Combination of bioautography with HPTLC-MS/NMR: a fast identification of acetylcholinesterase inhibitors from galbanum(†)

Acetylcholinesterase inhibitory activity of Ferula plants and their potential for treatment of Alzheimer's disease

One of the current strategies in the treatment of Alzheimer's disease is using drugs with acetylcholinesterase (AChE) inhibitory property. The existence of various compounds in plants as a potential source for finding new compounds to treat Alzheimer's disease is a scientific fact. Many secondary metabolites and plant extracts have been reported with the ability to inhibit the AChE activity and improve memory and learning. These compounds can increase the concentration of acetylcholine in the brain and improve cholinergic function in individuals with Alzheimer's disease and reduce the symptoms of this neurological disorder. Plants of Ferula genus are a good source of biologically active compounds such as sesquiterpene derivatives, coumarin derivatives and sulfur-containing compounds. Numerous studies on various extracts or purified compounds of Ferula genus have shown that members of this genus have the inhibitory properties on acetylcholinesterase and can also be effective in improving Alzheimer's and amnesia. This review article summarizes studies on plants of Ferula extracts and their derived compounds to find AChE inhibitors.

Cytotoxic and apoptotic effects of Ferula gummosa Boiss: extract on human breast adenocarcinoma cell line

PURPOSE

Ferula gummosa Boiss. is a well-known and valuable medicinal plant in Iran. Research has shown that this plant has several pharmacological properties, including anti-bacterial, anti-cancer and etc. In the present study, we investigated the cytotoxic properties of F. gummosa Boiss. extract in MCF-7 breast adenocarcinoma cells.

METHODS

The cytotoxicity and pro-apoptotic properties of the extract were assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) test and propidium iodide (PI) stained cells, respectively. Apoptosis and necrosis were evaluated by annexin V-PI staining. The levels of reactive oxygen species (ROS),malondialdehyde (MDA), glutathione (GSH), and superoxide dismutase (SOD) was determined to evaluate oxidative stress. The cell migration and the gene expression were assessed by scratch assay and quantitative real-time polymerase chain reaction (q-RT-PCR), respectively.

RESULTS

The extract of F. gummosa decreased the viability and cell cycle progression of MCF-7 cells by inducing apoptosis and necrosis, increasing ROS and MDA levels, and decreasing GSH levels and SOD activity. It also lowered the cells' migration capability by enhancing p53 mRNA levels and reducing MMP-9 mRNA expression.

CONCLUSION

F. gummosa exhibited pro-apoptotic, anti-proliferative, and anti-metastatic effects on MCF-7 cells. It is therefore recommended that detailed future research be done on different parts of the plant or its secondary metabolites to find anti-cancer lead compounds.

In silico molecular modeling, neuro-behavioral profile, and toxicity assessment of the essential oil of Ferula gummosa Boiss. as an anti-seizure agent

ETHNOPHARMACOLOGICAL RELEVANCE

Ferula gummosa Boiss., known in Persian as "Baridje," belongs to the Apiaceae family. All parts of this plant, especially the root, contain galbanum. Galbanum, the oleo-gum resin of F. gummosa, is one of the essential traditional herbal medicines in Iran, which is used as a tonic for epilepsy and chorea, memory enhancement, gastrointestinal diseases, and wound healing.

AIM OF THE STUDY

We investigated the toxicity, anticonvulsant effects, and molecular modeling of the essential oil (EO) distilled from the oleo-gum resin of F. gummosa.

MATERIALS AND METHODS

Gas chromatography-mass spectrometry was used to identify the EO components. The cytotoxicity of EO on HepG2 cell lines was assessed by the MTT method. Male mice were arranged as follows: negative control groups (sunflower oil (10 ml/kg, i.p.) or saline (10 ml/kg, p.o.)), EO groups (0.5, 1, 1.5, and 2.5 ml/kg, p.o.), and positive control groups (ethosuximide (150 mg/kg, p.o.) or diazepam (1.0 or 2 mg/kg, i.p.)). The motor coordination and neurotoxicity of EO were studied using the rota-rod test. Open-field, novel object recognition, and passive avoidance learning tests were used to investigate the effect of EO on locomotor activity and memory function. An acute pentylenetetrazole-induced seizure model was utilized to evaluate the anticonvulsant properties of the EO. The interaction of the EO main components with the GABA_A receptor was investigated by coarse-grained molecular dynamics simulations.

