Prolongation of the lag time preceding peroxidation of serum lipids: a measure of antioxidant capacity.

Antioxidants inhibit oxidation processes and by this affect many biological processes. This, in turn, promotes continuing efforts to synthesize new efficient antioxidants and discover compounds of natural origin capable of preventing peroxidation. Although many assays have been developed to evaluate antioxidants, the search for improved protocols is still actual. The presented protocol is based on the effect of antioxidant on the kinetics of peroxidation of lipids in human blood serum. Specifically, we evaluate the capacity of antioxidant by the relative prolongation of lag phase (delay) of copper-induced peroxidation of lipids in unfractionated serum. The main advantage of the assay is that it implements inhibition of peroxidation in physiologically relevant system. We propose expressing the results of the assay either in terms of the relative prolongation of the lag per 1 μM of antioxidant or as the concentration of antioxidant required to double the lag. To allow for comparing the results with those of other assays, these results may be normalized and expressed in terms of the unitless "TROLOX equivalents."