73 results on '"Stark TD"'
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2. Constant Volume Ring Shear Apparatus
- Author
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Chaney, RC, primary, Demars, K, additional, Stark, TD, additional, and Contreras, IA, additional
- Published
- 1996
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3. Modified Bromhead Ring Shear Apparatus
- Author
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Pincus, HJ, primary, Stark, TD, additional, and Eid, HT, additional
- Published
- 1993
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4. Bromhead Ring Shear Test Procedure
- Author
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Knodel, PC, primary, Stark, TD, additional, and Vettel, JJ, additional
- Published
- 1992
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5. Effective Stress Hyperbolic Stress-Strain Parameters for Clay
- Author
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Knodel, PC, primary, Stark, TD, additional, and Vettel, JJ, additional
- Published
- 1991
- Full Text
- View/download PDF
6. Constant Volume Ring Shear Apparatus
- Author
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Stark, TD and Contreras, IA
- Abstract
The paper describes a constant volume ring shear apparatus that allows the measurement of the undrained peak and residual shear strengths of cohesive soils. The undrained peak and residual strengths are applicable to seismic stability evaluations of slopes comprised of or founded on cohesive soil. The constant-volume ring shear apparatus is equipped with a mechanism to adjust the normal stress during shear and a new specimen container that allows undisturbed specimens to be trimmed directly into the container. The normal stress is adjusted during shear such that the height of the soil specimen remains constant. This results in a constant volume or undrained shear condition. The results of constant volume ring shear tests on normally consolidated Drammen clay are compared with the results of undrained direct simple shear tests. The comparison reveals that the undrained peak shear strength obtained using the constant volume ring shear and direct simple shear apparatuses are in agreement. However, the constant-volume ring shear apparatus allows the measurement of the undrained residual strength because it permits unlimited continuous shear displacement.
- Published
- 1996
- Full Text
- View/download PDF
7. Effective Stress Hyperbolic Stress-Strain Parameters for Clay
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Stark, TD and Vettel, JJ
- Abstract
This paper presents a procedure for estimating the effective stress hyperbolic stress-strain parameters for normally consolidated clays from the results of consolidation and direct shear tests. The procedure for calculating Young's modulus and the modulus number includes: (1) estimating the failure ratio from the shear stress-horizontal displacement curve obtained from a direct shear test; (2) using a tangent modulus at the end of each normally consolidated load increment in the consolidation test and the void ratio at the beginning of each load increment to calculate Young's modulus; and (3) multiplying the resulting modulus number by 1.9 to obtain a reasonable estimate of the isotropically consolidated-drained triaxial (CID) modulus number. The modulus exponent was approximately unity for both the consolidation and CID triaxial tests. A procedure for estimating the bulk modulus number, the bulk modulus exponent, and the unload-reload modulus number is also presented.
- Published
- 1991
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8. Modified Bromhead Ring Shear Apparatus
- Author
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Stark, TD and Eid, HT
- Abstract
The main factor affecting the drained residual strength measured in the Bromhead ring shear apparatus is the magnitude of wall friction developed along the inner and outer circumferences of the confined specimen. The magnitude of wall friction increases with the depth of the remolded specimen, and thus the plane of least wall friction occurs at or near the soil/top porous stone interface. As the top porous stone settles into the specimen container, the wall friction influencing the shear plane increases, causing an increase in the measured residual strength.A new specimen container is proposed for the Bromhead ring shear apparatus that allows a remolded specimen to be overconsolidated and precut prior to drained shearing. This minimizes settlement of the top platen and the horizontal displacement required to reach a residual strength condition. As a result, a multistage test can be conducted without excessive settlement and thus wall friction occurring in the new specimen container. The use of a multistage test significantly reduces the time required to establish a drained residual failure envelope. The use of an overconsolidated and precut specimen also provides a better simulation of the field conditions that lead to a large post-peak decrease in drained strength in clayshales, claystones, and mudstones, and residual strengths that are in excellent agreement with field case histories.
- Published
- 1993
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9. Bromhead Ring Shear Test Procedure
- Author
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Stark, TD and Vettel, JJ
- Abstract
Existing test procedures and a proposed modification for the Bromhead ring shear apparatus were found to yield drained residual strengths higher than values back-calculated from field case histories. A new test procedure is presented that yields drained residual strengths that are in excellent agreement with field case histories. The new test procedure utilizes the unmodified Bromhead ring shear apparatus and limits the settlement of the top porous stone, due to consolidation and/or soil extrusion during drained shear, to 0.75 mm. Since the specimen is confined radially by the specimen container, limiting the settlement of the top porous stone minimizes the wall friction that develops along the inner and outer circumferences of the specimen. The reduced wall friction results in the lowest measured residual strength and the best agreement with field case histories.
- Published
- 1992
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10. Xeroderris stuhlmannii (Taub.) Mendonça & E.P.Sousa (Fabaceae): Evidence of the antihypertensive and antioxidant activities of its leaf aqueous extract in cadmium chloride hypertensive rats.
- Author
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Nkojap Kuinze A, Nguemfo EL, Nana Yousseu W, Wanche Kojom JJ, Zangueu Bogning C, Sonfack CS, Tsopgni Dongmo Tekapi W, Stark TD, Azebaze GBA, and Dongmo AB
- Abstract
Xeroderris stuhlmannii (Fabaceae) is a medicinal reported in Cameroonian herbal medicine to treat hypertension. The aim of the study was to assess the antihypertensive and antioxidant activities of X. stuhlmannii aqueous leaf extract (AEXS) on cadmium chloride-induced hypertensive rats. The in vitro antioxidant activities of AEXS were investigated for their radical scavenging potency using 2,2-diphenyl-1-picrylhydrazyl (DPPH), Ferric reducing antioxidant power (FRAP), 2,2'-azino-bis-(3-ethylbenzothiazoline-6-sulfonic) acid (ABTS), Nitric oxide (NO) and OH- assays completed with oxidative stress markers analyses. Antihypertensive activity of AEXS (35, 100, and 300 mg/kg) was assessed in CdCl
2 induced-hypertensive rats. Antihypertensive activities performed include systolic (SBP), diastolic blood pressure (DBP) and heart rate (HR) variation, followed by evaluation of selected biochemical parameters in urine, blood (Alanine aminotransferase (ALT), aspartate aminotransferase (AST)), creatinine, urea and total protein) and histological examination of tissue samples (aorta, heart, kidneys and liver). The amount of the phenols of the leaf extract was estimated in mg gallic acid equivalent and identification of some compounds was done by UPLC-UV-ESI-TOF-MS. Accordingly, the identified phenols were stuhlmannione A ( 1 ), formononetin ( 2 ), stuhlmarotenoid A ( 3 ), 9-methoxymaackiain ( 4 ), 4-hydroxymaackiain ( 5 ) and 7-hydroxy-3',4'-methylenedioxy-isoflavone ( 6 ). The extract exhibited a significant ( P < 0.05-0.001 ) decrease of SBP, DBP and HR when compare to control. AEXS also reduced ( P < 0.05) serum rates of ALT, AST, and urea. The extract showed beneficial effects on alterations observed in the histological structures of the aorta, heart, kidneys and liver. AEXS highlighted high level of phenols (26.48 ± 2.89 mg GAE/g) and a strong antiradical activity on DPPH, ABTS+ , OH- and NO with IC50 of 148.8 μg/mL, 27.83 μg/mL, 22.29 μg/mL, 29.84 μg/mL respectively. An optical density of 1.79 nm was obtained with FRAP test. Thus, X. stuhlmannii leaf extract has in vitro antioxidant and antihypertensive effects that may support its use against hypertension., Competing Interests: The authors declare the following financial interests/personal relationships which may be considered as potential competing interests:DONGMO Alain Bertrand reports equipment, drugs, or supplies was provided by 10.13039/100005156Alexander von Humboldt Foundation. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2024 Published by Elsevier Ltd.)- Published
- 2024
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11. Molecular Changes during Germination of Cocoa Beans, Part 1.
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Brückel K, Stark TD, Dawid C, and Hofmann T
- Subjects
- Chromatography, High Pressure Liquid, Spectrometry, Mass, Electrospray Ionization, Catechin metabolism, Catechin analysis, Taste, Oxylipins metabolism, Cyclopentanes metabolism, Cacao chemistry, Cacao metabolism, Cacao growth & development, Germination, Seeds chemistry, Seeds growth & development, Seeds metabolism
- Abstract
Some germination is known to occur during the process of fermentation in cocoa beans. The impact of this biological process on the course of cocoa fermentation is not known and was thus investigated. In order to determine the impact of germination at the molecular level as well as on flavor, an untargeted metabolomics approach using Ultra Performance Liquid Chromatography-Electrospray Ionization-Time of Flight-Mass Spectrometry (UPLC-ESI-ToF-MS) with simultaneous acquisition of low- and high-collision energy mass spectra (MS
e ) was performed. Extracts of raw and germinated cocoa beans of the same origin were measured and compared for characteristic differences by unsupervised principal component analysis. OPLS-DA revealed 12-hydroxyjasmonic acid (HOJA) sulfate, (+)-catechin and (-)-epicatechin as most down-regulated compounds as well as two hydroxymethylglutaryl (HMG) glucosides A and B among others as decisive up-regulated compounds in the germinated material. Additionally, further HMG glucosides and 12-hydroxyjasmonic acid could be identified in cocoa for the first time by coelution with isolated and synthesized reference compounds. HOJA sulfate, which has been postulated in cocoa, and HOJA were revealed to impart bitter and astringent taste qualities.- Published
- 2024
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12. Molecular Changes during Germination of Cocoa Beans, Part 2.
