Research

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12 pages, 1404 KiB

Open AccessArticle

Prediction of Transformation Products of Monensin by Electrochemistry Compared to Microsomal Assay and Hydrolysis

by Lisa Kotthoff, Jan Lisec, Tanja Schwerdtle and Matthias Koch

Molecules 2019, 24(15), 2732; https://doi.org/10.3390/molecules24152732 - 27 Jul 2019

Cited by 2 | Viewed by 2765

The knowledge of transformation pathways and identification of transformation products (TPs) of veterinary drugs is important for animal health, food, and environmental matters. The active agent Monensin (MON) belongs to the ionophore antibiotics and is widely used as a veterinary drug against coccidiosis [...] Read more.

The knowledge of transformation pathways and identification of transformation products (TPs) of veterinary drugs is important for animal health, food, and environmental matters. The active agent Monensin (MON) belongs to the ionophore antibiotics and is widely used as a veterinary drug against coccidiosis in broiler farming. However, no electrochemically (EC) generated TPs of MON have been described so far. In this study, the online coupling of EC and mass spectrometry (MS) was used for the generation of oxidative TPs. EC-conditions were optimized with respect to working electrode material, solvent, modifier, and potential polarity. Subsequent LC/HRMS (liquid chromatography/high resolution mass spectrometry) and MS/MS experiments were performed to identify the structures of derived TPs by a suspected target analysis. The obtained EC-results were compared to TPs observed in metabolism tests with microsomes and hydrolysis experiments of MON. Five previously undescribed TPs of MON were identified in our EC/MS based study and one TP, which was already known from literature and found by a microsomal assay, could be confirmed. Two and three further TPs were found as products in microsomal tests and following hydrolysis, respectively. We found decarboxylation, O-demethylation and acid-catalyzed ring-opening reactions to be the major mechanisms of MON transformation. Full article

(This article belongs to the Special Issue Investigation of Transformation Products of Organic Compounds)

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14 pages, 2406 KiB

Open AccessArticle

Formation of Zearalenone Metabolites in Tempeh Fermentation

by Antje Borzekowski, Riyan Anggriawan, Maryeni Auliyati, Hans-Jörg Kunte, Matthias Koch, Sascha Rohn, Petr Karlovsky and Ronald Maul

Molecules 2019, 24(15), 2697; https://doi.org/10.3390/molecules24152697 - 24 Jul 2019

Cited by 15 | Viewed by 5491

Abstract

Tempeh is a common food in Indonesia, produced by fungal fermentation of soybeans using Rhizopus sp., as well as Aspergillus oryzae, for inoculation. Analogously, for economic reasons, mixtures of maize and soybeans are used for the production of so-called tempeh-like products. [...] Read more.

Tempeh is a common food in Indonesia, produced by fungal fermentation of soybeans using Rhizopus sp., as well as Aspergillus oryzae, for inoculation. Analogously, for economic reasons, mixtures of maize and soybeans are used for the production of so-called tempeh-like products. For maize, a contamination with the mycoestrogen zearalenone (ZEN) has been frequently reported. ZEN is a mycotoxin which is known to be metabolized by Rhizopus and Aspergillus species. Consequently, this study focused on the ZEN transformation during tempeh fermentation. Five fungal strains of the genera Rhizopus and Aspergillus, isolated from fresh Indonesian tempeh and authentic Indonesian inocula, were utilized for tempeh manufacturing from a maize/soybean mixture (30:70) at laboratory-scale. Furthermore, comparable tempeh-like products obtained from Indonesian markets were analyzed. Results from the HPLC-MS/MS analyses show that ZEN is intensely transformed into its metabolites α-zearalenol (α-ZEL), ZEN-14-sulfate, α-ZEL-sulfate, ZEN-14-glucoside, and ZEN-16-glucoside in tempeh production. α-ZEL, being significantly more toxic than ZEN, was the main metabolite in most of the Rhizopus incubations, while in Aspergillus oryzae fermentations ZEN-14-sulfate was predominantly formed. Additionally, two of the 14 authentic samples were contaminated with ZEN, α-ZEL and ZEN-14-sulfate, and in two further samples, ZEN and α-ZEL, were determined. Consequently, tempeh fermentation of ZEN-contaminated maize/soybean mixture may lead to toxification of the food item by formation of the reductive ZEN metabolite, α-ZEL, under model as well as authentic conditions. Full article

