Evaluation of Food Intake Biomarkers for Red Bell Peppers in Human Urine Based on HPLC-MS/MS Analysis

SCOPE

The validation of dietary biomarkers is essential for the use in objective and quantitative assessment of the human dietary intake. In this study, the urinary excretion of previously identified potential biomarkers after intake of red bell peppers is analyzed.

METHODS AND RESULTS

The urine samples obtained after a two-phase dietary intervention study in which 14 volunteers participated are quantitatively analyzed by high-performance liquid chromatography with tandem mass spectrometry (HPLC-MS/MS) after an extensive validation. In the first phase, the volunteers abstain completely from bell peppers and paprika products (control group) and in the second phase, the volunteers consume a defined amount of fresh red bell peppers (case group). After analysis, all potential biomarkers show high dispersions of their concentration, indicating interindividual differences. The glucuronidated apocarotenoid (compound 1), which probably resulted from the main carotenoids of red Capsicum fruits, shows a rapid urinary excretion. The other glucuronidated metabolites (compounds 2-8), described as potential derivatives of capsianosides from Capsicum, show a slightly delayed but longer urinary excretion.

CONCLUSIONS

A correlation between an intake of red bell pepper and the urinary excretion of recently described potential biomarkers is observed. Due to large interindividual differences, it is reasonable to assume that at least the qualitative detection of the consumption of bell peppers and possibly all Capsicum fruits is feasible.

An arrhythmogenic metabolite in atrial fibrillation

BACKGROUND

Long-chain acyl-carnitines (ACs) are potential arrhythmogenic metabolites. Their role in atrial fibrillation (AF) remains incompletely understood. Using a systems medicine approach, we assessed the contribution of C18:1AC to AF by analysing its in vitro effects on cardiac electrophysiology and metabolism, and translated our findings into the human setting.

METHODS AND RESULTS

Human iPSC-derived engineered heart tissue was exposed to C18:1AC. A biphasic effect on contractile force was observed: short exposure enhanced contractile force, but elicited spontaneous contractions and impaired Ca2+ handling. Continuous exposure provoked an impairment of contractile force. In human atrial mitochondria from AF individuals, C18:1AC inhibited respiration. In a population-based cohort as well as a cohort of patients, high C18:1AC serum concentrations were associated with the incidence and prevalence of AF.

CONCLUSION

Our data provide evidence for an arrhythmogenic potential of the metabolite C18:1AC. The metabolite interferes with mitochondrial metabolism, thereby contributing to contractile dysfunction and shows predictive potential as novel circulating biomarker for risk of AF.

Identification of Potential Urinary Biomarkers for Bell Pepper Intake by HPLC-HRMS-Based Metabolomics and Structure Elucidation by NMR

Dietary biomarkers show great promise for objectively assessing the food intake in humans. In this study, potential urinary biomarkers for red bell pepper intake were identified based on a dietary intervention study and a comprehensive metabolomics approach. Spot urine samples from 14 volunteers were collected in the two phases of the study (control phase: abstaining from any bell pepper/paprika products; case phase: consumption of a defined amount of fresh red bell pepper and abstaining from any further bell pepper/paprika products) and analyzed by high-performance liquid chromatography high-resolution mass spectrometry (HPLC-HRMS). Comparison of the obtained metabolomics data using statistical analysis revealed that the respective urine metabolomes differ significantly, which was attributable to the bell pepper intake. Some of the most discriminating metabolites were selected and isolated from human urine for unequivocal structure elucidation by nuclear magnetic resonance (NMR) spectroscopy. Herein, seven novel glucuronidated metabolites most likely derived from capsanthin and capsianosides were identified, implying their potential application as dietary biomarkers for the entire Capsicum genus.

Characterization of Oligomeric Proanthocyanidin-Enriched Fractions from Aronia melanocarpa (Michx.) Elliott via High-Resolution Mass Spectrometry and Investigations on Their Inhibitory Potential on Human Topoisomerases

Aronia melanocarpa (MICHX.) ELLIOTT, which belongs to the Rosaceae family, has increasingly come into focus of research due to the high content of polyphenols. In addition to antioxidative properties, further health-promoting effects of these polyphenols are still of interest. Especially, the proanthocyanidins offer thereby huge opportunities due to their high structural heterogeneity. Therefore, the present study focuses on the topoisomerase inhibiting effects of oligomeric proanthocyanidins (PACs), which are potentially depended on their degree of polymerization. The investigated PACs isolated from Aronia berries were characterized by chromatographic techniques and liquid chromatography-high-resolution mass spectrometry. Four PAC enriched fractions were obtained from Aronia pomace containing 47 PACs with a degree of polymerization from three to six. Due to the low yield of hexamers, the potential inhibiting effects against human topoisomerase were investigated for the trimer to pentamer fractions. The relaxation and decatenation assays were performed to examine the inhibiting effect on topoisomerases under cell-free conditions. Moreover, rapid isolation of topoisomerase cleavage complexes in human colon carcinoma HT29 cells was performed to evaluate the effect on topoisomerases in a cell-based system. The fractions demonstrated inhibitory potential on topoisomerases I and II. In sum, an increasing effect strength depending on the degree of polymerization was shown.