- Author
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Brückel K, Stark TD, Dawid C, and Hofmann T
- Subjects
- Chromatography, High Pressure Liquid, Tandem Mass Spectrometry, Catechin metabolism, Catechin analysis, Catechin analogs & derivatives, Metabolomics, Cacao chemistry, Cacao metabolism, Cacao growth & development, Cacao genetics, Germination, Seeds chemistry, Seeds growth & development, Seeds metabolism
- Abstract
A recently published untargeted metabolomics approach toward marker compounds of cocoa germination revealed and identified 12-hydroxyjasmonic acid sulfate, (+)-catechin, and (-)-epicatechin as the most downregulated compounds and two hydroxymethylglutaryl glucosides (HMG gluc) A and B, among others, as the decisive upregulated compounds in the germinated material. These findings were quantitatively evaluated using ultrahigh-performance liquid chromatography-tandem mass spectrometry not only in previously examined sample material but also in a vastly expanded array of cocoa samples of different provenience and process and in cocoa products such as cocoa liquor and chocolate. Hereby, yields of newly identified HMG gluc derivatives could be determined in raw, fermented, germinated, and alternatively processed cocoa, and isomers of HMG gluc A and B could be established as key process indicators. Based on unsupervised clustering and supervised classification, models could identify germinated samples in testing sets consisting of raw, fermented, and germinated samples.
- Published
- 2024
- Full Text
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13. UPLC-ESI-TOF MS Profiling Discriminates Biomarkers in Authentic and Adulterated Italian Samples of Saffron ( Crocus sativus L.).
- Author
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Angeli L, Morozova K, Dawid C, Scampicchio M, and Stark TD
- Abstract
Italian saffron ( Crocus sativus L.) is gaining visibility due to its high quality and difference in growing area. In this study, the metabolite composition and quality of Italian saffron samples purchased from local producers and supermarkets were investigated using an untargeted metabolomics approach using UPLC-ESI-TOF MS with simultaneous acquisition of low- and high-collision energy mass spectrometry (MS
e ). Unsupervised statistical method (PCA) highlighted significant differences in the metabolomes, even if not related to the geographical origin. OPLS-DA revealed 9( S )-,10-( S )-,13-( S )-tri-hydroxy-11-( E )-octadecenoic acid as the most decisive compound to distinguish supermarket saffron, while oxidized crocins represented the most valuable markers to further describe the quality of saffron, even in locally produced samples. Known adulterations with paprika and turmeric were detected at a limit of 10%, and the increasing signals of cyclocurcumin was a significant biomarker for turmeric contamination. The results were underlined with conventional and kinetic antioxidant assays., Competing Interests: The authors declare no competing financial interest., (© 2024 The Authors. Published by American Chemical Society.)- Published
- 2024
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14. Human Sensory, Taste Receptor, and Quantitation Studies on Kaempferol Glycosides Derived from Rapeseed/Canola Protein Isolates.
- Author
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Walser C, Spaccasassi A, Gradl K, Stark TD, Sterneder S, Wolter FP, Achatz F, Frank O, Somoza V, Hofmann T, and Dawid C
- Subjects
- Humans, Plant Extracts chemistry, Seeds chemistry, Seeds metabolism, Brassica rapa chemistry, Brassica rapa metabolism, Receptors, G-Protein-Coupled genetics, Receptors, G-Protein-Coupled metabolism, Kaempferols, Brassica napus chemistry, Brassica napus metabolism, Brassica napus genetics, Taste, Plant Proteins genetics, Plant Proteins metabolism, Plant Proteins chemistry, Glycosides chemistry
- Abstract
Beyond the key bitter compound kaempferol 3- O -(2‴- O -sinapoyl-β-d-sophoroside) previously described in the literature ( 1 ), eight further bitter and astringent-tasting kaempferol glucosides ( 2 - 9 ) have been identified in rapeseed protein isolates ( Brassica napus L.). The bitterness and astringency of these taste-active substances have been described with taste threshold concentrations ranging from 3.3 to 531.7 and 0.3 to 66.4 μmol/L, respectively, as determined by human sensory experiments. In this study, the impact of 1 and kaempferol 3- O -β-d-glucopyranoside ( 8 ) on TAS2R-linked proton secretion by HGT-1 cells was analyzed by quantification of the intracellular proton index. mRNA levels of bitter receptors TAS2R3, 4, 5, 13, 30, 31, 39, 40, 43, 45, 46, 50 and TAS2R8 were increased after treatment with compounds 1 and 8 . Using quantitative UHPLC-MS/MS
MRM measurements, the concentrations of 1 - 9 were determined in rapeseed/canola seeds and their corresponding protein isolates. Depending on the sample material, compounds 1 , 3 , and 5 - 9 exceeded dose over threshold (DoT) factors above one for both bitterness and astringency in selected protein isolates. In addition, an increase in the key bitter compound 1 during industrial protein production (apart from enrichment) was observed, allowing the identification of the potential precursor of 1 to be kaempferol 3- O -(2‴- O -sinapoyl-β-d-sophoroside)-7- O -β-d-glucopyranoside ( 3 ). These results may contribute to the production of less bitter and astringent rapeseed protein isolates through the optimization of breeding and postharvest downstream processing.- Published
- 2024
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15. A poisonous cocktail: interplay of cereulide toxin and its structural isomers in emetic Bacillus cereus .
- Author
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Kranzler M, Walser V, Stark TD, and Ehling-Schulz M
- Subjects
- Humans, Bacillus cereus, Emetics analysis, Food Contamination analysis, Food Microbiology, Protein Isoforms, Bacterial Toxins toxicity, Poisons, Foodborne Diseases, Depsipeptides
- Abstract
Food intoxications evoked by emetic Bacillus cereus strains constitute a serious threat to public health, leading to emesis and severe organ failure. The emetic peptide toxin cereulide, assembled by the non-ribosomal peptide synthetase CesNRPS, cannot be eradicated from contaminated food by usual hygienic measures due to its molecular size and structural stability. Next to cereulide, diverse chemical variants have been described recently that are produced concurrently with cereulide by CesNRPS. However, the contribution of these isocereulides to the actual toxicity of emetic B. cereus , which produces a cocktail of these toxins in a certain ratio, is still elusive. Since cereulide isoforms have already been detected in food remnants from foodborne outbreaks, we aimed to gain insights into the composition of isocereulides and their impact on the overall toxicity of emetic B. cereus . The amounts and ratios of cereulide and isocereulides were determined in B. cereus grown under standard laboratory conditions and in a contaminated sample of fried rice balls responsible for one of the most severe food outbreaks caused by emetic B. cereus in recent years. The ratios of variants were determined as robust, produced either under laboratory or natural, food-poisoning conditions. Examination of their actual toxicity in human epithelial HEp2-cells revealed that isocereulides A-N, although accounting for only 10% of the total cereulide toxins, were responsible for about 40% of the total cytotoxicity. An this despite the fact that some of the isocereulides were less cytotoxic than cereulide when tested individually for cytotoxicity. To estimate the additive, synergistic or antagonistic effects of the single variants, each cereulide variant was mixed with cereulide in a 1:9 and 1:1 binary blend, respectively, and tested on human cells. The results showed additive and synergistic impacts of single variants, highlighting the importance of including not only cereulide but also the isocereulides in routine food and clinical diagnostics to achieve a realistic toxicity evaluation of emetic B. cereus in contaminated food as well as in patient samples linked to foodborne outbreaks. Since the individual isoforms confer different cell toxicity both alone and in association with cereulide, further investigations are needed to fully understand their cocktail effect., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Kranzler, Walser, Stark and Ehling-Schulz.)
- Published
- 2024
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16. Toward Unified Flavor Quantitation in Cocoa-Based Products.
- Author
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Hofstetter CK, Dunkel A, Bussy U, Wimmer M, Kauz T, Stark TD, Didzbalis J, Dawid C, and Hofmann T
- Subjects
- Tandem Mass Spectrometry, Odorants analysis, Chromatography, High Pressure Liquid, Taste, Chocolate analysis, Cacao chemistry
- Abstract
Because food flavor is perceived through a combination of odor and taste, an analytical method that covers both dimensions would be very beneficial for mapping the consistent product quality over the entirety of a manufacturing process. Such a method, so-called "unified flavor quantitation", has been successfully applied to several different food products in recent years. The simultaneous detection of aroma and taste compounds by means of ultra-high-performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) enables the analysis and quantification of an enormously large number of compounds in a single run. To evaluate the limits of this method, chocolate, a high-fat, complex matrix, was selected. In 38 distinct commercial chocolate samples, 20 flavor-active acids, aldehydes, and sugars were analyzed after a simple, rapid extraction step followed by derivatization with 3-nitrophenylhydrazine using a single UHPLC-MS/MS method. The results obtained highlight the great potential of the "unified flavor quantitation" approach and demonstrate the possibility of high-throughput quantitation of key aroma- and taste-active molecules in a single assay.
- Published
- 2023
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17. (Bio)active Compounds in Daisy Flower ( Bellis perennis ).
