Qualitative and quantitative two-dimensional thin-layer chromatography/high performance liquid chromatography/diode-array/electrospray-ionization-time-of-flight mass spectrometry of cholinesterase inhibitors

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.

Natural Inhibitors of Cholinesterases: Chemistry, Structure-Activity and Methods of Their Analysis

This article aims to provide an updated description and comparison of the data currently available in the literature (from the last 15 years) on the studied natural inhibitors of cholinesterases (IChEs), namely, acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE). These data also apply to the likely impact of the structures of the compounds on the therapeutic effects of available and potential cholinesterase inhibitors. IChEs are hitherto known compounds with various structures, activities and origins. Additionally, multiple different methods of analysis are used to determine the cholinesterase inhibitor potency. This summary indicates that natural sources are still suitable for the discovery of new compounds with prominent pharmacological activity. It also emphasizes that further studies are needed regarding the mechanisms of action or the structure-activity correlation to discuss the issue of cholinesterase inhibitors and their medical application.

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.

Fractionation of Lycopodiaceae Alkaloids and Evaluation of Their Anticholinesterase and Cytotoxic Activities

In view of the abundant evidence that Lycopodiaceae alkaloids, including the well-known huperzine A (HupA), are among the potent acetylcholinesterase (AChE) inhibitors, an attempt was made to search for new compounds responsible for this property. For this purpose, three plant species belonging to the Lycopodiaceae family, commonly found in the Euro-Asia region, were subjected to the isolation of bioactive compounds, their identification and subsequent evaluation of their anticholinesterase and cytotoxic activities. Methanolic extracts of two Lycopodium and one Hupezia species were obtained via optimized pressurized liquid extraction (PLE) and then pre-purified using innovative gradient vacuum liquid chromatography (gVLC). For the first time, three sorbents of different porosity packed in polypropylene cartridges and mobile phase systems of different polarity were used to elute the target compounds. This technique proved to be a rapid tool for the obtainment of alkaloid fractions and allowed one to select the appropriate process conditions to yield potent AChE inhibitors in each of the species studied. More than 100 collected fractions were analyzed via HPLC/ESI-QTOF-MS, which enabled one to detect more than 50 compounds, including several new ones previously unreported. Some of them were present in high purity fractions (60-90% of the established purity). TLC bioautography assays proved that the analyzed species are rich sources of AChE inhibitors, but H. selago showed the highest anti-AChE activity. Additionally, the modified silanized silica gel sorbent used allowed one to isolate L. clavatum alkaloids more efficiently using an aqueous reversed-phase solvent system. Furthermore, the tested extracts from the three plant extracts were found to be safe, as they did not exhibit cytotoxicity to skin fibroblasts.

GC-MS analysis of Amaryllidaceae and Sceletium-type alkaloids in bioactive fractions from Narcissus cv. Hawera

RATIONALE

Narcissus cv. Hawera has been found to biosynthesize some Sceletium-type alkaloids with antidepressant and anxiolytic activities. This ornamental plant has been poorly studied as a source of bioactive alkaloids including some contraversive reports on in vitro and intact plants. In this study, a detailed GC-MS characterization of its alkaloid fractions is presented.

METHODS

GC-MS was used for the identification of compounds in the alkaloid fractions. Both underivatized and silylated samples were analyzed simultaneously. Elevated plus maze and tail suspension tests were used to assay the anxiolytic and antidepressant activities. Ellman's and MTT-dye reduction assays were used to evaluate the acetylcholinesterase (AChE) inhibitory and cytotoxicity activities, respectively.

RESULTS

Of the 29 alkaloids, 13 of Sceletium-type were detected. Two new alkaloids were identified as 2-oxo-mesembrine and 2-oxo-epi-mesembrenol. Lycorine was found as a major compound (43.5%) in the crude silylated methanol extract. After the elimination of lycorine by pre-crystallization, the major alkaloids were 40.8% 6-epi-mesembranol, 16.2% 6-epi-mesembrenol, and 13.8% sanguinine. This fraction showed anxiolytic and antidepressant-like activities as well as potent AChE inhibitory and antineoplastic activities.

CONCLUSIONS

Silylation of the alkaloid fractions from Narcissus cv. Hawera provides better separation, structural information, and improved sensitivity for compounds with two and more hydroxyl groups. The lycorine-free alkaloid fraction shows a great potential for further pharmacological studies.

