Non-target bioanalytical eight-dimensional hyphenation including bioassay, heart-cut trapping, online desalting, orthogonal separations and mass spectrometry

Towards non-target proactive food safety: identification of active compounds in convenience tomato products by ten-dimensional hyphenation with integrated simulated gastrointestinal digestion

Current strategies for non-target food screening focus mainly on known hazardous chemicals (adulterants, residues, contaminants, packaging migrants, etc.) instead of bioactive constituents in general and exclude the biological effect detection. To widen the perspective, a more proactive non-target effect-directed strategy is introduced to complement food safety in order to detect not only known but also unknown bioactive compounds. The developed 10-dimensional hyphenation included on-surface digestion (1D), planar chromatographic separation (2D), visualization using white light (3D), UV light (4D), fluorescence light (5D), effect-directed assay analysis (6D), heart-cut zone elution to an orthogonal reversed phase column chromatography including online desalting (7D) with subsequent diode array detection (8D), high-resolution mass spectrometry (9D), and fragmentation (10D). Metabolism, i.e., intestinal digestion of each sample, was simulated and integrated on the same adsorbent surface to study any changes in the compound profiles. As proof of principle, nine convenience tomato products and a freshly prepared tomato soup were screened via five different planar assays in a non-targeted mode. Non-digested and digested samples were compared side by side. In their effect-directed profiles, 14 bioactive compounds from classes of lipids, plant hormones, spices, and pesticides were identified. In particular, bioactive compounds coming from the lipid class were increased by gastrointestinal digestion, while spices and pesticides remained unaffected. With regard to food safety, the determination of the two dinitrophenol herbicides dinoterb and dinoseb in highly processed tomato products should be given special attention. The hyphenation covered a broad analyte spectrum and showed robust and reliable results.

Sample preparation for planar chromatography

High-performance thin-layer chromatography has favorable properties for high-throughput separations with a high matrix tolerance. Sample preparation, however, is sometimes required to control specific matrix interferences and to enhance the detectability of target compounds. Trends in contemporary applications have shifted from absorbance and fluorescence detection to methods employing bioassays and mass spectrometry. Traditional methods (shake-flask, heat at reflux, Soxhlet, and hydrodistillation) are being challenged by automated instrumental approaches (ultrasound-assisted and microwave-assisted solvent extraction, pressurized liquid extraction, and supercritical fluid extraction) and the quick, easy cheap, efficient, rugged, and safe extraction method for faster and streamlined sample processing. Liquid-liquid extraction remains the most widely used approach for sample clean-up with increasing competition from solid-phase extraction. On-layer sample, clean-up by planar solid-phase extraction is increasingly used for complex samples and in combination with heart-cut multimodal systems. The automated spray-on sample applicator, the elution head interface, biological detection of target and non-target compounds, and straightforward mass spectrometric detection are highlighted as the main factors directing current interest toward faster and simpler sample workflows, analysis of more complex samples, and the determination of minor contaminants requiring high concentration factors.

Bioactivity Profiling and Quantification of Gastrodin in Gastrodia elata Cultivated in the Field versus Facility via Hyphenated High-Performance Thin-Layer Chromatography

Gastrodia elata (Orchidaceae) is native to mountainous areas of Asia and is a plant species used in traditional medicine for more than two thousand years. The species was reported to have many biological activities, such as neuroprotective, antioxidant, and anti-inflammatory activity. After many years of extensive exploitation from the wild, the plant was added to lists of endangered species. Since its desired cultivation is considered difficult, innovative cultivation methods that can reduce the costs of using new soil in each cycle and at the same time avoid contamination with pathogens and chemicals are urgently needed on large scale. In this work, five G. elata samples cultivated in a facility utilizing electron beam-treated soil were compared to two samples grown in the field concerning their chemical composition and bioactivity. Using hyphenated high-performance thin-layer chromatography (HPTLC) and multi-imaging (UV/Vis/FLD, also after derivatization), the chemical marker compound gastrodin was quantified in the seven G. elata rhizome/tuber samples, which showed differences in their contents between facility and field samples and between samples collected during different seasons. Parishin E was also found to be present. Combining HPTLC with on-surface (bio)assays, the antioxidant activity and inhibition of acetylcholinesterase as well as the absence of cytotoxicity against human cells were demonstrated and compared between samples.

