A rapid and simple screening test for potential inhibitors of tocopherol-mediated peroxidation of LDL lipids

We report a rapid and convenient method for screening potential inhibitors of the initiation of low density lipoprotein (LDL) lipid peroxidation. The method uses positively and negatively charged micelles of either cetyltrimethyl ammonium chloride or sodium dodecyl sulfate with added alpha-tocopherol. It is based on the capacity of an antioxidant to attenuate alpha-tocopheroxyl radicals, generated by irradiation of the alpha-tocopherol-containing micelles with UV light, and measured directly by electron spin resonance spectroscopy. To establish the reliability of the method, we compared the alpha-to-copheroxyl radical attenuating ability (TRAA) of 53 natural and synthetic potential antioxidants with their respective ability to inhibit the early stages of LDL lipid peroxidation initiated by a low flux of water-soluble peroxyl radicals. The relationship between the measured TRAA and corresponding LDL antioxidation activity was highly significant (P < 0.00005, Rank test). Thus, the potency of a co-antioxidant for LDLs alpha-tocopherol could be predicted with > 98% probability by the TRAA test alone. The results suggest that this relatively simple method represents an effective and simple screening test that can be used for large numbers of potential inhibitors of the early stages of LDL lipid oxidation.