Ion identity molecular networking for mass spectrometry-based metabolomics in the GNPS environment

Molecular networking connects mass spectra of molecules based on the similarity of their fragmentation patterns. However, during ionization, molecules commonly form multiple ion species with different fragmentation behavior. As a result, the fragmentation spectra of these ion species often remain unconnected in tandem mass spectrometry-based molecular networks, leading to redundant and disconnected sub-networks of the same compound classes. To overcome this bottleneck, we develop Ion Identity Molecular Networking (IIMN) that integrates chromatographic peak shape correlation analysis into molecular networks to connect and collapse different ion species of the same molecule. The new feature relationships improve network connectivity for structurally related molecules, can be used to reveal unknown ion-ligand complexes, enhance annotation within molecular networks, and facilitate the expansion of spectral reference libraries. IIMN is integrated into various open source feature finding tools and the GNPS environment. Moreover, IIMN-based spectral libraries with a broad coverage of ion species are publicly available.

The burden of neurological comorbidities in six autoimmune bullous diseases: a population-based study

BACKGROUND

Apart from bullous pemphigoid (BP), the association of other autoimmune bullous diseases (AIBDs) with neurological conditions is poorly understood.

OBJECTIVE

To estimate the association between a wide array of AIBDs and neurological conditions.

METHODS

A retrospective cross-sectional study recruited patients with BP, mucous membrane pemphigoid (MMP), epidermolysis bullosa acquisita (EBA), pemphigoid gestationis (PG), pemphigus vulgaris (PV) and pemphigus foliaceus (PF). These patients were compared with their age- and sex-matched control subjects with regard to the lifetime prevalence of Parkinson's disease (PD), Alzheimer's disease (AD), stroke, epilepsy and multiple sclerosis (MS). Logistic regression was used to calculate OR for specified neurological disorders.

RESULTS

The current study included 1743, 251, 106, 126, 860 and 103 patients diagnosed with BP, MMP, EBA, PG, PV and PF, respectively. These patients were compared with 10 141, 1386, 606, 933, 5142 and 588 matched controls, respectively. Out of the investigated neurological conditions, PD associated with BP (OR, 2.71; 95% CI, 2.19-3.35); AD with BP (OR, 2.11; 95% CI, 1.73-2.57), MMP (OR, 2.37; 95% CI, 1.03-5.47), EBA (OR, 6.00; 95% CI, 1.90-18.97) and PV (OR, 2.24; 95% CI, 1.40-3.60); stroke with BP (OR, 1.84; 95% CI, 1.55-2.19) and EBA (OR, 2.79; 95% CI, 1.11-7.01); and epilepsy with BP (OR, 2.18; 95% CI, 1.72-2.77) and PV (OR, 1.80; 95% CI, 1.19-2.73). MS did not significantly cluster with any of the six AIBDs.

CONCLUSION

In addition to BP, EBA and PV were found to cluster with neurological comorbidities. Patients with these AIBDs with compatible symptoms may be carefully assessed for comorbid neurological disorders.

Incidence of pemphigoid diseases in Northern Germany in 2016 - first data from the Schleswig-Holstein Registry of Autoimmune Bullous Diseases

BACKGROUND

Autoimmune bullous diseases (AIBD) are rare disorders characterized by autoantibody formation against components of adhesion molecules; in pemphigoid diseases (PD), these are proteins of hemidesmosomes and basement membrane, important for cell-matrix adhesion in skin and/or mucous membranes. Incidences of these diseases vary considerably between different populations.

OBJECTIVES

To establish a registry prospectively recruiting all AIBD patients in a geographically well-defined region in Northern Germany (Schleswig-Holstein).

METHODS

Only patients with verified disease (by clinical presentation, histology, direct and/or indirect immunofluorescence and /or ELISA) living in Schleswig-Holstein were included. Incidences of PD were estimated based on the total number of inhabitants in Schleswig-Holstein, stratified by birth year and sex.