Chemical and cytotoxicity profiles of 11 pink pepper (Schinus spp.) samples via non-targeted hyphenated high-performance thin-layer chromatography

INTRODUCTION

Pink pepper is a worldwide used spice that corresponds to the berries of two species, Schinus terebinthifolia Raddi or S. molle L. (Anacardiaceae). Toxic and allergic reactions by ingestion or contact with these plants were reported, and classical in vitro studies have highlighted the cytotoxic properties of apolar extracts from the fruits.

OBJECTIVES

Perform a non-targeted screening of 11 pink pepper samples for the detection and identification of individual cytotoxic substances.

METHODS

After reversed-phase high-performance thin-layer chromatography (RP-HPTLC) separation of the extracts and multi-imaging (UV/Vis/FLD), cytotoxic compounds were detected by bioluminescence reduction from luciferase reporter cells (HEK 293 T-CMV-ELuc) applied directly on the adsorbent surface, followed by elution of detected cytotoxic substance into atmospheric-pressure chemical ionization high-resolution mass spectrometry (APCI-HRMS).

RESULTS

Separations for mid-polar and non-polar fruit extracts demonstrated the selectivity of the method to different substance classes. One cytotoxic substance zone was tentatively assigned as moronic acid, a pentacyclic triterpenoid acid.

CONCLUSION

The developed non-targeted hyphenated RP-HPTLC-UV/Vis/FLD-bioluminescent cytotoxicity bioassay-FIA-APCI-HRMS method was successfully demonstrated for cytotoxicity screening (bioprofiling) and respective cytotoxin assignment.

Investigation of the estrogenic potential of 15 rosé, white and red wines via effect-directed ten-dimensional hyphenation

Wine is consumed for thousands of years all over the world, however, its estrogenic potential is still underexplored. A non-target effect-directed screening was developed to reveal estrogen-like and antiestrogen-like compounds in 15 rosé, white and red wine samples of different origin and grape variety. Normal-phase high-performance thin-layer chromatography multi-imaging detection (NP-HPTLC-UV/Vis/FLD) was combined with the planar yeast estrogen screen (pYES) bioassay or the duplex planar yeast antagonist estrogen screen (pYAES) bioassay on the same adsorbent surface. Up to nine estrogen-like compound zones were detected and further characterized via heart-cut elution from the planar bioautogram to orthogonal reversed phase high-performance liquid chromatography (RP-HPLC) coupled with diode array detection (DAD) and high-resolution tandem mass spectrometry (HRMS/MS). Among the tentatively assigned estrogen-like substances, the HRMS/MS signals pointed to hexylresorcinol and diethyl esters from organic acids for the first time. This highlights the method suitability for non-target complex mixture screening and rapid dereplication. The 10D hyphenation NP-HPTLC-UV/Vis/FLD-pYAES-heart cut-RP-HPLC-DAD-HRMS/MS proved to be an efficient and powerful tool for detecting estrogens as well as antiestrogens in the matrix-rich wine samples. High-throughput capability and substantial reduction in the required resources for analysis were demonstrated by this straightforward hyphenation, if compared to bioassay-guided fractionation. The 10D information (via orthogonal chromatographic, versatile spectrometric and duplex endocrine activity data) obtained during a single chromatographic run for many samples in parallel was advantageous for the tentative molecule assignment.

