Thioctic acid

See also Alpha Lipoic Acid (ALA)- 

Thioctic acid is the technical name for the antioxidant ALA. Unlike many antioxidants that are either water-soluble or oil-soluble, thioctic acid is both. 

Alpha-Lipoic Acid (ALA) seems to be a great choice for topical use as studies show it can penetrate the skin rapidly where it's converted to DHLA (dihydrolipoic acid), an even more potent antioxidant molecule.  A nicely designed (we mean double-blind, placebo-controlled) 12-week study from 2003 confirmed that 5% ALA cream can decrease skin roughness and improve general signs of photoaging statistically significantly.  A slight catch, though, is that burning and warmth in the skin was quite a common side effect, especially in the first 4 weeks. 

Despite claims to the contrary, alpha lipoic acid isn’t the best antioxidant around. It is one of many that are beneficial for skin.