The detrimental effects of reactive oxygen and nitrogen species (ROS/RNS) in mammalian
systems are determined not only by the amounts and reactivity of the ROS/RNS formed, but also by the
status of cellular and tissue antioxidant defenses. Thus, detection and measurement of endogenous
antioxidants are an important part of investigation into the mechanism of oxidative stress in human
disease development. This chapter provides an overview of the general experimental approaches to
assessing antioxidant defenses and describes the basic methodologies for measuring the activities and
levels of the major cellular and tissue antioxidants.
Keywords: Antioxidants, Catalase, Glutaredoxin, Glutathione system, Heme oxygenase, Methionine
sulfoxide reductase, Methodologies, NAD(P)H:quinone oxidoreductase, Paraoxonase, Superoxide
dismutase, Thioredoxin system, Total antioxidant capacity.