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Publisher Summary Many methods to measure antioxidant capacity (2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonate) diammonium salt; 1,1-diphenyl-2-picrylhydrazyl) show a good response in vitro but a poor response in vivo. Diets that contain foods with significant quantities of antioxidants can increase the antioxidant capacity of plasma, adding to the effect of endogenous antioxidants. Antioxidants in biological samples are unstable, especially when exposed to air or light at room temperature. Antioxidant capacity (AC) has been determined in plasma by some authors and in serum by others, finding no differences in values between media in some cases and higher values in serum in others. This latter result is unexpected, since serum is obtained by a process of coagulation at room temperature (22°C) for 30 min. Both factors (time and temperature) can interfere with antioxidants such as ascorbic acid and glutathione, which can lower the AC value measured in the serum. Therefore, plasma is used to measure AC to avoid the reactive species generated in the coagulation process, which can compromise the AC measurement. It is recommended that plasma be centrifuged under refrigeration temperatures to minimize thermal stress to antioxidants. |