RESULTS

Of 67 patients with PD [35 male, 32 female, mean age 75 (standard deviation 14.3 years)], 83% were patients with bullous pemphigoid [n = 56, 28 male, 28 female, mean age 78 (SD 9.9)]. The resulting crude incidences were 23.4 patients/million/year for all pemphigoid patients, 19.6 patients/million/year for bullous pemphigoid (age-standardized 16.9 patients/million/year) with a strong increase in bullous pemphigoid patients in the age group of 85-90 years with 262 patients/million/year. Incidences for bullous pemphigoid were higher in urban compared to rural areas. Other PD (mucous membrane pemphigoid, linear IgA disease, anti-p200 pemphigoid) were less frequent with crude incidences of 2.1, 1.0 and 0.7 patients/million/year, respectively.

CONCLUSIONS

This study prospectively analyses the incidence of PD in a carefully defined geographical area. The highest incidence among PD patients was found for bullous pemphigoid. The incidence of bullous pemphigoid is considerably increased compared to previous reports and reveals regional differences. Further studies are needed in order to clarify these findings.

Identification of Novel Iso-Esculeoside B from Tomato Fruits and LC-MS/MS-Based Food Screening for Major Dietary Steroidal Alkaloids Focused on Esculeosides

Plants from the Solanaceae family are known to be sources of several nutritionally relevant steroidal glycoalkaloids (SGAs). With the aim of quantitatively investigating the occurrence of the main SGA from tomatoes, eggplants, and potatoes in various food samples and evaluating their relevance in the human diet, a rapid single-step extraction liquid chromatography-tandem mass spectrometry method was developed. Over the course of isolating several commercially unavailable SGAs from tomato products to use them as reference standards, a previously unknown derivative was detected, structurally characterized, and identified as a novel isomer of esculeoside B-1 and B-2. After validation of the method, 36 food items exclusively derived from Solanaceae plants were analyzed for their SGA contents and a specific occurrence of each alkaloid in tomato, eggplant, or potato products was revealed. This is the first study reporting quantitative data on the occurrence of esculeoside A, B-1, B-2, and iso-esculeoside B in tomato products obtained by using appropriate reference compounds rather than applying a semi-quantitative approach based on α-tomatine as a reference. Some of the analyzed tomato products contained the esculeosides in concentrations of >500 mg/kg, clearly indicating their relevance in the human diet and the need of investigating their potential bioactivities in the future.

Urinary Biomarkers for Orange Juice Consumption

SCOPE

As orange juice belongs to one of the most consumed juices worldwide, a human study is performed to identify urinary biomarkers for the consumption of orange juice in order to differentiate between low, medium, and high intake.

METHODS AND RESULTS

The 32 study participants abstained from citrus fruits, juices and products thereof, except for one portion of orange juice, for eight days. Throughout the study, spot urine samples are collected and quantitatively analyzed by high-performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS) regarding their content of several potential biomarkers for orange juice intake after enzymatic treatment with β-glucuronidase. Proline betaine is determined as a long-term biomarker: based on its urinary excretion, orange juice consumption is traceable for at least 72 h after intake. Naringenin and hesperetin are identified as qualitative short-term biomarkers. Synephrine sulfate also showed a fast increase and decrease in a semi-quantitative approach. In the case of phloretin, no correlation between orange juice consumption and the urinary concentration is observed.

CONCLUSION

Proline betaine is the most promising biomarker for orange juice consumption and allows to differentiate between low, medium, and high intake. Hesperetin and naringenin (as well as synephrine) are applicable as supporting biomarkers, whereas phloretin does not represent a reliable biomarker for orange juice consumption.

Artificial vs natural Stachybotrys infestation-Comparison of mycotoxin production on various building materials

The genus Stachybotrys belongs to filamentous fungi found in indoor environment, mostly on cellulose-rich substrates after water-damage. The major purpose of this study was to investigate the influence of different building materials in case of mold infestation on the mycotoxin production of Stachybotrys species. Fifteen Stachybotrys mycotoxins including satratoxins, phenylspirodrimanes, and recently discovered stachybotrychromenes were in the focus of the investigations. Artificial and natural infestations were compared to determine whether environmental factors, for example, time of growth, temperature, humidity, and material additives have an influence on the observed mycotoxin profiles. It turned out that mycotoxin profiles from Stachybotrys spp. on building materials can be influenced by cellulose, paints, and paste of the materials. The total toxin levels of artificially and naturally contaminated gypsum board samples ranged up to 30 µg/cm² , whereas wallpaper samples showed total toxin levels in the range of 20-66 µg/cm² . A naturally infested sample disclosed the conversion of the dialdehyde components to the corresponding lactone isomers under the influence of light.

Prevalence and age distribution of pemphigus and pemphigoid diseases among paediatric patients in Germany

BACKGROUND

Autoimmune bullous diseases are rare and mostly occur in adults. Several cases and small case series have been described in children, but no systematic study about the prevalence of autoimmune bullous diseases (AIBD) in children is available.

