Thioctic Acid and Lipoic Acid Are the Same Compound
Thioctic acid and lipoic acid (also called α-lipoic acid or ALA) are identical compounds—these are simply different names for the same molecule, chemically designated as 1,2-dithiolane-3-pentanoic acid 1, 2, 3.
Chemical Identity and Nomenclature
- The terms "thioctic acid," "lipoic acid," and "alpha-lipoic acid (ALA)" all refer to the exact same organosulfur compound 1, 2, 3
- The chemical structure is 1,2-dithiolane-3-pentanoic acid, regardless of which name is used 2
- "Thioctic acid" is simply an alternative nomenclature that has been used historically, particularly in European medical literature 1, 4
Enantiomeric Forms
The compound exists in two optical isomers (enantiomers) due to an asymmetrical carbon atom 1:
- R-lipoic acid (levogyrate isomer): This is the naturally occurring form synthesized in the human body and found in foods 1, 3
- S-lipoic acid (rightspinning isomer): The synthetic mirror image 1
- Most dietary supplements contain a racemic mixture of both R- and S-forms in equal proportions 1
Pharmacokinetic Differences Between Enantiomers
- The R-enantiomer demonstrates superior pharmacokinetic parameters, including increased bioavailability compared to the S-enantiomer 3
- R-lipoic acid is the biologically active form that functions as a cofactor for mitochondrial enzyme complexes 1, 3
Clinical Applications
Both names appear interchangeably in medical literature when discussing therapeutic uses 5:
- Treatment of diabetic peripheral neuropathy at 600 mg daily 5
- Antioxidant therapy for various metabolic conditions 1, 2, 6
- The compound has been evaluated (though not recommended) for prevention of chemotherapy-induced peripheral neuropathy 5
Common Pitfall
Do not assume these are different medications or that one is superior to the other based on nomenclature alone—the distinction that matters clinically is between the R-enantiomer (natural form) versus the racemic mixture (R+S combination), not between "thioctic" versus "lipoic" acid terminology 1, 3.