Oxidative Transformation of Fluoroquinolone Antibacterial Agents and Structurally Related Amines by Manganese Oxide

Abstract

Various members of the popular fluoroquinolone antibacterial agents (FQs) have been frequently detected in municipal wastewater and surface water bodies in recent years. This study was conducted to gain a better understanding of the fate of FQs in the sediment-water environment. Seven FQs were examined for adsorptive and oxidative interactions with delta-MnO2 under environmental conditions and exhibited reactivity in the order of ciprofloxacin approximately enrofloxacin approximately norfloxacin approximately ofloxacin > lomefloxacin > pipemidic acid >> flumequine. Four amines that are structurally related to the aniline and piperazine functional groups of FQs showed reactivity to oxidation by delta-MnO2 in the order of 1-phenylpiperazine > aniline > N-phenylmorpholine > 4-phenylpiperidine. Comparison among the above compounds clearly indicates thatthe piperazine moiety of FQs is the predominant adsorptive and oxidative site to MnO2. Product analyses showed that oxidation by MnO2 results in dealkylation and hydroxylation at the piperazine moiety of FQs, with the quinolone ring essentially intact. The reaction kinetics, reactivity comparison, and product characterization point to a surface reaction mechanism that likely begins with formation of a surface complex between FQ and the surface-bound MnIV, followed by oxidation at the aromatic N1 atom of FQ's piperazine moietyto generate an anilinyl radical intermediate. The radical intermediates subsequently undergo N-dealkylation, C-hydroxylation, and possibly coupling to yield a range of products. Even though the quinolone ring appears to be stable with respect to MnO2, it affects the overall reactivity and potentially product distribution of FQs via substituent effects. Results of this study strongly suggest that manganese oxides commonly present in soils will likely play an important role in the abiotic degradation of fluoroquinolone antibacterial agents in the environment.

Oxidative Degradation of Methylene Blue Using Mn3O4 Nanoparticles

“…Figure 9 shows the plot of lnC 0 /C against t where, C represents the concentration of MB at time, t, and C 0 represents the initial concentration of MB. The kinetics of the degradation process fitted to the pseudo-first-order kinetics model well which is in good agreement with the earlier works [12,13,42], where the authors reported the oxidative degradation of a number of organic pollutants with Mn oxides. In the present study, the rate constant (k) was found to be 0.0045 min −1 .…”

“…As manganese (Mn) oxides are powerful oxidants having high-reducing potential, for pollution remediation purpose, land-born natural Mn ores, synthetic nascent state Mn oxides, and materials coated/modified with Mn oxides have been tested as oxidants for degradation of organic pollutants [7,8]. It has already been reported that oxides and hydroxides of Mn 3+ and Mn 4+ can oxidize a variety of natural and xenobiotic organic compounds such as catechol, quinines, substituted phenols, aromatic amines, pesticides, and explosives (e.g., TNT) [9][10][11][12][13]. Trimanganese tetraoxide (Mn 3 O 4 ) is a mixed oxide of Mn containing both di-and tri-valents of Mn.…”

Enhanced catalytic degradation of ciprofloxacin over Ce-doped OMS-2 microspheres

“…8), acetic acid, formic acid and oxalic acid, further confirmed the deep oxidation of CIP in Ce(0.48)-OMS-2 suspension. In contrast, only the piperazine moiety of CIP was destructed in MnO 2 suspensions, due to the oxidation of Mn(IV) [32]. The higher oxidation ability of Ce-OMS-2 than MnO 2 indicated the possible existence of other active oxygen species.…”

The chemical fate of paroxetine metabolites. Dehydration of radicals derived from 4-(4-fluorophenyl)-3-(hydroxymethyl)piperidine

“…18 The ease of formation of N-centered radicals has been reported for a series of chloramines, which play an important role in environmental chemistry and biochemistry. [19][20][21][22][23] Once formed, the N-centered radical 1a can undergo fast protonation yielding the radical cation 1b. The most stable form of 1b adopts a chair conformation of the piperidine ring .…”