Eight different bioactivity profiles of 40 cinnamons by multi-imaging planar chromatography hyphenated with effect-directed assays and high-resolution mass spectrometry

African Under-Utilized Medicinal Leafy Vegetables Studied by Microtiter Plate Assays and High-Performance Thin-Layer Chromatography-Planar Assays

Biological activities of six under-utilized medicinal leafy vegetable plants indigenous to Africa, i.e., Basella alba, Crassocephalum rubens, Gnetum africanum, Launaea taraxacifolia, Solanecio biafrae, and Solanum macrocarpon, were investigated via two independent techniques. The total phenolic content (TPC) was determined, and six microtiter plate assays were applied after extraction and fractionation. Three were antioxidant in vitro assays, i.e., ferric reducing antioxidant power (FRAP), cupric reduction antioxidant capacity (CUPRAC), and 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging, and the others were enzyme (acetylcholinesterase, butyrylcholinesterase, and tyrosinase) inhibition assays. The highest TPC and antioxidant activity from all the methods were obtained from polar and medium polar fractions of C. rubens, S. biafrae, and S. macrocarpon. The highest acetyl- and butyrylcholinesterase inhibition was exhibited by polar fractions of S. biafrae, C. rubens, and L. taraxacifolia, the latter comparable to galantamine. The highest tyrosinase inhibition was observed in the n-butanol fraction of C. rubens and ethyl acetate fraction of S. biafrae. In vitro assay results of the different extracts and fractions were mostly in agreement with the bioactivity profiling via high-performance thin-layer chromatography-multi-imaging-effect-directed analysis, exploiting nine different planar assays. Several separated compounds of the plant extracts showed antioxidant, α-glucosidase, α-amylase, acetyl- and butyrylcholinesterase-inhibiting, Gram-positive/-negative antimicrobial, cytotoxic, and genotoxic activities. A prominent apolar bioactive compound zone was tentatively assigned to fatty acids, in particular linolenic acid, via electrospray ionization high-resolution mass spectrometry. The detected antioxidant, antimicrobial, antidiabetic, anticholinesterase, cytotoxic, and genotoxic potentials of these vegetable plants, in particular C. rubens, S. biafrae, and S. macrocarpon, may validate some of their ethnomedicinal uses.

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.

Bioactive profiles of edible vegetable oils determined using 10D hyphenated comprehensive high-performance thin-layer chromatography (HPTLC×HPTLC) with on-surface metabolism (nanoGIT) and planar bioassays

Introduction

Vegetable oils rich in unsaturated fatty acids are assumed to be safe and even healthy for consumers though lipid compositions of foods vary naturally and are complex considering the wealth of minor compounds down to the trace level.

Methods

The developed comprehensive high-performance thin-layer chromatography (HPTLC×HPTLC) method including the on-surface metabolization (nanoGIT) and bioassay detection combined all steps on the same planar surface. The pancreatic lipolysis (intestinal phase) experiment and the subsequent analysis of the fatty acid composition including its effect-directed detection using a planar bioassay was performed without elaborate sample preparation or fractionation to ensure sample integrity. Thus, no sample part was lost, and the whole sample was studied on a single surface regarding all aspects. This made the methodology as well as technology miniaturized, lean, all-in-one, and very sustainable.

Results and discussion

To prioritize important active compounds including their metabolism products in the complex oil samples, the nanoGIT method was used to examine the pancreatic lipolysis of nine different vegetable oils commonly used in the kitchen and food industry, e.g., canola oil, flaxseed oil, hemp oil, walnut oil, soybean oil, sunflower oil, olive oil, coconut oil, and palm oil. The digested oils revealed antibacterial and genotoxic effects, which were assigned to fatty acids and oxidized species via high-resolution tandem mass spectrometry (HRMS/MS). This finding reinforces the importance of adding powerful techniques to current analytical tools. The 10D hyphenated nanoGIT-HPTLC×HPTLC-Vis/FLD-bioassay-heart cut-RP-HPLC-DAD-HESI-HRMS/MS has the potential to detect any potential hazard due to digestion/metabolism, improving food safety and understanding on the impact of complex samples.

HPTLC-Bioluminescent Bioautography Screening of Herbal Teas for Adulteration with Hypolipidemic Drugs

Teas based on nutraceutical herbs are an effective tool against hyperlipidemia. However, the adulteration with chemical drugs is frequently detected. By coupling bioluminescent bioautography with high performance thin-layer chromatography (HPTLC), we developed a facile method suitable for screening hypolipidemic drugs (ciprofibrate and bezafibrate) adulteration in five different herbal teas (lotus leaf, Apocynum, Ginkgo biloba, Gynostemia and chrysanthemum). First, the sensitivity of a bioluminescent bacteria to the analyte was evaluated on different HPTLC layer materials, revealing that the best performance was achieved on the silica gel layer. On this basis, sample extracts were separated on silica gel plates via a standardized HPTLC procedure, forming a selective detection window for the targeted compound. Then, the separation results were rapidly visualized by the bioluminescence inhibition of bacteria cells within 6 min after dipping. The observed inhibition displayed an acceptable limit of detection (<20 ng/zone or 2 mg/kg) and linearity (R² ≥ 0.9279) within a wide concentration range (50-1000 ng/zone). Furthermore, the optimized method was performed with artificially adulterated samples and the recovery rates were determined to be within the range of 71% to 91%, bracing its practical reliability. Showing superiorly high simplicity, throughput and specificity, this work demonstrated that the analytical method jointly based on HPTLC and bioautography was an ideal tool for screening bioactive compounds in complex biological matrix.

