Nonvitamin Plasma Antioxidants

The chemical composition of human blood plasma is widely studied and well-known, however, the exact nature of the antioxidants of plasma is very much open to dispute. The study of plasma antioxidants has been given a fresh stimulus in recent years by the development of new methods for the measurement of hydrogen-donating antioxidant activity, the majority using fluorescent or chemiluminescent endpoints. The feature that these systems have in common with the older techniques (1 ) is that they are all inhibition assays (Fig. 1 ). In these assays, a free radical is generated and its generation is then linked to an endpoint that can be observed and quantified. Addition of an antioxidant inhibits the development of this endpoint and in each case from this measured inhibition, the antioxidant activity is quantitated (2 ).