*4.9. Statistical Analysis*

All experiments were carried out 3 times in triplicate. Statistical significance was calculated compared to the control. All results are presented as mean ± SEM (standard error of the mean) relative to the control—differentiated and untreated PC12 cells. Positive assay control (DMSO) was the reference value in the MTT assay. Positive assay control (H2O2) was the reference value in the Griess and DCF-DA assays. As data have normal distribution confirmed by Shapiro–Wilk test, a parametric test was used (one-way ANOVA with Tukey post hoc tests), and the Pearson correlation was performed between Griess, DCF-DA and DBS results.

**Author Contributions:** Conceptualization, A.K.-K. and B.W.; methodology, A.K.-K. and B.W.; writing—original draft preparation, A.K.-K., B.W.; writing—review and editing, A.K.-K. and B.W.; visualization, A.K.-K. and B.W.; revision and funding acquisition, A.P.; final approval of manuscript— A.P. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research received no external funding.

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** The data generated and analyzed during the current study are available from the corresponding author upon reasonable request.

**Conflicts of Interest:** The authors declare no conflict of interest.

#### **References**

