Institut für Lebensmittelchemie

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New fluorogenic triacylglycerols as sensors for dynamic measurement of lipid oxidation
(2025) Handke, Maria; Beierlein, Frank; Imhof, Petra; Schiedel, Matthias; Hammann, Simon
Lipids are major constituents of food but are also highly relevant substructures of drugs and are increasingly applied for the development of lipid-based drug delivery systems. Lipids are prone to oxidative degradation, thus affecting the quality of food or medicines. Therefore, analytical methods or tools that enable the degree of lipid oxidation to be assessed are of utmost importance to guarantee food and drug safety. Herein, we report the design, synthesis and application of the first-in-class fluorogenic triacylglycerols that enable dynamic monitoring of lipid oxidation via straightforward fluorescence readout. Our fluorogenic triacylglycerols can be used in both aqueous and lipid-based environments. Furthermore, we showed that the sensitivity of our fluorescent tracers towards oxidation could be tuned by incorporating either saturated or unsaturated acyl chains in their triacylglycerol core structure. With this, we provide a first proof of principle for the applicability of fluorescently labelled triacylglycerols as tracers to monitor the dynamics of lipid oxidation, thus paving the way for novel discoveries in the area of lipid analytics.
High abundance of pyrrolizidine alkaloids in bee pollen collected in July 2019 from Southern Germany
(2022) Friedle, Carolin; Kapp, Thomas; Wallner, Klaus; Alkattea, Raghdan; Vetter, Walter
Pyrrolizidine alkaloids (PA) are secondary plant defense compounds and known pre-toxins when containing a 1,2-double bond. They are commonly produced by various plants and may thus be present in bee pollen which may be consumed by humans as food supplements. In this study, PA were determined in bee pollen samples from 57 locations in Southern Germany sampled by means of pollen traps in July 2019. Samples were analyzed by using palynological methodology and solid-phase extraction (SPE) followed by LC–MS/MS. In total, 52 pollen samples featured total pyrrolizidine alkaloids (ΣPA) with concentrations up to 48,000 ng/g bee pollen, while the N-oxides (NO) echinatine-NO and rinderine-NO clearly dominated. In contrast, the palynological analysis only detected 33 samples with pollen from PA-producing plants. Accordingly, the results showed that palynological analysis is not sufficient to determine PA in pollen. In addition, a risk assessment was followed to estimate the risk of the detected PA concentrations to humans.
The furan fatty acids 11M5 and 11D5 can act as activators of human peroxisome proliferator‐activated receptor gamma
(2025) Pospiech, Jonas; Caspi, Ayelet; Vetter, Walter; Kerem, Zohar; Frank, Jan; Kufer, Thomas A.; Pospiech, Jonas; Institute of Nutritional Medicine, University of Hohenheim, Stuttgart, Germany; Caspi, Ayelet; Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot, Israel; Vetter, Walter; Institute of Food Chemistry (170b), University of Hohenheim, Stuttgart, Germany; Kerem, Zohar; Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot, Israel; Frank, Jan; Department of Food Biofunctionality, Institute of Nutritional Sciences, University of Hohenheim, Stuttgart, Germany; Kufer, Thomas A.; Institute of Nutritional Medicine, University of Hohenheim, Stuttgart, Germany
Furan fatty acids (FuFA) are a minor class of fatty acids in food that are characterized by a furan ring within the alkyl chain. Furan fatty acids have strong antioxidant properties but their biological functions remain largely elusive. Using molecular docking combined with biomolecular validation, we investigated the regulatory activities of the key furan fatty acids 9M5, 11M5, and 11D5 on human nuclear receptors, including PPARγ, LXR, PXR, FXR, and HNF4α. Using computational methods, 11M5 and 11D5 and to a lesser extend 9M5 were predicted to bind to PPARγ. The activation of both PPARγ1 and PPARγ2 was confirmed in human HEK293T cells and structure‐activity experiments revealed that this was dependent on the furan fatty acid backbone. In summary, our data provide novel insights into the biological activities of furan fatty acids in human cells and indicate that activation of peroxisome proliferator‐activated receptor gamma underlies their beneficial health effects. These findings establish a clear mechanistic basis, supported by the inactivity of related compounds, and we are confident that future expanded studies will further confirm this mechanism.
