Advances in Analytical Strategies for Precise Quantification of Topoisomerase Inhibitors: Current Trends and Future...

Topoisomerase inhibitors (TIs) are a cornerstone class of anticancer and antimicrobial agents, yet their accurate quantification in pharmaceutical formulations and biological matrices remains analytically challenging. These difficulties stem from marked structural diversity, poor aqueous solubility, narrow therapeutic windows, very low circulating concentrations, chemical instability, and, for camptothecin derivatives, pH-dependent interconversion between active lactone and inactive carboxylate forms. This review critically evaluates current analytical approaches for determining widely used TIs, including topotecan, irinotecan, etoposide, epirubicin, dexrazoxane, and camptothecin, with emphasis on selectivity, sensitivity, applicability, and robustness in complex matrices. Conventional spectroscopic methods and HPLC with UV or fluorescence detection remain useful for formulation analysis and preliminary screening but often lack sufficient selectivity and sensitivity for biological samples. Electrochemical techniques, especially those employing nanomaterials or molecular recognition elements, offer high sensitivity and low sample consumption; however, their routine application is limited by matrix effects and scarce regulatory validation. In contrast, ultrahigh-performance liquid chromatography coupled with tandem or high-resolution mass spectrometry (UHPLC-MS/MS or UHPLC-HRMS) provides superior selectivity, sub-ng mL^-1 sensitivity, and reliable discrimination of parent drugs and metabolites across diverse matrices. Overall, UHPLC-MS-based methods emerge as the current gold standard for TI quantification, supporting clinical, pharmacokinetic, and regulatory applications in modern analytical science.