(This article belongs to the Special Issue Investigation of Transformation Products of Organic Compounds)

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15 pages, 1637 KiB

Open AccessArticle

Effects of pH and Cultivation Time on the Formation of Styrene and Volatile Compounds by Penicillium expansum

by Hye Won Kim, Sang Mi Lee, Jeong-Ah Seo and Young-Suk Kim

Molecules 2019, 24(7), 1333; https://doi.org/10.3390/molecules24071333 - 04 Apr 2019

Cited by 7 | Viewed by 2865

Abstract

Styrene can be formed by the microbial metabolism of bacteria and fungi. In our previous study, styrene was determined as a spoilage marker of Fuji apples decayed by Penicillium expansum, which is responsible for postharvest diseases. In the present study, P. expansum [...] Read more.

Styrene can be formed by the microbial metabolism of bacteria and fungi. In our previous study, styrene was determined as a spoilage marker of Fuji apples decayed by Penicillium expansum, which is responsible for postharvest diseases. In the present study, P. expansum was cultivated in potato dextrose broth added with phenylalanine—which is a precursor of styrene—using different initial pH values and cultivation times. Volatile compounds were extracted and analyzed using gas chromatography-mass spectrometry (GC-MS) combined with stir-bar sorptive extraction. The 76 detected volatile compounds included 3-methylbutan-1-ol, 3-methyl butanal, oct-1-en-3-ol, geosmin, nonanal, hexanal, and γ-decalactone. In particular, the formation of 10 volatile compounds derived from phenylalanine (including styrene and 2-phenylethanol) showed different patterns according to pH and the cultivation time. Partial least square-discriminant analysis (PLS-DA) plots indicated that the volatile compounds were affected more by pH than by the cultivation time. These results indicated that an acidic pH enhances the formation of styrene and that pH could be a critical factor in the production of styrene by P. expansum. This is the first study to analyze volatile compounds produced by P. expansum according to pH and cultivation time and to determine their effects on the formation of styrene. Full article

(This article belongs to the Special Issue Investigation of Transformation Products of Organic Compounds)

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6 pages, 778 KiB

Open AccessCommunication

Evidence for the Formation of Difluoroacetic Acid in Chlorofluorocarbon-Contaminated Ground Water

by Ute Dorgerloh, Roland Becker and Melanie Kaiser

Molecules 2019, 24(6), 1039; https://doi.org/10.3390/molecules24061039 - 15 Mar 2019

Cited by 5 | Viewed by 3580

Abstract

The concentrations of difluoroacetic acid (DFA) and trifluoroacetic acid (TFA) in rainwater and surface water from Berlin, Germany resembled those reported for similar urban areas, and the TFA/DFA ratio in rainwater of 10:1 was in accordance with the literature. In contrast, nearby ground [...] Read more.

The concentrations of difluoroacetic acid (DFA) and trifluoroacetic acid (TFA) in rainwater and surface water from Berlin, Germany resembled those reported for similar urban areas, and the TFA/DFA ratio in rainwater of 10:1 was in accordance with the literature. In contrast, nearby ground water historically contaminated with 1,1,2-trichloro-1,2,2-trifluoroethane (R113) displayed a TFA/DFA ratio of 1:3. This observation is discussed versus the inventory of microbial degradation products present in this ground water along with the parent R113 itself. A microbial transformation of chlorotrifluoroethylene (R1113) to DFA so far has not been reported for environmental media, and is suggested based on well-established mammalian metabolic pathways. Full article