Enrichment and structural assignment of geometric isomers of unsaturated furan fatty acids
(2023) Müller, Franziska; Conrad, Jürgen; Hammerschick, Tim; Vetter, Walter
Furan fatty acids (FuFAs) are valuable minor fatty acids, which are known for their excellent radical scavenging properties. Typically, the furan moiety is embedded in an otherwise saturated carboxyalkyl chain. Occasionally, these classic FuFAs are accompanied by low amounts of unsaturated furan fatty acids (uFuFAs), which additionally feature one double bond in conjugation with the furan moiety. A recent study produced evidence for the occurrence of two pairs of E -/ Z -uFuFA isomers structurally related to saturated uFuFAs. Here, we present a strategy that allowed such trace compounds to be enriched to a level suited for structure determination by NMR. Given the low amounts and the varied abundance ratio of the four uFuFA isomers, the isolation of individual compounds was not pursued. Instead, the entire isomer mixture was enriched to an amount and purity suitable for structure investigation with contemporary NMR methods. Specifically, lipid extracted from 150 g latex, the richest known source of FuFAs, was subsequently fractionated by countercurrent chromatography (CCC), silver ion, and silica gel column chromatography. Analysis of the resulting mixture of four uFuFAs isomers (2.4 mg in an abundance ratio of 56:23:11:9) by different NMR techniques including PSYCHE verified that the structures of the two most abundant isomers were E -9-(3-methyl-5-pentylfuran-2-yl)non-8-enoic acid and E -9-(3-methyl-5-pent-1-enylfuran-2-yl)nonanoic acid. Additionally, we introduced a computer-based method to generate an averaged chromatogram from freely selectable GC/MS runs of CCC fractions without the necessity of pooling aliquots. This method was found to be suitable to simplify subsequent enrichment steps.
Monitoring a coffee roasting process based on near‐infrared and raman spectroscopy coupled with chemometrics
(2025) Munyendo, Leah; Schuster, Katharina; Armbruster, Wolfgang; Babor, Majharulislam; Njoroge, Daniel; Zhang, Yanyan; von Wrochem, Almut; Schaum, Alexander; Hitzmann, Bernd
Roasting is a fundamental step in coffee processing, where complex reactions form chemical compounds related to the coffee flavor and its health‐beneficial effects. These reactions occur on various time scales depending on the roasting conditions. To monitor the process and ensure reproducibility, the study proposes simple and fast techniques based on spectroscopy. This work uses analytical tools based on near‐infrared (NIR) and Raman spectroscopy to monitor the coffee roasting process by predicting chemical changes in coffee beans during roasting. Green coffee beans of Robusta and Arabica species were roasted at 240°C for different roasting times. The spectra of the samples were taken using the spectrometers and modeled by the k‐nearest neighbor regression (KNR), partial least squares regression (PLSR), and multiple linear regression (MLR) to predict concentrations from the spectral data sets. For NIR spectra, all the models provided satisfactory results for the prediction of chlorogenic acid, trigonelline, and DPPH radical scavenging activity with low relative root mean square error of prediction (pRMSEP < 9.649%) and high coefficient of determination ( R 2 > 0.915). The predictions for ABTS radical scavenging activity were reasonably good. On the contrary, the models poorly predicted the caffeine and total phenolic content (TPC). Similarly, all the models based on the Raman spectra provided good prediction accuracies for monitoring the dynamics of chlorogenic acid, trigonelline, and DPPH radical scavenging activity (pRMSEP < 7.849% and R 2 > 0.944). The results for ABTS radical scavenging activity, caffeine, and TPC were similar to those of NIR spectra. These findings demonstrate the potential of Raman and NIR spectroscopy methods in tracking chemical changes in coffee during roasting. By doing so, it may be possible to control the quality of coffee in terms of its aroma, flavor, and roast level.
