Towards an improved Global Antioxidant Response method (GAR+): Physiological-resembling in vitro antioxidant capacity methods.

Many methods have been developed to measure the antioxidant capacity of foods under non physiological-relevant conditions. In this study, three methods (TEAC, GEAC and TEAC) are developed to measure antioxidant capacity at physiological pH, using indigo carmine as a redox dye. TEAC and TEAC determine foodstuffs' scavenging capacity against hydroxyl (OH) and AAPH radicals, while the third method measures the global reducing capacity of the sample. The results obtained for commercial teas, commercial beverages containing tea as the main ingredient and different solid foods (spinach, onion, salami, etc.) were compared with well-established protocols. The new methods demonstrated good linearity-reproducibility, providing reliable data about the antioxidant capacity of foods under physiological-resembling conditions. The new methods were also useful for evaluating the antioxidant capacity of human plasma after acute intake of tea. The physiological-resembling conditions of these assays and the use of absorbance readings make them suitable for application by any laboratory.