Design and Synthesis of (Z)-5-(Substituted benzylidene)-3-cyclohexyl-2-thioxothiazolidin-4-one Analogues as Anti-Tyrosinase and Antioxidant Compounds: In Vitro and In Silico Insights

Many compounds containing the beta-phenyl-alpha,beta-unsaturated carbonyl (PUSC) scaffold, including cinnamamide derivatives, have been shown to inhibit tyrosinase potently in vitro and in vivo. Structural changes to cinnamamide derivatives were produced by adding a dithionate functional group to provide eight (Z)-5-(substituted benzylidene)-3-cyclohexyl-2-thioxothiazolidin-4-one analogs with high log p values for skin. These analogs were synthesized using a two-step reaction, and their stereochemistry was confirmed using the (3)J(C4-H beta) values of C4 measured in proton-coupled C-13 mode. Analogs 2 (IC50 = 5.21 +/- 0.86 mu M) and 3 (IC50 = 1.03 +/- 0.14 mu M) more potently inhibited mushroom tyrosinase than kojic acid (IC50 = 25.26 +/- 1.10 mu M). Docking results showed 2 binds strongly to the active site of tyrosinase, while 3 binds strongly to an allosteric site. Kinetic studies using l-tyrosine as substrate indicated 2 and 3 competitively and non-competitively inhibit tyrosinase, respectively, which was supported by our docking results. In B16F10 cells, 3 significantly and concentration-dependently reduced alpha-MSH plus IBMX induced increases in cellular tyrosinase activity and melanin production and the similarity between these inhibitory patterns implied that the anti-melanogenic effect of 3 might be due to its tyrosinase-inhibitory ability. In addition, 2 and 3 exhibited strong antioxidant effects; for example, they reduced ROS and ONOO- levels and exhibited radical scavenging activities, suggesting that these effects might underlie their anti-melanogenic effects. Furthermore, 3 suppressed the expressions of melanogenesis-associated proteins and genes in B16F10 cells. These results suggest (Z)-5-(substituted benzylidene)-3-cyclohexyl-2-thioxothiazolidin-4-one analogs offer a means of producing novel anti-melanogenesis agents.

Automated summary

Many compounds with the PUSC structure, including cinnamamide derivatives, have been found to effectively inhibit tyrosinase. The addition of a dithionate functional group to cinnamamide derivatives produces new compounds with high skin permeability and stronger inhibitory effects on tyrosinase. Kinetic studies and docking results confirm the mechanism of inhibition, and further research reveals the antioxidant and anti-melanogenic effects of these compounds. These findings provide a reference for the development of novel anti-melanogenesis agents.