Methods of isolation and bioactivity of alkaloids obtained from selected species belonging to the Amaryllidaceae and Lycopodiaceae families

Alkaloids obtained from plants belonging to the Amaryllidaceae and Lycopodiaceae families are of great interest due to their numerous properties. They play a very important role mainly due to their strong antioxidant, anxiolytic and anticholinesterase activities. The bioactive compounds obtained from these two families, especially galanthamine and huperzine A, have found application in the treatment of the common and incurable dementia-like Alzheimer’s disease. Thanks to this discovery, there has been a breakthrough in its treatment by significantly improving the patient’s quality of life and slowing down disease symptoms – albeit with no chance of a complete cure. Therefore, a continuous search for new compounds with potent anti-AChE activity is needed in modern medicine. In obtaining new therapeutic bioactive phytochemicals from plant material, the isolation process and its efficiency are crucial. Many techniques are known for isolating bioactive compounds and determining their amounts in complex samples. The most commonly utilized methods are extraction using different variants of organic solvents allied with chromatographic and spectrometric techniques. Optimization of these methods and modification of their procedures potentially allows researchers to obtain the expected results. The aim of this paper is to present known techniques for the isolation of alkaloids, especially from three species Narcissus, Lycopodium and Huperzia that are a rich source of AChE inhibitors. In addition, innovative combinations of chromatographic and spectrometric methods and novel TLC-bioautography will be presented to enable researchers to better study the bioactivity of alkaloids.

Evaluation of the Therapeutic Effect of Lycoramine on Alzheimer's Disease in Mouse Model

BACKGROUND

Alzheimer's disease is one of the leading health problems characterized by the accumulation of Aβ and hyperphosphorylated tau that account for the senile plaque formations causing extensive cognitive decline. Many of the clinical diagnoses of Alzheimer's disease are made in the late stages, when the pathological changes have already progressed.

OBJECTIVE

The objective of this study is to evaluate the promising therapeutic effects of a natural compound, lycoramine, which has been shown to have therapeutic potential in several studies and to understand its mechanism of action on the molecular level via differential protein expression analyses.

METHODS

Lycoramine and galantamine, an FDA approved drug used in the treatment of mild to moderate AD, were administered to 12 month-old 5xFAD mice. Effects of the compounds were investigated by Morris water maze, immunohistochemistry and label- free differential protein expression analyses.

RESULTS

Here we demonstrated the reversal of cognitive decline via behavioral testing and the clearance of Aβ plaques. Proteomics analysis provided in-depth information on the statistically significant protein perturbations in the cortex, hippocampus and cerebellum sections to hypothesize the possible clearance mechanisms of the plaque formation and the molecular mechanism of the reversal of cognitive decline in a transgenic mouse model. Bioinformatics analyses showed altered molecular pathways that can be linked with the reversal of cognitive decline observed after lycoramine administration but not with galantamine.

CONCLUSION

Lycoramine shows therapeutic potential to halt and reverse cognitive decline at the late stages of disease progression, and holds great promise for the treatment of Alzheimer's disease.

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.

Optimization of Pressurized Liquid Extraction of Lycopodiaceae Alkaloids Obtained from Two Lycopodium Species

Alkaloids of the Lycopodiaceae family are of great interest to researchers due to their numerous properties and wide applications in medicine. They play a very important role mainly due to their potent antioxidant, antidepressant effects and a reversible ability to inhibit acetylcholinesterase (AChE) enzyme activity. This property is of immense importance due to the growing problem of an increasing number of patients with neurodegenerative diseases in developed countries and a lack of effective and efficient treatment for them. Numerous studies have shown that Lycopodiaceae alkaloids are a rich source of AChE inhibitors. In the obtaining of new therapeutic phytochemicals from plant material, the extraction process and its efficiency is crucial. Therefore, the aim of this work was to optimize the conditions of modern PLE to obtain bioactive alkaloids from two Lycopodium species: L. clavatum L. and L. annotinum L. Five different solvents of different polarity were used for prepared plant extracts in order to compare the alkaloid content in and thereby effectiveness of the entire extraction. PLE parameters were used based on multiple studies conducted that gave the highest alkaloids recovery. Crude extracts were purified using solid-phase extraction (SPE) on Oasis HLB cartridge and examined by HPLC/ESI-QTOF-MS of the highly abundant alkaloids. To the best of our knowledge, this is the first time such high recoveries have been obtained for known Lycopodiaceae alkaloids. The best extraction results of alkaloid-lycopodine were detected in the dichloromethane extract from L. clavatum, where the yield exceeded 45%. The high recovery of annotinine above 40% presented in L. annotinum was noticed in dichloromethane and ethyl acetate extracts. Moreover, chromatograms were obtained with all isolated alkaloids and the best separation and quality of the bands in methanolic extracts. Interestingly, no alkaloid amounts were detected in cyclohexane extracts belonging to the non-polar solvent. These results could be helpful for understanding and optimizing the best conditions for isolating potent AChE inhibitors.