- Author
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Albien AL and Stark TD
- Subjects
- Antioxidants metabolism, Wound Healing, Flowers, Plant Extracts pharmacology, Plant Extracts metabolism, Anti-Infective Agents metabolism, Asteraceae metabolism
- Abstract
The common daisy ( Bellis perennis ) belongs to the family Asteraceae and, in recent years, some new research has been published on the bioactive compounds and biological activities of its extracts. In 2014, the knowledge was partially summarized, but several new studies have been published in the last nine years. In addition, the substances were tabularly consolidated to give a comprehensive overview of over 310 individual components, compound classes, and bioactivities, as well as their accurate plant organ origin. The latest results have shown that the plant has antioxidative, antimicrobial, anticancerogenic, wound healing, antidepressive, anxiolytic, nephroprotective, and insulin mimetic effects, as well as an effect on lipid metabolism. Some studies in the field of homeopathy were also listed. Ideally, a biological effect and one or several compound(s) can be correlated. However, the compounds of the extracts used have often been qualified and quantified, but it remains unclear which of these substances have an activity. The works often stick at the level of the crude extract or a fraction, but not at a single purified and tested compound and, consequently, they are hampered by a missing comprehensive bioactivity workflow. This review provides a critical overview and gaps and offers a basis for further research in this area.
- Published
- 2023
- Full Text
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18. The toxicological spectrum of the Bacillus cereus toxin cereulide points towards niche-specific specialisation.
- Author
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Jenull S, Bauer T, Silbermayr K, Dreer M, Stark TD, and Ehling-Schulz M
- Subjects
- Humans, Food Microbiology, Emetics, Exotoxins, Potassium, Bacillus cereus, Depsipeptides toxicity
- Abstract
Most microbes share their environmental niches with very different forms of life thereby engaging in specialised relationships to enable their persistence. The bacterium Bacillus cereus occurs ubiquitously in the environment with certain strain backgrounds causing foodborne and opportunistic infections in humans. The emetic lineage of B. cereus is capable of producing the toxin cereulide, which evokes emetic illnesses. Although food products favouring the accumulation of cereulide are known, the ecological role of cereulide and the environmental niche of emetic B. cereus remain elusive. To better understand the ecology of cereulide-producing B. cereus, we systematically assayed the toxicological spectrum of cereulide on a variety of organisms belonging to different kingdoms. As cereulide is a potassium ionophore, we further tested the effect of environmental potassium levels on the action of cereulide. We found that adverse effects of cereulide exposure are species-specific, which can be exacerbated with increased environmental potassium. Additionally, we demonstrate that cereulide is produced within an insect cadaver indicating its potential ecological function for a saprophytic lifestyle. Collectively, distinct cereulide susceptibilities of other organisms may reflect its role in enabling competitive niche specialization of emetic B. cereus., (© 2023 The Authors. Environmental Microbiology published by Applied Microbiology International and John Wiley & Sons Ltd.)
- Published
- 2023
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19. Primary and Secondary Metabolites in Lotus japonicus .
- Author
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Ranner JL, Schalk S, Martyniak C, Parniske M, Gutjahr C, Stark TD, and Dawid C
- Subjects
- Tandem Mass Spectrometry, Chromatography, Liquid, Gas Chromatography-Mass Spectrometry methods, Symbiosis physiology, Lotus metabolism, Mycorrhizae physiology
- Abstract
Lotus japonicus is a leguminous model plant used to gain insight into plant physiology, stress response, and especially symbiotic plant-microbe interactions, such as root nodule symbiosis or arbuscular mycorrhiza. Responses to changing environmental conditions, stress, microbes, or insect pests are generally accompanied by changes in primary and secondary metabolism to account for physiological needs or to produce defensive or signaling compounds. Here we provide an overview of the primary and secondary metabolites identified in L. japonicus to date. Identification of the metabolites is mainly based on mass spectral tags (MSTs) obtained by gas chromatography linked with tandem mass spectrometry (GC-MS/MS) or liquid chromatography-MS/MS (LC-MS/MS). These MSTs contain retention index and mass spectral information, which are compared to databases with MSTs of authentic standards. More than 600 metabolites are grouped into compound classes such as polyphenols, carbohydrates, organic acids and phosphates, lipids, amino acids, nitrogenous compounds, phytohormones, and additional defense compounds. Their physiological effects are briefly discussed, and the detection methods are explained. This review of the exisiting literature on L. japonicus metabolites provides a valuable basis for future metabolomics studies.
- Published
- 2023
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20. Toward High-Throughput Analysis of Aroma Compounds Using Ultrahigh-Performance Liquid Chromatography-Tandem Mass Spectrometry: Screening of Key Food Odorants in Various Foods.
- Author
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Bösl M, Dunkel A, Hartl D, Dollinger A, Spaccasassi A, Stark TD, Dawid C, and Hofmann TF
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- Tandem Mass Spectrometry methods, Chromatography, High Pressure Liquid methods, Chromatography, Liquid, Odorants analysis, Volatile Organic Compounds chemistry
- Abstract
Recent studies show the immense capacities of the unified quantitation of aroma and taste compounds using liquid chromatography-mass spectrometry (LC-MS). The goal of this study was to highlight the broad application of this unified method. Thus, a stable isotope dilution analysis quantification method of the most important key food odorants in various food categories by LC-MS was developed. Using the well-known derivatization agent 3-nitrophenylhydrazine for carbonyl derivatization and a newly developed approach for alcohol and thiol derivatization, a method for the quantitation of 20 key food odorants was established. Intraday precision was determined to be ≤26%, and interday precision was between 24 and 31%. Limits of quantitation were determined between 0.014 and 283 μg/kg. The work shows that a wide array of aroma compounds can be analyzed accurately by LC-MS.
- Published
- 2023
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21. Rotenoids and Isoflavones from Xeroderris stuhlmannii (Taub.) Mendonça & E.P. Souza and Their Biological Activities.
- Author
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Mekuete LBK, Tsopgni WDT, Nkojap AK, Kojom JJW, Stark TD, Fouokeng Y, Dongmo AB, Azeufack LT, and Azebaze AGB
- Subjects
- Antifungal Agents pharmacology, Antifungal Agents chemistry, Plant Extracts chemistry, Anti-Bacterial Agents pharmacology, Anti-Bacterial Agents chemistry, Candida albicans, Microbial Sensitivity Tests, Isoflavones pharmacology, Fabaceae chemistry
- Abstract
The phytochemical study of the ethanolic extract of the leaf of Xeroderris stuhlmannii led to the isolation of five hitherto unreported compounds including two isoflavones ( 1 - 2 ), and three rotenoids ( 3 - 5 ), along with eight known isoflavonoid derivatives ( 6 - 13 ) and one pterocarpan derivative ( 14 ). The structures of the new compounds and those of the known ones were established by the spectroscopic (1D and 2D NMR) and spectrometric (HRESIMS) techniques as well as a comparison of their spectroscopic data with those reported in the literature. The leaf extract, fractions, and isolated compounds were tested for their antibacterial effects against nine bacterial strains. Compounds 3 , 8 , 11, and 12 showed a significant antibacterial effect, with a minimum inhibitory concentration (MIC) value of 62.5 µg/mL each, against Salmonella typhi , Staphylococcus aureus , Klessiella pneumonae , and Escherichia coli , respectively. In addition, the leaf extract, fractions, and isolated compounds were tested for their antifungal effects against four fungal strains. The hexane fraction showed a significant antifungal effect with an MIC value of 125 µg/mL against Candida parasilosis , whereas compounds 3 , 8 , and 12 showed significant antifungal activity with an MIC value of 62.5 µg/mL, each against Candida parasilosis , Candida albicans , and Candida krusei , respectively.
- Published
- 2023
- Full Text
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22. Volatile-mediated signalling in barley induces metabolic reprogramming and resistance against the biotrophic fungus Blumeria hordei.
- Author
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Laupheimer S, Kurzweil L, Proels R, Unsicker SB, Stark TD, Dawid C, and Hückelhoven R
- Subjects
- Plant Diseases microbiology, Plants metabolism, Fungi, Hordeum metabolism, Volatile Organic Compounds metabolism
- Abstract
Plants have evolved diverse secondary metabolites to counteract biotic stress. Volatile organic compounds (VOCs) are released upon herbivore attack or pathogen infection. Recent studies suggest that VOCs can act as signalling molecules in plant defence and induce resistance in distant organs and neighbouring plants. However, knowledge is lacking on the function of VOCs in biotrophic fungal infection on cereal plants. We analysed VOCs emitted by 13 ± 1-day-old barley plants (Hordeum vulgare L.) after mechanical wounding using passive absorbers and TD-GC/MS. We investigated the effect of pure VOC and complex VOC mixtures released from wounded plants on the barley-powdery mildew interaction by pre-exposure in a dynamic headspace connected to a powdery mildew susceptibility assay. Untargeted metabolomics and lipidomics were applied to investigate metabolic changes in sender and receiver barley plants. Green leaf volatiles (GLVs) dominated the volatile profile of wounded barley plants, with (Z)-3-hexenyl acetate (Z3HAC) as the most abundant compound. Barley volatiles emitted after mechanical wounding enhanced resistance in receiver plants towards fungal infection. We found volatile-mediated modifications of the plant-pathogen interaction in a concentration-dependent manner. Pre-exposure with physiologically relevant concentrations of Z3HAC resulted in induced resistance, suggesting that this GLV is a key player in barley anti-pathogen defence. The complex VOC mixture released from wounded barley and Z3HAC induced e.g. accumulation of chlorophyll, linolenic acid and linolenate-conjugated lipids, as well as defence-related secondary metabolites, such as hordatines in receiving plants. Barley VOCs hence induce a complex physiological response and disease resistance in receiver plants., (© 2022 The Authors. Plant Biology published by John Wiley & Sons Ltd on behalf of German Society for Plant Sciences, Royal Botanical Society of the Netherlands.)
- Published
- 2023
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23. Garcinia buchananii stem bark extract and its bioactive constituents manniflavanone, GB-2 and buchananiflavanone attenuate intestinal inhibitory neuromuscular transmission.
