*4.4. Determination of IC50 Values*

The enzyme assays were performed at a fixed concentration of the substrate kynuramine (80 μM for MAO-A and 50 μM for MAO-B) and different concentrations of the test compounds (**1**–**6**). The dose–response enzyme-inhibition curves were generated using Microsoft® Excel and the IC50 values were computed with XLfit®.