Antifungal properties of bioactive compounds isolated from Fucus vesiculosus supercritical carbon dioxide extract
(2024) Tyśkiewicz, Katarzyna; Rüttler, Felix; Tyśkiewicz, Renata; Nowak, Artur; Gruba, Marcin; Wziątek, Anita; Dębczak, Agnieszka; Sandomierski, Michał; Vetter, Walter; Cacciola, Francesco
The exploration of natural antifungal substances from algal origins is significant due to the increasing resistance of pathogens to conventional antifungal agents and the growing consumer demand for natural products. This manuscript represents the inaugural investigation into the antifungal attributes of bioactive compounds extracted from Fucus vesiculosus via supercritical carbon dioxide (scCO2) extraction utilizing contemporary countercurrent chromatography (CCC). In aligning with the prospective utilization of this extract within the agricultural sector, this study also serves as the preliminary report demonstrating the capability of Fucus vesiculosus scCO2 extract to enhance the activity of plant resistance enzymes. The fractions obtained through CCC were subjected to evaluation for their efficacy in inhibiting the macrospores of Fusarium culmorum. The CCC methodology facilitated the successful separation of fatty acids (reaching up to 82.0 wt.% in a given fraction) and fucosterol (attaining up to 79.4 wt.% in another fraction). All CCC fractions at the concentration of 1.0% were found to inhibit 100% of Fusarium culmorum growth. Moreover, Fucus vesiculosus scCO2 extract was able to activate plant resistance enzymes (Catalase, Ascorbic Peroxidase, Guaiacol Peroxidase, Phenylalanine Ammonia-Lyase, and Phenylalanine Ammonia-Lyase Activity).
Hydroxylated transformation products obtained after UV irradiation of the current-use brominated flame retardants hexabromobenzene, pentabromotoluene, and pentabromoethylbenzene
(2023) Klimm, Alexandra; Vetter, Walter
Hexabromobenzene (HBB), pentabromotoluene (PBT), and pentabromoethylbenzene (PBEB) are current-use brominated flame retardants (cuBFRs) which have been repeatedly detected in environmental samples. Since information on hydroxylated transformation products (OH-TPs) was scarcely available, the three polybrominated compounds were UV irradiated for 10 min in benzotrifluoride. Fractionation on silica gel enabled the separate collection and identification of OH-TPs. For more insights, aliquots of the separated OH-TPs were UV irradiated for another 50 min (60 min total UV irradiation time). The present investigation of polar UV irradiation products of HBB, PBT, and PBEB was successful in each case. Altogether, eight bromophenols were detected in the case of HBB (three Br3-, four Br4-, and one Br5-isomer), and nine OH-TPs were observed in the case of PBT/PBEB (six Br3- and three Br4-congeners). In either case, Br➔OH exchange was more relevant than H➔OH exchange. Also, such exchange was most relevant in meta- and ortho-positions. As a further point, and in agreement with other studies, the transformation rate decreased with decreasing degree of bromination. UV irradiation of HBB additionally resulted in the formation of tri- and tetrabrominated dihydroxylated compounds (brominated diphenols) that were subsequently identified. These dihydroxylated transformation products were found to be more stable than OH-TPs.
Effect of relative humidity on the thin-layer chromatographic separation of E 472 emulsifiers
(2023) Schuster, Katharina; Oellig, Claudia
E 472 emulsifiers are organic acid esters of mono- and diacylglycerides. These emulsifiers are categorized into six subgroups (E 472a-f) based on the specific acid component, e.g., acetic acid, lactic acid, citric acid, tartaric acid, or mixtures of tartaric and acetic acid. The present study investigated the effect of relative humidity (RH) on the thin-layer chromatographic separation of four E 472 emulsifier subgroups, addressing practical concerns due to RH variations between seasons and within laboratories. Three RH-setting techniques affecting plate activity and chamber climate were assessed using saturated salt and aqueous sulfuric acid solutions. Aqueous sulfuric acid solutions for RH adjustment resulted in decreased hRF values, while no trends in hRF value changes were observed for saturated salt solutions. Unlike RH itself, the RH setting technique led to substantial changes in the chromatographic fingerprint. Thus, the choice of the RH setting method should be tailored to the specific analyte and analysis goal. Despite variations in chromatographic fingerprints between the three RH setting techniques, the fingerprint remained consistent within the same technique across the tested RH range.
