Glutathione (γ-glutamyl-cysteinyl-glycine; also known as GSH) is an endogenous antioxidant that plays a crucial role in cell defense mechanisms against oxidative stress. It is thus not surprising that this molecule can serve as a biomarker for oxidative stress monitoring. As capillary blood is a highly accessible target for biomarking, it is a valuable bodily fluid for diagnosing human GSH levels. This study focused on the optimization of GSH measurements from micro volumes of capillary blood prior to using electrochemical detection. The optimization of experimental parameters, including the sample volume and its stability, was performed and evaluated. Moreover, we tested the optimized method as part of a short-term study. The study consisted of examining 10 subjects within 96 h of their consumption of high amounts of antioxidants, attained from a daily dose of 2 g/150 mL of green tea. The subjects' capillary blood (5 μL) was taken at 0 h, 48 h, and 96 h for subsequent analysis. The short-term supplementation of diet with green tea showed an increase of GSH pool by approximately 38% (between 0 and 48 h) within all subjects.

Central European Institute of Technology Brno University of Technology Purkyňova 656 123 CZ 612 00 Brno Czech Republic

Department of Chemistry and Biochemistry Mendel University in Brno Zemedelska 1 CZ 613 00 Brno Czech Republic

University Sports Centre Faculty of Sports Studies Masaryk University Komenskeho namesti 2 CZ 662 43 Brno Czech Republic

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