Miniaturized open-source 2LabsToGo screening of lactose-free dairy products and saccharide-containing foods

The open-source 2LabsToGo system is the only one in its nature. It combines in one miniaturized instrument all relevant steps normally performed in a chemical and biological laboratory. For the first time, the applicability of the 2LabsToGo system was studied for screening 17 food products. As examples, saccharides were analyzed in eight products of different matrix complexity, and the absence of lactose was studied in nine lactose-free dairy products. Derivatization including homogeneous reagent application and plate heating via the 2LabsToGo system was explored for saccharide detection, and its performance was investigated. The visual detection sensitivity of lactose was comparable to previous studies. The precision of lactose in milk matrix (%RSD 4.6%) as well as the coefficient of determination of the calibration function (0.9995) were highly satisfying. The obtained lactose content of milk (4.5%) was plausible. Screening eight saccharide-containing food samples showed the saccharides in agreement with the expectations for the respective food product. The lactose content of nine different lactose-free dairy products was proven to be below the 0.1% lactose limit value. As proof-of-principle and for verification, these screening results obtained with the miniaturized 2LabsToGo system were reproduced using conventional state-of-the-art instrumentation, which led to the same results. However, instrumental costs were comparably low for the 2LabsToGo system. The application of the new 2LabsToGo system was successfully shown for saccharide screening, which is attractive to the field of quality control or official food control.

Planar chromatography - Current practice and future prospects

Planar chromatography, in the form of thin-layer or high-performance thin-layer chromatography (TLC, HPTLC), continues to provide a robust and widely used separation technique. It is unrivaled as a simple and rapid qualitative method for mixture analysis, or for finding bioactive components in mixtures. The format of TLC/HPTLC also provides a unique method for preserving the separation, enabling further investigation of components of interest (including quantification/structure determination) separated in both time and space from the original analysis. The current practice of planar chromatography and areas of development of the technology are reviewed and promising future directions in the use of TLC/HPTLC are outlined.

Natural Products Drug Discovery: On Silica or In-Silico?

Natural products have been the most important source for drug development throughout the human history. Over time, the formulation of drugs has evolved from crude drugs to refined chemicals. In modern drug discovery, conventional natural products lead-finding usually uses a top-down approach, namely bio-guided fractionation. In this approach, the crude extracts are separated by chromatography and resulting fractions are tested for activity. Subsequently, active fractions are further refined until a single active compound is obtained. However, this is a painstakingly slow and expensive process. Among the alternatives that have been developed to improve this situation, metabolomics has proved to yield interesting results having been applied successfully to drug discovery in the last two decades. The metabolomics-based approach in lead-finding comprises two steps: (1) in-depth chemical profiling of target samples, e.g. plant extracts, and bioactivity assessment, (2) correlation of the chemical and biological data by chemometrics. In the first step of this approach, the target samples are chemically profiled in an untargeted manner to detect as many compounds as possible. So far, NMR spectroscopy, LC-MS, GC-MS, and MS/MS spectrometry are the most common profiling tools. The profile data are correlated with the biological activity with the help of various chemometric methods such as multivariate data analysis. This in-silico analysis has a high potential to replace or complement conventional on-silica bioassay-guided fractionation as it will greatly reduce the number of bioassays, and thus time and costs. Moreover, it may reveal synergistic mechanisms, when present, something for which the classical top-down approach is clearly not suited. This chapter aims to give an overview of successful approaches based on the application of chemical profiling with chemometrics in natural products drug discovery.

Deciphering the origin of total estrogenic activity of complex mixtures

Introduction

Identifying compounds with endocrine properties in food is getting increasingly important. Current chemical analysis methodology is mainly focused on the identification of known substances without bringing insight for biological activity. Recently, the application of bioassays has been promoted for their potential to detect unknown bioactive substances and to provide information on possible interactions between molecules. From the toxicological perspective, measuring endocrine activity cannot inform on endocrine disruption and/or health risks without sufficient knowledge on the nature of the responsible factors.

Methods

The present study addresses a promising approach using High Performance Thin-Layer Chromatography (HPTLC) coupled to bioassays were analyzed using the Liquid Chromatography Mass-Spectrometry (LC-MS). The estrogen receptor activation was assessed using the transcription activation Estrogen Receptor Alpha Chemical Activated LUciferase gene eXpression assay (ERα- CALUX) and the HPTLC coupled to the Estrogen Screen Yeast assay (p-YES).

