Figure 4.

The mushroom tyrosinase inhibition screen of pyrazoles, pyrazolones, and isoxazoles P1–P25 identified several relatively active tyrosinase inhibitors (P4, P8, P11, P12, P14, P17, P18, and P21). (A) Initial single-concentration tyrosinase inhibition screening for derivatives P1–P25, with arbutin as a positive control. Ten compounds at a fixed concentration of 500 µM showed comparable or better percentage activity than arbutin. Data are expressed as mean ± SD from at least six independent experiments performed in triplicate. (B) Response vs. concentration curves for the above-listed potent pyrazole and pyrazolone compounds, with calculated 50% inhibitory activity (IC₅₀) values. Data are expressed as mean ± SD from at least six independent experiments performed in quadruplicate.