What is alpha-Lipoic acid? Alpha-Lipoic acid (also known as thioctic acid) is a vitamin-like substance which plays an important role in the bodys energy supply processes. Alpha-lipoic acid is also important within the body as a powerful antioxidant capable of protecting both the lipid (cell membrane) and aqueous (cytoplasmic) cellular compartments from free radical induced damage. Alpha-lipoic acid is mainly obtained from the diet, although small amounts are also manufactured within the body. Red meat (especially liver, spinach and brewers yeast are good sources of alpha-lipoic acid.