Synthesis of a fluorogenic probe for thiols based on a coumarin schiff base copper complex and its use for the detection of glutathione

Glutathione is the most abundant non-protein thiols compound in cells and plays important metabolic roles. Changes in the amount of glutathione or its metabolic dysregulation can lead to a series of diseases. The determination of glutathione levels is very helpful to the diagnosis and treatment of the related diseases. A coumarin schiff base (compound 1) was synthesized from coumarin hydrazide and 2,6-pyridine dicarboxaldehyde and the fluorogenic probe for thiols (compound 1-Cu2+) was prepared by coordinating compound 1 with copper ions. Compound 1 showed strong fluorescence, while compound 1-Cu2+ hardly had fluorescence due to the paramagnetism and/or photoinduced electron transfer of Cu2+. However, after the addition of thiols-containing compounds, the fluorescence of compound 1 was restored. The UV–vis absorption and fluorescence spectra indicated that the fluorogenic probe had good thiols selectivity and sensitivity, particularly for glutathione in CH3CN:HEPES (3:2, v/v) buffer. It was successfully applied to the fluorescence imaging detection of glutathione in human cervical squamous cancer cells (SiHa cells).