A Comprehensive Study of a New Norfloxacin-Niflumate Hydrate: Structural and Physicochemical Properties, Antibiotic Potency, Anti-Inflammatory Effect, and Drug Safety

Multicomponent antibiotic–anti-inflammatory systems have recently attracted considerable attention, as this combination is becoming a standard therapy for infectious diseases. This study aimed to develop a multicomponent system comprising norfloxacin (NOR), an old fluoroquinolone antibiotic, and niflumic acid (NIF), another old, poorly soluble anti-inflammatory drug, to improve the physicochemical properties, antibiotic potency, and anti-inflammation effect, as well as their safety. First, a phase diagram was constructed to ensure solid-state reaction and to predict its stoichiometry; subsequently, the multicomponent system was prepared by solvent-drop grinding. The product was analyzed by a series of thermal analyses and powder X-ray diffraction (PXRD). Next, Fourier-transform infrared spectroscopy and nuclear magnetic resonance elucidated the molecular interactions, and the final 3D structure was determined by single-crystal X-ray diffraction, followed by Hirshfeld surface analysis. Afterward, the solubility and chemical stability were assessed using high-performance liquid chromatography, and the physical stability of the multicomponent system was evaluated by PXRD. Antimicrobial potency against Gram-negative and Gram-positive bacteria, as well as anti-inflammatory activity in vivo, were also evaluated. The results demonstrated that a newly formed antibiotic–anti-inflammatory multicomponent system, named norfloxacin–niflumate (NORNIF), in a salt dihydrate form, significantly improved the stability and antibiotic potency of NOR, including against the resistant microbe, as well as the solubility and in vivo anti-inflammatory effect of NIF simultaneously. In addition, preliminary in silico studies using Swiss-ADME and ProTox-3 predicted that the salt was well absorbed in the gastrointestinal tract and could be classified as toxicity class 4 (non-toxic).