- Author
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Patterson S, Waters ME, Braman N, Willson R, Hill RA, Magolan J, Hofmann T, Stark TD, and Balemba OB
- Subjects
- Animals, Guinea Pigs, Plant Bark, Colon, Garcinia, Flavones pharmacology
- Abstract
Garcinia buchananii stem bark extract (GBB), commonly used for treating diarrhea in Africa, triggers ectopic aboral contractions, causing inhibition of propulsive motility in the colon ex vivo. To determine whether or not these effects were associated with decreased inhibitory neuromuscular transmission, the responsible constituent compounds, and mechanisms of action, we studied the effects of GBB and specific fractions and flavanones isolated from GBB on intestinal motility using pellet propulsion assays in guinea pig distal colons. In addition, microelectrode recordings were used to measure the effects on the inhibitory junction potentials (IJPs) in the porcine ileum and descending colon smooth muscle. Psychoactive Drug Screening Program secondary receptor functional assays were used to determine whether or not GBB and its constituent compounds act via purinergic (P2Y) and muscarinic receptors. GBB inhibited propulsive motility, but (2R,3S,2″R,3″R)-manniflavanone (MNF), (2R,3S,2″R,3″R)-GB-2 (GB-2) and (2R,3S,2″S)-buchananiflavanone (BNF), the main ingredients of GBB, did not affect motility. We discovered that, in the porcine descending colon, IJPs contained purinergic, nitrergic, and nonpurinergic nonnitrergic components. Furthermore, ileal IJPs were purely purinergic. GBB blocked all components of IJPs, while MNF and GB-2 inhibited purinergic IJPs only. BNF inhibited the purinergic and nonpurinergic components of IJPs. MRS2365, a Y1 (P2Y) agonist, did not evoke sustained membrane hyperpolarization in the presence of GBB. However, GBB, MNF, GB-2 and BNF did not affect P2Y or muscarinic receptors. In conclusion, inhibitory neuromuscular transmission in the porcine descending colon involves all components of IJPs. GBB decreases inhibitory neuromuscular transmission, likely by the actions of MNF, GB-2 and BNF. These effects do not involve P2Y or muscarinic receptors.
- Published
- 2023
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24. Impact of a Novel PagR-like Transcriptional Regulator on Cereulide Toxin Synthesis in Emetic Bacillus cereus .
- Author
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Kalbhenn EM, Kranzler M, Gacek-Matthews A, Grass G, Stark TD, Frenzel E, and Ehling-Schulz M
- Subjects
- Bacillus cereus, Emetics, Transcription Factors genetics, Transcription Factors metabolism, Bacillus anthracis metabolism, Depsipeptides genetics, Depsipeptides metabolism
- Abstract
The emetic type of foodborne disease caused by Bacillus cereus is produced by the small peptide toxin cereulide. The genetic locus encoding the Ces nonribosomal peptide synthetase (CesNRPS) multienzyme machinery is located on a 270 kb megaplasmid, designated pCER270, which shares its backbone with the Bacillus anthracis toxin plasmid pXO1. Although the ces genes are plasmid-borne, the chromosomally encoded pleiotropic transcriptional factors CodY and AbrB are key players in the control of ces transcription. Since these proteins only repress cereulide synthesis during earlier growth phases, other factors must be involved in the strict control of ces expression and its embedment in the bacterial life cycle. In silico genome analysis revealed that pCER270 carries a putative ArsR/SmtB family transcription factor showing high homology to PagR from B. anthracis . As PagR plays a crucial role in the regulation of the protective antigen gene pagA , which forms part of anthrax toxin, we used a gene-inactivation approach, combined with electrophoretic mobility shift assays and a bacterial two-hybrid system for dissecting the role of the PagR homologue PagRBc in the regulation of cereulide synthesis. Our results highlight that the plasmid-encoded transcriptional regulator PagRBc plays an important role in the complex and multilayered process of cereulide synthesis.
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- 2022
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25. Correction to Quantitation of Toxic Steroidal Glycoalkaloids and Newly Identified Saponins in Post-Harvest Light-Stressed Potato ( Solanum tuberosum L.) Varieties.
- Author
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Baur S, Bellé N, Hausladen H, Wurzer S, Brehm L, Stark TD, Hückelhoven R, Hofmann T, and Dawid C
- Published
- 2022
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26. Quantitation of Toxic Steroidal Glycoalkaloids and Newly Identified Saponins in Post-Harvest Light-Stressed Potato ( Solanum tuberosum L.) Varieties.
- Author
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Baur S, Bellé N, Hausladen H, Wurzer S, Brehm L, Stark TD, Hücklhoven R, Hofmann T, and Dawid C
- Subjects
- Plant Tubers chemistry, Saponins analysis, Solanine, Solanum tuberosum chemistry
- Abstract
Although domesticated potatoes contain a large variety of steroidal glycoalkaloids (SGAs) and saponins, in the past, many research projects mainly focused on the two major SGAs, α-solanine and α-chaconine. This study investigates the quantitative changes, induced by post-harvest LED light exposure, of six SGAs and four saponins in 12 potato cultivars at three different time points (1, 7, and 16 days), by using ultra-performance liquid chromatography tandem mass spectrometry. Altogether, SGA contents of 3.0-17.1 mg/100 g fresh weight (FW) could be observed in the analyzed tubers with potato varieties highly exceeding the newly discussed safety limit of 10 mg/100 g. The overall contents of 0.1-5.4 mg/100 g FW of the so far barely studied saponins, like protoneodioscin or barogenin-solatrioside, highly differed between the assayed potato cultivars. Furthermore, cultivar-specific regulations of SGAs and saponins could be observed due to light exposure.
- Published
- 2022
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27. Discovery and Identification of Tastants and Taste-Modulating N -Acyl Amino Acid Derivatives in Traditional Korean Fermented Dish Kimchi Using a Sensomics Approach.
- Author
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Christa P, Dunkel A, Krauss A, Stark TD, Dawid C, and Hofmann T
- Subjects
- Amino Acids chemistry, Chromatography, Liquid, Republic of Korea, Tandem Mass Spectrometry, Fermented Foods, Taste
- Abstract
Sensory-guided fractionation by means of ultrafiltration and gel permeation chromatography followed by high-performance liquid chromatography, synthesis, liquid chromatography-tandem mass spectrometry (LC-MS/MS) quantitation, and taste re-engineering experiments revealed taste-active and taste-enhancing compounds contributing to the umami, mouthful and complex taste profile of the fermented Korean dish, kimchi. Besides basic taste-active compounds, in particular, various N -acylated amino acids deriving from succinic acid and lactic acid imparted taste-modulating properties in food matrices. Taste threshold concentrations were determined to evaluate intrinsic and modulating effects. Quantitation of N -acylated amino acids in kimchi following synthesis revealed the presence of numerous derivatives showing taste-active properties. Sensory evaluation including recombination and partial addition experiments highlighted that both the N -lactoyl- and the N -succinoyl amino acid derivatives contribute to increasing the fullness, volume, and complexity of food matrices, whereas the latter directly contributes to the overall taste of kimchi in natural concentrations.
- Published
- 2022
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28. Sensomics-Assisted Aroma Decoding of Pea Protein Isolates ( Pisum sativum L.).
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Utz F, Spaccasassi A, Kreissl J, Stark TD, Tanger C, Kulozik U, Hofmann T, and Dawid C
- Abstract
The aroma of pea protein ( Pisum sativum L.) was decrypted for knowledge-based flavor optimization of new food products containing pea protein. Sensomics helped to determine several volatiles via ultra-high performance liquid chromatography tandem mass spectrometry and 3-nitrophenylhydrazine derivatization. Among the investigated volatiles, representatives of aldehydes, ketones, and acids were reported in literature as especially important in pea and pea-related matrices. After validation of the method and quantitation of the corresponding analytes, sensory reconstitution as well as omission studies of a selected pea protein were performed and revealed nine odor-active compounds as key food odorants (3-methylbutanal, hexanal, acetaldehyde, ( E,E )-2,4-nonadienal, ( E )-2-octenal, benzaldehyde, heptanal, 2-methylbutanal, and nonanoic acid). Interestingly, eight out of nine compounds belonged to the chemical class of aldehydes. Statistical heatmap and cluster analysis of all odor activity values of different pea proteins confirmed the obtained sensory results and generalize these nine key food odorants in other pea proteins. The knowledge of key components gained shows potential for simplifying industrial flavor optimization of pea protein-based food.
- Published
- 2022
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29. Bacillus cereus Toxin Repertoire: Diversity of (Iso)cereulide(s).
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Walser V, Kranzler M, Dawid C, Ehling-Schulz M, Stark TD, and Hofmann TF
- Subjects
- Food Microbiology, Bacillus cereus chemistry, Bacterial Toxins chemistry, Depsipeptides chemistry, Mass Spectrometry, Nuclear Magnetic Resonance, Biomolecular
- Abstract
The emetic Bacillus cereus toxin cereulide ( 1 ) poses a significant safety risk in the food industry, causing emesis and nausea after consumption of contaminated foods. Analogously to cereulide, the structures of various isocereulides, namely, isocereulides A-G, have been recently reported and could also be identified in B. cereus -contaminated food samples. The HPLC fractionation of B. cereus extracts allows us to isolate additional isocereulides. By applying MS
n sequencing, post-hydrolytic dipeptide, amino acid and α-hydroxy acid analyses using UPLC-ESI-TOF-MS to purify the analytes, seven new isocereulides H-N ( 2 - 8 ) could be elucidated in their chemical structures. The structure elucidation was supported by one-dimensional and two-dimensional NMR spectra of the isocereulides H ( 2 ), K ( 5 ), L and N ( 6 + 8 ) and M ( 7 ). The toxicity of 2 - 8 was investigated in a HEp-2 cell assay to determine their respective 50% effective concentration (EC50 ). Thus, 2 - 8 exhibited EC50 values ranging from a 0.4- to 1.4-fold value compared to cereulide ( 1 ). Missing structure-activity correlations indicate the necessity to determine the toxic potential of all naturally present isocereulides as single compounds to be able to perform a thorough toxicity evaluation of B. cereus -contaminated foods in the future.- Published
- 2022
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30. Acute Liver Failure after Ingestion of Fried Rice Balls: A Case Series of Bacillus cereus Food Poisonings.