(This article belongs to the Special Issue Investigation of Transformation Products of Organic Compounds)

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12 pages, 3298 KiB

Open AccessFeature PaperArticle

Glucosylation and Glutathione Conjugation of Chlorpyrifos and Fluopyram Metabolites Using Electrochemistry/Mass Spectrometry

by Tessema Fenta Mekonnen, Ulrich Panne and Matthias Koch

Molecules 2019, 24(5), 898; https://doi.org/10.3390/molecules24050898 - 04 Mar 2019

Cited by 14 | Viewed by 5069

Abstract

Xenobiotics and their reactive metabolites are conjugated with native biomolecules such as glutathione and glucoside during phase II metabolism. Toxic metabolites are usually detoxified during this step. On the other hand, these reactive species have a potential health impact by disrupting many enzymatic [...] Read more.

Xenobiotics and their reactive metabolites are conjugated with native biomolecules such as glutathione and glucoside during phase II metabolism. Toxic metabolites are usually detoxified during this step. On the other hand, these reactive species have a potential health impact by disrupting many enzymatic functions. Thus, it is crucial to understand phase II conjugation reactions of xenobiotics in order to address their fate and possible toxicity mechanisms. Additionally, conventional methods (in vivo and in vitro) have limitation due to matrix complexity and time-consuming. Hence, developing fast and matrix-free alternative method is highly demandable. In this work, oxidative phase I metabolites and reactive species of chlorpyrifos (insecticide) and fluopyram (fungicide) were electrochemically produced by using a boron-doped diamond electrode coupled online to electrospray mass spectrometry (ESI-MS). Reactive species of the substrates were trapped by biomolecules (glutathione and glucoside) and phase II conjugative metabolites were identified using liquid chromatography (LC)-MS/MS, and/or Triple time of flight (TripleTOF)-MS. Glutathione conjugates and glucosylation of chlorpyrifos, trichloropyridinol, oxon, and monohydroxyl fluopyram were identified successfully. Glutathione and glucoside were conjugated with chlorpyrifos, trichloropyridinol, and oxon by losing a neutral HCl. In the case of fluopyram, its monohydroxyl metabolite was actively conjugated with both glutathione and glucoside. In summary, seven bioconjugates of CPF and its metabolites and two bioconjugates of fluopyram metabolites were identified using electrochemistry (EC)/MS for the first time in this work. The work could be used as an alternative approach to identify glutathione and glucosylation conjugation reactions of other organic compounds too. It is important, especially to predict phase II conjugation within a short time and matrix-free environment. Full article

(This article belongs to the Special Issue Investigation of Transformation Products of Organic Compounds)

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Review

Jump to: Research

21 pages, 7832 KiB

Open AccessReview

Research Advances of Purple Sweet Potato Anthocyanins: Extraction, Identification, Stability, Bioactivity, Application, and Biotransformation

by Aoran Li, Ruoshi Xiao, Sijia He, Xiaoyu An, Yi He, Chengtao Wang, Sheng Yin, Bin Wang, Xuewei Shi and Jingren He

Molecules 2019, 24(21), 3816; https://doi.org/10.3390/molecules24213816 - 23 Oct 2019

Cited by 93 | Viewed by 14234

Abstract

Purple sweet potato anthocyanins are kinds of natural anthocyanin red pigments extracted from the root or stem of purple sweet potato. They are stable and have the functions of anti-oxidation, anti-mutation, anti-tumor, liver protection, hypoglycemia, and anti-inflammation, which confer them a good application [...] Read more.