RESULTS

β-pinene, sabinene, α-pinene, and ρ-cymene were the main components of EO. The IC₅₀ of the EO at 24, 48, and 72 h was found to be 59.90, 12.96, and 3.93 μl/ml, respectively. No adverse effects were observed in memory, motor coordination, and locomotor activity in mice treated with EO. Administration of EO (1, 1.5, and 2.5 ml/kg) improved survival rates in mice receiving pentylenetetrazole (PTZ; to induce an epileptic seizure). Sabinene was able to bind to the binding site of benzodiazepines at the GABA_A receptor.

CONCLUSIONS

Acute treatment with the EO of F. gummosa caused antiepileptic effects and could effectively increase the survival rate in PTZ-treated mice with no significant toxicity.

Sesquiterpene Coumarin Ethers with Selective Cytotoxic Activities from the Roots of Ferula huber-morathii Peşmen (Apiaceae) and Unequivocal Determination of the Absolute Stereochemistry of Samarcandin

Ancient physicians frequently used the resin of Ferula species to treat cancer. Today, some folkloric recipes used for cancer treatment also contain the resin of Ferula species. The dichloromethane extract of the roots of Ferula huber-morathii exhibited cytotoxic activities against COLO 205 (colon), K-562 (lymphoblast), and MCF-7 (breast) cancer cell lines (IC₅₀ = 52 µg/mL, 72 µg/mL, and 20 µg/mL, respectively). Fifteen sesquiterpene coumarin ethers with cytotoxic activity were isolated from the dichloromethane extract of the roots of F. huber-morathii using bioactivity-directed isolation studies. Extensive spectroscopic analyses and chemical transformations have elucidated the structures of these sesquiterpene coumarin ethers as conferone (1), conferol (2), feselol (3), badrakemone (4), mogoltadone (5), farnesiferol A (6), farnesiferol A acetate (7), gummosin (8), ferukrin (9), ferukrin acetate (10), deacetylkellerin (11), kellerin (12), samarcandone (13), samarcandin (14), and samarcandin acetate (15). The absolute configuration of samarcandin (14) was unequivocally determined by the X-ray crystallographic analysis of the semi-synthetic (R)-MTPA ester of samarcandin (24). Conferol (2) and mogoltadone (5) were found to be the most potent cytotoxic compounds against all three cancer cell lines; furthermore, these compounds exhibit low cytotoxic activity against the non-cancerous human umbilical vein epithelial cells (HUVEC) cell line. Investigation of the biological activity mechanisms of mogoltadone (5) revealed that while suppressing the levels of Bcl-XL and procaspase-3 in the COLO 205 cancer cell line, it did not have a significant effect on the Bcl-XL, caspase-3, and β-catenin protein levels of the HUVEC cell line, which may explain the cytotoxic selectivity of mogoltadone (5) on cancer cell lines.

Bioautography-guided HPTLC-MS as a rapid hyphenated technique for the identification of antimicrobial compounds from selected South African Combretaceae species

INTRODUCTION

Many species within Combretaceae are traditionally used for the treatment of bacterial infections. The similarity in chemistry and antimicrobial activities within the family pose a challenge in selecting suitable species for herbal drug development.

OBJECTIVE

This study aimed at rapidly identifying antimicrobial compounds using bioautography-guided high-performance thin-layer chromatography coupled with mass spectrometry (HPTLC-MS).

METHODS

Hierarchical cluster analysis of ultra-performance liquid chromatography-mass spectrometry data from the methanol extracts of 77 samples, representing four genera within Combretaceae, was carried out. Based on groupings on the dendrogram, 15 samples were selected for bioautography analysis against four pathogens (Staphylococcus aureus, Bacillus cereus, Escherichia coli and Salmonella typhimurium). Active compounds were identified using HPTLC-MS analysis of bands corresponding to the inhibition zones.

RESULTS

Bioautography revealed 15 inhibition zones against the four pathogens, with the most prominent present for Combretum imberbe. Analysis of the active bands, using HPTLC-MS indicated that flavonoids, triterpenoids and combretastatin B5 contributed to the antibacterial activity. The compounds corresponding to molecular ions m/z 471 (Combretum imberbe) and 499 (Combretum elaeagnoides) inhibited all four pathogens, and were identified as imberbic acid and jessic acid, respectively. Chemotaxonomic analysis indicated that arjunic acid, ursolic acid and an unidentified triterpenoid (m/z 471) were ubiquitous in the Combretaceae species and could be responsible for their antibacterial activities.

