Comparison of antioxidant effectiveness of lipoic acid and dihydrolipoic acid

Abstract The abilities of dihydrolipoic acid (DHLA) to scavenge peroxynitrite (ONOO − ), galvinoxyl radical, 2,2′‐azinobis(3‐ethylbenzothiazoline‐6‐sulfonate) cation radical (ABTS +• ), and 2,2′‐diphenyl‐1‐picrylhydrazyl radical (DPPH) were higher than those of lipoic acid (LA). The effectiveness of DHLA to protect methyl linoleate against 2,2′‐azobis(2‐amidinopropane hydrochloride) (AAPH)‐induced oxidation was about 2.2‐fold higher than that of LA, and DHLA can retard the autoxidation of linoleic acid (LH) in the β‐carotene‐bleaching test. DHLA can also trap ∼0.6 radicals in AAPH‐induced oxidation of LH. Moreover, DHLA can scavenge ∼2.0 radicals in AAPH‐induced oxidation of DNA and AAPH‐induced hemolysis of erythrocytes, whereas LA can scavenge ∼1.5 radicals at the same experimental conditions. DHLA can protect erythrocytes against hemin‐induced hemolysis, but accelerate the degradation of DNA in the presence of Cu 2+ . Therefore, the antioxidant capacity of –SH in DHLA is higher than S‐S in LA. © 2010 Wiley Periodicals, Inc. J Biochem Mol Toxicol 25:216–223, 2011; View this article online at wileyonlinelibrary.com . DOI 10.1002/jbt.20378