Curcumin-based sulfenic acid as a light switch for the binding of biothiols

Curcumin was used as a starting compound for the synthesis of a fluorescent precursor of sulfenic acid. The curcumin-derived sulfenic acid, generated in situ by thermolysis, was reacted with cysteine (Cys) and glutathione (GSH) as models of biologically relevant targets containing the thiol function. The disulfides thus obtained were subjected to a photophysical comparison with the precursor of curcuminsulfenic acid to demonstrate that, in principle, the condensation reaction with biothiols, such as Cys and GSH, can be used to identify their presence in a biological environment. In fact, the luminescence of the sulfinyl precursor is quenched in the unsymmetrical curcumin-biothiol disulfides so generated.