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

Julia Modrzejewska,Marcin Szala,Radosław Podsiadły,Małgorzata Zakłos-Szyda,Jacek Zielonka,Aleksandra Grzelakowska

doi:10.3390/molecules26195940

Julia Modrzejewska, Marcin Szala + Show 4 more

Open Access

https://doi.org/10.3390/molecules26195940

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Abstract

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 (BC-BE) as a fluorescent probe for the detection of peroxynitrite (ONOO–), with high stability and a fast response time. The BC-BE probe hydrolyzes in phosphate buffer to 3-(2-benzothiazolyl)-7-coumarin boronic acid (BC-BA) which is stable in the solution even after a prolonged incubation time (24 h). BC-BA is slowly oxidized by H2O2 to form the phenolic product, 3-benzothiazol-2-yl-7-hydroxy-chromen-2-one (BC-OH). On the other hand, the BC-BA probe reacts rapidly with ONOO−. The ability of the BC-BA probe to detect ONOO– was measured using both authentic ONOO– and the system co-generating steady-state fluxes of O2•– and •NO. BC-BA is oxidized by ONOO– to BC-OH. However, in this reaction 3-benzothiazol-2-yl-chromen-2-one (BC-H) is formed in the minor pathway, as a peroxynitrite-specific product. BC-OH is also formed in the reaction of BC-BA with HOCl, and subsequent reaction of BC-OH with HOCl leads to the formation of a chlorinated phenolic product, which could be used as a specific product for HOCl. We conclude that BC-BA 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.

Highlights

Coumarin skeleton is frequently used to construct a range of fluorescent dyes due to high fluorescent quantum yields and tunable emission wavelengths
The emission of coumarin-based fluorophores can be finely tuned by appropriate substitution in 2Hchromen-2-one skeleton
Derivatives of coumarin generally show good photostability which is rather unusual among fluorescent dyes [3]

Summary

Introduction

Coumarin skeleton is frequently used to construct a range of fluorescent dyes due to high fluorescent quantum yields and tunable emission wavelengths. The emission of coumarin-based fluorophores can be finely tuned by appropriate substitution in 2Hchromen-2-one skeleton. Fluorescence can be red shifted by the placement of electrondonating groups in the six- or seven-position or electron-accepting groups in the three- or four-position of the skeleton [1]. A widely used example of coumarin dyes is C.I. Disperse Yellow 82 [2] which, in the 7position of the coumarin ring, contains the N,N-diethylamino group and, in the 3-position, a benzimidazole residue. Derivatives of coumarin generally show good photostability which is rather unusual among fluorescent dyes [3]

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