Analysis of acrylamide in vegetable chips after derivatization with 2-mercaptobenzoic acid by liquid chromatography–mass spectrometry
(2022) Oellig, Claudia; Gottstein, Eva; Granvogl, Michael
Since many years, acrylamide (AA) is a well-known toxicologically relevant processing contaminant (“food-borne toxicant”). However, only during the recent years, high levels of acrylamide have been reported in vegetable chips. In the present study, AA was quantitated via a modified derivatization procedure with 2-mercaptobenzoic acid based on stable isotope dilution analysis and liquid chromatography–mass spectrometry. Extraction with a modified QuEChERS (quick, easy, cheap, efficient, rugged, safe) method, defatting with n -hexane, and a solid phase extraction clean-up with strong cation-exchange material were performed prior to the derivatization step. Limits of detection and quantitation (LoD and LoQ) were 12 and 41 µg of AA/kg of vegetable chips (estimated via signal-to-noise ratios of 3:1 and 10:1, respectively), and thus below the LoQ of 50 µg/kg requested by the European Food Safety Authority. Recovery rates between 92 and 101% at four spiking levels with a good precision expressed as a relative standard deviation < 7% were determined. With this method at hand, a survey of the current AA amounts in 38 vegetable chips from the worldwide market was performed, showing a remarkable variability between the different vegetables, but also between different products of the same vegetable. Thereby, the AA amounts ranged between 77.3 and 3090 µg/kg, with an average of 954 µg/kg which was distinctly higher in comparison to commercially available potato chips also analyzed in the present study (12 samples, range: 117–832 µg/kg, average: 449 µg/kg). While for sweet potato and parsnip relatively low AA amounts were found, beetroot and carrot showed rather high contents.
High-performance thin-layer chromatography for the detection of compositional changes in LACTEM emulsifiers during storage
(2025) Schuster, Katharina; Blankart, Max; Hinrichs, Jörg; Oellig, Claudia
Quality control of food emulsifiers, such as lactic acid esters of mono- and diacylglycerols (LACTEM), is crucial in the reproducible production of food products. The current study investigated compositional changes of LACTEM emulsifiers using high-performance thin-layer chromatography (HPTLC) during storage at 60 °C for 8 weeks. Ultraviolet (UV) and fluorescence images of the HPTLC silica gel F254s plates after primuline derivatization and densitometric data were analyzed to assess changes in the composition. Significant changes were observed for minor LACTEM components (< 10% relative intensity), specifically a decrease in higher-lactylated monoacylglycerols and an increase in triacylglycerols. Techno-functional properties, such as particle size distribution, apparent viscosity, overrun, foam firmness, drainage, and residual cream of aerosol whipping cream (0.8 g 100 g−1 LACTEM) were investigated. While emulsion stability was not affected, the foam firmness increased significantly, corresponding to a visibly more brittle foam. On the basis of these results, monitoring compositional changes in the food-manufacturing process is necessary to maintain constant food quality.
