Dihydrolipoic Acid (DHLA) is the reduced form of alpha-lipoic acid, and is a carboxylic acid containing two thiol groups (Moini et al.) It acts as a general antioxidant that is highly reactive against a variety of reactive oxygen species (ROS), including hydroxyl radicals, peroxynitrite, hydrogen peroxide, and hypochlorite, at concentrations ranging from 0.01 - 0.5 mM (Moini et al.) Dihydrolipoic acid has also been shown to recycle ubiquinone to the antioxidant active divalently reduced form (Nohl & Gille)
Conversely, at concentrations higher than 50 - 100 μM, Dihydrolipoic acid directly increases the ROS content, along with a significant increase in cytoplasmic free calcium and nitric oxide (NO) levels, loss of mitochondrial membrane potential, activation of caspases-9 and -3, and cell death (Chan et al.; Houng et al.)