Results

Seven isoflavones were identified in the soy isolates. Estrogen receptor activation was assessed for both, the identified isoflavones and the soy isolates with ERα-CALUX test. Correlation between the soy isolates extracts and the identified isoflavones was shown. Moreover, p-YES revealed the presence of an estrogenic bioactive zone. Analysis of the bioactive zone through LCHRMS highlighted signals corresponding to several isoflavones already detected in the isolates as well as two additional ones. For all detected isoflavones, an estrogenic activity dose-response was established in both bioassays.

Conclusion

Finally, genistein, daidzein, and naringenin were found as the most active substances. A concordance analysis integrating the analytical and bioassay data indicated that genistein and daidzein were the drivers of the estrogenic activity of these soy protein isolates. Altogether, these data suggest that the integration of HPTLC-bioassay together with chemical analysis is a powerful approach to characterize the endocrine activity of complex mixtures.

2LabsToGo─Recipe for Building Your Own Chromatography Equipment Including Biological Assay and Effect Detection

A complete recipe for building your own chromatography equipment from readily available materials is introduced. It combines sample separation (chemistry laboratory) with biological effect detection (biology laboratory). This hyphenation of two disciplines is necessary for prioritizing important compounds in complex samples. Among the thousands of compounds therein, it is often not clear which compounds are the important ones. On the same separation surface, additional detection of biological effects enables and guides substance prioritization. The newly developed open-source 2LabsToGo system for chemical and biological analysis is completely solvent-resistant and, due to miniaturization, environmentally friendly regarding the consumption of materials. It produces comparable results but is 10 times more compact (26 cm × 31 cm × 34 cm), 10 times lighter (6.8 kg), and 55 times less expensive (€ 1717) than current sophisticated commercial devices. As a proof of concept of the first 2LabsToGo system, the quality of different water samples was analyzed since clean water is becoming increasingly rare. In water, most of the thousands of substance signals or features can neither be identified nor classified toxicologically. However, methods that exploit this hyphenated strategy provide answers to such essential safety issues. Drinking or tap water did not show bioactive or toxic compounds, which was expected, whereas biogas or landfill water samples did. The hyphenated 2LabsToGo strategy is affordable and extremely useful for all laboratories with limited equipment but pressing challenges. It is ready to be used in various analytical tasks and applications.

Non-target bioactive compound profiles of coffee roasts and preparations

Coffee is an inherent part of our daily nutrition and seems to have protective effects against diseases, whereby it is often not fully understood, which ingredients are responsible for the observed effect. Hence, a non-targeted bioactivity profiling was developed to investigate 27 hand-filtered coffee brews of differently roasted coffee beans and 14 differently prepared and stored coffee brews. After separation, multi-imaging, and densitometry, six planar effect-directed assays were performed to reveal individual antioxidative, antibacterial, anti-cholinesterase, anti-diabetic, and estrogenic effects. Individual compounds were mainly responsible for the observed effects, e.g. 5-O-caffeoylquinic acid regarding antioxidative potential and α-glucosidase inhibition, while coffee brews made by a fully automated coffee machine showed the highest antioxidative potential. Unlike preparation and storage conditions, applied roasting conditions and origin of coffee samples played a less important role. Therefore, the way we daily consume our coffee has an impact on the magnitude of potential health effects.