Ten-dimensional hyphenation including simulated static gastro-intestinal digestion on the adsorbent surface, planar assays, and bioactivity evaluation for meal replacement products

Meal replacement products are normally consumed in weight-loss interventions and the treatment of obesity and diabetes. Changing lifestyles and eating habits made meal replacement products in the forms of shakes and bars a good alternative as To-go-meals, promoted as balanced in its composition and thus healthier compared to other ready-to-eat meals. This study aimed to evaluate the bioactivity of six differently flavoured powdered meal replacement products. Their analysis was made by a ten-dimensional hyphenation composed of digestion on the adsorbent surface, followed by normal-phase high-performance thin-layer chromatographic separation, multi-imaging, and planar assay application (effect-directed analysis), and then heart-cut elution/transfer of bioactive compound zones to reversed-phase high-performance liquid chromatography, diode array detection, and high-resolution tandem mass spectrometry. The on-surface digestion of saccharides, fats, and proteins through intestinal enzymatic activity revealed new breakdown products. These exhibited bioactivity in their different effect-profiles obtained by the Gram-negative Aliivibrio fischeri bioassay as well as α-/β-glucosidase and acetyl-/butyrylcholinesterease inhibition assays. The main bioactive compounds arising through simulated static pancreatic digestion were saturated and unsaturated free fatty acids. The synthetic sweetener sucralose was not influenced by simulated static intestinal digestion, but showed antimicrobial activity. In the prepared drinking meals with coffee and choco flavour, the acetylcholinesterase-inhibiting methylxanthines caffeine and theobromine were identified as bioactive compounds. Some other bioactive constituents could not be assigned to specific molecules and require further analyses. Although the studied meal replacement products showed health-beneficial properties through antimicrobial properties or inhibition of enzymes involved in the expression of the civilisation diseases, such as diabetes and Alzheimer's disease, plant foods, herbs and spices have been shown to be even richer and more versatile in bioactive compounds.

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.

Effect-Directed Profiling of Monofloral Honeys from Ethiopia by High-Performance Thin-Layer Chromatography and High-Resolution Mass Spectrometry

Ethiopian honey is used not only as food but also for treatment in traditional medicine. For its valorization, bioactive compounds were analyzed in nine types of monofloral Ethiopian honey. Therefore, a non-target effect-directed profiling was developed via high-performance thin-layer chromatography combined with multi-imaging and planar effect-directed assays. Characteristic bioactivity profiles of the different honeys were determined in terms of antibacterial, free-radical scavenging, and various enzyme inhibitory activities. Honeys from Hypoestes spp. and Leucas abyssinica showed low activity in all assays. In contrast, others from Acacia spp., Becium grandiflorum, Croton macrostachyus, Eucalyptus globulus, Schefflera abyssinica, Vernonia amygdalina, and Coffea arabica showed more intense activity profiles, but these differed depending on the assay. In particular, the radical scavenging activity of Croton macrostachyus and Coffea arabica honeys, the acetylcholinesterase-inhibiting activity of Eucalyptus globulus and Coffea arabica honeys, and the antibacterial activity of Schefflera abyssinica honey are highlighted. Bioactive compounds of interest were further characterized by high-resolution mass spectrometry. Identifying differences in bioactivity between mono-floral honey types affects quality designation and branding. Effect-directed profiling provides new insights that are valuable for food science and nutrition as well as for the market, and contributes to honey differentiation, categorization, and authentication.

Acetylcholinesterase inhibitors in the giant goldenrod root

Eight bioactive clerodane diterpenes from the root extract of Solidago gigantea Ait. (giant goldenrod) were quantified by high-performance thin-layer chromatography (HPTLC) and two newly developed hyphenated methods. One uses vanillin sulphuric acid derivatization and densitometry, and the other an inhibition assay of acetylcholinesterase (AChE) and video densitometry. Both methods gave figures of merit for quantification including 5.8-33.9 ng and 175.5-448.7 ng LOQs and 2.7-6.9 RSD% and 8.8-13.9 RSD% inter-day precisions, respectively. Based on the diterpenes' content of 14 root samples collected over a year from the same plant population, the fully flowering plant is suggested to collect the root as a source of these compounds. Excepting one diterpene (with the lowest retardation factor), the quantitative results for the richest sample obtained by the two methods were in harmony. The difference could be due to a matrix effect.

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

It is still a challenge to discover and identify individual bioactive compounds directly in multicomponent mixtures. Current workflows are too tedious for routine use. Hence, the hyphenation of separation and detection techniques is a powerful tool to maximize the information obtained by a single sample run. A robust eight-dimensional (8D) hyphenation was developed. Orthogonal separations, biological assay detection, analyte trapping, desalting, and physico-chemical detections were arranged in the following order, i.e. 1) normal phase high-performance thin-layer chromatography (NP-HPTLC) separation, 2) Vis detection, 3) UV detection, 4) fluorescence detection (FLD), 5) bioassay for effect-directed analysis (EDA), 6) heart-cut trapping/desalting/elution to reversed phase high-performance liquid chromatography (RP-HPLC) separation, 7) photodiode array (PDA) and 8) mass spectrometry (MS) detection. For the first time, the hyphenation exploited online analyte trapping to desalt the eluted bioactive zone from the plate containing highly salted bioassay media. Subsequent valve switching guided the trapped analyte(s) to the main column, followed by multiple detection. As proof-of-principle, cinnamon samples were analyzed by NP-HPTLC-UV/Vis/FLD-EDA-RP-HPLC-PDA-MS, whereby a bioactive zone was separated into two distinct peaks detected by PDA and MS to be 2-methoxy cinnamaldehyde and cinnamaldehyde. The developed 8D hyphenation is applicable for routine, allowing the non-target high-throughput screening of complex samples for individual bioactive compounds.