Influence of distillation parameters on the fractionation behaviour of aroma compounds in the production of Williams-Christ pear brandies and Golden Delicious apple brandies
(2025) Yagishita, Manami; Vetter, Walter
Aroma compounds are central to the sensory attributes and overall organoleptic quality of fruit brandies, yet their behavior during distillation remains insufficiently understood. The relative volatility of these compounds, a fundamental property that defines their evaporation tendency in relation to ethanol, plays a crucial role in distillation, governing their separation efficiency, distribution between vapor and liquid phases, and overall impact on the composition and sensory quality of the final product. Despite its importance, the concept of relative volatility has not been introduced in the production of fruit brandies. The aim of the first publication was to develop a quick and simple method using a basic distillation apparatus to determine the relative volatilities of flavor compounds in hydro-alcoholic solutions. This approach provides a practical alternative to the time-consuming and costly Gillespie dynamic recirculation method. Seventeen representative flavor compounds from apple and pear brandies were investigated, including unpublished data for five compounds. Relative volatilities of methanol, isobutanol, isoamyl alcohol, ethyl acetate, acetaldehyde, and 1,1-diethoxyethane were compared to reference data, showing high correlation for all compounds except 1,1-diethoxyethane. Vapor-liquid equilibrium data for an ethanol-water mixture also exhibited strong agreement with reference data. These results demonstrate that the proposed method is a reliable, fast, and cost-effective alternative to standard techniques for determining relative volatilities. The second publication investigated the impact of partial condensation in dephlegmators on the behavior of ethanol and flavor compounds, comparing setups with and without dephlegmators in both lab-scale and large-scale experiments. Lab-scale experiments demonstrated that dephlegmation led to significant enrichment of ethanol in the distillate through the selective condensation of water. The behavior of flavor compounds varied, with some showing enrichment, others depletion, and some remaining unaffected. In large-scale experiments, a distillation apparatus relying solely on dephlegmation was compared with a standard setup containing an enrichment section with three trays. The dephlegmator-based system exhibited less efficient separation of tail components, such as fusel alcohols, resulting in a lower yield of hearts fraction. Sensory triangle tests confirmed that the spirits from the two systems were distinguishable, though no clear preference emerged. This study provides the first detailed insights into the influence of dephlegmators on flavor compound behavior and separation efficiency during fruit brandy distillation, offering valuable guidance for optimizing distillation processes. The third publication explored distillation processes from the perspective of relative volatility, aiming to control behaviors of key odor-active compounds in pear brandies and enhance product quality through novel fractionation strategies. Two novel fractionation strategies were tested: one involving a high cooling water flow rate combined with a slow distillate flow, and the other employing a 12-tray distillation column. Both approaches successfully increased ethanol concentration on the top tray, altering the relative volatility of compounds in the liquid phase. Elevated ethanol concentrations reduced the relative volatility of higher alcohols, delaying their release and producing sharper, well defined peaks compared to broader profiles observed in the control distillation. This enabled selective separation of desirable compounds, such as beta-damascenone and ethyl (E,Z)-2,4-decadienoate (pear ester), from higher alcohols, resulting in an aroma-rich tails fraction. Blending this enriched tails fraction with the hearts fraction produced a final product that was significantly preferred in sensory evaluations over the standard hearts fraction. These findings demonstrate the importance of tailoring operational distillation conditions to exploit differential volatility, enabling more effective compound separation and improving the sensory quality of fruit brandies.
The natural product 2,4,6-tribromoanisole is the predominant polyhalogenated compound in representative Australian passive air samples
(2025) Schweizer, Sina; Wang, Xianyu; Paxman, Chris; Mueller, Jochen F.; Vetter, Walter
Passive air samplers are well-suited for monitoring persistent organic pollutants (POPs) in ambient air. While the presence of POPs had been documented in Australian air, no data existed on structurally similar, halogenated natural products (HNPs), although these were frequently found in marine biota samples from Australia at levels exceeding those of anthropogenic POPs. This study reports quantitative data of the HNP 2,4,6-tribromoanisole (2,4,6-TBA) along with three POPs (polychlorinated biphenyls (PCBs) 153 and 138 as well as hexachlorobenzene (HCB)) in six selected passive air samples from different Australian regions (islands, coastal cities, and inland). For the most abundant HNP, 2,4,6-TBA, time-averaged concentrations for one year were determined at up to 420 pg/m 3 (One Tree Island), indicating its predominant natural production in the Great Barrier Reef (GBR). High concentrations of 2,4,6-TBA (17 pg/m 3 ), even in the remote inland sample (~ 800 km from the sea), led to the conclusion that the marine-derived 2,4,6-TBA was transported over long distances in air and can be found ubiquitously in Australian air. Even in the coastal cities of Brisbane and Darwin, 2,4,6-TBA levels were comparable to those of the PCBs. The HNP 2,3,3',4,4',5,5'-heptachloro-1'-methyl-1,2'-bipyrrole (Q1) was also detected in air from two islands. Its presence in air from One Tree Island was in line with expectations, given the high levels in marine mammal samples from the GBR. In direct comparison, the ~15 times higher ratio of Q1/2,4,6-TBA in air from Phillip Island indicated Q1 could be even more abundant in this marine region than in the GBR.