Validated Screening Method for 81 Multiclass Veterinary Drug Residues in Food via Online-Coupling High-Throughput Planar Solid-Phase Extraction to High-Performance Liquid Chromatography-Orbitrap Tandem Mass Spectrometry

Current screening capabilities for veterinary drugs (VDs) in foods are limited, requiring time-consuming and expensive trace-level analyses. For the first time, a high-throughput planar solid-phase extraction (HTpSPE) cleanup, controlled by UV/vis/FLD imaging, was developed for screening 81 VDs from 6 different groups (glucocorticoids, anthelmintics, antiparasitics, coccidiostats, nonsteroidal anti-inflammatory drugs, and antibiotics) in 4 different matrices (honey, pig muscle, cow milk, and chicken eggs). It consumed 13 times less solvent and was more eco-friendly and 5 times faster than routine methods. The VDs were automatically eluted using the autoTLC-LC-MS interface, separated online on a high-performance liquid chromatography column via a 10-min gradient, and detected by Orbitrap high-resolution tandem mass spectrometry. The screening method was validated according to the latest European Commission Implementing Regulation 2021/808. Most VDs except penicillins and cephalosporins were detected at the 5-μg/kg level in pig muscle, cow milk, and chicken eggs and 25-μg/kg level in honey.

Incorporation of Metabolic Activation in the HPTLC-SOS-Umu-C Bioassay to Detect Low Levels of Genotoxic Chemicals in Food Contact Materials

The safety evaluation of food contact materials requires excluding mutagenicity and genotoxicity in migrates. Testing the migrates using in vitro bioassays has been proposed to address this challenge. To be fit for that purpose, bioassays must be capable of detecting very low, safety relevant concentrations of DNA-damaging substances. There is currently no bioassay compatible with such qualifications. High-performance thin-layer chromatography (HPTLC), coupled with the planar SOS Umu-C (p-Umu-C) bioassay, was suggested as a promising rapid test (~6 h) to detect the presence of low levels of mutagens/genotoxins in complex mixtures. The current study aimed at incorporating metabolic activation in this assay and testing it with a set of standard mutagens (4-nitroquinoline-N-oxide, aflatoxin B1, mitomycin C, benzo(a)pyrene, N-ethyl nitrourea, 2-nitrofluorene, 7,12-dimethylbenzanthracene, 2-aminoanthracene and methyl methanesulfonate). An effective bioactivation protocol was developed. All tested mutagens could be detected at low concentrations (0.016 to 230 ng/band, according to substances). The calculated limits of biological detection were found to be up to 1400-fold lower than those obtained with the Ames assay. These limits are lower than the values calculated to ensure a negligeable carcinogenic risk of 10^-5. They are all compatible with the threshold of toxicological concern for chemicals with alerts for mutagenicity (150 ng/person). They cannot be achieved by any other currently available test procedures. The p-Umu-C bioassay may become instrumental in the genotoxicity testing of complex mixtures such as food packaging, foods, and environmental samples.

Multiplex planar bioassay detecting estrogens, antiestrogens, false-positives and synergists as sharp zones on normal phase

BACKGROUND

Phytoestrogens are found in many plants used in traditional medicines. Increasingly, plant extracts (botanicals) are also being added to foods or marketed as dietary supplements. Especially such powder formulations are susceptible to adulteration and falsification, given the global processing chain. To detect estrogen-like compounds in such multicomponent mixtures, non-target screening for hormonally active or endocrine disrupting compounds in plant products is becoming more important. Unfortunately, the current planar yeast estrogen screen (pYES) is prone to zone diffusion on the normal-phase high-performance thin-layer chromatography (NP-HPTLC) plate due to long incubation times in the aqueous bioassay.

PURPOSE

The present study aimed to reduce zone diffusion on NP plates, which provides the basis for extending pYES to a multiplex bioassay, offering 4 different biological activity principles, followed by targeted identification of active zones.

STUDY DESIGN AND METHODS

The reduction of substance diffusion via a polyisobutyl methacrylate polymer coating was studied. After successful zone fixation (^fix), a multiplex bioassay was developed, in which a 17β-estradiol-strip was applied along each sample track to detect synergists and antagonists (A), and for verification (V), a 4-methyl umbelliferone-strip to exclude false-positives. After multiplex bioassay screening of 68 botanicals, the zones with hormonal activities were heart-cut eluted to reversed-phase high-performance liquid chromatography-diode array detection-high-resolution tandem mass spectrometry (RP-HPLC-DAD-HESI-HRMS/MS).

