R-lipoic acid is the isomer that is synthesized by plants and animals and functions as a cofactor for mitochondrial enzymes in its protein-bound form (see Biological Activities). Direct comparisons of the bioavailability of the oral racemic mixture and R-lipoic acid supplements have not been published.
Following the ingestion of R,S-lipoic acid, peak plasma concentrations of R-lipoic acid were found to be 40%-50% higher than S-lipoic acid, suggesting better absorption of R-lipoic acid. Both isomers were nonetheless rapidly metabolized and eliminated (6, 8, 11). In rats, R-lipoic acid was more effective than S-lipoic acid in enhancing insulin-stimulated glucose transport and metabolism in skeletal muscle (110), and R-lipoic acid was more effective than R,S-lipoic acid and S-lipoic acid in preventing cataracts (111).
However, all of the published human studies have used R,S-lipoic acid (racemic mixture). It has been suggested that the presence of S-lipoic acid in the racemic mixture may limit the polymerization of R-lipoic acid and enhance its bioavailability (52). At present, it remains unclear which supplemental form is best to use in clinical trials.
While R-lipoic acid is the more beneficial component of the racemic form, the S-lipoic acid does lend enhanced bioavailability to the R, by keeping it in it's smaller molecular form.
Alpha-lipoic acid is one of the most powerful antioxidants ever discovered. It is a vitamin-like sulfur-containing compound that is synthesized naturally in the human body. Sometimes it is referred to as alpha-lipoate, thioctic acid, or just lipoic acid. One of its most important characteristics is that it is both fat-soluble and water-soluble. This enables it to provide antioxidant protection in a much wider range of physiological environments throughout the body, which has resulted in some scientists referring to alpha-lipoic acid as the "universal" antioxidant.
In the body, alpha-lipoic acid is converted to dihydrolipoic acid (DHLA), which also functions as a strong antioxidant. Lipoic acid is part of two enzyme systems: PDH (pyruvate dehydrogenase) and alphaketoglutarate dehydrogenase. These enzymes are part of the Krebs cycle and are essential in the production of energy.
Contains NO Wheat, Gluten, Corn, Dairy, Soy or Yeast
