Browsing by Person "Vetter, Walter"

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Einfluss moderner Pflanzenschutzmittel auf die Mobilität von POP-belasteten Agrarflächen am Beispiel von DDT : ein Feldversuch
(2023) Neitsch, Julia Simone; Vetter, Walter
Due to their recalcitrance, the chloropesticide DDT and its structurally related compounds (DDX) are difficult to degrade. Consequently, farmers are still frequently confronted with DDX contamination in their fields that was left over from the 1960s. This problem is particularly prevalent in contaminated soils that are intended to cultivate plants of the Cucurbitaceae family. These plants release so-called root exudates, which function as natural surfactants that mobilize the DDX present in the soils. Furthermore, surfactants are a common constituent of modern plant protection product (PPP) formulations, which can likewise cause DDX mobilization. The higher mobility of DDX caused by these surfactants can result in the absorption and accumulation of chlorinated pesticides in plants. The side effects of such surfactant-containing PPP formulations have historically been overlooked in the context of standard spraying protocols. The potential mobilization of DDX in soils and its accumulation in Cucurbita pepo due to the surfactants present in standard PPPs formulations was investigated using two field trials. One field was treated with a conventional PPP, while the other was treated with a biological PPP; a control field was left untreated, within which pumpkins were cultivated. Soil samples were taken before and after the application of PPP. The DDX content was subsequently determined in extracts from the soil phase samples and soil water fractions. The background DDX contamination of the soils was comparable in all three test fields. The comparative evaluation showed that the field treated with the biological PPP formulation exhibited a considerable increase in DDX mobility compared to the untreated and conventionally cultivated areas (Paper 1). An analysis of its respective water fraction revealed that it was more contaminated with DDX than the control treatments. This increase suggests a higher bioavailability that can be traced back to the presence of surfactants and oils in the PPP formulations (Paper 1). This higher bioavailability may have been accompanied by an increase in the DDX uptake of the cultivated plants. Furthermore, it was found that treatment with specific formulations of emulsifiable concentrates (EC) promoted DDX mobilization. This mobilizing effect was most likely due to the differing composition of the surfactant and proportions of oils in the PPPs. The second field test focused on differential DDX accumulation in Cucurbita pepo cv. Howden by different PPPs. Fields were treated with PPP in accordance with the official spraying plans and regulations set out by the Federal Ministry of Food and Agriculture (BMEL). Samples from the pumpkin plants roots, shoots, as well as the pumpkins themselves were taken during the cultivation period. The DDX content in the roots from the control fields and the fields with conventional PPP treatments remained virtually unchanged; however, the DDX content increased in the biologically treated area (Paper 2). The pumpkin shoots did not exhibit any increases in DDX concentration during the growing phase regardless of the field sampled. However, an increased DDX content was detected in the shoots of the plants in all test fields shortly before harvesting. At the end of the growing phase, fruits from the biologically treated area showed a higher DDX content than those from the control and conventionally treated areas. In addition, the most critical DDT metabolite, DDE, was found to have been transported to distant parts of the plant, while DDD was detectable in the roots and shoots but not in the fruits of the pumpkins (Paper 2). An assessment of the results of both experiments confirmed a direct correlation between DDX mobilization in the soil and plant uptake. In addition, the bioaccumulation factors of the biologically treated areas were markedly higher than those seen in the conventionally treated and control areas. The results of the field trials show that the mobilization of DDT, as well as the likely mobilization of other lipophilic contaminants, can become problematic for farmers using surfactant-containing EC formulations. However, this observation also provides opportunities for improved phytoremediation by applying EC formulations with high mobilization potentials. The field trials indicate that the mobilizing effects of DDT prompted by EC mixtures depend on the surfactant content in the PPP formulations as well as environmental conditions such as soil conditions, soil water content, and precipitation. Unravelling the optimal range of surfactant-rich formulations and environmental conditions could lead to a promising strategy for soil phytoremediation.