RESULTS

The separated substances were successfully fixed by the chromatogram coating. The zone sharpness (achieved after the bioassay) made it possible to add two strips, the 17β-estradiol-strip for antagonistic and synergistic, and the 4-methyl umbelliferone-strip for false-positive effect detection, resulting in a multiplex bioassay. Using the 12D hyphenation NP-HPTLC^fix-UV/Vis/FLD-pYAVES-FLD heart-cut RP-HPLC-DAD-HESI-HRMS/MS, it was possible to obtain information on estrogens, antiestrogens, false-positives, and synergists, and (tentatively) assign 17 hormonally active compounds, of which only 7 have been known to affect the human estrogen receptor, while another 4 had structural similarity to common phytoestrogens and antiestrogens.

CONCLUSIONS

The streamlined 12D hyphenation including a multiplex bioassay has been shown to differentiate hormonal effects, leading to new insights and better understanding. It can generally be used to identify unknown hormonally active compounds in complex samples.

Evidence that Indo-Pacific bottlenose dolphins self-medicate with invertebrates in coral reefs

Indo-Pacific bottlenose dolphins (Tursiops aduncus) have been observed queueing up in natural environments to rub particular body parts against selected corals (Rumphella aggregata, Sarcophyton sp.) and sponges (Ircinia sp.) in the Egyptian Northern Red Sea. It was hypothesized that the presence of bioactive metabolites accounts for this selective rubbing behavior. The three invertebrates preferentially accessed by the dolphins, collected and analyzed by hyphenated high-performance thin-layer chromatography contained seventeen active metabolites, providing evidence of potential self-medication. Repeated rubbing allows these active metabolites to come into contact with the skin of the dolphins, which in turn could help them achieve skin homeostasis and be useful for prophylaxis or auxiliary treatment against microbial infections. This interdisciplinary research in behavior, separation science, and effect-directed analysis highlighted the importance of particular invertebrates in coral reefs, the urgent need to protect coral reefs for dolphins and other species, and calls for further vertebrate-invertebrate interaction studies.

•

Dolphins rubbed body parts against specifically selected corals and sponges

•

Behavioral studies were linked with hyphenated bioanalytical technique

•

Vertebrate-invertebrate interaction in coral reefs may serve self-medication

•

Molecular formulae were assigned to known and unknown bioactive molecules

Is Our Natural Food Our Homeostasis? Array of a Thousand Effect-Directed Profiles of 68 Herbs and Spices

The beneficial effects of plant-rich diets and traditional medicines are increasingly recognized in the treatment of civilization diseases due to the abundance and diversity of bioactive substances therein. However, the important active portion of natural food or plant-based medicine is presently not under control. Hence, a paradigm shift from quality control based on marker compounds to effect-directed profiling is postulated. We investigated 68 powdered plant extracts (botanicals) which are added to food products in food industry. Among them are many plants that are used as traditional medicines, herbs and spices. A generic strategy was developed to evaluate the bioactivity profile of each botanical as completely as possible and to straightforwardly assign the most potent bioactive compounds. It is an 8-dimensional hyphenation of normal-phase high-performance thin-layer chromatography with multi-imaging by ultraviolet, visible and fluorescence light detection as well as effect-directed assay and heart-cut of the bioactive zone to orthogonal reversed-phase high-performance liquid chromato-graphy-photodiode array detection-heated electrospray ionization mass spectrometry. In the non-target, effect-directed screening via 16 different on-surface assays, we tentatively assigned more than 60 important bioactive compounds in the studied botanicals. These were antibacterials, estrogens, antiestrogens, androgens, and antiandrogens, as well as acetylcholinesterase, butyrylcholinesterase, α-amylase, α-glucosidase, β-glucosidase, β-glucuronidase, and tyrosinase inhibitors, which were on-surface heart-cut eluted from the bioautogram or enzyme inhibition autogram to the next dimension for further targeted characterization. This biological-physicochemical hyphenation is able to detect and control active mechanisms of traditional medicines or botanicals as well as the essentials of plant-based food. The array of 1,292 profiles (68 samples × 19 detections) showed the versatile bioactivity potential of natural food. It reveals how efficiently and powerful our natural food contributes to our homeostasis.

