Figure 2.

Antioxidant property of the dipeptide of ψ-GSH (2) and its ability to protect against Aβ^1–42 cytotoxicity in SH-SY5Y cells. (A) Analysis of antioxidant property of compound 2 by DPPH assay. (B) Glutathione peroxidase enzymatic assay. Measurement of glutathione peroxidase activity was performed using the purified enzyme in the presence of GSH or 2 as cofactors. In this coupled enzymatic assay, consumption of NADPH by glutathione reductase to reduce oxidized glutathione or 2 was measured. Differences in the levels of NADPH measured as absorbance at 340 nm compared to time zero are plotted. (C) Cytotoxicity of Aβ^1–42 in SH-SY5Y cells was mitigated by co-incubation with compound 2 in a dose-dependent manner. Plot (D) shows dose-dependent protective effect of 2 calculated in relation to Aβ-only group. Data are presented as the mean ± SEM of three independent experiments. Treatment groups were analyzed for statistical significance using one-way ANOVA with Tukey’s post-hoc test. **** p < 0.0001.