Green spectrofluorimetric determination of Ibrexafungerp using NBD-Cl derivatization

Ibrexafungerp (IBX) is the first approved triterpenoid antifungal indicated for the treatment of vulvovaginal candidiasis, particularly in cases resistant to azole and echinocandin therapies. In this study, a sensitive, simple, and environmentally sustainable spectrofluorimetric method was developed for the quantitative determination of IBX in pharmaceutical tablets. The method is based on chemical derivatization of IBX with 4-chloro-7-nitrobenzo-2-oxa-1,3-diazole (NBD-Cl), forming a highly fluorescent adduct measured at an emission wavelength of 554 nm following excitation at 472 nm. The reaction proceeds via nucleophilic substitution between the primary amine group of IBX and NBD-Cl. Experimental conditions affecting derivatization and fluorescence intensity were systematically optimized. The method exhibited excellent linearity over the concentration range of 150-2000 ng/mL (r² = 0.9996), with limits of detection and quantification of 39.196 and 118.774 ng/mL, respectively. Validation according to ICH guidelines confirmed satisfactory accuracy, precision, and robustness. The method was successfully applied without interference from excipients. Greenness assessment using Analytical Eco-Scale, AGREE, and GAPI tools confirmed the environmentally friendly nature of the proposed method, supporting its suitability for routine quality control applications.