Elucidation of antioxidant activity of alpha-lipoic acid toward hydroxyl radical.
The photosensitive organic hydroperoxide, NP-III, which produces hydroxyl radicals on illumination by UVA light, was used to examine the antioxidant activity of alpha-lipoic acid and its derivatives toward hydroxyl radical. Apolipoprotein (apo-B) of human low density lipoprotein (LDL) and bovine serum alubumin (BSA) were irradiated with UVA in the presence of NP-III and alpha-lipoic acid. The oxidation of BSA and the apo-B protein of LDL by NP-III was completely suppressed by alpha-lipoic acid. ESR studies using dimethylpyrroline oxide (DMPO) as a spin trapping reagent also revealed that in the presence of alpha-lipoic acid, the DMPO-OH adduct produced from the irradiation of NP-III and DMPO completely disappeared. DMPO-OH quenching experiments were performed in the presence or absence of desferoxamine but no change in the signal intensity was found. Hence, the quenching activity of alpha-lipoic acid is not due to its chelating activity toward transition metals (ferrous ions). The results lead us to conclude that alpha-lipoic acid is an efficient hydroxyl radical quencher owing to the disulfide bond in the dithiolane ring.
Matsugo
S
S
Department of Molecular and Cell Biology, University of California at Berkeley 94720-3200.
Yan
L J
LJ
Han
D
D
Trischler
H J
HJ
Packer
L
L
D000975:Antioxidants / Q000494:pharmacology; D001055:Apolipoproteins B / Q000187:drug effects* / Q000528:radiation effects; D003497:Cyclic N-Oxides; D004578:Electron Spin Resonance Spectroscopy; D006801:Humans; D017665:Hydroxyl Radical; D007700:Kinetics; D009281:Naphthalenes; D011838:Radiation-Sensitizing Agents; D012459:Salicylates; D020156:Salicylic Acid; D012710:Serum Albumin, Bovine / Q000187:drug effects* / Q000528:radiation effects; D013113:Spin Labels; D008063:Thioctic Acid / Q000494:pharmacology; D014466:Ultraviolet Rays
D000975:Antioxidants; D001055:Apolipoproteins B; D003497:Cyclic N-Oxides; D009281:Naphthalenes; D011838:Radiation-Sensitizing Agents; D012459:Salicylates; D013113:Spin Labels; C067580:N,N'-bis(2-hydroxyperoxy-2-methoxyethyl)-1,4,5,8-naphthalenetetracarboxylic diimide; D012710:Serum Albumin, Bovine; D017665:Hydroxyl Radical; C017245:5,5-dimethyl-1-pyrroline-1-oxide; D008063:Thioctic Acid; D020156:Salicylic Acid