Enzymatically formed fatty acid hydroperoxides determined through GC‐MS analysis of enantiomeric excess of hydroxy fatty acids after reduction and ibuprofen derivatization
(2025) Hotz, Lisa; Zartmann, Anne; Noack, Isabelle; Drees, Luca J.; Kuschow, Meret K.; Heinrich, Markus R.; Janssen, Hans‐Gerd; Hammann, Simon
Unsaturated fatty acids are susceptible to lipid oxidation through autoxidation, photooxygenation or enzymatical oxidation. A characteristic feature of enzyme‐catalyzed oxidation is the high regio‐ and stereospecificity of the formed fatty acid hydroperoxides. In this study, we present a method to quantify enzymatic lipid oxidation through reducing hydroperoxy fatty acid methyl esters to hydroxy fatty acid methyl esters and derivatizing them with enantiopure (S)‐ibuprofen, allowing the resolution of the enantiomer pairs as diastereomers via achiral GC‐MS. After application to enantiopure reference fatty acids, the approach was applied to autoxidation products of linoleic acid, and the expected racemic mixtures of the 9‐ and 13‐hydroperoxide derived hydroxy fatty acids were detected. On the other hand, when linoleic acid was oxidized using soybean lipoxygenase, clear enantiomeric excess of the (13S) enantiomer could be detected, proving the applicability of this method to detect enzymatic oxidation through enantiomeric excess.
A sterol database: GC/MS data and occurrence of 150 sterols in seventy-four oils
(2024) Schlag, Sarah; Schäfer, Sabrina; Sommer, Katrin; Vetter, Walter
Comprehensive data on the occurrence of sterols in plant oils is currently hardly available since only a few sterols are obtainable as standard compounds. Accordingly, many peaks are rarely labeled in gas chromatograms due to missing or outdated information. This lack of information hampers the progress in sterol research. For this reason, gas chromatography with mass spectrometry in selected ion monitoring mode (GC/MS-SIM) was used to create a database that summarizes the occurrence and semi-quantitative levels of 150 sterols with 27–32 carbon atoms and 0–4 double bonds in 66 different vegetable oils and eight other matrices. The highest number of sterols was detected in rice bran and tamanu oil (40 sterols), eggplant (39 sterols), moringa, chili seed, and amaranth oil (37 sterols). Several sterols were detected in >60 of the 74 matrices. This detailed information in the database will serve users working in food authentication and the biosynthesis of sterols.
Characterization of the key odorants in goji wines in three levels of sweetness by applications of sensomics approach
(2024) Zheng, Yan; Oellig, Claudia; Zhang, Youfeng; Liu, Yuan; Chen, Yanping; Zhang, Yanyan
The correlations and differences of the key odorants were systematically conducted among three sweetness of goji wines by the sensomics approach. After aroma (extract) dilution analysis, 67, 67, and 66 odorants were screened in sweet goji wine, semi-dry goji wine, and dry goji wine, in which, 63 odorants were identified in all goji wines. Determination of 53 odorants revealed a total of 30 odorants with the concentrations surpassing their olfactory thresholds. Overall, the odor activity values (OAVs) of ketones decreased, while esters, alcohols, phenols, and aldehydes increased with the decrease in sweetness in goji wine samples. Nevertheless, (E)-β-damascenone, trans- and cis-whisky lactones, and 3-methyl-2,4-nonanedione, evoked cooked apple-like, coconut-like, and hay-like odor impressions in goji wines and showed the highest OAVs. A reliable evaluation of the aroma contributions was executed as aroma recombinations and suggested a successful evaluation of key odorants in goji wines.