PATIENTS AND METHODS

We analysed data of 1.7 million children insured in the largest German health insurance company based on the ICD-10-GM classification for the year 2015. Data were adjusted to the general German population based on the data of the Federal Statistical Office for the year 2015.

RESULTS

The prevalence of AIBD was calculated to 101.1/million children in 2015, resulting in about 1351 patients below the age of 18 years in Germany. The highest prevalence of all AIBD was seen for pemphigus vulgaris (30.5/million children) followed by linear IgA disease (24.5/million children) and bullous pemphigoid (4.9/million children).

CONCLUSION

Autoimmune bullous diseases in minors are scarce but should be taken into consideration in patients with pruritus and/or blisters and erosions on the skin and/or mucous membranes. Treatment is challenging, and due to the rarity of AIBD in minors, the management of these disorders in this patient population is best performed in specialized centres in a multidisciplinary approach, including paediatric dermatologists or dermatologists and paediatricians.

Identification of a novel N-caprylhistamine-β-glucoside from tomato fruits and LC-MS/MS-based food screening for imidazole alkaloids

The present study aimed at the identification of novel imidazole alkaloids derived from histamine or histidinol and generally investigating the occurrence of suchlike alkaloids in a variety of foodstuffs. Herein, N-caprylhistamine was synthesized and the glucosidic derivative N-caprylhistamine-β-glucoside was isolated from ripe tomato fruits and structurally characterized. The obtained reference standards were used for the extension of an established LC-MS/MS-based method for the quantitation of several imidazole alkaloids in tomato products. After validation for the two additional analytes and demonstrating the applicability of the method to nine other food matrices, 104 food items were screened for the occurrence of the described imidazole alkaloids. Remarkably, all of the investigated alkaloids were only quantifiable in tomato-based products and the occurrence of N-caprylhistamine and N-caprylhistamine-β-glucoside was reported for the first time. These imidazole alkaloids could thus be applicable as specific intake biomarkers for tomatoes and their biological activities as well as metabolic fate should be investigated in future research.

Mass Spectrometry-Based Analysis of Urinary Biomarkers for Dietary Tomato Intake

SCOPE

In this study, the applicability of several β-carboline, imidazole, and steroidal alkaloids as biomarkers for tomato juice intake is evaluated.

METHODS AND RESULTS

Over the course of a 2-week crossover dietary intervention study, 14 volunteers were given low and high doses of tomato juice after 3 days of avoiding tomato-based products. On the day of consumption and the following days, volunteers provided urine samples that were quantitatively analyzed by high-performance liquid chromatography-tandem mass spectrometry. Herein, glucose-derived β-carboline alkaloids are determined as supporting, yet non-specific dietary biomarkers for tomato juice intake. Several imidazole alkaloids represent further biomarkers, which are shown to specifically indicate consumption of tomato juice for 24 h and partly >24 h. Additionally, steroidal alkaloids derived from esculeogenin B are determined to be specific biomarkers for tomato juice detectable for at least 48 h after consumption. The intake of low and high amounts of tomato juice is significantly distinguishable based on the urinary excretion of all determined biomarkers as well.

CONCLUSIONS

The dietary intake of tomato juice is conclusively traceable based on urinary excretion of multiple β-carboline, imidazole, and steroidal alkaloids, and can be determined for up to 48 h after consumption. Furthermore, different intake doses can clearly be distinguished based on their urinary excretion.

Large-Scale Screening of Foods for Glucose-Derived β-Carboline Alkaloids by Stable Isotope Dilution LC-MS/MS

The occurrence of glucose-derived β-carboline alkaloids tangutorid E (Tan E) and tangutorid F (Tan F) as well as their dehydroxy-derivatives (DH-Tan E/F) was investigated in a broad variety of foodstuffs by LC-MS/MS-based stable isotope dilution analysis (SIDA). For that purpose, the target compounds and their ¹³C₆-stable isotope-labeled analogues were synthesized from l-tryptophan and (¹³C₆-)d-glucose and used to develop a rapid LC-MS/MS-SIDA method. After validation for several food matrices, the method was applied to the analysis of these β-carbolines in 80 food items. Quantitative amounts were detected in 46.3, 50.0, and 42.5% of the samples regarding Tan E, Tan F, and DH-Tan E/F, respectively, with corresponding ranges of 0.01-6.75, 0.01-5.07, and 0.01-0.75 mg/kg; the highest amounts were found in processed tomato products. A combination of the obtained occurrence data in foods with average food consumption data led to the calculation of rough estimates for the chronic daily intake of those alkaloids, yielding values of 0.44, 0.36, and 0.13 μg/kg body weight/day for Tan E, Tan F, and DH-Tan E/F, respectively. Evidently, the consumption of processed tomato-based products accounts for the majority of the total daily intake of the investigated β-carbolines; the potential bioactivities of Tan E, Tan F, and DH-Tan E/F have yet to be investigated.