CONCLUSION

Application of HPTLC-MS enabled the rapid screening of extracts to identify active compounds within taxonomically related species. This approach allows for greater efficiency in the natural product research workflow to identify bioactive compounds in crude extracts.

An Evolving Technology That Integrates Classical Methods with Continuous Technological Developments: Thin-Layer Chromatography Bioautography

Thin-layer chromatography (TLC) bioautography is an evolving technology that integrates the separation and analysis technology of TLC with biological activity detection technology, which has shown a steep rise in popularity over the past few decades. It connects TLC with convenient, economic and intuitive features and bioautography with high levels of sensitivity and specificity. In this study, we discuss the research progress of TLC bioautography and then establish a definite timeline to introduce it. This review summarizes known TLC bioautography types and practical applications for determining antibacterial, antifungal, antitumor and antioxidant compounds and for inhibiting glucosidase, pancreatic lipase, tyrosinase and cholinesterase activity constitutes. Nowadays, especially during the COVID-19 pandemic, it is important to identify original, natural products with anti-COVID potential compounds from Chinese traditional medicine and natural medicinal plants. We also give an account of detection techniques, including in situ and ex situ techniques; even in situ ion sources represent a major reform. Considering the current technical innovations, we propose that the technology will make more progress in TLC plates with higher separation and detection technology with a more portable and extensive scope of application. We believe this technology will be diffusely applied in medicine, biology, agriculture, animal husbandry, garden forestry, environmental management and other fields in the future.

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.

HPTLC-Based Chemical Profiling: An Approach to Monitor Plant Metabolic Expansion Caused by Fungal Endophytes

Fungal endophytes isolated from two latex bearing species were chosen as models to show their potential to expand their host plant chemical diversity. Thirty-three strains were isolated from Alstonia scholaris (Apocynaceae) and Euphorbia myrsinites (Euphorbiaceae). High performance thin layer chromatography (HPTLC) was used to metabolically profile samples. The selected strains were well clustered in three major groups by hierarchical clustering analysis (HCA) of the HPTLC data, and the chemical profiles were strongly correlated with the strains' colony size. This correlation was confirmed by orthogonal partial least squares (OPLS) modeling using colony size as "Y" variable. Based on the multivariate data analysis of the HPTLC data, the fastest growing strains of each cluster were selected and used for subsequent experiments: co-culturing to investigate interactions between endophytes-phytopathogens, and biotransformation of plant metabolites by endophytes. The strains exhibited a high capacity to fight against fungal pathogens. Moreover, there was an increase in the antifungal activity after being fed with host-plant metabolites. These results suggest that endophytes play a role in plant defense mechanisms either directly or by biotransformation/induction of metabolites. Regarding HPTLC-based metabolomics, it has proved to be a robust approach to monitor the interactions among fungal endophytes, the host plant and potential phytopathogens.

Sesquiterpene coumarins from Ferula sinkiangensis K.M.Shen and their cytotoxic activities

Five undescribed sesquiterpene coumarins, one undescribed coumarin derivative, and twenty-five known analogues, were isolated from the resin of Ferula sinkiangensis K.M.Shen. The planar structures and relative configurations of the undescribed compounds were determined by NMR experiment and HRESIMS data. The absolute configurations were established by Electrostatic Circular Dichroism method. Among these analogues, Sinkiangenol E showed the best cytotoxic activity against HeLa cervical cancer cells. Annexin V-FITC/PI staining indicated that Sinkiangenol E induced apoptosis in HeLa cells. Cell cycle analysis showed Sinkiangenol E arrested cell cycle at G0/G1 phase. Western blot results proved that Sinkiangenol E affected apoptosis-related and cell cycle regulation-related protein expression by activating the MAPK pathway.

