Reaction of HO sub 2 /O sub 2- with alpha -Tocopherol in Ethanolic Solutions

摘要

The HO sub 2 perhydroxyl radical reacts with alpha -tocopherol in 85% ethanol containing some H sub 2 SO sub 4 , EDTA, and O sub 2 . The resulting transient has a spectral maximum near 390 mu . The final product is mostly alpha -tocopherylquinone. Best reproducibility for reaction of O sub 2- with alpha -tocopherol was obtained in a deoxygenated reaction mixture of 26 +- 3 mu M O sub 2- , 0.0565M alpha -tocopherol, 5 mu M EDTA, and 0.005 M KOH in 85% EtOH; the upper limit for the reaction was 6.0 +- 3.0 M exp -1 s exp -1 , indicating that for all practical purposes O sub 2- does not react at all with alpha -tocopherol. Preliminary experiments with Trolox, a vitamin E model compound, indicates that it too reacts with HO sub 2 but not with O sub 2- . Membrane-bound tocopherols in vivo may fulfil a dual antioxidant role. (ERA citation 08:000844)