A fluorescent probe for sulfur dioxide reveals intracellular reductive stress triggered by natural antioxidants.

Sulfur dioxide (SO2), a pivotal gasotransmitter, is intricately linked to cellular redox homeostasis. Here, we developed the red-emissive DCM-MQE probe for rapid and sensitive detection of intracellular SO2. Using this probe, we have demonstrated that natural antioxidants significantly elevate SO2 levels in both cells and tumor-bearing mice, and confirmed that antioxidants modulate SO2-mediated redox homeostasis through induction of reductive stress.