Highly selective fluorescence turn-on probe for glutathione

An activated coumarin-3-phenyl enone (1) by an intramolecular hydrogen bond has shown a selective and ratiometric response toward GSH and Cys over other natural amino acids through the Michael addition reaction of a thiol group to 1. When GSH was added to 1, a prominent color change together with a fluorescence turn-on property was observed so that submillimolar GSH was detectable.