Characterization of the major odor-active compounds in fresh rhizomes and leaves of Houttuynia cordata by comparative aroma extract dilution analysis
(2025) Xu, Zhenli; Liu, Jing; Kreissl, Johanna; Oellig, Claudia; Vetter, Walter; Steinhaus, Martin; Frank, Stephanie; Rodov, Victor
Houttuynia cordata is a culinary herb from Asia. Its edible rhizomes and leaves have a fishy aroma, the molecular background of which was unknown. A comparative aroma extract dilution analysis applied to fresh rhizomes and leaves resulted in 44 and 41 odorants, respectively, 38 of which were present with FD factors ≥1 in both samples. The odorant with the highest FD factors, whether in the rhizomes or leaves, was identified as metallic, soapy, fishy smelling 3-oxododecanal. Toward clarifying its tautomeric composition, quantum calculations suggested a predominance of the enol forms in the plant. However, the form perceived at the sniffing port during GC–O remained unclear.
Stable isotope analysis confirms substantial changes in the fatty acid composition of bacteria treated with antimicrobial random peptide mixtures (RPMs)
(2022) Wiedmaier-Czerny, Nina; Schroth, Dorothee; Krauß, Stephanie; Topman-Rakover, Shiri; Brill, Aya; Burdman, Saul; Hayouka, Zvi; Vetter, Walter
Resistance of plant-pathogenic bacteria to classic antibiotics has prompted the search for suitable alternative antimicrobial substances. One promising strategy could be the use of purposely synthesized random peptide mixtures (RPMs). Six plant-pathogenic bacteria were cultivated and treated with two RPMs previously found to show antimicrobial activity mainly by bacterial membrane disruption. Here, we show that bacteria treated with RPMs showed partly remarkable changes in the fatty acid pattern while those unaffected did not. Quantitative changes could be verified by compound specific isotope analysis of δ 13 C values (‰). This technique was employed due to the characteristic feature of stronger bonds between heavier isotopes in (bio)chemical reactions. As a proof of concept, the increase in abundance of a fatty acid group after RPM treatment was accompanied with a decrease in the 13 C content and vice versa. We propose that our findings will help designing and synthesizing more selective antimicrobial peptides.
Monodopsis subterranea is a source of α‐tocomonoenol, and its concentration, in contrast to α‐tocopherol, is not affected by nitrogen depletion
(2024) Montoya‐Arroyo, Alexander; Muñoz‐González, Alejandra; Lehnert, Katja; Frick, Konstantin; Schmid‐Staiger, Ulrike; Vetter, Walter; Frank, Jan
α-Tomonoenols (αT1) are tocochromanols structurally related to tocopherols (T) and tocotrienols (T3), the bioactive members of the vitamin E family. However, limited evidence exists regarding the sources and biosynthesis of tocomonoenols. Nitrogen depletion increases the content of α-tocopherol (αT), the main vitamin E congener, in microalgae, but little is known regarding its effect on other tocochromanols, such as tocomonoenols and tocotrienols. We therefore quantified the concentrations of T, T1, and T3, in freeze-dried biomass from nitrogen-sufficient, and nitrogen-depleted Monodopsis subterranea (Eustigmatophyceae). The identities of isomers of αT1 were confirmed by LC–MS and GC–MS. αT was the predominant tocochromanol (82% of total tocochromanols). αT1 was present in higher quantities than the sum of all T3 (6% vs. 1% of total tocochromanols). 11′-αT1 was the main αT1 isomer. Nitrogen depletion increased αT, but not αT1 or T3 in M. subterranea. In conclusion, nitrogen depletion increased the content of αT, the biologically most active form of vitamin E, in M. subterranea without affecting αT1 and T3 and could potentially be used as a strategy to enhance its nutritional value but not to increase αT1 content, indicating that αT1 accumulation is independent of that of αT in microalgae.