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Schreiber N, Hackl G, Reisinger AC, Zollner-Schwetz I, Eller K, Schlagenhaufen C, Pietzka A, Czerwenka C, Stark TD, Kranzler M, Fickert P, Eller P, and Ehling-Schulz M
- Subjects
- Adult, Austria, Humans, Male, Bacillus cereus, Depsipeptides analysis, Foodborne Diseases microbiology, Liver Failure, Acute microbiology, Oryza microbiology
- Abstract
Bacillus cereus foodborne intoxications and toxicoinfections are on a rise. Usually, symptoms are self-limiting but occasionally hospitalization is necessary. Severe intoxications with the emetic Bacillus cereus toxin cereulide, which is notably resistant heat and acid during cooking, can cause acute liver failure and encephalopathy. We here present a case series of food poisonings in five immunocompetent adults after ingestion of fried rice balls, which were massively contaminated with Bacillus cereus . The patients developed a broad clinical spectrum, ranging from emesis and diarrhoea to life-threatening acute liver failure and acute tubular necrosis of the kidney in the index patient. In the left-over rice ball, we detected 8 × 10
6 Bacillus cereus colony-forming units/g foodstuff, and cereulide in a concentration of 37 μg/g foodstuff, which is one of the highest cereulide toxin contaminations reported so far from foodborne outbreaks. This report emphasizes the potential biological hazard of contaminated rice meals that are not freshly prepared. It exemplifies the necessity of a multidisciplinary approach in cases of Bacillus cereus associated food poisonings to rapidly establish the diagnosis, to closely monitor critically ill patients, and to provide supportive measures for acute liver failure and-whenever necessary-urgent liver transplantation.- Published
- 2021
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31. Engineering of benzoxazinoid biosynthesis in Arabidopsis thaliana: Metabolic and physiological challenges.
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Abramov A, Hoffmann T, Stark TD, Zheng L, Lenk S, Hammerl R, Lanzl T, Dawid C, Schön CC, Schwab W, Gierl A, and Frey M
- Subjects
- Benzoxazines, Poaceae, Triticum, Zea mays, Arabidopsis genetics
- Abstract
Plant specialised metabolites constitute a layer of chemical defence. Classes of the defence compounds are often restricted to a certain taxon of plants, e.g. benzoxazinoids (BX) are characteristically detected in grasses. BXs confer wide-range defence by controlling herbivores and microbial pathogens and are allelopathic compounds. In the crops maize, wheat and rye high concentrations of BXs are synthesised at an early developmental stage. By transfer of six Bx-genes (Bx1 to Bx5 and Bx8) it was possible to establish the biosynthesis of 2,4-dihydroxy-1,4-benzoxazin-3-one glucoside (GDIBOA) in a concentration of up to 143 nmol/g dry weight in Arabidopsis thaliana. Our results indicate that inefficient channeling of substrates along the pathway and metabolisation of intermediates in host plants might be a general drawback for transgenic establishment of specialised metabolite biosynthesis pathways. As a consequence, BX levels required for defence are not obtained in Arabidopsis. We could show that indolin-2-one (ION), the first specific intermediate, is phytotoxic and is metabolised by hydroxylation and glycosylation by a wide spectrum of plants. In Arabidopsis, metabolic stress due to the enrichment of ION leads to elevated levels of salicylic acid (SA) and in addition to its intrinsic phytotoxicity, ION affects plant morphology indirectly via SA. We could show that Bx3 has a crucial role in the evolution of the pathway, first based on its impact on flux into the pathway and, second by C3-hydroxylation of the phytotoxic ION. Thereby BX3 interferes with a supposedly generic detoxification system towards the non-specific intermediate., (Copyright © 2021 The Authors. Published by Elsevier Ltd.. All rights reserved.)
- Published
- 2021
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32. Comprehensive structure-activity-relationship studies of sensory active compounds in licorice (Glycyrrhiza glabra).
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Schmid C, Brockhoff A, Shoshan-Galeczki YB, Kranz M, Stark TD, Erkaya R, Meyerhof W, Niv MY, Dawid C, and Hofmann T
- Subjects
- Phytochemicals, Plant Extracts, Glycyrrhiza, Saponins, Triterpenes
- Abstract
Licorice saponins, the main constituents of Glycyrrhiza glabra L. roots, are highly appreciated by the consumer for their pleasant sweet and long lasting licorice taste. The objective of the present study was to understand the molecular features that contribute to bitter, sweet and licorice sensation of licorice roots, and whether individual compounds elicit more than one of these sensations. Therefore, a sensomics approach was conducted, followed by purification of the compounds with highest sensory impact, and by synthesis as well as full characterization via HRESIMS, ESIMS/MS and 1D/2D-NMR experiments. This led to the discovery and structure determination of 28 sweet, bitter and licorice tasting key phytochemicals, including two unknown compounds. A combination of sensorial, cell-based and computational analysis revealed distinct structural features, such as spatial arrangement of functional groups in the triterpenoid E-ring, driving to different taste sensations and sweet receptor hTAS1R2/R3 stimulation., (Copyright © 2021 The Authors. Published by Elsevier Ltd.. All rights reserved.)
- Published
- 2021
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33. Impact of Phytochemicals on Viability and Cereulide Toxin Synthesis in Bacillus cereus Revealed by a Novel High-Throughput Method, Coupling an AlamarBlue-Based Assay with UPLC-MS/MS.
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Kranzler M, Frenzel E, Walser V, Hofmann TF, Stark TD, and Ehling-Schulz M
- Subjects
- Biological Assay methods, Chromatography, High Pressure Liquid methods, Tandem Mass Spectrometry methods, Bacillus cereus drug effects, Bacillus cereus metabolism, Depsipeptides metabolism, Depsipeptides toxicity, Foodborne Diseases drug therapy, Foodborne Diseases microbiology, Phytochemicals pharmacokinetics, Phytochemicals therapeutic use
- Abstract
Due to its food-poisoning potential, Bacillus cereus has attracted the attention of the food industry. The cereulide-toxin-producing subgroup is of particular concern, as cereulide toxin is implicated in broadscale food-borne outbreaks and occasionally causes fatalities. The health risks associated with long-term cereulide exposure at low doses remain largely unexplored. Natural substances, such as plant-based secondary metabolites, are widely known for their effective antibacterial potential, which makes them promising as ingredients in food and also as a surrogate for antibiotics. In this work, we tested a range of structurally related phytochemicals, including benzene derivatives, monoterpenes, hydroxycinnamic acid derivatives and vitamins, for their inhibitory effects on the growth of B. cereus and the production of cereulide toxin. For this purpose, we developed a high-throughput, small-scale method which allowed us to analyze B. cereus survival and cereulide production simultaneously in one workflow by coupling an AlamarBlue-based viability assay with ultraperformance liquid chromatography-mass spectrometry (UPLC-MS/MS). This combinatory method allowed us to identify not only phytochemicals with high antibacterial potential, but also ones specifically eradicating cereulide biosynthesis already at very low concentrations, such as gingerol and curcumin.
- Published
- 2021
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34. Distribution of the Emetic Toxin Cereulide in Cow Milk.
- Author
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Walser V, Kranzler M, Dawid C, Ehling-Schulz M, Stark TD, and Hofmann TF
- Subjects
- Animals, Bacillus cereus, Bacterial Toxins chemistry, Cattle, Chromatography, Liquid, Depsipeptides chemistry, Emetics chemistry, Food Contamination analysis, Hydrophobic and Hydrophilic Interactions, Lipids chemistry, Tandem Mass Spectrometry, Bacterial Toxins analysis, Depsipeptides analysis, Emetics analysis, Milk chemistry
- Abstract
Bacillus cereus is frequently associated with food-borne intoxications, and its emetic toxin cereulide causes emesis and nausea after consumption of contaminated foods. The major source for contamination is found within contaminated raw materials containing the highly chemically resistant cereulide, independent of vegetative bacteria cells. Up to date, non-existing removal strategies for cereulide evoke the question of how the toxin is distributed within a food sample, especially cow milk. Milk samples with different milk fat contents were incubated with purified cereulide, separated by centrifugation into a lipid and an aqueous phase, and cereulide was quantified in both fractions by SIDA-LC-MS/MS. By artificially increasing the milk fat content from 0.5% to 50%, the amount of cereulide recovered in the lipid phase and could be augmented from 13.3 to 78.6%. Further, the ratio of cereulide increased in the lipid phase of milk with additional plant-based lipid (sunflower oil) to 47.8%. This demonstrated a clear affinity of cereulide towards the hydrophobic, lipid phase, aligning with cereulide's naturally strong hydrophobic properties. Therefore, an intensified cereulide analysis of lipid enriched dairy products to prevent severe cereulide intoxications or cross-contamination in processed foods is suggested.
