Novel Boronate Probe Based on 3-Benzothiazol-2-yl-7-hydroxy-chromen-2-one for the Detection of Peroxynitrite and Hypochlorite.

Derivatives of coumarin, containing oxidant-sensitive boronate group, were recently developed for fluorescent detection of inflammatory oxidants. Here, we report the synthesis and the characterization of 3-(2-benzothiazolyl)-7-coumarin boronic acid pinacol ester () as a fluorescent probe for the detection of peroxynitrite (ONOO), with high stability and a fast response time. The probe hydrolyzes in phosphate buffer to 3-(2-benzothiazolyl)-7-coumarin boronic acid () which is stable in the solution even after a prolonged incubation time (24 h). is slowly oxidized by HO to form the phenolic product, 3-benzothiazol-2-yl-7-hydroxy-chromen-2-one (). On the other hand, the probe reacts rapidly with ONOO. The ability of the probe to detect ONOO was measured using both authentic ONOO and the system co-generating steady-state fluxes of O and NO. is oxidized by ONOO to . However, in this reaction 3-benzothiazol-2-yl-chromen-2-one () is formed in the minor pathway, as a peroxynitrite-specific product. is also formed in the reaction of with HOCl, and subsequent reaction of with HOCl leads to the formation of a chlorinated phenolic product, which could be used as a specific product for HOCl. We conclude that shows potential as an improved fluorescent probe for the detection of peroxynitrite and hypochlorite in biological settings. Complementation of the fluorescence measurements by HPLC-based identification of oxidant-specific products will help to identify the oxidants detected.