checking alpha-lipoic acid suppliers now
Every listing is checked against the supplier’s own website before it goes live, so this list fills in over the coming weeks. The specs and COA checklist above are ready today.
Sell alpha-lipoic acid? Request a listingFrequently asked questions
What forms of alpha-lipoic acid can brands buy?
Common forms include dL-alpha-lipoic acid, r-alpha-lipoic acid, sodium R-lipoate and granulated and direct-compression grades. Ask each supplier for the specification sheet of the exact grade they quote.
What should the COA for alpha-lipoic acid include?
Expect assay, optical rotation, melting range, related substances and polymer, residual solvents and heavy metals and microbiology, each with its method, specification and result for that lot.
How should alpha-lipoic acid be stored?
Store alpha-lipoic acid sealed in a cool, dry place away from light; R-lipoic acid in particular should be kept below the supplier's stated temperature limit because warm storage leads to melting and polymerization. The powder has a sulfur odor and can pick up moisture once opened. Shelf life is set by the supplier's specification, with assay and appearance checked at retest.
What is the regulatory status of alpha-lipoic acid?
Health Canada's natural health product monograph for DL-alpha-lipoic acid and R-alpha-lipoic acid lists both as synthetic medicinal ingredients, including sodium R-(+)-lipoate as a source ingredient for the R-form.
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