An ROS-Responsive Donor That Self-Reports Its H₂S Delivery by Forming a Benzoxazole-Based Fluorophore.

Area of Science:

• Biochemistry
• Chemical Biology
• Medicinal Chemistry

Background:

• Hydrogen sulfide (H₂S) is a crucial endogenous signaling molecule involved in neuroprotection, vasodilation, and hormonal regulation.
• Developing precise H₂S donors for controlled biological delivery, particularly under specific physiological or pathological conditions, is essential for further research.

Purpose of the Study:

• To design and synthesize novel thioamide-based donors for controlled hydrogen sulfide (H₂S) release.
• To investigate dual H₂S release mechanisms (Lewis acid hydrolysis and ROS-induced oxidation/cyclization) from ortho-substituted aryl boronate esters.
• To develop a self-reporting H₂S donor with a mechanism to prevent false positives.

Main Methods:

• Synthesis of ortho-substituted aryl boronate esters as thioamide-based H₂S donors.
• Structure-activity relationship studies to identify donors with specific H₂S release mechanisms.
• Development of an ROS-activated H₂S donor (QH642) coupled with a benzoxazole fluorophore synthesis.
• Evaluation of donor performance and H₂S release accuracy in complex cellular environments.

Main Results:

• Two distinct H₂S release pathways were identified: Lewis acid-facilitated hydrolysis and ROS-induced oxidation/cyclization.
• Donors resistant to hydrolysis and releasing H₂S solely via ROS-induced oxidation were successfully developed.
• A novel ROS-activated donor, QH642, was synthesized, which generates a benzoxazole fluorophore only upon H₂S release.
• This design ensures fluorophore formation is contingent on H₂S discharge, eliminating false positives.

Conclusions:

• Ortho-substituted aryl boronate esters offer versatile platforms for designing H₂S donors with tunable release mechanisms.
• The developed ROS-activated donor (QH642) provides a reliable and accurate method for monitoring H₂S delivery in biological systems.
• This self-reporting system enhances the study of H₂S signaling by confirming donor activity and minimizing experimental artifacts.