*3.2. Urolithin A Inhibits Oxidases (Monoamine Oxidase A and Tyrosinase)*

As described above, the potential neuroprotective activity of urolithin A was tested on different enzymes present in the central nervous system (tyrosinase, monoamine oxidase A, and acetylcholinesterase). IC50 values were calculated by non-linear regression for kojic acid, clorgyline, and galantamine reference inhibitors, respectively.

Figure 7 shows the profile of urolithin A as an enzyme inhibitor; in particular, Figure 7A compares the reference inhibitor and urolithin against tyrosinase (IC50 values were 24.39 ± 5.97 μM and 71.44 ± 10.07 μM for kojic acid and urolithin A, respectively). Figure 7B shows how clorgyline and urolithin A are able to inhibit MAO-A. In the case of the reference inhibitor, its IC50 value is relatively lower than urolithin A (0.09 ± 0.02 μM and 29.41 ± 9.01 μM, respectively). Again, it is seen how the metabolite draws a dose-dependent curve.

Finally, urolithin A was not considered as an inhibitor of AChE because very high non-physiological concentrations (876 μM) were used to reach 50% of inhibition.

**Figure 7.** Enzymatic inhibition of urolithin A. IC50 values were calculated by non-linear regression. (**A**) Tyrosinase inhibition profiles of urolithin A and kojic acid. (**B**) Monoamine oxidase A (MAO-A) inhibition profiles of urolithin A and clorgyline.