- Published
- 2021
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35. Influence of the Abiotic Stress Conditions, Waterlogging and Drought, on the Bitter Sensometabolome as Well as Agronomical Traits of Six Genotypes of Daucus carota .
- Author
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Schmid C, Sharma S, Stark TD, Günzkofer D, Hofmann TF, Ulrich D, Dunemann F, Nothnagel T, and Dawid C
- Abstract
Cultivated carrot is one of the most important vegetable plants in the world and favored by consumers for its typically sweet flavor. Unfortunately, the attractive sensory quality is hindered by a sporadic bitter off-taste. To evaluate the influence of the abiotic stress conditions, waterlogging and drought, on the bitter sensometabolome as well as agronomical traits of six genotypes of Daucus carota , a field trial was performed. Enabling the accurate tracing of carrots' bitter compounds and therefore their metabolic changes, a fast and robust high-throughput UHPLC-MS/MS was developed and validated. Remarkably, the genotypes are the driving source for the biological fate of the bitter metabolites that are reflected in concentrations, dose-over-threshold factors, and fold changes. A certain influence of the irrigation level is observable but is overruled by its cultivar. Therefore, metabolic stress response in carrots seems to be genotype dependent. Hence, this study might help to plant specific carrot genotypes that are adapted to stress conditions evoked by future climatic changes.
- Published
- 2021
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36. Sensory-Directed Identification of Creaminess-Enhancing Semi-Volatile Lactones in Crumb Chocolate.
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Samfaß J, Stark TD, and Hofmann TF
- Abstract
In order to gain a more comprehensive knowledge of the chemical nature of creaminess-related flavor compounds in milk chocolates on a molecular level, crumb chocolate was analyzed by means of activity guided screening techniques. Sensory studies of a triglyceride-free lipid emulsion indicated that the n-pentane extract showed the highest impact regarding creaminess sensation. Enhancement of creaminess by adding anhydrous milk fat fractions to chocolate was demonstrated by fractionated high-vacuum distillation of different fats associated with the chocolate production combined with sensory experiments. Syntheses of various δ-lactones and the quantification of these sensory active semi-volatiles led to the conclusion that the anhydrous milk fat contains a series of γ- and δ-lactones. Cocoa butter revealed a high concentration of δ-hexadecalactone, too. Experiments suggested that lactones are generated from the potential precursors monohydroxyalkanoic acid(s) esterified (mono-tri)glyceride(s) during heating. Sensory studies exhibited recognition thresholds of 29-40 µmol/kg for the long-chain δ-lactones in crumb chocolate. Furthermore, significant enhancement of the retro-nasal creamy flavor was found for δ-tetradecalactone.
- Published
- 2021
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37. Sensomics-Assisted Flavor Decoding of Dairy Model Systems and Flavor Reconstitution Experiments.
- Author
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Utz F, Kreissl J, Stark TD, Schmid C, Tanger C, Kulozik U, Hofmann T, and Dawid C
- Subjects
- Gas Chromatography-Mass Spectrometry, Odorants analysis, Solid Phase Microextraction, Taste, Flavoring Agents, Volatile Organic Compounds analysis
- Abstract
The whole sensometabolome of a typical dairy milk dessert was decoded to potentially serve as a blueprint for further flavor optimization steps of functional fat-reduced food. By applying the sensomics approach, a wide range of different dairy volatiles, semi and nonvolatiles, were analyzed by ultrahigh-performance liquid chromatography tandem mass spectrometry with or without derivatization presteps. While for volatile sulfur compounds with low odor thresholds, headspace solid-phase microextraction gas chromatography was established, abundant carbohydrates and organic acids were quantified by quantitative
1 H nuclear magnetic resonance spectroscopy. Validated quantitation, sensory reconstitution, and omission studies highlighted eight flavor-active compounds, namely, diacetyl, δ-tetra-, δ-hexa-, and δ-octadecalactone, sucrose, galactose, lactic acid, and citric acid as indispensable for flavor recombination. Furthermore, eight odorants (acetaldehyde, acetic acid, butyric acid, methanethiol, phenylacetic acid, dimethyl sulfide, acetoin, and hexanoic acid), all with odor activity values >1, additionally contributed to the overall flavor blueprint. Within this work, a dairy flavor analytical toolbox covering four different high-throughput methods could successfully be established showing potential for industrial applications.- Published
- 2021
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38. Structure Revision of Isocereulide A, an Isoform of the Food Poisoning Emetic Bacillus cereus Toxin Cereulide.
- Author
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Walser V, Kranzler M, Ehling-Schulz M, Stark TD, and Hofmann TF
- Subjects
- Depsipeptides isolation & purification, Food Microbiology, Mass Spectrometry, Protein Isoforms, Bacillus cereus metabolism, Depsipeptides chemistry
- Abstract
The emetic Bacillus cereus toxin cereulide presents an enormous safety hazard in the food industry, inducing emesis and nausea after the consumption of contaminated foods. Additional to cereulide itself, seven structurally related isoforms, namely the isocereulides A-G, have already been elucidated in their chemical structure and could further be identified in B. cereus contaminated food samples. The newly performed isolation of isocereulide A allowed, for the first time, 1D- and 2D-NMR spectroscopy of a biosynthetically produced isocereulide, revealing results that contradict previous assumptions of an l- O -Leu moiety within its chemical structure. By furthermore applying posthydrolytical dipeptide analysis, amino acid and α -hydroxy acid analysis by means of UPLC-ESI-TOF-MS, as well as MS
n sequencing, the structure of previously reported isocereulide A could be corrected. Instead of the l- O -Leu as assumed to date, one l- O -Ile unit could be verified in the cyclic dodecadepsipeptide, revising the structure of isocereulide A to [(d- O -Leu-d-Ala-l- O -Val-l-Val)2 (d- O -Leu-d-Ala-l- O -Ile-l-Val)].- Published
- 2021
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39. Detection and Isolation of Emetic Bacillus cereus Toxin Cereulide by Reversed Phase Chromatography.
- Author
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Kalbhenn EM, Bauer T, Stark TD, Knüpfer M, Grass G, and Ehling-Schulz M
- Subjects
- Bacillus cereus genetics, Humans, Reproducibility of Results, Bacillus cereus metabolism, Chromatography, Reverse-Phase, Depsipeptides isolation & purification, Foodborne Diseases microbiology, Gram-Positive Bacterial Infections microbiology, Vomiting microbiology
- Abstract
The emetic toxin cereulide is a 1.2 kDa dodecadepsipeptide produced by the food pathogen Bacillus cereus . As cereulide poses a serious health risk to humans, sensitive and specific detection, as well as toxin purification and quantification, methods are of utmost importance. Recently, a stable isotope dilution assay tandem mass spectrometry (SIDA-MS/MS)-based method has been described, and an method for the quantitation of cereulide in foods was established by the International Organization for Standardization (ISO). However, although this SIDA-MS/MS method is highly accurate, the sophisticated high-end MS equipment required for such measurements limits the method's suitability for microbiological and molecular research. Thus, we aimed to develop a method for cereulide toxin detection and isolation using equipment commonly available in microbiological and biochemical research laboratories. Reproducible detection and relative quantification of cereulide was achieved, employing reversed phase chromatography (RPC). Chromatographic signals were cross validated by ultraperformance liquid chromatography-mass spectrometry (UPLC-MS/MS). The specificity of the RPC method was tested using a test panel of strains that included non-emetic representatives of the B. cereus group, emetic B. cereus strains, and cereulide-deficient isogenic mutants. In summary, the new method represents a robust, economical, and easily accessible research tool that complements existing diagnostics for the detection and quantification of cereulide.
- Published
- 2021
- Full Text
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40. Supernatants of intestinal luminal contents from mice fed high-fat diet impair intestinal motility by injuring enteric neurons and smooth muscle cells.
- Author
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Nyavor Y, Brands CR, Nicholson J, Kuther S, Cox KK, May G, Miller C, Yasuda A, Potter F, Cady J, Heyman HM, Metz TO, Stark TD, Hofmann T, and Balemba OB
- Subjects
- Animals, Mice, Myenteric Plexus pathology, Solid Phase Extraction, Diet, High-Fat, Gastrointestinal Contents, Gastrointestinal Motility physiology, Intestinal Pseudo-Obstruction physiopathology, Myocytes, Smooth Muscle pathology, Neurons pathology
- Abstract
Background: Damage to enteric neurons and impaired gastrointestinal muscle contractions cause motility disorders in 70% of diabetic patients. It is thought that enteric neuropathy and dysmotility occur before overt diabetes, but triggers of these abnormalities are not fully known. We tested the hypothesis that intestinal contents of mice with and without high-fat diet- (HFD-) induced diabetic conditions contain molecules that impair gastrointestinal movements by damaging neurons and disrupting muscle contractions., Methods: Small and large intestinal segments were collected from healthy, standard chow diet (SCD) fed mice. Filtrates of ileocecal contents (ileocecal supernatants; ICS) from HFD or SCD mice were perfused through them. Cultured intact intestinal muscularis externa preparations were used to determine whether ICS and their fractions obtained by solid-phase extraction (SPE) and SPE subfractions collected by high-performance liquid chromatography (HPLC) disrupt muscle contractions by injuring neurons and smooth muscle cells., Key Results: ICS from HFD mice reduced intestinal motility, but those from SCD mice had no effect. ICS, aqueous SPE fractions and two out of twenty HPLC subfractions of aqueous SPE fractions from HFD mice blocked muscle contractions, caused a loss of nitrergic myenteric neurons through inflammation, and reduced smooth muscle excitability. Lipopolysaccharide and palmitate caused a loss of nitrergic myenteric neurons but did not affect muscle contractions., Conclusions & Inferences: Unknown molecules in intestinal contents of HFD mice trigger enteric neuropathy and dysmotility. Further studies are required to identify the toxic molecules and their mechanisms of action., (© 2020 John Wiley & Sons Ltd.)