Goldenrod Root Compounds Active against Crop Pathogenic Fungi

Root extracts of three goldenrods were screened for antimicrobial compounds. 2Z,8Z- and 2E,8Z-matricaria esters from European goldenrod (Solidago virgaurea) and E- and Z-dehydromatricaria esters from grass-leaved goldenrod (Solidago graminifolia) and first from showy goldenrod (Solidago speciosa) were identified by high-performance thin-layer chromatography combined with effect-directed analysis and high-resolution mass spectrometry or nuclear magnetic resonance spectroscopy after liquid chromatographic fractionation and isolation. Next to their antibacterial effects (against Bacillus subtilis, Aliivibrio fischeri, and Pseudomonas syringae pv. maculicola), they inhibited the crop pathogenic fungi Fusarium avenaceum and Bipolaris sorokiniana with half maximal inhibitory concentrations (IC₅₀) between 31 and 107 μg/mL. Benzyl 2-hydroxy-6-methoxybenzoate, for the first time found in showy goldenrod root, showed the strongest antifungal effect, with IC₅₀ of 25-26 μg/mL for both fungal strains.

A bioimaging system combining human cultured reporter cells and planar chromatography to identify novel bioactive molecules

For the first time, a human cancer cell line was shown to grow and be functionally active on the particulate porous adsorbent surface of separated sample mixtures. This allowed the novel combination of chromatographic separations with human cells as biological detector. As exemplary screening for cancer treatment drugs, cytotoxic substances were directly discovered in Saussurea costus and ginseng samples using the Cytotox CALUX® osteosarcoma cells (with luciferase expressing reporter gene) as detector. In addition, rosiglitazone and pioglitazone were detected as luminescent zones upon binding to the PPARγ receptor expressed in the respective CALUX cell line that was grown on the surface of the adsorbent. This demonstrates the ability to address receptor-mediated signaling with this method, and opens the perspective to use our novel bioimaging method to identify bioactive molecules targeting a wide range of pathways with toxicological, pharmaceutical and nutraceutical relevance. The new bioimaging directly pointed to individual effective compounds in multi-component mixtures. Furthermore, discovered effective compounds were directly characterized by online elution to high-resolution mass spectrometry and fragmentation.

Nanomole-scaled high-throughput chemistry plus direct bioautography on the same chromatography plate for drug discovery

The powerful fusion of on-surface synthesis and effect-directed analysis was introduced as novel tool for synthetic drug discovery, all on the same high-performance thin-layer chromatography plate. Precise automated sample application allowed both, high-throughput chemistry of 60 reactions at once and reaction miniaturization down to the 15-nmol scale. The antibiotic activity of all on-surface synthesized compounds was evaluated on the same surface via the Gram-positive Bacillus subtilis bioassay. For one product, synthesis (reaction, purification and identification) took 5.3 min and semi-quantitative biological evaluation took 2.8 min. Out of 60 on-surface reactions 10 products (17%) were identified to be more active than a well-known antibiotic reference. The concept was transferred to the Gram-negative Aliivibrio fischeri bioassay. For the first time, a new analytical platform was shown for a streamlined workflow at the most miniaturized scale from synthesis, purification, identification and quantification to semi-quantitative biological activity evaluation (all on the same chromatography plate).

