Detection, transformation, and toxicity of indole-derivative nonsteroidal anti-inflammatory drugs during chlorine disinfection

Construction of artificial peroxidase based on myoglobin scaffold for efficient degradation of meloxicam

A novel artificial peroxidase has been developed for the efficient degradation of the non-steroidal anti-inflammatory drug meloxicam by combining computer simulation and genetic engineering techniques. The results showed that the artificial peroxidase was able to completely degrade meloxicam within 90 s, with a degradation rate of 100 %, which was much higher than that of natural lacquer (46 %). The reaction time of the artificial enzyme was significantly shorter than that of natural peroxidase (10 min) and laccase (48 h). Further studies showed that the amino acid arrangement of the active site of the protein plays an important role in the catalytic performance. The degradation pathway of meloxicam was revealed using UPLC-MS analysis. In vitro toxicity assay showed complete disappearance of toxicity after meloxicam degradation. Therefore, the biocatalytic system proved to be an effective route for the green degradation of meloxicam with important application potential.

A group of emerging heterocyclic nitrogenous disinfection byproducts: Formation and cytotoxicity of halopyridinols in drinking water

Recently, a new group of halopyridinol disinfection byproducts (DBPs) was reported in drinking water. The in vivo developmental and acute toxicity assays have shown that they were more toxic than a few commonly known aliphatic DBPs such as bromoform and iodoacetic acid. However, many pyridinol DBPs with the same main structures but different halogen substitutions were still unknown due to complicated water quality conditions and various disinfection methods applied in drinking water treatment plants. Studies on their transformation mechanisms in drinking water disinfection were quite limited. In this study, comprehensive detection and identification of halopyridinols were conducted, and five new halopyridinols were first reported, including 2-chloro-3-pyridinol, 2,6-dichloro-3-pyridinol, 2-bromo-5-chloro-3-pyridinol, 2,4,6-trichloro-3-pyridinol and 2,5,6-trichloro-3-pyridinol. Formation conditions and mechanisms of the halopyridinols were explored, and results showed that chlorination promoted their formation compared with chloramination. Halopyridinols were intermediate DBPs that could undergo further transformation/degradation with increasing contact time, disinfectant dose, bromide concentration, and pH. The in vitro cytotoxicity of the halopyridinols was evaluated using human hepatocellular carcinoma cells. Results showed that the cytotoxicity of 3,5,6-trichloro-2-pyridinol was the highest (EC50 = 474.3 μM), which was 13.0 and 1.6 times higher than that of 2-bromo-3-pyridinol (EC50 = 6214.5 μM) and tribromomethane (EC50 = 753.6 μM), respectively.

Recent progress in identification of water disinfection byproducts and opportunities for future research

Numerous disinfection by-products (DBPs) are formed from reactions between disinfectants and organic/inorganic matter during water disinfection. More than seven hundred DBPs that have been identified in disinfected water, only a fraction of which are regulated by drinking water guidelines, including trihalomethanes, haloacetic acids, bromate, and chlorite. Toxicity assessments have demonstrated that the identified DBPs cannot fully explain the overall toxicity of disinfected water; therefore, the identification of unknown DBPs is an important prerequisite to obtain insights for understanding the adverse effects of drinking water disinfection. Herein, we review the progress in identification of unknown DBPs in the recent five years with classifications of halogenated or nonhalogenated, aliphatic or aromatic, followed by specific halogen groups. The concentration and toxicity data of newly identified DBPs are also included. According to the current advances and existing shortcomings, we envisioned future perspectives in this field.

Characterization of halogenated organic compounds by the Fourier transform ion cyclotron resonance mass spectrometry: A critical review

Halogenated organic compounds (HOCs), widely present in various environments, are generally formed by natural processes (e.g., photochemical halogenation) and anthropogenic activities (e.g., water disinfection and anthropogenic discharge of HOCs), posing health and environmental risks. Therefore, in-depth knowledge of the molecular composition, transformation, and fate of HOCs is crucial to regulate and reduce their formation. Because of the extremely complex nature of HOCs and their precursors, the molecular composition of HOCs remains largely unknown. The Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) offers the most powerful resolution and mass accuracy for the simultaneous molecular-level characterization of HOCs and their precursors. However, there is still a paucity of reviews regarding the comprehensive characterization of HOCs by FT-ICR MS. Based on the FT-ICR MS, the formation mechanism, sample pretreatment, and analysis methods were summarized for two typical HOCs classes, namely halogenated disinfection byproducts and per- and polyfluoroalkyl substances in this review. Moreover, we have highlighted data analysis methods and some typical applications of HOCs using FT-ICR MS and proposed suggestions for current issues. This review will deepen our understanding of the chemical characterization of HOCs and their formation mechanisms and transformation at the molecular level in aquatic systems, facilitating the application of the state-of-the-art FT-ICR MS in environmental and geochemical research.