Detection of Novel Cytotoxic Imidazole Alkaloids in Tomato Products by LC-MS/MS

Imidazole alkaloids represent a rather small group of alkaloids and are assumed not to be of significance to the human food chain so far. In this study, novel imidazole alkaloids occurring in tomato products were synthesized and structurally characterized by nuclear-magnetic-resonance spectroscopy and high-resolution mass spectrometry. These alkaloids are amides of either histidinol or histamine and short-chain fatty acids and could be quantitated in all of the 28 analyzed tomato products using a newly developed and validated LC-MS/MS-based method. Levels ranged from approximately 5 μg/kg to almost 3 mg/kg in the analyzed tomato products, and N-caprylhistidinol and its putative isomer were shown to occur in the highest amounts. These imidazole alkaloids are thus regularly ingested in considerable amounts as part of the human diet. In the course of evaluating their effects on the viability of HT-29 cells, all compounds were shown to significantly reduce cell viability starting at concentrations of 100 μM.

Identification of potential human urinary biomarkers for tomato juice intake by mass spectrometry-based metabolomics

PURPOSE

Dietary biomarkers allow the accurate and objective determination of the dietary intake of humans and can thus be valuable for investigating the relation between consumption of foods and biochemical as well as physiological responses. The objective of this study was the identification of potential urinary biomarkers for consumption of tomato juice.

METHODS

In the course of a dietary intervention study, the human urine metabolome of a study cohort was compared between a tomato-free diet and after intake of tomato juice by application of an LC-HRMS-based metabolomics approach. The data acquisition was achieved using an orbitrap mass spectrometer, followed by multistage data processing and univariate as well as multivariate statistical analysis to identify discriminating features.

RESULTS

Statistical analysis revealed several unique features detectable after tomato juice intake. The most discriminating markers were putatively identified as hydroxylated and sulfonated metabolites of esculeogenin B, aglycone of the steroidal glycoalkaloid esculeoside B recently found in tomato juice. Furthermore, the β-carboline alkaloids tangutorid E and F and glucuronidated derivatives thereof were identified in urine.

CONCLUSIONS

Steroidal glycoalkaloids in tomato juice are cleaved after ingestion, and hydroxylated and sulfonated metabolites of their aglycones might serve as urinary biomarkers for tomato juice intake. Similarly, β-carboline alkaloids and glucuronidated derivatives were identified as potential urinary biomarkers. Both the aglycones of the steroidal alkaloids and the β-carboline alkaloids might exhibit biological activities worth investigating.

Exploring Secondary Metabolite Profiles of Stachybotrys spp. by LC-MS/MS

The genus Stachybotrys produces a broad diversity of secondary metabolites, including macrocyclic trichothecenes, atranones, and phenylspirodrimanes. Although the class of the phenylspirodrimanes is the major one and consists of a multitude of metabolites bearing various structural modifications, few investigations have been carried out. Thus, the presented study deals with the quantitative determination of several secondary metabolites produced by distinct Stachybotrys species for comparison of their metabolite profiles. For that purpose, 15 of the primarily produced secondary metabolites were isolated from fungal cultures and structurally characterized in order to be used as analytical standards for the development of an LC-MS/MS multimethod. The developed method was applied to the analysis of micro-scale extracts from 5 different Stachybotrys strains, which were cultured on different media. In that process, spontaneous dialdehyde/lactone isomerization was observed for some of the isolated secondary metabolites, and novel stachybotrychromenes were quantitatively investigated for the first time. The metabolite profiles of Stachybotrys species are considerably influenced by time of growth and substrate availability, as well as the individual biosynthetic potential of the respective species. Regarding the reported adverse effects associated with Stachybotrys growth in building environments, combinatory effects of the investigated secondary metabolites should be addressed and the role of the phenylspirodrimanes re-evaluated in future research.

Stachybotrychromenes A-C: novel cytotoxic meroterpenoids from Stachybotrys sp

In the course of gaining new insights into the secondary metabolite profile of various Stachybotrys strains, in particular concerning triprenyl phenol-like compounds, so far, unknown metabolites with analogous structural features were discovered. Three novel meroterpenoids containing a chromene ring moiety, namely stachybotrychromenes A–C, were isolated from solid culture of the filamentous fungus Stachybotrys chartarum DSMZ 12880 (chemotype S). Their structures were elucidated by means of comprehensive spectroscopic analysis (1D and 2D NMR, ESI-HRMS, and CD) as well as by comparison with spectroscopic data of structural analogues described in literature. Stachybotrychromenes A and B exhibited moderate cytotoxic effects on HepG2 cells after 24 h with corresponding IC₅₀ values of 73.7 and 28.2 μM, respectively. Stachybotrychromene C showed no significant cytotoxic activity up to 100 μM. Moreover, it is noteworthy that stachybotrychromenes A–C are produced not only by S. chartarum chemotype S but also S. chartarum chemotype A and Stachybotrys chlorohalonata.

