Fluoroquinolones metal complexation and its environmental impacts

Fluoroquinolones (FQs), the group of broad spectrum antimicrobials, are frequently detected in different environmental compartments, mostly due to incomplete metabolism in the target organism, inefficient wastewater treatment, and disposal of expired FQs directly into the environment. Another group of the contaminants, widely present in water, air, and soils, are the metal ions (Me). In general, FQs can form stable complexes with metal ions and their co-existence with Me in the environment leads to metal complexation. The most stable complexes are formed between FQs and trivalent ions, whereas FQs and alkali-earth metal ions, i.e. Ca2+ and Mg2+, are the least stable composites. This interaction between FQs and metal ions may alter antibiotic properties. Antibacterial activity of metal complexes is generally comparable with the parent compound; however, some FQs-metal complexes are found to exhibit higher antibacterial activity. Moreover, it was proved that FQs-Me complex can display antifungal potency toward Candida albicans. The mobility of FQs in soil and/or water strongly depends on pH, temperature, and type of metal ions, present in the environment. This review provides a brief description of FQs, their properties, and capacity to form complexes with metal ions. It summarizes influence of FQs-Me complexes on microorganisms and their mobility in different media. Further, the review provides a linkage between the presence of these metal ions in the environment and their effect on the chemistry and biology of fluoroquinolone antibiotics.