Alkyl N-Benzylthiocarbamates, the First Copper(II) Ion-Chelating Tyrosinase Inhibitors with a Thiocarbamate Group and ROS-Scavenging Activity, Exhibit Different Inhibitory Activities Depending on the Origin of Tyrosinase

<i>N</i>-Benzylthiocarbamate (NBTC) analogs <b>1</b>-<b>10</b> were synthesized as potential Cu²⁺-chelating tyrosinase inhibitors. Most analogs exhibited strong Cu²⁺-chelating activity, but none inhibited mushroom tyrosinase (mTYR) activity better than kojic acid (KA). However, owing to their potent cellular TYR inhibitory activity, all analogs, except <b>8</b>, inhibited melanin formation in B16F10 cells more than KA. Analogs <b>3</b>, <b>4</b>, and <b>9</b> exhibited stronger antimelanogenic properties than <i>N</i>-phenylthiourea. The TYR inhibitory activity of the analogs of mTYR and B16F10 TYR was probably different because mTYR and mammalian TYR have different structural characteristics. All analogs had a potency to significantly scavenge reactive oxygen species (ROS). Analog <b>1</b> was very effective in reducing browning in potato juice. Furthermore, analog <b>3</b> inhibited zebrafish larval pigmentation 2000 times more potently than KA and was more effective than <i>N</i>-phenylthiourea. It is believed that their capacity to scavenge ROS amplifies their antimelanogenic effects. Exogenously added CuSO₄ attenuated the inhibitions of cellular TYR activity and melanin formation in B16F10 cells caused by analog <b>9</b>. This result might have been due to the externally added Cu²⁺ ions forming chelates with <b>9</b>. The differential TYR inhibitory activity of NBTC analogs appeared to be due to their high sensitivity to interactions with TYRs of different origins.