A fast gas chromatography coupled with electron capture negative ion mass spectrometry in selected ion monitoring mode screening method for short‐chain and medium‐chain chlorinated paraffins
(2022) Schweizer, Sina; Schulz, Tobias; Vetter, Walter
Rationale Chlorinated paraffins (CPs) are a group of anthropogenic pollutants that consist of complex mixtures of polychlorinated n-alkanes of different chain lengths (~C10 to C30). Persistence, bioaccumulation, toxicity, and long-range transport of short-chain chlorinated paraffins (SCCPs, C10- to C13-CPs) have prompted their classification as persistent organic pollutants (POPs) by the Stockholm Convention in 2017. Due to the varying chain lengths and chlorination degrees, quantification of SCCPs and medium-chain chlorinated paraffins (MCCPs, C14- to C17) using gas chromatography coupled with electron capture negative ion mass spectrometry in selected ion monitoring mode (GC/ECNI-MS-SIM) is not only challenging but also very time consuming. In particular, up to eight GC runs per sample are required for the comprehensive GC/ECNI-MS-SIM quantification of SCCPs and MCCPs. These efforts are high especially if the samples do not contain CPs above the limit of detection (LOD), subsequently. Methods We developed a semi-quantitative and sensitive method for the examination of SCCPs and MCCPs in one GC run. This GC/ECNI-MS-SIM screening method was based on the recording of Cl− (m/z 35 and 37), Cl2− (m/z 70 and 72), and HCl2− (m/z 71 and 73) isotope ions and evaluation of the ratios between them. Results Correctness of the results of the screening method was verified by analysis of edible oils with and without CPs, CP standards, as well as a technical CP mixture. Polychlorinated biphenyls (PCBs) and other polyhalogenated aromatic compounds, as well as brominated flame retardants, do not form all of the fragment ions analyzed by the screening method. Conclusions After the screening, only CP-positive samples may need to be measured in detail. Measurement time will already be gained in the case of ~10% samples without CPs.
Furan fatty acid amounts and their occurrence in triacylglycerols of white asparagus (Asparagus officinalis) from the German market
(2023) Müller, Franziska; Bauer, Vanessa; Vetter, Walter
Vegetables including asparagus contain a wide range of fatty acids, mainly stored in triacylglycerols. One class of interesting minor fatty acids is the family of furan fatty acids (FuFAs) because of their antioxidant properties. Since FuFAs have not been studied previously in asparagus (Asparagus officinalis L.), we developed and applied a simplified method for their analysis in 20 fresh and three preserved samples. Four FuFAs were detected with clear dominance of the dimethyl‐substituted FuFAs (D‐FuFAs) 11D5 and 9D5 as well as small amounts of the monomethyl‐substituted FuFAs (M‐FuFAs) 11M5 and 9M5. The total amounts of FuFAs in fresh white asparagus ranged from 1.4 to 4.6 mg/100 g dry weight (mean 3.0 mg/100 g dry weight). Subsequent LC‐Q‐Orbitrap‐HRMS measurements enabled the detection of 22 different FuFA‐containing TAGs. These were predominantly found together with one or two polyunsaturated fatty acid.
Geometrical and positional isomers of unsaturated furan fatty acids in food
(2022) Müller, Franziska; Hammerschick, Tim; Vetter, Walter
Furan fatty acids (FuFA) are important antioxidants found in low concentrations in many types of food. In addition to conventional FuFA which normally feature saturated carboxyalkyl and alkyl chains, a few previous studies indicated the FuFA co‐occurrence of low shares of unsaturated furan fatty acids (uFuFA). For their detailed analysis, the potential uFuFA were enriched by centrifugal partition chromatography (CPC) or countercurrent chromatography (CCC) followed by silver ion chromatography from a 4,7,10,13,16,19‐docosahexaenoic acid ethyl ester oil, a 5,8,11,14,17‐eicosapentaenoic acid ethyl ester oil and a latex glove extract. Subsequent gas chromatography with mass spectrometry (GC/MS) analysis enabled the detection of 16 individual uFuFA isomers with a double bond in conjugation with the central furan moiety. In either case, four instead of two uFuFA isomers previously reported in food, respectively, were detected by GC/MS. These isomers showed characteristic elution and abundance patterns in GC/MS chromatograms which indicated the presence of two pairs of cis/trans‐isomers (geometrical isomers).
