Comparative evaluation of the antioxidant activity of alpha-tocopherol, alpha-tocopherol polyethylene glycol 1000 succinate and alpha-tocopherol succinate in isolated hepatocytes and liver microsomal suspensions

The antioxidant activity of alpha-tocopherol polyethylene glycol 1000 succinate (TPGS) and of alpha-tocopherol succinate (TS) has been examined in isolated hepatocytes and microsomal fractions from rat liver. Both TPGS and TS require esterase activity to yield free alpha-tocopherol and, hence, antioxidant activity. TPGS and TS consistently exerted a more effective antioxidant protection than an equivalent amount of directly-added free alpha-tocopherol. The low antioxidant efficiency of directly added free alpha-tocopherol in such water-based experimental systems as used here seems to be due to its extreme hydrophobicity. TPGS, on the other hand, is an extremely hydrophilic compound that is being examined as a useful source of alpha-tocopherol in certain clinical situations and is here shown to be a convenient and effective source for experimental studies into lipid peroxidation and antioxidant mechanisms.