The Bioassay-Guided Fractionation and Identification of Potent Acetylcholinesterase Inhibitors from Narcissus c.v. 'Hawera' Using Optimized Vacuum Liquid Chromatography, High Resolution Mass Spectrometry and Bioautography

Bioassay-guided isolation of bioactive compound is a modern and efficient technique in metabolites screening. It may shorten the total time of the entire process and reduce some costs of it. The aim of this paper was to fractionate and isolate alkaloids by developing an innovative vacuum liquid chromatography method for a species of Narcissus c.v. ‘Hawera’ rarely investigated so far and establishing the inhibitory activity of acetylcholinesterase (AChE). The studies consisted of the extraction of plant material by modern pressurized liquid extraction (PLE), followed by the isolation of alkaloidal fractions. For this purpose, the pioneering gradient vacuum liquid chromatography (gVLC) technique was employed by using two sorbents in various proportions packed in polypropylene cartridges for the first time. This step was performed in order to pre-clean the samples but also to establish the best combination of sorbents which permits obtaining potentially strong AChE inhibitors. The collected fractions were examined by HPLC/ESI-QTOF-MS in order to compare which combination of sorbents would allow us to obtain the highest concentration of alkaloids. The combination of these techniques confirmed the presence of the alkaloids and enabled the development of a modern method for the fractionation and isolation of the compounds with strong anti-AChE activity.

The TLC-Bioautography as a Tool for Rapid Enzyme Inhibitors detection - A Review

Microorganisms and plants can be important sources of many compounds with potential pharmaceutical applications. Extraction of these matrices is one of the ways of identifying the presence of inhibitory active substances against enzymes whose high activity leads to serious human diseases including cancer, Parkinson's or Crohn's diseases. The isolation and purification of inhibitors are time-consuming and expensive steps in the analysis of the crude extract and therefore, it is necessary to find a fast, efficient, and inexpensive method for screening extracts of interest. TLC-Bioautography combines the separation of the extract on a thin layer with its subsequent biological analysis. TLC-Bioautography methods have been developed for several classes of enzymes including oxidoreductases, hydrolases and isomerases, and there is a potential for developing functional methods for other classes of enzymes. This review summarizes known TLC-Bioautography methods and their applications for determining the presence of enzyme inhibitors in extracts and compares the effectiveness of different methodological approaches. It also indicates the current state and perspective of the development of TLC-Bioautography and its possible future applications.

Identification of acetylcholinesterase inhibitors in water by combining two-dimensional thin-layer chromatography and high-resolution mass spectrometry

Effect-directed analysis (EDA) is increasingly used in environmental monitoring to detect and identify key toxicants. High-performance thin-layer chromatography (HPTLC) has proven to be a very suitable fractionation technique for this purpose. However, HPTLC is limited in its separation efficiency. Thus, separated fractions could still contain many different components and identification of the effective substances remains difficult. Therefore, in this study a workflow for selective EDA with two-dimensional HPTLC in combination with high-performance liquid chromatography-high-resolution mass spectrometry (HPLC-HRMS) was developed. The aim of the workflow was the stepwise reduction of the sample complexity in order to reduce the number of signals that could be responsible for the measured effects. As a consequence, the identification of effective substances should be facilitated. The acetylcholinesterase inhibition assay (AChE assay) for the detection of potential neurotoxic compounds was applied for biotesting. The transfer of effective zones from the first to the second dimension and also to the mass spectrometric measurement was enabled by extraction. A proof of concept was performed by spiking six acetylcholinesterase inhibiting substances into three different water matrices that were investigated with the developed workflow. The successful prioritization of all spiked compounds confirmed the efficiency of the workflow, regardless of the sample matrix. Biotesting of different water samples resulted in numerous potentially neurotoxic effects, which overlapped strongly in the first separation dimension. The higher peak capacity reached by two-dimensional HPTLC, on the other hand, resulted in discrete effective zones and enabled the identification of several compounds. For the substances lumichrome, a derivate of riboflavin and paraxanthine as well as for linear alkylbenzene sulfonates that were applied as anionic surfactants in detergents, the inhibiting effect to the AChE could be confirmed.

