Solid-state properties and antibiotic potency of levofloxacin - dicarboxylate salts prepared by the green method

This research dealt with the green methods to react levofloxacin (LF) with dicarboxylate acids: oxalic acid (OX), succinic acid (SA), malonic acid (MN), and maleic acid (MA) and investigated its impact on the LF's stability, solubility, and antimicrobial potency, which never been reported before. Solvent-dropped grinding (SDG) using ethanol 95 % was used to prepare the organic antibiotic salts, reducing the solvent usage significantly compared to the conventional solvent evaporation method, supported with solid-state characterization using electrothermal, differential scanning calorimetry and powder X-ray diffractometry. Next, Fourier Transform Infrared Spectroscopy and Nuclear Magnetic Resonance (1H-NMR) confirmed and determined the interaction structure between LF and the acids. Afterward, the benefits of the LF-dicarboxylate salts were investigated, including stability, solubility, and antibiotic potency. The results demonstrated that the SDG could produce LF-OX hydrate, LF-SA hydrate, and anhydrous LF-MN in a (1:1) molar ratio, with a diffractogram never yet explained. Meanwhile, the LF-MA (1:1) salt solid-state structure was identical to the reported one. Notably, these LF-dicarboxylates showed better solubility, stability, and potency than LF alone, suggesting potential for further dosage formulations.