A Fluorescently Ratiometric Natural Probe for Selective Detection of Sulfur Dioxide Derivative and Host-Guest Supramolecular Regulation.

Natural sanguinarine (SG) was first used as a fluorescent probe to develop a novel ratiometric sensor for selective HSO3- detection. The nucleophilic addition reaction of HSO3- occurs at the C=N+ group of SG, and subsequent breakage of the conjugated π cycle leads to a decrease in the SG iminium fluorescence that is accompanied by an increase in the alkanolamine fluorescence. Therefore, a ratiometric fluorescence method with a large wavelength shift can be established for HSO3- detection. Furthermore, cucurbit[8]uril was used as an efficient host to encapsulate SG for an improved selectivity for HSO3- detection over H2S. Our method benefits include little interference from other common anions and cations for HSO3- detection, suggesting a promising application in real sample analysis. Besides sensor development, the interaction of the natural SG with HSO3- was first demonstrated in this work to further get an insight into SG's pharmacology.