Investigations into heat- and light-induced terpene modifications in essential oils
(2023) Bitterling, Hannes; Vetter, Walter
Essential oils belong to secondary plant metabolites, with terpenoids and phenylpropanoids being among the main constituents in terms of quantity. Due to their lipophilic character and high volatility, they are mainly obtained by steam distillation. Citrus essential oils (agrumen oils) are an exception , since they are usually extracted from the peels by means of pressing, whereby less volatile components such as coumarins and furocoumarins are also introduced. Due to their odor and taste-giving properties, essential oils are used in the food, beverage, and cosmetics industries. In addition, due to a wide range of pharmacological properties, they are used in phytotherapy as well as in aromatherapy. However, most essential oils are highly susceptible to oxidation, polymerization, dehydrogenation, and isomerization reactions in the presence of atmospheric oxygen, light, and at high temperatures. The resulting organoleptic changes usually lead to a significant quality reduction. The formation of terpene hydroperoxides is another problem, as these are suspected of causing intolerances such as redness and itching in 1-3% of the European population upon contact with the skin. The detection of these chemical changes forms an integral part of quality control and can be prevented as far as possible by suitable production, transport, and storage strategies. Due to their volatility, essential oils are mainly analyzed by gas chromatography. However, due to their instability, the detection of hydroperoxides places considerable demands on common analytical methods. For this reason, a novel spectrophotometric method for the detection of peroxides and hydroperoxides in terpenes and essential oils was developed (paper 1). The oxidation of N-N-dimethyl-p-phenylenediamine by peroxides yielding an intensely red-colored cation (Wursters red) allowed colorimetric detection and quantitation of even smallest amounts (LOD: 0.5 ppm). The minimal sample amount of only a few milligrams, as well as simple and fast performance predestine this method for daily laboratory routine (paper 1). Among plant terpenoids, the monoterpene R-(+)-limonene is very widespread. Thus, it is not only found in citrus oils but also of in caraway oil, where its proportion amounts to almost 50%. To investigate the storage stability, R-(+)-limonene, S-(+)-carvone, different caraway oils, and the corresponding caraway seeds were stored in desiccators at 25 °C and 40 °C for eighteen months (paper 2). The samples were analyzed monthly by GC/MS and GC/FID, as well as HPLC/DAD-MS/MS. This showed that the comparison of seed, isolated essential oil, and pure substance, whichhad not been considered in storage studies so far, was of extraordinary importance. Here, both the plant matrix and the essential oil had a protective effect on individual terpenes and delayed their degradation (paper 2). Further, a clear difference between photo-oxidation and autoxidation was observed. Light-induced oxidation of terpenes primarily resulted in the formation of hydroperoxides, whereas autoxidation led to a variety of compounds such as alcohols, ketones, and epoxides. Thus, the secondary products can serve as specific markers for conclusions about the preload and quality of essential oils. In the study presented in paper 3, further photo-oxidation experiments were conducted with beta-pinene, R-(+)-limonene, and gamma-terpinene, with added furocoumarins. Furocoumarins can absorb UV-A light in the range of 320 – 380 nm and enter an energetically excited state. This energy difference between the ground state and excited state can be dissipated again by the emission of fluorescent and phosphorescent light. In this process, short-wave energy-rich UV light is converted into lower-energy visible light (bathochromic shift). For this reason, the UV light-induced degradation of the terpenes beta-pinene, R-(+)-limonene, and gamma-terpinene could be significantly reduced by adding 5% each of xanthotoxin, bergapten, bergaptol, and bergamottin. The effect of adding bergaptol was most pronounced in the photooxidation of gamma-terpinene (paper 3). Consequently, in citrus essential oils from which the natural furocoumarins had been previously removed, irradiation with UV light resulted in a strong degradation of the terpenes. This process could be markedly reduced by the re-addition of 5% of the previously removed plant-specific furocoumarins (paper 4). In summary, it can be concluded that not only the plant matrix and the essential oil as a multicomponent mixture but also potential interactions with other substances forming part of the essential oil such as furocoumarins may significantly slow down the oxidation of terpenoids.
LC‐Orbitrap‐HRMS determination of two novel plastochromanol homologues
(2023) Hammerschick, Tim; Graf, Jana; Vetter, Walter
Scope: The antioxidant plastochromanol-8 (PC-8) is a tocochromanol which differs from γ-tocotrienol in having an unsaturated side chain of eight instead of three isoprene units. The recent isolation of PC-8 from flaxseed oil indicates the additional presence of lower shares of two previously unknown homologues, plastochromanol-7 (PC-7) and plastochromanol-9 (PC-9), which feature seven and nine isoprenoid units respectively on the γ-chromanol backbone. Here, a fast LC-Orbitrap-HRMS method is applied for the determination of PC-7 and PC-9 in seven plant oils and a plant extract. Methods and results: The presence of PC-7, PC-8, and PC-9 is confirmed in all eight investigated samples by LC-Orbitrap-HRMS analysis after saponification. PC-8 amounts of ≈315–350 mg kg−1 in two flaxseed oils, ≈75 mg kg−1 in rapeseed oil, ≈38 mg kg−1 in camelina oil, ≈80–120 mg kg−1 in two mustard oils, ≈90 mg kg−1 in candle nut oil, and ≈900 mg kg−1 dry weight in Cecropia leaves are determined by quantification. Semi-quantification of PC-7 and PC-9 indicated the presence of ≈0.1–1% of PC-7 and PC-9 in varied relative ratios. Conclusion: The novel plastochromanol homologues are of particular interest to researchers with focus on vitamin E and other tocochromanols because of their unexplored bioactivity.