Purple sweet potato anthocyanins are kinds of natural anthocyanin red pigments extracted from the root or stem of purple sweet potato. They are stable and have the functions of anti-oxidation, anti-mutation, anti-tumor, liver protection, hypoglycemia, and anti-inflammation, which confer them a good application prospect. Nevertheless, there is not a comprehensive review of purple sweet potato anthocyanins so far. The extraction, structural characterization, stability, functional activity, application in the food, cosmetics, medicine, and other industries of anthocyanins from purple sweet potato, together with their biotransformation in vitro or by gut microorganism are reviewed in this paper, which provides a reference for further development and utilization of anthocyanins. Full article

(This article belongs to the Special Issue Investigation of Transformation Products of Organic Compounds)

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21 pages, 3481 KiB

Open AccessReview

Recent Advances in Biotransformation of Saponins

by Yi He, Zhuoyu Hu, Aoran Li, Zhenzhou Zhu, Ning Yang, Zixuan Ying, Jingren He, Chengtao Wang, Sheng Yin and Shuiyuan Cheng

Molecules 2019, 24(13), 2365; https://doi.org/10.3390/molecules24132365 - 26 Jun 2019

Cited by 86 | Viewed by 7250

Abstract

Saponins are a class of glycosides whose aglycones can be either triterpenes or helical spirostanes. It is commonly recognized that these active ingredients are widely found in various kinds of advanced plants. Rare saponins, a special type of the saponins class, are able [...] Read more.

Saponins are a class of glycosides whose aglycones can be either triterpenes or helical spirostanes. It is commonly recognized that these active ingredients are widely found in various kinds of advanced plants. Rare saponins, a special type of the saponins class, are able to enhance bidirectional immune regulation and memory, and have anti-lipid oxidation, anticancer, and antifatigue capabilities, but they are infrequent in nature. Moreover, the in vivo absorption rate of saponins is exceedingly low, which restricts their functions. Under such circumstances, the biotransformation of these ingredients from normal saponins—which are not be easily adsorbed by human bodies—is preferred nowadays. This process has multiple advantages, including strong specificity, mild conditions, and fewer byproducts. In this paper, the biotransformation of natural saponins—such as ginsenoside, gypenoside, glycyrrhizin, saikosaponin, dioscin, timosaponin, astragaloside and ardipusilloside—through microorganisms (Aspergillus sp., lactic acid bacteria, bacilli, and intestinal microbes) will be reviewed and prospected. Full article

(This article belongs to the Special Issue Investigation of Transformation Products of Organic Compounds)

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23 pages, 1204 KiB

Open AccessFeature PaperReview

Transformation Products of Organic Contaminants and Residues—Overview of Current Simulation Methods

by Lisa Kotthoff, Julia Keller, Dominique Lörchner, Tessema F. Mekonnen and Matthias Koch

Molecules 2019, 24(4), 753; https://doi.org/10.3390/molecules24040753 - 19 Feb 2019

Cited by 21 | Viewed by 4928

Abstract

The formation of transformation products (TPs) from contaminants and residues is becoming an increasing focus of scientific community. All organic compounds can form different TPs, thus demonstrating the complexity and interdisciplinarity of this topic. The properties of TPs could stand in relation to [...] Read more.

The formation of transformation products (TPs) from contaminants and residues is becoming an increasing focus of scientific community. All organic compounds can form different TPs, thus demonstrating the complexity and interdisciplinarity of this topic. The properties of TPs could stand in relation to the unchanged substance or be more harmful and persistent. To get important information about the generated TPs, methods are needed to simulate natural and manmade transformation processes. Current tools are based on metabolism studies, photochemical methods, electrochemical methods, and Fenton’s reagent. Finally, most transformation processes are based on redox reactions. This review aims to compare these methods for structurally different compounds. The groups of pesticides, pharmaceuticals, brominated flame retardants, and mycotoxins were selected as important residues/contaminants relating to their worldwide occurrence and impact to health, food, and environmental safety issues. Thus, there is an increasing need for investigation of transformation processes and identification of TPs by fast and reliable methods. Full article

(This article belongs to the Special Issue Investigation of Transformation Products of Organic Compounds)

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