- Published
- 2021
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41. Fast and Sensitive LC-MS/MS Method for the Quantitation of Saponins in Various Sugar Beet Materials.
- Author
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Edelmann M, Dawid C, Ralla T, Stark TD, Salminen H, Weiss J, and Hofmann T
- Subjects
- Beta vulgaris classification, Glycosides chemistry, Molecular Structure, Plant Leaves chemistry, Plant Roots chemistry, Triterpenes chemistry, Beta vulgaris chemistry, Chromatography, High Pressure Liquid methods, Plant Extracts chemistry, Saponins chemistry, Tandem Mass Spectrometry methods
- Abstract
An LC-MS/MS method was developed for the simultaneous quantitative analysis of the following 11 triterpene saponins within different sugar beet materials and plant compartments: betavulgaroside I ( 1 ), betavulgaroside II ( 2 ), betavulgaroside III ( 3 ), betavulgaroside IV ( 4 ), betavulgaroside VIII ( 5 ), boussingoside A2 ( 6 ), 3- O -[β-d-glucopyranosyl-(1 → 2)-(β-d-xylopyranosyl-(1 → 3))-β-d-glucuronopyranosyl]-28- O -β-d-glucopyranosyl-3β-hydroxyolean-12-en-28-oic acid ( 7 ), betavulgaroside V ( 8 ), chikusetsusaponin IVa ( 9 ), calenduloside E ( 10 ), and ginsenoside R0 ( 11 ). Our results showed highly varying amounts of saponins within different varieties, roots, and leaves as well as different plant compartments. The amounts for sugar beet roots were in the range of 862 mg/kg to 2 452 mg/kg. They were mostly higher for leaves compared to roots of the same variety with amounts ranging from 907 mg/kg to 5 398 mg/kg. Furthermore, the occurrence of sugar beet saponins within different side streams was examined; in this context, sugar beet fiber contained the highest amounts of saponins for all investigated plant constituents and byproduct streams with a total amount of 12.7 g/kg. Finally, this is the first publication about the occurrence of individual saponins in sugar beets.
- Published
- 2020
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42. Evaluation of MALDI-ToF Mass Spectrometry for Rapid Detection of Cereulide From Bacillus cereus Cultures.
- Author
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Doellinger J, Schneider A, Stark TD, Ehling-Schulz M, and Lasch P
- Abstract
Bacillus cereus plays an often unrecognized role in food borne diseases. Food poisoning caused by this pathogen is manifested by either diarrhea or emesis. Due to the relatively high prevalence of emetic toxin cereulide associated food poisoning, methods for simple and reliable detection of cereulide producing strains are of utmost importance. Recently, two different studies reported on the application of MALDI-ToF MS for either the differentiation of emetic and non-emetic strains of B. cereus or for direct detection of cereulide from bacterial colony smears. However, for implementation of cereulide detection using MALDI-ToF MS in routine microbiological diagnostics additional investigations on the sensitivity and specificity as well as on the fitting into common workflows for bacterial identification are needed. These aspects prompted us to investigate open issues and to test sample preparation methods, commonly used for microbial identification for their suitability to detect the emetic toxin from bacteria. Based on our experimental findings we propose a workflow that allows identification of B. cereus and sensitive detection of cereulide in parallel, using linear-mode MALDI-ToF MS equipment. The protocol was validated in a blinded study and is based on the well-established ethanol/formic acid extraction method. Cereulide is detected in the ethanol wash solution of samples identified as B. cereus as peaks at m/z 1175 and 1191. Peak position difference of 16 Th (Thomson) indicates detection of the sodium and potassium adducts of cereulide. This sample treatment offers possibilities for further characterization by more sophisticated LC-MS-based methods. In summary, the ease of use and the achieved level of analytical sensitivity as well as the wide-spread availability of MALDI-ToF MS equipment in clinical microbiological laboratories provides a promising tool to improve and to facilitate routine diagnostics of B. cereus associated food intoxications., (Copyright © 2020 Doellinger, Schneider, Stark, Ehling-Schulz and Lasch.)
- Published
- 2020
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43. Molecularization of Foam-Active Saponins from Sugar Beet Side Streams ( Beta vulgaris ssp. vulgaris var. altissima ).
- Author
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Edelmann M, Dawid C, Hochreiter K, Ralla T, Stark TD, Salminen H, Weiss J, and Hofmann T
- Subjects
- Chromatography, Liquid, Molecular Structure, Plant Tubers chemistry, Tandem Mass Spectrometry, Waste Products analysis, Beta vulgaris chemistry, Flavoring Agents chemistry, Plant Extracts chemistry, Saponins chemistry
- Abstract
This work focuses on the isolation and characterization of saponins with a very low bitter intensity originating from sustainable plant materials, in particular the sugar beet pulp by-product stream. Via a concise foam activity screening of saponin-containing materials, which gives indications for their emulsifying ability, sugar beet root extract was selected and examined for low bitter saponins by means of activity guided fractionation. Individual saponins were isolated from sugar beet pulp, which was identified as the most convenient sugar beet saponin source. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis and one-dimensional (1D) and two-dimensional (2D) nuclear magnetic resonance (NMR) spectroscopy led to the unequivocal identification of the major, slightly bitter tasting compounds as a series of eight saponins. The complete assignment of
1 H and13 C NMR signals for several saponins was carried out for the first time. A small-scale foam activity assay was established and applied to a broad spectrum of the isolated and commercially available saponins. Additionally, orosensory recognition thresholds were determined. Not only high recognition thresholds were determined (thresholds >1000 μmol/L) but also fundamental information about the foaming behavior of mono- and bidesmosidic saponins was collected. The obtained results are relevant to the utilization of saponins from other plant materials or by-product streams and for the use of sugar beet saponins as food additives.- Published
- 2020
- Full Text
- View/download PDF
44. Formation and Characterization of Polyphenol-Derived Red Chromophores. Enhancing the Color of Processed Cocoa Powders: Part 2.
- Author
-
Germann D, Stark TD, and Hofmann T
- Subjects
- Chocolate analysis, Color, Food Handling, Hydrogen-Ion Concentration, Molecular Structure, Oxidation-Reduction, Powders chemistry, Tandem Mass Spectrometry, Cacao chemistry, Plant Preparations chemistry, Polyphenols chemistry
- Abstract
Very recently, we described the formation of (+)-catechin- and (-)-epicatechin-derived polar chromophores by means of a cocoa alkalization process. In this study we focus on the generation of unpolar chromophores using model reactions via Dutching with softer alkaline conditions. UPLC-HR-ESI-TOF-MS
e analysis and one-dimensional and two-dimensional NMR spectroscopy led to the unequivocal identification of dehydrodicatechin- and hydroxyxanthene-derived chromophores. The previously unknown 6- C-linked constitutional isomers of C-6'B/C-6D-(2 R,3 S)-dehydrodicatechin (3, 5) were first described, and furthermore, the dimers dehydrocatechin-C-6'B/C-8D-(2 S,3 S)-epicatechin (2) and dehydrocatechin-C-6'B/C-6D-(2 S,3 S)-epicatechin (4, 6) as well as the reddish-colored chromophores 8- C-xanthenocatechin (7), 8- C-xanthenoepicatechin (8), 6- C-xanthenocatechin (9), and 6- C-xanthenoepicatechin (10) were identified as new compounds. A LC-MS/MS method was developed to screen and quantify both classes of chromophores as well as their precursors in alkalized cocoa powders. The dehydrocatechin dimers showed degradation via the alkalization process; in contrast, the xanthenocatechins highlighted an increase in concentration with stronger alkalization, and, therefore, contribute to cocoa reddening. These results, together with those previously published, give a clear insight into the chemistry of polyphenol-derived chromophores generated by cocoa powder alkalization and enable a better understanding of chromophore formation mechanisms toward a more comprehensive color design of cocoa powders.- Published
- 2019
- Full Text
- View/download PDF
45. Formation and Characterization of Polyphenol-Derived Red Chromophores. Enhancing the Color of Processed Cocoa Powders: Part 1.
- Author
-
Germann D, Stark TD, and Hofmann T
- Subjects
- Chocolate analysis, Color, Food Handling, Hydrogen-Ion Concentration, Molecular Structure, Oxidation-Reduction, Powders chemistry, Tandem Mass Spectrometry, Cacao chemistry, Plant Preparations chemistry, Polyphenols chemistry
- Abstract
Although cocoa powder alkalization (Dutching) is a widely used industrial process to improve taste, dispersibility, and coloring of the final product, nevertheless knowledge about the compounds causing a change in coloring is fragmentary. By means of alkaline model reactions starting from the major cocoa polyphenol monomers, (+)-catechin or (-)-epicatechin, eight chromophores were derived from the first rearrangement product catechinic acid. LC-MS/MS analysis, one- and two dimensional-NMR, and electron paramagnetic resonance (EPR) spectroscopy led to the unequivocal identification of 6'-hydroxycatechinic acids (1a, 2a) and their radical states (1b, 2b), which were highlighted as main red chromophores. Six new dehydrocatechinic acid dimers (dehydrocatechinic acid-C-6'B/C-8D-(2 R,3 S)-catechin (3), dehydrocatechinic acid-C-6'B/C-6D-(2 R,3 S)-catechin (4, 5), dehydrocatechinic acid-C-6'B/C-8D-(2 R,3 R)-epicatechin (6), and dehydrocatechinic acid-C-6'B/C-6D-(2 R,3 R)-epicatechin (7, 8)) were also characterized as chromophores. 1-8 as well as their precursors were detected and quantified in alkalized cocoa powders via LC-MS/MS. With the increasing grade of alkalization, a decrease in catechin and epicatechin together with an increase in catechinic acid was observed. Compounds 1b, 2b, and 3-8 also showed a decrease in concentration by Dutching, which correlates to the accumulation of/to higher ordered chromophore oligomers and underlined the increase of the high molecular weight fraction. These findings give a first insight into the formation of structures causing the red coloring of cocoa, which offers the opportunity to optimize the alkalization process toward a better color design of cocoa powders.