Acute and Transgenerational Effects of Non-Steroidal Anti-Inflammatory Drugs on Daphnia magna

Pharmaceuticals pose a great threat to organisms inhabiting the aquatic environment. Non-steroidal anti-inflammatory drugs (NSAIDs) are major pharmaceutical pollutants with a significant presence in freshwater ecosystems. In this study, the impact of indomethacin and ibuprofen, two of the most commonly prescribed NSAIDs, was assessed on Daphnia magna. Toxicity was assessed as the immobilization of animals and used to determine non-lethal exposure concentrations. Feeding was assessed as a phenotypic endpoint and key enzymes were used as molecular endpoints of physiology. Feeding was decreased in mixture exposures for five-day-old daphnids and neonates. Furthermore, animals were exposed to NSAIDs and their mixture in chronic and transgenerational scenarios revealing changes in key enzyme activities. Alkaline and acid phosphatases, lipase, peptidase, β-galactosidase, and glutathione-S-transferase were shown to have significant changes in the first generation at the first and third week of exposure, and these were enhanced in the second generation. On the other hand, the third recovery generation did not exhibit these changes, and animals were able to recover from the induced changes and revert back to the control levels. Overall, our study points towards transgenerational exposures as more impactful laboratory studies to understand pharmaceutical stressors with a combination of molecular and phenotypic markers of physiology.

Formation of Larger Molecular Weight Disinfection Byproducts from Acetaminophen in Chlorine Disinfection

Acetaminophen is widely used to treat mild to moderate pain and to reduce fever. Under the worldwide COVID-19 pandemic, this over-the-counter pain reliever and fever reducer has been drastically consumed, which makes it even more abundant than ever in municipal wastewater and drinking water sources. Chlorine is the most widely used oxidant in drinking water disinfection, and chlorination generally causes the degradation of organic compounds, including acetaminophen. In this study, a new reaction pathway in the chlorination of acetaminophen, i.e., oxidative coupling reactions via acetaminophen radicals, was investigated both experimentally and computationally. Using an ultraperformance liquid chromatograph coupled to an electrospray ionization-triple quadrupole mass spectrometer, we detected over 20 polymeric products in chlorinated acetaminophen samples, some of which have structures similar to the legacy pollutants "polychlorinated biphenyls". Both C-C and C-O bonding products were found, and the corresponding bonding processes and kinetics were revealed by quantum chemical calculations. Based on the product confirmation and intrinsic reaction coordinate computations, a pathway for the formation of the polymeric products in the chlorination of acetaminophen was proposed. This study suggests that chlorination may cause not only degradation but also upgradation of a phenolic compound or contaminant.

The key role of hydrophobicity in the determination of pharmaceuticals by liquid chromatography-electrospray ionization-mass spectrometry under the interference of natural organic matter

The determination of trace-level pharmaceuticals in water is generally performed using liquid chromatography combined with mass spectrometry, which is susceptible to interference from non-target substances, such as natural organic matter (NOM). In this study, the interference of NOM on the determination of 20 typical pharmaceuticals using solid-phase extraction followed by ultra-performance liquid chromatography-electrospray ionization-triple quadrupole mass spectrometry (UPLC-ESI-tqMS) was investigated with a combined consideration of recoveries, matrix effects, and process efficiencies. The results showed that the recoveries of most pharmaceuticals were not significantly affected by NOM concentrations of 1-50 mg/L. The matrix effects and process efficiencies decreased linearly with increasing logarithmic NOM concentrations, and the changes in matrix effects and process efficiencies both exhibited negative linear correlations with the pharmaceuticals' hydrophobicity (logK_ow). This result indicated that the determination of hydrophilic pharmaceuticals suffered from more severe NOM interference, as NOM entered the ESI source together with hydrophilic pharmaceuticals after UPLC separation and subsequently weakened the ionization efficiency of these pharmaceuticals. According to the correlations between logK_ow and the changes in matrix effects and process efficiencies, the pharmaceutical determination in positive/negative ESI modes with logK_ow ≤ 3.80/4.27 is considered to be significantly affected by NOM, accompanied by > 20% changes in matrix effects and process efficiencies.

