Cell Meter? Colorimetric Antioxidant Activity Assay Kit. Reactive oxygen species (ROS) are important in cell signaling and maintaining physiological cell metabolism. Excessive level of ROS damages cellular components, which links to numerous diseases, including cancer, metabolic disorders, neurodegenerative disease etc. Antioxidants, including enzymes, macromolecules and small molecules are generated to combat the ROS induced damages in the living organisms. Quantitative analysis of antioxidant activity in body fluids, tissues and cells provides important biological information.