Novel fluorescent probes for L-cysteine based on the xanthone skeleton

Abstract

Two novel derivatives of xanthone (9H-xanthen-9-one, dibenzo-γ-pyrone) containing a maleimide moiety have been synthesized. Their properties were characterized by the combination of NMR, MS, electronic absorption and fluorescence spectroscopy. The reactivity of these compounds toward L-Cys as well other analytes was determined. The results show that the novel derivatives of xanthone demonstrate a high “turn-on” fluorescence response and selectivity toward L-cysteine and have the potential to act as probes to L-cysteine under physiological conditions. Reaction of 2-maleimidoxanthone (4a) and 2,7-dimaleimidoxanthone (4b) with L-Cys lead to the formation of the fluorescent products. In the presence of L-Cys, the fluorescence intensities of probes 4a and 4b have greatly enhanced 25-fold and 60-fold, respectively. Finally, the probes 4a-4b were used to detection of thiols in the human cell line HeLa.