Same analytical method for both (bio)assay and zone isolation to identify/quantify bioactive compounds by quantitative nuclear magnetic resonance spectroscopy

Differing sensitivity is the main obstacle for a direct combination of HPTLC with NMR spectroscopy. A sufficient amount of the isolated compound zone must be provided by HPTLC for subsequent offline NMR detection (HPTLC//NMR). To fill the gap, a straightforward procedure was developed using the same analytical HPTLC system for both bioprofiling and isolation of bioactive zones from multicomponent mixtures. The HPTLC-effect-directed analysis (EDA) revealed several bioactive compounds in five botanical extracts, i.e. Salvia officinalis, Thymus vulgaris and Origanum vulgare, all Lamiaceae, and peels of red and green apples (Jonagored and Granny Smith, respectively), both Rosaceae. A tricky case study was designed to show how to deal with potentially coeluting bioactive structural isomers, e.g., ursolic (UA), oleanolic (OA) and betulinic acids (all C30H48O3), which are most difficult to identify and assign. A multipotent bioactive HPTLC zone showed the same hRF value and mass signal in HPTLCHRMS, though containing the coeluting structural isomers UA and OA. After zone isolation from the HPTLC plate, first the 1H NMR spectrum allowed to distinguish distinct allylic H-18 protons, i.e. 2.20 ppm for UA and 2.85 ppm for OA, and at the same time, to quantify the two isomers by using the PUlse Length-based CONcentration methodology (HPTLC//1H qNMR-PULCON). In case of a partial overlap of the diagnostic signal with that of the matrix, results were corroborated with those obtained by using the 1H deconvoluted or 2D 1H-13C Heteronuclear Single Quantum Coherence spectra. The comparison of the quantitative results showed a good correlation (R2 = 0.9718) between the two orthogonal methods HPTLC-Vis and HPTLC//1H qNMR-PULCON. A sufficient zone isolation from the HPTLC plate (mean isolation rate of 82%) for both UA and OA (0.27 - 4.67 mM) was achieved for HPTLC//qNMR, comparing the isolated bioactive compound zone with the respective zone in the botanical extract via HPTLC-Vis densitometry. The HPTLC-EDA-Vis//1H qNMR-PULCON procedure for bioprofiling and quantification/identification/confirmation of bioactive compounds in botanical extracts is considered as straightforward, eco-friendly (only 16 mL solvent required), simple (NMR calibration used over weeks) and reliable new alternative to the status quo of bioactivity-guided fractionation.

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.

Evaluation of the potential aphrodisiac activity of sesquiterpenoids from roots of Ferula huber-morathii Peşmen in male rats

ETHNOPHARMACOLOGICAL RELEVANCE

Several species of Ferula L. genus have been used in traditional Turkish medicine as aphrodisiac to treat male sexual dysfunction. Especially, roots and oleo gum resin of F. elaeochytris Korovin, F. communis L., F. assa-foetida L. and F. gummosa Boiss. were claimed to be used for aphrodisiac activity, menstrual regulation and treatment of gastric pain in Anatolia. Ferula L. is represented by 23 taxa in Turkey, 13 of which are endemic species. F. huber-morathii Peşmen (FHM), an endemic plant, is popularly known as ''helizan, çağşır''.

AIM OF THE STUDY

This study aimed to isolate sesquiterpenoids from the roots of Ferula huber-morathii (FHM) and to confirm their aphrodisiac potential in male rats.

MATERIAL AND METHODS

In a preliminary experiment, the effects of aqueous (H₂O) and chloroform (CHCl₃) extracts of FHM were tested for their potential aphrodisiac activities in male rats. Then, sesquiterpene derivatives were isolated from the active chloroform extract of FHM roots (FHM-R) and characterized (TLC, 1D, 2D NMR, HR-MS and CD). Moreover, some of the isolates with adequate quantities were evaluated for their possible aphrodisiac effects on male rats. Single doses (10 mg/kg BW) of sildenafil citrate (SC, positive control), gummosin, mogoltavidin, deacetylkellerin, ferukrin acetate with kellerin, elaeochytrin-A and ferutinin were administered orally by gavages to male Wistar albino rats. Mount latency (ML), mount frequency (MF), intromission latency (IL), intromission frequency (IF), ejaculation latency (EL) and postejaculatory interval (PEI) were studied. In addition, copulatory efficiency (CE) and intercopulatory efficiency (ICE) were calculated.