Effect of the Mediterranean diet on the faecal long-chain fatty acid composition and intestinal barrier integrity: An exploratory analysis of the randomised controlled LIBRE trial
(2024) Seethaler, Benjamin; Basrai, Maryam; Neyrinck, Audrey M.; Vetter, Walter; Delzenne, Nathalie M.; Kiechle, Marion; Bischoff, Stephan C.
We recently showed that adherence to the Mediterranean diet increased the proportion of plasma n-3 PUFA, which was associated with an improved intestinal barrier integrity. In the present exploratory analysis, we assessed faecal fatty acids in the same cohort, aiming to investigate possible associations with intestinal barrier integrity. Women from the Lifestyle Intervention Study in Women with Hereditary Breast and Ovarian Cancer (LIBRE) randomised controlled trial, characterised by an impaired intestinal barrier integrity, followed either a Mediterranean diet (intervention group, n 33) or a standard diet (control group, n 35). At baseline (BL), month 3 (V1) and month 12 (V2), plasma lipopolysaccharide-binding protein, faecal zonulin and faecal fatty acids were measured. In the intervention group, faecal proportions of palmitoleic acid (16:1, n-7) and arachidonic acid (20:4, n-6) decreased, while the proportion of linoleic acid (18:2, n-6) and α linoleic acid (18:3, n-3) increased (BL-V1 and BL-V2, all P < 0·08). In the control group, faecal proportions of palmitic acid and arachidic acid increased, while the proportion of linoleic acid decreased (BL-V1, all P < 0·05). The decrease in the proportion of palmitoleic acid correlated with the decrease in plasma lipopolysaccharide-binding protein (ΔV1-BL r = 0·72, P < 0·001; ΔV2-BL r = 0·39, P < 0·05) and correlated inversely with adherence to the Mediterranean diet (Mediterranean diet score; ΔV1-BL r = –0·42, P = 0·03; ΔV2-BL r = -0·53, P = 0·005) in the intervention group. Our data show that adherence to the Mediterranean diet induces distinct changes in the faecal fatty acid composition. Furthermore, our data indicate that the faecal proportion of palmitoleic acid, but not faecal n-3 PUFA, is associated with intestinal barrier integrity in the intervention group.
Risk assessment of caffeine and epigallocatechin gallate in coffee leaf tea
(2022) Tritsch, Nadine; Steger, Marc C.; Segatz, Valerie; Blumenthal, Patrik; Rigling, Marina; Schwarz, Steffen; Zhang, Yanyan; Franke, Heike; Lachenmeier, Dirk W.
Coffee leaf tea is prepared as an infusion of dried leaves of Coffea spp. in hot water. It is a traditional beverage in some coffee-producing countries and has been authorized in 2020 within the European Union (EU) according to its novel food regulation. This article reviews current knowledge on the safety of coffee leaf tea. From the various ingredients contained in coffee leaves, only two were highlighted as possibly hazardous to human health, namely, caffeine and epigallocatechin gallate (EGCG), with maximum limits implemented in EU legislation, which is why this article focuses on these two substances. While the caffeine content is comparable to that of roasted coffee beans and subject to strong fluctuations in relation to the age of the leaves, climate, coffee species, and variety, a maximum of 1–3 cups per day may be recommended. The EGCG content is typically absent or below the intake of 800 mg/day classified as hepatotoxic by the European Food Safety Authority (EFSA), so this compound is suggested as toxicologically uncritical. Depending on selection and processing (age of the leaves, drying, fermentation, roasting, etc.), coffee leaf tea may exhibit a wide variety of flavors, and its full potential is currently almost unexplored. As a coffee by-product, it is certainly interesting to increase the income of coffee farmers. Our review has shown that coffee leaf tea is not assumed to exhibit risks for the consumer, apart from the well-known risk of caffeine inherent to all coffee-related beverages. This conclusion is corroborated by the history of its safe use in several countries around the world.

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