Xanthurenic acid: a natural ionophore with high selectivity and sensitivity for potassium ions in an aqueous solution

Abstract

Xanthurenic acid (H₃L), a simple natural molecule and a well known tryptophan metabolite involved in the biosynthesis of quinolobactin siderophore, was developed as an efficient “turn-on” fluorosensor for potassium ions in aqueous HEPES buffer solutions. The natural ionophore, H₃L, showed high selectivity for K⁺ at physiological pH and in the context of interference from other competing metal ions, particularly Na⁺, the specific response of H₃L towards K⁺ did not change. The detection limit was found to be 53 nM. This study demonstrates the first example in which a non-cyclic system bearing monocarboxylate functionality was used as an efficient fluorosensor for the detection of K⁺ in water.