Utility of a green fluorone-based turn-off fluorescence probe for submicromolar determination and stability testing of two macrolides. Insights into reaction thermodynamics, quenching mechanism, and identification of the oxidative degradation products by ESI+-MS

Abstract

A smart, sensitive, and green turn-off fluorescence probe was developed and validated for the determination of two macrolides; spiramycin (SPM) and josamycin (JSM) at submicromolar concentration levels. The probe is based on the fluorone-based dye, eosin Y that efficiently interacts with the two compounds through ground-state ion-pair complex formation with quenching of its native fluorescence (λex/λem of 524/548 nm). The Stern-Volmer relationship confirmed the static fluorescence quenching mechanism. Furthermore, the thermodynamic parameters of the reaction were explored via the van't Hoff plot. The values of the fluorescence quenching were linearly correlated to the drug concentration over the ranges of 0.12–5.93 and 0.30–9.66 μM (0.1–5.0 and 0.25–8.0 μg/mL) for SPM and JSM, respectively. Therefore, the probe was utilized for quality control of the two compounds in their tablets with mean %recoveries of 98.12 ± 1.72 and 97.22 ± 1.51% for SPM and JSM, respectively. Statistical analysis of the results by t- and F-tests showed excellent agreement with the results of the comparison methods. Moreover, the developed probe was applied for stability testing of the two compounds under oxidative condition along with ESI+-MS identification of the potential degradants. Besides, the greenness of the developed probe was ensured by different assessment metrics. Hence, the developed method is the first stability-indicating fluorimetric assay for the two compounds, and its chief merits include effortlessness, rapidness, sensitivity, cheapness and harmony with the green chemistry rules.