Microbial incubations of 8‐phenyloctanoic acid and furan fatty acids in rumen fluid
(2022) Wiedmaier‐Czerny, Nina; Blumberg, Olga; Schulz, Tobias; Kemmler, Franziska; Titze, Natascha; Wild, Katharina; Vetter, Walter
Aims: The digestive tract of ruminants is specialized in the digestion of various plant components. One of the largest parts of the stomach is the so-called rumen, which contains a large number of micro-organisms that may degrade or modify fatty acids, for example by β-oxidation, chain elongation and/or hydrogenation. Methods and Results: Here we performed incubation experiments with less com- mon fatty acids by in vitro incubations with rumen fluid of fistulated cows for 24 h. Sample extracts were analysed by gas chromatography with mass spectrometry. As substrates, we selected one phenyl fatty acid and four furan fatty acids (FuFAs). All studied fatty acids were degraded by β-oxidation (two or three chain-shortening steps) while chain elongation or saturation of the aromatic part (terminal phenyl or central furan moiety) was not observed in any case. Conclusions: The percentage of β-oxidation products was low, especially in the case of the FuFAs. This could be due to the rather long carbon number of FuFAs (19–22 carbon atoms). In addition, compound-specific differences in the degradation rates were observed in our experiments. Significance and Impact of the Study: Our results produce evidence that FuFAs, which are valuable antioxidants that are known to be present in various feed items of the cow, can be effectively passed on the rumen into the milk.
Previtamin D2, vitamin D2, and vitamin D4 amounts in different mushroom species irradiated with ultraviolet (UV) light and occurrence of structurally related photoproducts
(2024) Sommer, Katrin; Hillinger, Marissa; Vetter, Walter
Mushrooms are rich in ergosterol and ergosta‐5,7‐dienol, which can be partly converted into vitamin D2 and D4 through ultraviolet (UV) light exposure. Typically, mushrooms have very low vitamin D contents, but it can be increased by UV irradiation. This process generates additional photoisomers scarcely studied in mushrooms due to analytical challenges. Here, we developed a new solid phase extraction (SPE) method to separate vitamin D2, vitamin D4, and other tri‐ and pentacyclic photoisomers from the much higher abundant ergosterol. Subsequent GC/MS analysis enabled the detection of ten photoisomers in eight UV‐treated mushroom species, including vitamin D2 (previtamin D2, tachysterol2, two suprasterol2 and trans‐vitamin D2 isomers) and vitamin D4 (previtamin D4). Quantitated vitamin D2 contents of 10–540 µg/100 g dry weight agreed well with the sparse literature data available for the investigated mushroom species. In addition, previtamin D2 (nd–1950 µg/100 g dry weight) and vitamin D4 (10–140 µg/100 g dw) were quantified in the samples. The content and photoproduct compositions varied considerably between different mushroom species. Practical applications: The novel SPE method can be applied to study the vitamin D and photoisomer content of mushrooms.
Silver ion chromatography enables the separation of 2‐methylalkylresorcinols from alkylresorcinols
(2023) Hammerschick, Tim; Vetter, Walter
Alkylresorcinols (∑ARs) is the generic term for a highly varied class of lipids found mainly in cereals. These bioactive compounds consist mainly of 5‐alkylresorcinols (ARs), which differ in length, unsaturation, and substituents on the alkyl side chain on C‐5. In addition, 2‐methyl‐5‐alkylresorcinols (mARs) are scarcely studied minor compounds that are supposed to exist with the same structural diversity. In the first step, ∑ARs were enriched by solid‐phase extraction from wheat grain and quinoa seed extracts. The subsequent application of silver ion chromatography (SIC), silica gel, coated with 20% AgNO3, then deactivated with 1% water) enabled an unprecedented full separation of saturated mARs from conventional ARs. Specifically, saturated mARs were eluted with n‐hexane/ethyl acetate (92:8, v/v), and conventional ARs with n‐hexane/ethyl acetate (80:20, v/v). The unpreceded separation indicated that the SIC method could be useful not only for separations according to the degree of unsaturation, but also in the case of steric hindrance by additional (alkyl) substituents. Continued fractionation enabled the collection of unsaturated ARs in wheat and quinoa extracts. In this way, 35 ∑ARs (including five mARs) were detected by gas chromatography/mass spectrometry analysis in wheat and 45 ∑ARs (including 21 mARs) in quinoa. These included several low abundant and partly unknown ∑ARs such as 1,3‐dihydroxy‐5‐tricosadienylbenzene.