New Pyrrole Derivatives as Promising Biological Agents: Design, Synthesis, Characterization, In Silico, and Cytotoxicity Evaluation

The current study describes the synthesis, physicochemical characterization and cytotoxicity evaluation of a new series of pyrrole derivatives in order to identify new bioactive molecules. The new pyrroles were obtained by reaction of benzimidazolium bromide derivatives with asymmetrical acetylenes in 1,2-epoxybutane under reflux through the Huisgen [3 + 2] cycloaddition of several ylide intermediates to the corresponding dipolarophiles. The intermediates salts were obtained from corresponding benzimidazole with bromoacetonitrile. The structures of the newly synthesized compounds were confirmed by elemental analysis, spectral techniques (i.e., IR, 1H-NMR and 13C-NMR) and single-crystal X-ray analysis. The cytotoxicity of the synthesized compounds was evaluated on plant cells (i.e., Triticum aestivum L.) and animal cells using aquatic crustaceans (i.e., Artemia franciscana Kellogg and Daphnia magna Straus). The potential antitumor activity of several of the pyrrole derivatives was studied by performing in vitro cytotoxicity assays on human adenocarcinoma-derived cell lines (i.e., LoVo (colon), MCF-7 (breast), and SK-OV-3 (ovary)) and normal human umbilical vein endothelial cells (HUVECs). The obtained results of the cytotoxicity assessment indicated that the tested compounds had nontoxic activity on Triticum aestivum L., while on Artemia franciscana Kellogg nauplii, only compounds 2c and 4c had moderate toxicity. On Daphnia magna, 4b and 4c showed high toxicity; 2a, 2b, and 2c moderate to high toxicity; only 4a and 4d were nontoxic. The compound-mediated cytotoxicity assays showed that several pyrrole compounds demonstrated dose- and time-dependent cytotoxic activity against all tested tumor cell lines, the highest antitumor properties being achieved by 4a and its homologue 4d, especially against LoVo colon cells.

Underlying mechanisms of promoted formation of haloacetic acids disinfection byproducts after indometacin degradation by non-thermal discharge plasma

Indometacin (IDM), as a kind of non-steroidal anti-inflammatory drugs, has ecological and health risks, which is the potential precursor of chlorination disinfection byproducts (DBPs). Non-thermal discharge plasma was attempted to eliminate IDM and control subsequent DBPs formation. Satisfactory removal performance for IDM was realized by the plasma oxidation; almost 100% of IDM was removed within 2 min. Relatively greater removal efficiency was gained at a higher plasma voltage and a lower pH level. Electron paramagnetic resonance spectrometer revealed that reactive species ·OH, O₂·^-, and ¹O₂ were responsible for IDM decomposition. Based on analyses of Fourier transform infrared spectroscopy, two-dimensional correlation spectroscopy, three-dimensional fluorescence spectrum, and gas chromatography-mass spectrometer, attacks of reactive species resulted in sequence breakages in functional groups of IDM, leading to production of small molecular alcohols, acids, and amines. Possible decomposition pathways of IDM were proposed. The produced acetamide and 1H-indol-5-ol were important precursors of DBPs. Formation and toxicity of nitrogen-containing DBPs were dramatically inhibited after IDM degradation; however, those of haloacetic acids were strengthened. The relevant roadmaps among DBPs and degradation intermediates were figured out. This study revealed the underlying mechanisms of IDM degradation by discharge plasma and its potential risks in chlorination disinfection.

