Electrochemical oxidation of fluoroquinolone antibiotics: Mechanism, residual antibacterial activity and toxicity change

Linyan Zhu; Beatrix Santiago-Schübel; Hongxia Xiao; Henner Hollert; Stephan Kueppers

doi:10.1016/j.watres.2016.06.005

Electrochemical oxidation of fluoroquinolone antibiotics: Mechanism, residual antibacterial activity and toxicity change

Linyan Zhu, Beatrix Santiago-Schübel, Hongxia Xiao, Henner Hollert, Stephan Kueppers^*

^*Corresponding author for this work

Department of Environmental Science - Environmental chemistry & toxicology

Research output: Contribution to journal/Conference contribution in journal/Contribution to newspaper › Journal article › Research › peer-review

Abstract

In this paper, we studied the electrochemical oxidation mechanisms of three typical fluoroquinolone antibiotics (FQs), and investigated residual antibacterial activity and toxicity changes after oxidation processes. Electrochemistry coupled to mass spectrometry (EC-MS) was used to study the oxidation processes of ciprofloxacin (CIP), norfloxacin (NOR) and ofloxacin (OFL). Eight oxidation products for each parent compound were identified and their chemical structures were elucidated. The transformation trend of each product, with the continuous increase of voltage from 0 to 3000 mV, was recorded by online EC-MS. The oxidation pathways were proposed based on the structural information and transformation trends of oxidation products. We found the oxidation mechanisms of FQs consisted of the hydroxylation and cleavage of piperazinyl ring via reactions with hydroxyl radicals, while the fluoroquinolone core remained intact. The antibacterial activity of the parent compounds and their oxidation mixtures was estimated using zone inhibition tests for gram-negative bacteria Salmonella typhimurium. It was found that the oxidation mixtures of CIP and NOR retained the antibacterial properties with lower activity compared to their parent compounds, while the antibacterial activity of OFL was almost eliminated after oxidation. Furthermore, the toxicity of the three FQs and their oxidation mixtures were evaluated using algal growth inhibition test (Desmodesmus subspicatus). The median effective concentration (EC ₅₀ ) values for the algal inhibition tests were calculated for the end point of growth rate. The toxicity of CIP and NOR to green algae after electrochemical oxidation, remained unchanged, while that of OFL significantly increased. The results presented in this paper contribute to an understanding of the electrochemical oxidation mechanisms of FQs, and highlight the potential environmental risks of FQs after electrochemical oxidation processes.

Original language	English
Journal	Water Research
Volume	102
Pages (from-to)	52-62
Number of pages	11
ISSN	0043-1354
DOIs	https://doi.org/10.1016/j.watres.2016.06.005
Publication status	Published - 1 Oct 2016

Keywords

Antibacterial activity
Electrochemistry-mass spectrometry
Fluoroquinolone antibiotics
Toxicity change

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10.1016/j.watres.2016.06.005

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@article{91a4e3a3c56f407cb687974d7eb62827,

title = "Electrochemical oxidation of fluoroquinolone antibiotics: Mechanism, residual antibacterial activity and toxicity change",

abstract = " In this paper, we studied the electrochemical oxidation mechanisms of three typical fluoroquinolone antibiotics (FQs), and investigated residual antibacterial activity and toxicity changes after oxidation processes. Electrochemistry coupled to mass spectrometry (EC-MS) was used to study the oxidation processes of ciprofloxacin (CIP), norfloxacin (NOR) and ofloxacin (OFL). Eight oxidation products for each parent compound were identified and their chemical structures were elucidated. The transformation trend of each product, with the continuous increase of voltage from 0 to 3000 mV, was recorded by online EC-MS. The oxidation pathways were proposed based on the structural information and transformation trends of oxidation products. We found the oxidation mechanisms of FQs consisted of the hydroxylation and cleavage of piperazinyl ring via reactions with hydroxyl radicals, while the fluoroquinolone core remained intact. The antibacterial activity of the parent compounds and their oxidation mixtures was estimated using zone inhibition tests for gram-negative bacteria Salmonella typhimurium. It was found that the oxidation mixtures of CIP and NOR retained the antibacterial properties with lower activity compared to their parent compounds, while the antibacterial activity of OFL was almost eliminated after oxidation. Furthermore, the toxicity of the three FQs and their oxidation mixtures were evaluated using algal growth inhibition test (Desmodesmus subspicatus). The median effective concentration (EC 50 ) values for the algal inhibition tests were calculated for the end point of growth rate. The toxicity of CIP and NOR to green algae after electrochemical oxidation, remained unchanged, while that of OFL significantly increased. The results presented in this paper contribute to an understanding of the electrochemical oxidation mechanisms of FQs, and highlight the potential environmental risks of FQs after electrochemical oxidation processes.",

keywords = "Antibacterial activity, Electrochemistry-mass spectrometry, Fluoroquinolone antibiotics, Toxicity change",

author = "Linyan Zhu and Beatrix Santiago-Sch{\"u}bel and Hongxia Xiao and Henner Hollert and Stephan Kueppers",

note = "Publisher Copyright: {\textcopyright} 2016 Elsevier Ltd.",

year = "2016",

month = oct,

day = "1",

doi = "10.1016/j.watres.2016.06.005",

language = "English",

volume = "102",

pages = "52--62",

journal = "Water Research",

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Electrochemical oxidation of fluoroquinolone antibiotics: Mechanism, residual antibacterial activity and toxicity change. / Zhu, Linyan; Santiago-Schübel, Beatrix; Xiao, Hongxia et al.
In: Water Research, Vol. 102, 01.10.2016, p. 52-62.