Detection and identification of acetylcholinesterase inhibitors in Annona cherimola Mill. by effect-directed analysis using thin-layer chromatography-bioassay-mass spectrometry

INTRODUCTION

Acetylcholinesterase (AChE) inhibitors are considered an important strategy in the treatment of neurological disorders such as Alzheimer's disease. A simple and fast planar chromatography-bioassay methodology has been established to detect bioactive molecules in cherimoya fruit.

OBJECTIVE

Detect and identify AChE inhibitors in cherimoya by high-performance thin-layer chromatography (HPTLC)-bioassay-mass spectrometry (MS) and related techniques.

METHODOLOGY

Effect-directed analysis by planar chromatography-bioassay-mass spectrometry was applied to detect and identify AChE inhibitors in pulp, peel and cherimoya seed. Bioassay was optimised establishing the following conditions: enzymatic solution (1.0 U mL^-1 ), 1-naphtyl acetate substrate (1.5 mg mL^-1 ) and Fast Blue B salt (1.0 mg mL^-1 ). TLC-MS interface was used to directly elute the active zones into a mass spectrometer or to a micro-vial for further off-line studies.

RESULTS

Two AChE inhibitory bands were detected in peel extracts. An analysis via HPTLC-MS and high-performance liquid chromatography diode array detector tandem mass spectrometry (HPLC-DAD-MS/MS) allowed to characterise three potential AChE inhibitors: anonaine (m/z 266 [M + H]⁺ ; UV λ_max = 269.6 nm), glaucine (m/z 256 [M + H]⁺ ; UV λ_max = 282.9 and 300.6 nm) and xylopine (m/z 296 [M + H]⁺ ; UV λ_max = 278.5 nm).

CONCLUSIONS

The application of this optimised high throughput method allowed to establish the presence of three potential AChE inhibitors in cherimoya peel. For the first time AChE inhibitory capacity of these alkaloids is reported.

Adsorbed hollow fiber-based biological fingerprinting for the discovery of platelet aggregation inhibitors from Danshen-Honghua decoction

For lead compound discovery from natural products, hollow fiber cell fishing with chromatographic analysis is a newly developed method. In this study, an adsorbed hollow fiber-based biological fingerprinting method was firstly developed to discover potential platelet aggregation inhibitors from Danshen-Honghua decoction. Platelets were seeded on the fiber and their survival rate was tested. Results indicated that more than 92% platelets survived during the whole operation process. Ranitidine and tirofiban were used as positive and negative control respectively to verify the reliability of the presented approach. The main variables such as amount of extract and stirring time that affect the adsorbed hollow fiber-based biological fingerprinting process were optimized, and the repeatability of this method was also investigated. Finally, 12 potential active compounds in Danshen-Honghua decoction were successfully detected using the established approach and structures for nine of them were tentatively identified by liquid chromatography with mass spectrometry analysis. In addition, the in vitro platelet aggregation inhibition test was carried out for five of the nine hit compounds, and three active components, namely, lithospermic acid, salvianolic acid A, and salvianolic acid B were confirmed. These results proved that the proposed method could be an effective approach for screening platelet inhibitors from plant extracts.

Bioconversion, health benefits, and application of ginseng and red ginseng in dairy products

Ginseng and red ginseng are popular as functional foods in Asian countries such as Korea, Japan, and China. They possess various pharmacologic effects, including antioxidant, anti-inflammatory, anti-cancer, anti-obesity, and anti-viral activities. Ginsenosides are a class of pharmacologically active components in ginseng and red ginseng. Major ginsenosides are converted to minor ginsenosides, which have better bioavailability and cellular uptake, by microorganisms and enzymes. Studies have shown that ginseng and red ginseng can affect the physicochemical and sensory properties, ginsenosides content, and functional properties of dairy products. In addition, lactic acid bacteria in dairy products can convert into minor ginsenosides and ginseng and red ginseng improve functionality of products. This review will discuss the characteristics of ginseng and red ginseng, and their bioconversion, functionality, and application in dairy products.