Risk assessments of emerging contaminants in various waters and changes of microbial diversity in sediments from Yangtze River chemical contiguous zone, Eastern China

Over recent decades, increasing chemical contamination has greatly affected aquatic life and human health, even though most contaminants are present at low concentrations. The large-scale chemical industrial parks (CIPs) concentrated in the Yangtze River Delta account for over half of the total in China, and Jiangsu Province occupies one fifth of the Yangtze River Delta. Inevitably, the ecosystems could be affected by these CIPs. In this study, we collected 35 water and 12 sediment samples from the Yangtze River (Taizhou section) surrounding waters adjacent to concentrated CIPs and determined their cumulative chemical levels to be 0.2 to 28.4 μg/L and cumulative detections to be 11 to 39 contaminants with a median of 20 contaminants. 61 out of 153 screened chemicals were detected from at least one sampling site, and 6 contaminants, mostly semi-volatile organic compounds, appeared at all sites. Among these detected chemicals, di-n-octyl phthalate and dibutyl phthalate were at the highest levels. Ecological assessment revealed that 4-chloroaniline, phenol and dibutyl phthalate possibly would induce adverse effects on Yangtze River (Taizhou) ecosystems. Further aided with an evaluation of integrated biomarker response (IBR) index, it was found that site W06 (downstream of Binjiang CIP wastewater inlet) was the location in greatest need of urgent action. As a result, the microbial diversity of sediments in the Yangtze River mainstream was significantly higher than that of tributaries, where CIPs wastewater entered.

Comparative Toxicity Analyses from Different Endpoints: Are New Cyclic Disinfection Byproducts (DBPs) More Toxic than Common Aliphatic DBPs?

In recent years, dozens of halogenated disinfection byproducts (DBPs) with cyclic structures were identified and detected in drinking water globally. Previous in vivo toxicity studies have shown that a few new cyclic DBPs possessed higher developmental toxicity and growth inhibition rate than common aliphatic DBPs; however, in vitro toxicity studies have proved that the latter exhibited higher cytotoxicity and genotoxicity than the former. Thus, to provide a more comprehensive toxicity comparison of DBPs from different endpoints, 11 groups of cyclic DBPs and nine groups of aliphatic DBPs were evaluated for their comparative in vitro and in vivo toxicity using human hepatoma cells (Hep G2) and zebrafish embryos. Notably, results showed that the in vitro Hep G2 cytotoxicity index of the aliphatic DBPs was nearly eight times higher than that of the cyclic DBPs, whereas the in vivo zebrafish embryo developmental/acute toxicity indexes of the cyclic DBPs were roughly 48-50 times higher than those of the aliphatic DBPs, indicating that the toxicity rank order differed when different endpoints were applied. For a broader comparison, a Pearson correlation analysis of DBP toxicity data from nine different endpoints was conducted. It was found that the observed Hep G2 cytotoxicity and zebrafish embryo developmental/acute toxicity in this study were highly correlated with the previously reported in vitro CHO cytotoxicity and in vivo toxicity in aquatic organisms (P < 0.01), respectively. However, the observed in vitro toxicity had no correlation with the in vivo toxicity (P > 0.05), suggesting that the toxicity rank orders obtained from in vitro and in vivo bioassays had large discrepancies. According to the observed toxicity data in this study and the candidate descriptors, two quantitative structure-activity relationship (QSAR) models were established, which help to further interpret the toxicity mechanisms of DBPs from different endpoints.

Photocatalytic-persulfate- oxidation for diclofenac removal from aqueous solutions: Modeling, optimization and biotoxicity test assessment

In this paper, the influence of several aquatic factors (the nature of catalyst, the initial pH and the initial concentration of the pollutant) on the photocatalytic degradation of diclofenac (DFC), one of the most widely prescribed anti-inflammatory non-steroidal drug, was studied. Also, in order to examine the intensification process, the variation of the photocatalytic DFC degradation in the presence of sodium persulfate (PPS) was analyzed. It was found that, compared to titanium dioxide (TiO₂), the zinc oxide (ZnO) photocatalyst performed exceptionally well, with a 96.13% DFC degradation efficiency after 150 min. The photodegradation of DFC by ZnO catalyst fitted well the Langmuir-Hinshelwood kinetic model. The maximum efficiency is 97.27% for simulated solar-UVA/ZnO/PPS and 77% for simulated solar-UVA/ZnO. In order to determine the optimal conditions leading to the maximization of DFC removal, an artificial neural network (ANN) modeling approach combined with genetic algorithm (GA) was applied. The best ANN determined had a correlation of 0.999 and it was further used in the process optimization where a 99.7% degradation efficiency was identified as the optimum under the following conditions: DFC initial concentration 37,9 mg L^-1, pH 5,88 and PPS initial concentration 500 mg L^-1. The effectiveness of the process and the toxicity of the pharmaceutical pollutants and their by-products were also evaluated and confirmed by the biological tests using liver and kidney of Mus musculus mice.