Preparation, Characterization, and In Vitro Evaluation of the Biological Activity of Several Metal-Based Complexes with Two Widely Used Fluoroquinolone Antibiotics: Lomefloxacin and Pefloxacin Drugs

Abstract

Lomefloxacin (F1) and pefloxacin (F2) have a broad spectrum of antimicrobial activities against gram-positive and gram-negative bacteria. In this study, we investigated the complexation mode, morphological, and biological properties of four metal-based complexes of F1 and F2 molecules with Mg(II), Ca(II), Zn(II), and Fe(III) metal ions. These complexes were prepared at ~60–70 °C in a neutral medium using a 5% NH3 solution at ph ~7–8 with a 1:1 ratio. Multiple physicochemical methods were employed to characterize the binding mode between F1 and F2 with the metal ions under investigation. The results of these methods suggested that the gross formula of the complexes obtained with the metal ions were [mgf1(H2O)Cl]⋅2H2O, [caf1(H2O)Cl]⋅3H2O, [znf1(H2O)Cl], [fef1(H2O)2Cl2]⋅Cl⋅2H2O, [mgf2(H2O)Cl]⋅2H2O, [caf2(H2O)Cl]⋅3H2O, [znf2(H2O)Cl], and [fef2(H2O)2Cl2]⋅Cl⋅2H2O. The microscopic characterizations indicated that the Ca(II)-F1 complex had an interesting surface topography. Its particles had a homogenous, short, rod-like shaped structure that clustered together to form a tree shape. Using the Kirby–Bauer disc diffusion protocol, the synthesized metal-based complexes were screened in vitro against different gram-positive and gram-negative bacterial and fungal species. The antimicrobial profile of the Fe(III)-F1 complex indicated that it had remarkable inhibitory activity against all the tested bacterial and fungal species with a potency equal to that of the standard drugs (streptomycin and ketoconazole).