FROM:
Alternative Medicine Review 2006 (Sep); 11 (3): 232–237 ~ FULL TEXT
Alpha-lipoic acid (ALA – also known as thioctic acid) was discovered in 1951 as a molecule that assists in acyl-group transfer and as a coenzyme in the Krebs cycle. In the 1980s, the scientific community realized alpha-lipoic acid is
a powerful antioxidant. Several qualities distinguish alpha-lipoic acid from other antioxidants: ALA can be synthesized
by animals and humans; [1] it neutralizes free radicals in both the fatty and watery regions of cells, in contrast
to vitamin C (water soluble) and vitamin E (fat soluble); and, ALA functions as an antioxidant in both its reduced
and oxidized forms. [2]
Alpha-lipoic acid is a potent antioxidant in both fat- and water-soluble mediums. Furthermore, its antioxidant
activity extends to both its oxidized and reduced forms. DHLA is capable of directly regenerating ascorbic
acid from dehydroascorbic acid and indirectly regenerating vitamin E. [7] Researchers have also found ALA increases
intracellular glutathione [8] and coenzyme Q10 [9] levels.
Alpha-lipoic acid appears capable of chelating certain metals. It forms stable complexes with copper, manganese,
and zinc. [10] In animal studies, it has been found to protect against arsenic poisoning, [11] and, in both animal and in vitro studies, ALA reduced cadmium-induced hepatotoxicity. [12] In vitro, ALA chelated mercury from renal slices. [13]
Mechanisms that may account for lipoic acid’s benefit in preventing diabetic complications include prevention of protein glycosylation [14] and inhibition of the enzyme aldose reductase, the latter of which subsequently inhibits conversion of glucose and galactose to sorbitol. [15, 16] Accumulation of sorbitol has been implicated in the pathogenesis of various diabetic complications, including “sugar cataracts” where sorbitol accumulates in the lens.