RESULTS

The preliminary experiment revealed that the chloroform extract was the main source of the active compounds as it showed the higher aphrodisiac activity while the aqueous extract was found to be inactive. Eleven sesquiterpene derivatives, viz. gummosin, mogoltavidin, farnesiferol A, deacetylkellerin, ferukrin acetate, kellerin, teuclatriol, feruhermonin C, ferutinin, elaeochytrin A and teferidin, were isolated from the FHM-CHCl₃ extract. Oral administration of deacetylkellerin, elaeochytrin-A and ferutinin significantly increased MF and IF. The ML and IL were significantly reduced, and ejaculation latencies were prolonged. Administration of these sesquiterpenoids also reduced the PEI. The present results revealed that ferutinin was the most effective aphrodisiac compound compared to other sesquiterpenoids. The results of 10 mg/kg of ferutinin are comparable to SC, the positive control. The results revealed that gummosin, mogoltavidin and ferukrin acetate with kellerin did not significantly alter the aphrodisiac parameters.

CONCLUSIONS

This study has established that the CHCl₃ extract of FHM root contains sesquiterpene derivatives, especially coumarin ethers and benzoic esters. Findings of the present study demonstrate that the chloroform extract and some of the sesquiterpene derivatives significantly stimulates sexual behavior in male rats, thus suggesting that F. huber-morathii possesses an aphrodisiac activity.

TLC Bioautography on Screening of Bioactive Natural Products: An Update Review

Background:

TLC bioautography is a hyphenated technique combining planar chromatographic separation and in situ biological activity detection. This coupled method has been receiving much attention in screening bio-active natural products because of its properties of being simple, rapid, inexpensive, and effective.

Methods:

The recent progress in the development of method of TLC bioautography for detecting antimicrobial and enzyme inhibitory activities dating between 2012 and early 2018 has been reviewed. The applications of this method in biological screening of natural products were also presented.

Results:

Some anaerobic and microaerophilic bacteria and a causative bacterium of tuberculosis have been adopted to TLC direct bioautography. Seven types of enzymes including acetylcholinesterase, glucosidase, lipase, xanthine oxidase, tyrosinase, monoamine oxidase, and dipeptidyl peptidase IV have so far been adopted on TLC bioautography. Its new application in screening antiurolithiatic agents was included.

Conclusion:

The standard experimental procedures are required for TLC antioxidant and antimicrobial assays. Some new enzymes should be attempted and adopted on TLC bioautography. The existing TLC methods for enzyme inhibition need more application studies to assess their screening capacity in the discovery of active compounds. The GC-MS or LC-MS approaches have gradually been coupled to TLC bioautography for fast structural characterization of active compounds.

Pharmacological and Therapeutic Aspects of Plants from the Genus Ferula: A Comprehensive Review

Inspired by nature, humankind has been able to attain significant achievements in the drug and food industries. Particularly, medicinal plants are a rich source of medicinal, cosmetic, sanitary, and aromatic substances. Genus Ferula from the Apiaceae family is a plant genus that possesses over 170 species, which have been carefully documented with regard to their medicinal properties. Ferula spp. affects many body organs, and their respective functions, in humans, such as the immune system, gastrointestinal tract, genitourinary, endocrine, respiratory, cardiovascular, nervous system, bone (skeleton), and teeth. In spite of the benefits, ferulosis (Ferula toxicity) is an important aspect of Ferula consumption in humans and animals. Hemorrhagic problems and infertility are important signs of ferulosis. In this review, we have described all of the effects of the active ingredients of Ferula spp. and their mechanisms of actions, when known, based on an extensive literature review. Thus, our review opens a window of the benefits of Ferula as a phyto-pharmaceutical and its therapeutic applications in pharmacy, dentistry, and medicine.

Medicinal Plant Analysis: A Historical and Regional Discussion of Emergent Complex Techniques

The analysis of medicinal plants has had a long history, and especially with regard to assessing a plant's quality. The first techniques were organoleptic using the physical senses of taste, smell, and appearance. Then gradually these led on to more advanced instrumental techniques. Though different countries have their own traditional medicines China currently leads the way in terms of the number of publications focused on medicinal plant analysis and number of inclusions in their Pharmacopoeia. The monographs contained within these publications give directions on the type of analysis that should be performed, and for manufacturers, this typically means that they need access to more and more advanced instrumentation. We have seen developments in many areas of analytical analysis and particularly the development of chromatographic and spectroscopic methods and the hyphenation of these techniques. The ability to process data using multivariate analysis software has opened the door to metabolomics giving us greater capacity to understand the many variations of chemical compounds occurring within medicinal plants, allowing us to have greater certainty of not only the quality of the plants and medicines but also of their suitability for clinical research. Refinements in technology have resulted in the ability to analyze and categorize plants effectively and be able to detect contaminants and adulterants occurring at very low levels. However, advances in technology cannot provide us with all the answers we need in order to deliver high-quality herbal medicines and the more traditional techniques of assessing quality remain as important today.

