of ot-lipoic acid on copper have re

of ot-lipoic acid on copper have recently been extended
to oxidation situations, a-Lipoic acid was effective in
preventing Cu2+-catalyzed ascorbic acid oxidation, increased
the partitioning of Cu 2÷ into n-octanol from
aqueous solution, and inhibited Cu2÷-catalyzed liposomal
peroxidation. 24 These observations indicate that alipoic
acid is a copper chelator.
In summary, a-lipoic acid scavenges hydroxyl radicals,
HOCI, and singlet oxygen, but is ineffective
against hydrogen peroxide and superoxide radical. It
chelates iron, copper, and other transition metals. Further
work is required to determine whether a-lipoic
acid is effective against peroxyl radicals.
Dihydrolipoic acid.Dihydrolipoic acid. With a redox
potential of -0.32 V (ref. 25) for the DHLA/a-lipoic
acid redox couple, dihydrolipoic acid is a potent reductant;
for comparison, the redox potential of the GSH/
GSSG couple is -0.24 V (ref. 26)-DHLA will reduce
GSSG to GSH, but GSH is incapable of reducing ctlipoic
acid to DHLA. 27
Like a-lipoic acid, DHLA is a potent antioxidant,
although there is more uncertainty as to its effects
(Table 2). There is agreement that DHLA scavenges
hypochlorous acid and peroxyl radicals and probably
scavenges hydroxyl radicals. It does not appear to react