Validation of a mathematical model for laser-induced thermotherapy in liver tissue

The purpose of the study was to develop a simulation approach for laser-induced thermotherapy (LITT) that is based on mathematical models for radiation transport, heat transport, and tissue damage. The LITT ablation was applied to ex vivo pig liver tissue. Experiments were repeated with different laser powers, i.e., 22-34 W, and flow rates of the cooling water in the applicator system, i.e., 47-92 ml/min. During the procedure, the temperature was measured in the liver sample at different distances to the applicator as well as in the cooling circuit using a fiber optic thermometer. For validation, the simulation results were compared with the results of the laser ablation experiments in the ex vivo pig liver samples. The simulated and measured temperature curves presented a relatively good agreement. The Bland-Altman plot showed an average of temperature differences of -0.13 ^∘C and 95%-limits-of-agreement of ±7.11 ^∘C. The standard deviation amounted to ±3.63 ^∘C. The accuracy of the developed simulation is comparable with the accuracy of the MR thermometry reported in other clinical studies. The simulation showed a significant potential for the application in treatment planning.

Short-term biomarkers of apple consumption

SCOPE

Urinary biomarkers are used to estimate the nutritional intake of humans. The aim of this study was to distinguish between low, medium, and high apple consumption by quantifying possible intake biomarkers in urine samples after apple consumption by HPLC-MS/MS. Apples were chosen as they are the most consumed fruits in Germany.

METHODS AND RESULTS

Thirty subjects took part in 7-day study. They abstained from apples and apple products except for one weighed apple portion resembling one, two, or four apples. Before apple consumption and during the following days spot urine samples were collected. These urine samples were incubated with β-glucuronidase, diluted, and directly measured by HPLC-MS/MS. Phloretin, epicatechin, procyanidin B2, and quercetin were detected in urine using Scheduled MRM^TM mode. Phloretin was confirmed as a urinary biomarker of apple intake and had the ability to discriminate between low or medium (one or two apples) and high apple consumption (four apples). The groups also differ in the excretion of epicatechin and procyanidin B2.

CONCLUSION

Apple consumption can be monitored by urinary biomarkers for a period of at least 12 h after consumption. Furthermore the amount of apples consumed can be estimated by the concentration of certain biomarkers.

Pharmacokinetics of the Experimental Non-Nucleosidic DNA Methyl Transferase Inhibitor N-Phthalyl-L-Tryptophan (RG 108) in Rats

DNA methyl transferase (DNMT) inhibitors can re-establish the expression of tumour suppressor genes in malignant diseases, but might also be useful in other diseases. Inhibitors in clinical use are nucleosidic cytotoxic agents that need to be integrated into the DNA of dividing cells. Here, we assessed the in vivo kinetics of a non-nucleosidic inhibitor that is potentially free of cytotoxic effects and does not require cell division. The non-specific DNMT inhibitor N-phthalyl-L-tryptophan (RG 108) was injected subcutaneously in rats. Blood was drawn 0, 0.5, 1, 2, 4, 6, 8 and 24 hr after injection and RG 108 in plasma was measured by high-performance liquid chromatography coupled to mass spectrometry. Trough levels and area under the curve (AUC) were significantly higher with multiple-dose administration and cytochrome inhibition. In this group, time to maximal plasma concentration (tmax , mean ± S.D.) was 37.5 ± 15 min., terminal plasma half-life was approximately 3.7 h (60% CI: 2.1-15.6 h), maximal plasma concentration (Cmax) was 61.3 ± 7.6 μM, and AUC was 200 ± 54 μmol·h/l. RG 108 peak levels were not influenced by cytochrome inhibition or multiple-dose administration regimens. Maximal tissue levels (Cmax in μmol/kg) were 6.9 ± 6.7, 1.6 ± 0.4 and 3.4 ± 1.1 in liver, skeletal and heart muscle, respectively. We conclude that despite its high lipophilicity, RG 108 can be used for in vivo experiments, appears safe and yields plasma and tissue levels in the range of the described 50% inhibitory concentration of around 1 to 5 μM. RG 108 can therefore be a useful tool for in vivo DNMT inhibition.

Toxicity of arsenite and thio-DMAV after long-term (21 days) incubation of human urothelial cells: cytotoxicity, genotoxicity and epigenetics

This study aims to further mechanistically understand toxic modes of action after chronic arsenic species exposure.

