2.9. Tyrosinase Inhibitory Activity Test

The mushroom tyrosinase inhibition assay was performed as previously described [30]. Briefly, 40 μL of mushroom tyrosinase solution (100 units/mL), 40 μL of L-tyrosine solution (0.1 mg/mL), 40 μL of S. nigra extract in hydroalcoholic solution, and 80 μL of phosphate-buffered saline (PBS) solution (25 mM, pH 6.8) were added to a 96-well microplate and incubated for 30 min at 37 °C. The amount of the produced dopachrome was measured at 492 nm before and after incubation. Kojic acid was used as positive control. The percentage of tyrosinase inhibition was calculated as follows:

where A and A^’ are the absorbance values of the blank solution after and before incubation, respectively; B and B^’ are the absorbance values of the extract solution after and before incubation, respectively.