Turn-on Coumarin Precursor: From Hydrazine Sensor to Covalent Inhibition and Fluorescence Detection of Rabbit Muscle Aldolase

• Published in: Molecules (Basel, Switzerland) Vol. 29; no. 10; p. 2175
• Main Authors: Amer, Sara, Miles, Uri, Firer, Michael, Grynszpan, Flavio
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 07.05.2024
• Subjects: aldolase inhibitor; Animals; Chemical tests and reagents; coumarin; Coumarins - chemistry; Design; Fluorescence; fluorescent detection; Fluorescent Dyes - chemistry; Fluorides; Food contamination; hydrazine sensor; Hydrazines - chemistry; Molecular Structure; Muscles - metabolism; Phenols; Rabbits; Sensors; theranostics; turn-on; Israel; fluorescent detection; theranostics; turn-on; coumarin; hydrazine sensor; aldolase inhibitor
• ISSN: 1420-3049; 1420-3049
• DOI: 10.3390/molecules29102175

Hydrazine, a highly toxic compound, demands sensitive and selective detection methods. Building upon our previous studies with pre-coumarin OFF-ON sensors for fluoride anions, we extended our strategy to hydrazine sensing by adapting phenol protecting groups (propionate, levulinate, and γ-bromobutanoate) to our pre-coumarin scaffold. These probes reacted with hydrazine, yielding a fluorescent signal with low micromolar limits of detection. Mechanistic studies revealed that hydrazine deprotection may be outperformed by a retro-Knoevenagel reaction, where hydrazine acts as a nucleophile and a base yielding a fluorescent diimide compound (6,6'-((1 ,1' )-hydrazine-1,2diylidenebis(methaneylylidene))bis(3(diethylamino)phenol, ). Additionally, our pre-coumarins unexpectedly reacted with primary amines, generating a fluorescent signal corresponding to phenol deprotection followed by cyclization and coumarin formation. The potential of compound as a theranostic Turn-On coumarin precursor was also explored. We propose that its reaction with ALDOA produced a γ-lactam, blocking the catalytic nucleophilic amine in the enzyme's binding site. The cleavage of the ester group in compound induced the formation of fluorescent coumarin . This fluorescent signal was proportional to ALDOA concentration, demonstrating the potential of compound for future theranostic studies in vivo.