- Published
- 2019
- Full Text
- View/download PDF
46. Taste Modulating Peptides from Overfermented Cocoa Beans.
- Author
-
Salger M, Stark TD, and Hofmann T
- Subjects
- Adult, Chromatography, High Pressure Liquid, Female, Fermentation, Humans, Hydrogen-Ion Concentration, Male, Tandem Mass Spectrometry, Taste, Young Adult, Cacao chemistry, Flavoring Agents chemistry, Peptides chemistry, Seeds chemistry
- Abstract
Activity-guided fractionation of an aqueous extract of overfermented cocoa beans, which were recently found to be a rich source of previously unknown taste enhancing substances, revealed the presence of a series of taste modulating short peptides. Fractionation was achieved by means of sequential solvent extraction, medium pressure liquid chromatography, as well as preparative high pressure liquid chromatography, and the taste modulating activity was determined by means of matrix assisted taste dilution analysis. By means of ultra performance liquid chromatography-time-of-flight-mass spectrometry (UPLC-ToF-MS) screening, liquid chromatography-MS/MS methods, and customized syntheses, numerous short peptides could be identified in the taste modulating fractions. Sensory experiments of the target peptides showed umami enhancing and salt taste enhancing properties as well as kokumi effects when applied in a savory taste matrix. Evaluation of the taste threshold concentrations in model broth demonstrated a high taste modulating potential of 11 out of 13 identified peptides. Lowest threshold concentrations were determined for the salt taste enhancing tripeptide pEEE (55 μmol/L) and the kokumi active tripeptide VPA (90 μmol/L). Furthermore, a large number of dipeptides, carrying either a prolyl- or pyro-glutamyl moiety were located in the aqueous extract, exhibiting taste modulating properties and revealing a pH dependency of the taste modulating effect of the savory taste matrix. Additionally, synergistic effects of a mixture of five umami enhancing pyro-glutamyl dipeptides in the model matrix were demonstrated.
- Published
- 2019
- Full Text
- View/download PDF
47. Antioxidative Maillard Reaction Products Generated in Processed Aged Garlic Extract.
- Author
-
Wakamatsu J, Stark TD, and Hofmann T
- Subjects
- Chromatography, High Pressure Liquid, Cooking, Hot Temperature, Magnetic Resonance Spectroscopy, Maillard Reaction, Molecular Structure, Tandem Mass Spectrometry, Antioxidants chemistry, Garlic chemistry, Glycation End Products, Advanced chemistry, Plant Extracts chemistry
- Abstract
A powder formulation of aged garlic extract was heated at 100 °C for 1 day to obtain higher antioxidant activity determined with 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) radical scavenging (ARS) and oxygen radical absorbance capacity (ORAC) assays. Activity-guided fractionation afforded 12 new in vitro antioxidative Maillard-type products, α-[(2-formyl-5-hydroxymethyl)pyrrol-1-yl]arginine (3), 4-[7-hydroxy-6-(hydroxymethyl)-7,8-dihydro-6 H-pyrano[2,3- b] pyrazine-3-yl]butane-1,2,3-triol (4), 4-[6-(1,2-dihydroxyethyl)-6,7-dihydro-furo[2,3- b]pyrazin-3-yl]-butane-1,2,3-triol (5), α-[(2-formyl-5-hydroxymethyl)-pyrrol-1-yl] aspartic acid (12), 1-[5-(1,2-dihydroxyethyl)-2-oxotetrahydrofuran-3-yl]-5-(hydroxymethyl)-1 H-pyrrole-2-carbaldehyde (14), 4-(6-ethyl-2-pyrazinyl)-1,2,3-butanetriol (17), α-[(2-formyl-5-hydroxymethyl)pyrrol-1-yl] glutamic acid (19), ( S)-1-[(5-hydroxymethyl)furan-2-yl]methyl]-5-oxopyrrolidine-2-carboxylic acid (20), 3-hydroxy-1 H-[{5-(hydroxymethyl)furan-2-yl}methyl]-2,5-dioxo-3-pyrrolidine acetic acid (21), ( E)-4-(5-methylpyrazin-2-yl)but-3-ene-7,2-diol (23), 4-acetyl-6-(hydroxymethyl)picolinic acid (24), ( E)-4-(6-methylpyrazin-2-yl)but-3-ene-1,2-diol (26) and 14 known compounds, 1, 2, 6-11, 13, 15, 16, 18, 22 and 25, which were characterized via 1D/2D-NMR, CD spectroscopy, and mass spectrometry. ARS and ORAC activities of these antioxidants ranged from 0.01 to 0.49 μmol TE/μmol and from 0.01 to 3.50 μmol TE/μmol, respectively. Additionally, plausible formation pathways for the new organic acid-type products (15, 20, and 21) were proposed based on proving their generation in model reactions detected via liquid chromatography-mass spectrometry (LC-MS/MS).
- Published
- 2019
- Full Text
- View/download PDF
48. Construction and Application of a Database for a Five-Dimensional Identification of Natural Compounds in Garcinia Species by Means of UPLC-ESI-TWIMS-TOF-MS: Introducing Gas Phase Polyphenol Conformer Drift Time Distribution Intensity Ratios.
- Author
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Stark TD, Ranner J, Stiglbauer B, Weiss P, Stark S, Balemba OB, and Hofmann T
- Subjects
- Garcinia classification, Spectrometry, Mass, Electrospray Ionization, Databases, Chemical, Garcinia chemistry, Plant Extracts chemistry, Polyphenols chemistry
- Abstract
Thirty-four reference compounds from G. buchananii were analyzed by means of UPLC-ESI-IMS-TOF-MS to build a database consisting of retention time, accurate m/ z of precursors and fragment ions, and rotationally averaged collision cross-sectional area (CCS). The CCS value of six selected compounds analyzed in bark extract in different concentrations and solvent systems showed excellent intra- and interday precision (RSD ≤ 0.9%). The established database was applied on different organs of G. buchananii as well as G. kola, G. mangostana, and G. cambogia enabling a fast and reliable identification of these natural bioactives. For several compounds, more than one drift time species could be highlighted, which we propose to be hydrogen bond stabilized rotational isomers transferred from solution to gas phase. We used all CCS values of one compound, and we propose to add also the intensity ratio of the conformers as a new and additional characteristic compound parameter in compound identification/screening/database applications to reduce dereplication and false positives and to strengthen the identification.
- Published
- 2019
- Full Text
- View/download PDF
49. First Insights Into Within Host Translocation of the Bacillus cereus Toxin Cereulide Using a Porcine Model.
- Author
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Bauer T, Sipos W, Stark TD, Käser T, Knecht C, Brunthaler R, Saalmüller A, Hofmann T, and Ehling-Schulz M
- Abstract
Bacillus cereus is a gram-positive pathogen mainly known to evoke two types of foodborne poisonings. The diarrheal syndrome is caused by enterotoxins produced during growth in the intestine. In contrast, the emetic type is caused by the dodecadepsipeptide cereulide pre-formed in food. Usually, both diseases are self-limiting but occasionally more severe forms, including fatal ones, are reported. Since the mechanisms of cereulide toxin uptake and translocation within the body as well as the mechanism of its toxic action are still unknown, we used a porcine model to investigate the uptake, routes of excretion and distribution of cereulide within the host. Pigs were orally challenged with cereulide using single doses of 10-150 μg cereulide kg
-1 body weight to study acute effects or using daily doses of 10 μg cereulide kg-1 body weight administered for 7 days to investigate effects of longtime, chronic exposure. Our study showed that part of cereulide ingested with food is rapidly excreted with feces while part of the cereulide toxin is absorbed, passes through membranes and is distributed within the body. Results from the chronic trial indicate bioaccumulation of cereulide in certain tissues and organs, such as kidney, liver, muscles and fat tissues. Beside its detection in various tissues and organs, our study also demonstrated that cereulide is able to cross the blood-brain-barrier, which may partially explain the cerebral effects reported from human intoxication cases. The neurobehavioral symptoms, such as seizures and lethargy, observed in our porcine model resemble those reported from human food borne intoxications. The rapid onset of these symptoms indicates direct effects of cereulide on the central nervous system (CNS), which warrant further research. The porcine model presented here might be useful to study the specific neurobiological effect in detail. Furthermore, our study revealed that typical diagnostic specimens used in human medicine, such as blood samples and urine, are not suitable for diagnostics of food borne cereulide intoxications. Instead, screening of fecal samples by SIDA-LC-MS may represent a simple and non-invasive method for detection of cereulide intoxications in clinical settings as well as in foodborne outbreak situations.- Published
- 2018
- Full Text
- View/download PDF
50. Spatial and temporal characteristics of elevated temperatures in municipal solid waste landfills.
- Author
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Jafari NH, Stark TD, and Thalhamer T
- Subjects
- Refuse Disposal, Solid Waste, Temperature, Waste Disposal Facilities
- Published
- 2018
- Full Text
- View/download PDF
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