Effects of the Probiotic Activity of Bacillus subtilis DSM 29784 in Cultures and Feeding Stuff

The European Union banned the usage of antibiotic growth promoters in animal production. The probiotic microorganism of the genus Bacillus appeared to be an attractive candidate to replace antibiotics. The Bacillus subtilis DSM 29784 is one of these strains. To date, the probiotic effect has not been completely understood, but it is supposed that the effect depends on metabolites of the microorganism. Imaging high-performance thin-layer chromatography (HPTLC) is a powerful tool to visualize differences in the metabolite profile of bacteria with high genetic similarity to allow a better understanding of the probiotic effect. In comparison to other bacteria, especially these bacterial cells were more robust to harsh cultivation conditions and produced a higher level of antioxidants or bioactive substances such as surfactin. HPTLC enabled the comparison of pure cell cultures to the spore cultivation in the feed, and the results explain and support the probiotic effect.

Effect-directed profiling of 32 vanilla products, characterization of multi-potent compounds and quantification of vanillin and ethylvanillin

Food testing is of great importance to the food industry and organizations to verify the authenticity claims, to prove the quality of raw materials and products, and to ensure food safety. The market prices of vanilla differed by a factor of about 20 in the last three decades. Therefore the risk of adulteration and counterfeiting of vanilla products is high. Instead of commonly used target analyses and sum parameter assays, a complementary non-target multi-imaging effect-directed screening was developed, which provided a new perspective on the wide range of vanilla product qualities on the market. Planar chromatography was combined with effect-directed assays, and the obtained biological and biochemical profiles of 32 vanilla products from nine different categories revealed a variety of active ingredients. Depending on the region, typical vanilla product profiles and activity patterns were obtained for pods, tinctures, paste (inner part), oleoresin and powders. However, some vanilla products showed additional active compounds and a different intensity pattern. The vanilla product profiles substantially differed from those of vanilla aroma or products containing synthetic vanillin or vanilla-flavored food products. Bioactive compounds of interest were online eluted and further characterized via HPTLC-HRMS, which allowed their tentative assignment. After purchase of the standards, these were successfully confirmed by co-chromatography. Quantification of vanillin across nine different product categories revealed levels ranging from 1 µg/g to 36 mg/g with a mean repeatability of 1.9%. The synthetic ethylvanillin was not detected in the investigated samples in significant concentrations. The assessment of differences in the activity patterns pointed to highly active compounds, which were not detected at UV/Vis/FLD but first via the biological and enzymatic assays. This effect-directed profiling bridges the gap from analytical food chemistry to food toxicology, and thus, makes an important contribution to consumer safety. In the same way, it would accelerate investigations for Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH) according to Regulation (EC) No. 1907/2006.

On-surface autosampling for liquid chromatography-mass spectrometry

An on-surface multi-purpose autosampler was built for liquid chromatography-mass spectrometry (LC-MS) based on the autoTLC-MS interface, taking advantage of open-source hard- and software developments as well as 3D printing. Termed autoTLC-LC-MS system, it is introduced for orthogonal hyphenation of normal phase high-performance thin-layer chromatography with reversed phase high-performance LC (HPLC) and high-resolution MS (HRMS). For verification of its functionality, a multi-class antibiotic mixture was applied as a calibration band pattern on an adsorbent layer and detected by the Bacillus subtilis bioassay. This effect-image was uploaded as a template in the updated TLC-MS_manager software. The clicked-on antibiotic zones were sequentially eluted without intervention from the planar counterpart (without bioassay) via a monolithic HPLC column into the HRMS system. For elution of antibiotics of 7 structural classes at 5 different calibration levels, the new on-surface autosampler achieved intra-day precisions of 2.1-14.1%, while inter-day precisions ranged 2.5-16.1% (all n = 3). The new hyphenation offers potential for planar sample clean-up prior to HPLC, concentration of liquid samples, increase of peak capacity and proof of peak purity or isomers. The integrated autoTLC-LC-MS system enabled high sample throughput, efficiency and reproducibility for the first time through fully automated TLC-LC-MS sequence operation. Its contact-closure signal functionality, versatile 3D printed planar sample holder and open-source software made it readily adjustable for new analytical tasks. Undoubtedly, any planar material can be investigated for leachables, such as textiles, foils, papers and other packagings, as well as planar biological samples for ingredients.