Alpha Lipoic Acid

Alpha lipoic acid, also called thioctic acid, is a sulfur-containing fatty acid with a 1,2-dithiolane ring and a molar mass of 206.3 g/mol. Manufacturers buy it in bulk as a light-yellow powder for capsules, tablets and powder blends. In EU food supplements it is an “other substance”, not a vitamin or mineral, so national rules decide most of its use. It belongs to the Coenzymes & Longevity Actives category.

Grades and forms of alpha lipoic acid

Most alpha lipoic acid used in supplements is the racemate, an equal mixture of the R- and S-enantiomers. The CAS number on this page identifies that racemic material. The R-enantiomer alone is a different substance with its own identity, specification and regulatory position. Specify it separately if a formulation calls for it.

Alpha lipoic acid powder comes in two broad physical types:

• Crystalline powder: the usual choice for capsule filling, dry blending and powder sticks.
• Granulated or directly compressible grades: processed for flow and compression on tablet presses.

The choice depends on the format, the flow your filling or tableting line needs and whether your specification requires a pharmacopoeia grade. Assay, particle size, impurity and residue limits appear on the specification sheet. SoleChem sends the specification sheet and the certificate of analysis with its quote, so state the grade you need in the quote form.

EU regulatory status

Directive 2002/46/EC governs the finished food supplement. Its Annexes I and II list only vitamins, minerals and their permitted forms, so alpha lipoic acid does not appear there. The site guide to permitted vitamin and mineral forms explains how those annexes work.

Use of other substances is not harmonised at EU level. Member states differ: some require notification before marketing, some set a maximum amount per daily portion, and some require specific label warnings. In some member states, products containing thioctic acid may also be assessed case by case at the border with medicinal products. Check the rules of each target market with its competent authority.

Article 8 of Regulation (EC) No 1925/2006 allows the Commission to restrict or prohibit other substances in foods, through Annex III of that Regulation. Confirm in the consolidated text that no measure covers alpha lipoic acid.

Novel food status must be checked before launch, separately for the racemate and for the R-enantiomer. The relevant acts are Regulation (EU) 2015/2283 and the Union list in Implementing Regulation (EU) 2017/2470. Our novel food guide explains how to check.

Alpha lipoic acid has no E number and is not used as a food additive. On the label, Article 8 of Directive 2002/46/EC requires the amount of the substance per daily portion in numerical form. The labelling guide covers the full set of mandatory particulars.

Formulation notes

Heat and light. Alpha lipoic acid has a low melting point. When heated or exposed to light, the dithiolane ring can open and the material can polymerise into a sticky, less soluble mass. Keep process temperatures low and avoid long high-shear mixing that builds heat.

Tablets. The low melting point and frictional heat during compression cause sticking to punches. Granulated grades, a glidant such as silicon dioxide, adequate lubrication and moderate press speeds reduce the problem. A film coat also shields the core from light. See the tablets guide for excipient choices.

Capsules. The powder fills well into hard shells of gelatin or HPMC. Check that the bulk density on the specification sheet fits your label claim in the chosen capsule size. Opaque shells give light protection. More detail is in the capsules guide.

Powders and softgels. The free acid is poorly soluble in water and has a characteristic sulfurous odour and pronounced taste. Drink powders therefore need suspension and taste masking; see the powders guide. In softgels it is usually suspended in an oil carrier.

Blends. Combinations with other light- or oxidation-sensitive actives, such as coenzyme Q10, need the same protection: low process temperatures, opaque packaging and closed containers.

Label-claim arithmetic. Alpha lipoic acid is itself the declared substance, so no elemental conversion applies. Divide the label claim by the assay fraction on the certificate of analysis. At 100 % assay, 300 mg of powder delivers 300 mg; a lower assay raises the input proportionally. Add any shelf-life overage with the overage calculator.