Stable isotope dilution analysis of small molecules with carboxylic acid functions using 18O labeling for HPLC-ESI-MS/MS: analysis of fumonisin B1

(18)O labeling is a well-known method for the stable isotope labeling of proteins and peptides. This study describes a modified procedure for using (18)O labeling on small molecules. Fumonisin B1, a worldwide occurring mycotoxin, which is routinely analyzed by HPLC-MS/MS, was chosen as model compound. (18)O labeling was achieved by acid-catalyzed oxygen exchange from H2(18)O. A mixture of different isotopologues was obtained from the exchange, which, however, could be used as an internal standard for HPLC-MS/MS analysis. The identity of the (18)O-labeled fumonisin B1 was confirmed by NMR and HRMS measurements. The applicability as internal standard has been verified by comparison of results obtained from the method described in this paper to results obtained by reference methods. The presented method is of special interest as the (18)O labeling can be generally applied to a large group of small molecules containing carboxylic groups.

Systematic approach for structure elucidation of polyphenolic compounds using a bottom-up approach combining ion trap experiments and accurate mass measurements

Polyphenols are a group of plant secondary metabolites with a wide range of structural differences. In many cases, in vitro and in vivo studies of polyphenols revealed beneficial health effects. The mass spectrometric characterization of polyphenols can be the key to understanding the metabolism and resorption of this group of substances. For structure elucidation of polyphenolic compounds nuclear magnectic resonance spectroscopy is the method of choice. Due to the broad structure variability and the sometimes relatively low concentrations of polyphenols and/or their metabolites in foods as well as physiological samples, mass spectrometry could be an alternative for structure elucidation. Especially high-resolution mass spectrometry, for example, Fourier transformation mass spectrometry (FTMS), is a valuable tool. Using a FTMS system, a systematic approach to the fragmentation behavior of phenolic and polyphenolic compounds was chosen to verify the influence of the structure on the fragmentation pattern of the different substances. Depending on the structure, specific fragment ions could be detected. Therefore, it is possible to gain reliable information about the structure of the pseudomolecular ion from its fragmentation spectrum, which is of great aid in the structure elucidation of unknown polyphenols and/or their metabolites.

Identification and apoptotic potential of T-2 toxin metabolites in human cells

The mycotoxin T-2 toxin, produced by various Fusarium species, is a widespread contaminant of grain and grain products. Knowledge about its toxicity and metabolism in the human body is crucial for any risk assessment as T-2 toxin can be detected in processed and unprocessed food samples. Cell culture studies using cells of human origin represent a potent model system to study the metabolic fate of T-2 toxin as well as the cytotoxicity in vitro. In this study the metabolism of T-2 toxin was analyzed in a cell line derived from human colon carcinoma cells (HT-29) and primary human renal proximal tubule epithelial cells (RPTEC) using high-performance liquid chromatography coupled with Fourier transformation mass spectrometry (HPLC-FTMS). Both cell types metabolized T-2 toxin to a variety of compounds. Furthermore, cell cycle analysis in RPTEC proved the apoptotic effect of T-2 toxin and its metabolites HT-2 toxin and neosolaniol in micromolar concentrations.

Intestinal metabolism of two A-type procyanidins using the pig cecum model: detailed structure elucidation of unknown catabolites with Fourier transform mass spectrometry (FTMS)

Procyanidins, as important secondary plant metabolites in fruits, berries, and beverages such as cacao and tea, are supposed to have positive health impacts, although their bioavailability is yet not clear. One important aspect for bioavailability is intestinal metabolism. The investigation of the microbial catabolism of A-type procyanidins is of great importance due to their more complex structure in comparison to B-type procyanidins. A-type procyanidins exhibit an additional ether linkage between the flavan-3-ol monomers. In this study two A-type procyanidins, procyanidin A2 and cinnamtannin B1, were incubated in the pig cecum model to mimic the degradation caused by the microbiota. Both A-type procyanidins were degraded by the microbiota. Procyanidin A2 as a dimer was degraded by about 80% and cinnamtannin B1 as a trimer by about 40% within 8 h of incubation. Hydroxylated phenolic compounds were quantified as degradation products. In addition, two yet unknown catabolites were identified, and the structures were elucidated by Fourier transform mass spectrometry.

Large scale purification of B-type fumonisins using centrifugal partition chromatography (CPC)

For toxicological studies of B-type fumonisin in animals, high amounts of pure fumonisins are needed. In the past, several methods for the isolation and purification of fumonisins have been published, stating the problem of high losses of fumonisins during chromatography on solid phases. In this manuscript we describe a new approach based on liquid-liquid partition techniques using centrifugal partition chromatography in combination with ion exchange chromatography for the large-scale isolation of B-type fumonisins with good recovery rates, minimizing losses of fumonisins during the purification. A batch of cultures grown on solid media of 2 kg maize yields approximately 1 g of pure fumonisins with a purity of >98%.

