Design and synthesis of 3,5-diaryl-4,5-dihydro-1H-pyrazoles as new tyrosinase inhibitors.

In this study, twenty 3,5-diaryl-4,5-dihydro-1H-pyrazole derivatives with hydroxyl(s) (1a–1p, 2a–2d) were synthesized and their inhibitory activity on mushroom tyrosinase was examined. The results showed that among these compounds, 1-(5-(3,4-dihydroxyphenyl)-3-(4-hydroxyphenyl)-4,5-dihydro-1H-pyrazol-1-yl)ethanone 1d was found to be the most potent tyrosinase inhibitor with IC50 value of 0.301μM. Kinetic study revealed that these compounds were competitive inhibitors of tyrosinase and their structure–activity relationships were investigated in this article.