Research output: Contribution to journal/Conference contribution in journal/Contribution to newspaper › Journal article › Research › peer-review

TY - JOUR

T1 - Electrochemical oxidation of fluoroquinolone antibiotics

T2 - Mechanism, residual antibacterial activity and toxicity change

AU - Zhu, Linyan

AU - Santiago-Schübel, Beatrix

AU - Xiao, Hongxia

AU - Hollert, Henner

AU - Kueppers, Stephan

PY - 2016/10/1

Y1 - 2016/10/1

N2 - In this paper, we studied the electrochemical oxidation mechanisms of three typical fluoroquinolone antibiotics (FQs), and investigated residual antibacterial activity and toxicity changes after oxidation processes. Electrochemistry coupled to mass spectrometry (EC-MS) was used to study the oxidation processes of ciprofloxacin (CIP), norfloxacin (NOR) and ofloxacin (OFL). Eight oxidation products for each parent compound were identified and their chemical structures were elucidated. The transformation trend of each product, with the continuous increase of voltage from 0 to 3000 mV, was recorded by online EC-MS. The oxidation pathways were proposed based on the structural information and transformation trends of oxidation products. We found the oxidation mechanisms of FQs consisted of the hydroxylation and cleavage of piperazinyl ring via reactions with hydroxyl radicals, while the fluoroquinolone core remained intact. The antibacterial activity of the parent compounds and their oxidation mixtures was estimated using zone inhibition tests for gram-negative bacteria Salmonella typhimurium. It was found that the oxidation mixtures of CIP and NOR retained the antibacterial properties with lower activity compared to their parent compounds, while the antibacterial activity of OFL was almost eliminated after oxidation. Furthermore, the toxicity of the three FQs and their oxidation mixtures were evaluated using algal growth inhibition test (Desmodesmus subspicatus). The median effective concentration (EC 50 ) values for the algal inhibition tests were calculated for the end point of growth rate. The toxicity of CIP and NOR to green algae after electrochemical oxidation, remained unchanged, while that of OFL significantly increased. The results presented in this paper contribute to an understanding of the electrochemical oxidation mechanisms of FQs, and highlight the potential environmental risks of FQs after electrochemical oxidation processes.

AB - In this paper, we studied the electrochemical oxidation mechanisms of three typical fluoroquinolone antibiotics (FQs), and investigated residual antibacterial activity and toxicity changes after oxidation processes. Electrochemistry coupled to mass spectrometry (EC-MS) was used to study the oxidation processes of ciprofloxacin (CIP), norfloxacin (NOR) and ofloxacin (OFL). Eight oxidation products for each parent compound were identified and their chemical structures were elucidated. The transformation trend of each product, with the continuous increase of voltage from 0 to 3000 mV, was recorded by online EC-MS. The oxidation pathways were proposed based on the structural information and transformation trends of oxidation products. We found the oxidation mechanisms of FQs consisted of the hydroxylation and cleavage of piperazinyl ring via reactions with hydroxyl radicals, while the fluoroquinolone core remained intact. The antibacterial activity of the parent compounds and their oxidation mixtures was estimated using zone inhibition tests for gram-negative bacteria Salmonella typhimurium. It was found that the oxidation mixtures of CIP and NOR retained the antibacterial properties with lower activity compared to their parent compounds, while the antibacterial activity of OFL was almost eliminated after oxidation. Furthermore, the toxicity of the three FQs and their oxidation mixtures were evaluated using algal growth inhibition test (Desmodesmus subspicatus). The median effective concentration (EC 50 ) values for the algal inhibition tests were calculated for the end point of growth rate. The toxicity of CIP and NOR to green algae after electrochemical oxidation, remained unchanged, while that of OFL significantly increased. The results presented in this paper contribute to an understanding of the electrochemical oxidation mechanisms of FQs, and highlight the potential environmental risks of FQs after electrochemical oxidation processes.

KW - Antibacterial activity

KW - Electrochemistry-mass spectrometry

KW - Fluoroquinolone antibiotics

KW - Toxicity change

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U2 - 10.1016/j.watres.2016.06.005

DO - 10.1016/j.watres.2016.06.005

M3 - Journal article

C2 - 27318447

AN - SCOPUS:84974855150

SN - 0043-1354

VL - 102

SP - 52

EP - 62

JO - Water Research

JF - Water Research

ER -

Electrochemical oxidation of fluoroquinolone antibiotics: Mechanism, residual antibacterial activity and toxicity change

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Keywords

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