Re-examination of the anion derivatives of isoflavones by radical fragmentation in negative electrospray ionization tandem mass spectrometry: experimental and computational studies

This paper reports theoretical and experimental studies of gas-phase fragmentation reactions of four naturally occurring isoflavones. The samples were analyzed in negative ion mode by direct infusion in ESI-QqQ, ESI-QqTOF and ESI-Orbitrap systems. The MS/MS and MS(n) spectra are in agreement with the fragmentation proposals and high-resolution analyses have confirmed the formulae for each ion observed. As expected, compounds with methoxyl aromatic substitution have showed a radical elimination of •CH(3) as the main fragmentation pathway. A second radical loss (•H) occurs as previously observed for compounds which exhibit a previous homolytic •CH(3) cleavage (radical anion) and involves radical resonance to stabilize the anion formed. However, in this study we suggest another mechanism for the formation of the main ions, on the basis of the enthalpies for each species. Compounds without methoxy substituent dissociate at the highest energies and exhibit the deprotonated molecule as the most intense ion. Finally, energy-resolved experiments were carried out to give more details about the gas-phase dissociation reaction of the isoflavones and the results are in agreement with the theoretical approaches.

Analysis of mechanical interaction between human gluteal soft tissue and body supports

Pressure sores are the most common complication associated with patient immobilization. They develop through sustained localized tissue strain and stress, primarily caused by body supports. Modifying support design can reduce the risk and extent of pressure sore development with computational simulations helping to provide insight into tissue stress-strain distribution. Appropriate material parameters for human soft tissue and support material, as well as precise anatomical modelling, are indispensable in this process. A finite element (FE) model of the human gluteal region based on magnetic resonance imaging (MRI) data has been developed. In vivo human gluteal skin/fat and muscle long-term material parameters as well as open-cell polyurethane foam support long-term material parameters have been characterised. The Ogden form for slightly compressible materials was employed to describe human gluteal soft tissue behaviour. Altering support geometries and support materials, effects on human gluteal soft tissue could be quantified. FE-analysis indicated maximal tissue stress at the muscle-bone interface, not at the skin. Shear strain maxima were found in the muscle layer near the fat-muscle interface. Maximum compressive stress magnitude at the sacral bone depended strongly on the behaviour of the pelvic diaphragm musculature. We hypothesize that the compliance of the muscles forming the pelvic diaphragm govern the relative motion of the buttock tissue to the adjacent bone structure under compression, thus influencing tissue stress magnitudes.

MR-Thermometrie bei 1,5 Tesla zur thermischen Ablation mittels laserinduzierter Thermotherapie

PURPOSE

Evaluation of thermometry with fast MR sequences for laser-induced interstitial laser therapy (LITT) and verification of the thermometric results with a fiber-optic thermometer.

METHOD AND MATERIALS

In vitro experiments were conducted using an agarose gel mixture and pig liver lobes. MR-guided LITT was performed using a laser power between 3 and 15 watts. Thermometry was performed using longitudinal relaxation time T1 and proton resonance frequency shift (PRF) methods under acquisition of amplitude and phase shift images. PRF was measured with a fast spoiled GRE sequence. Four different sequences were used for T1 thermometry: gradient echo (GE), TrueFISP (TRUFI), Saturation Recovery Turbo-FLASH (SRTF) and Inversion Recovery Turbo-FLASH (IRTF) sequences. The temperature was controlled using a fiber-optic Luxtron device and correlated with the MR temperature. The range of applied and monitored temperatures exceeded 80 degrees Celsius.

RESULTS

The temperature dependence showed a good linear relationship up to 60 degrees Celsius. Calibration experiments for the T1 method delivered coefficients of determination from 0.977 to 0.997 for agarose and from 0.958 to 0.995 for the pig liver samples. The IRTF sequence had the highest temperature sensitivity (agarose 0.99, liver 1.19). During LITT the TRUE-FISP sequence exhibited a strong nonlinear relationship. R (2) of this sequence was 0.809 in the agarose experiments. The average temperature errors when heated up to 80 degrees Celsius were 3.86-11.38 degrees Celsius for Agarose gel and 5.7-12.16 degrees Celsius for the liver tissue. SRTF and IRTF sequences exhibited the most linear relationship with temperature but were more dependent on tissue differences.

CONCLUSION

The accuracy of the temperature measurement is sufficient for controlling the coagulation area of the LITT. PRF is the method of choice since it shows the best linear correlation with fiber-optic temperature. If only T1 sequences are concerned, the FLASH sequence is preferred. It is the most robust, though not the most accurate, T1 sequence.