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.

Quantitative inkjet application on self-printed, binder-free HPTLC layers for submicromole-scaled analytical 1H NMR spectroscopy

High-performance thin-layer chromatography (HPTLC) combined with ¹H nuclear magnetic resonance (NMR) spectroscopy has only been demonstrated over a small spectral range so far. The self-printing of chromatographic plates with a modified 3D slurry printer allowed the operator to influence the composition of the adsorbent slurry and thus the purity of the adsorbent layer. The combination of such self-printed, binder-free HPTLC plates with inkjet-driven sample application made possible submicromole-scaled analytical ¹H NMR spectroscopy. This was proven using pure HPTLC adsorbents. For comparison, commercial silica gel HPTLC plates were purified by pre-development with solvents for spectroscopy, whereas commercial silica gel HPTLC particles were self-printed on the glass plate after purification under solvent pressure in a recycled HPLC cartridge. Evaluating the signals from different treatments, seven background signals disappeared in the proton spectra and three were reduced to a minimum by use of pre-developed commercial HPTLC plates. In the case of the self-printed, binder-free HPTLC plates made of purified adsorbent, most of the spectral background signals were reduced to a minimum, thus these spectra showed the highest cleanness and most pure analyte proton spectra. For the first time, the full ¹H NMR spectroscopy range was made available after an HPTLC separation. This proof of principle opens the avenue for submicromole-scaled analytical ¹H NMR spectroscopy.

Guided isolation of new iridoid glucosides from Anarrhinum pubescens by high-performance thin-layer chromatography-acetylcholinesterase assay

Plants are an important source of natural iridoids. This study demonstrates for the first time the acetylcholinesterase (AChE) inhibitory activity of iridoids belonging to the class of antirrhinosides. As iridoids distinguish the chemical composition of most species of the Plantaginaceae family, the active AChE inhibitors were investigated in the hydro-alcoholic extract of Anarrhinum pubescens Fresen. High-performance thin-layer chromatography (HPTLC) in combination with the AChE inhibition assay is a time and material saving methodology, and thus was employed to directly point to the individual enzyme inhibitors occurring in the plant. The effect-directed screening successfully discovered three active metabolites. These were characterized as antirrhinoside-derived iridoids. Two of these are here reported as newly isolated natural compounds. Identification of the two new metabolites was based on analysis of their collected spectroscopic data (HRMS, 1D and 2D NMR). Their structures were elucidated to be 6-O-, 6'-O-di-trans-cinnamoyl-antirrhinoside (1) and 5-O-, 6-O-difoliamenthoyl-antirrhinoside (3), while the previously known compound 6-O-foliamenthoyl-(6'-O-cinnamoyl)-antirrhinoside (2) was assigned by extensive analysis of its HRMS and HRMS/MS data. The activity of the isolated compounds was referred to the known AChE inhibitor rivastigmine, i.e. their activity were calculated and expressed as values equivalently to rivastigmine. This neuroprotective potential of iridoids mediated through AChE inhibition promote them to compete as natural curatives for neurodegenerative disorders like Alzheimer's disease.

An improved method for a fast screening of α-glucosidase inhibitors in cherimoya fruit (Annona cherimola Mill.) applying effect-directed analysis via high-performance thin-layer chromatography-bioassay-mass spectrometry

α-glucosidase inhibitors (AGIs) are very attractive bioactive compounds due to their therapeutic profile that includes beneficial effects over glycemic control in type 2 diabetes mellitus and viral infections. Its detection and identification in plants and fruits has gained growing attention, and certainly requires efficient screening methodologies. The objective of the present work was to develop a fast methodology to detect and identify AGIs in cherimoya fruit (Annona cherimola Mill.) applying effect-directed analysis via high-performance thin layer-chromatography (HPTLC) linked with bioassay and mass spectrometry (MS). Both, HPTLC and bioassay conditions, were optimized accomplishing 50% and 83% reduction on enzyme concentration and incubation time respectively, compared to the original method. Additionally, the contrast between inhibitory bands and purple background was also enhanced by enzyme substrate impregnation on HPTLC plate. The optimized detection conditions established were the following: 5.0 U mL^-1 of enzyme solution, 1.0 mg mL^-1 of 2-naphthyl-α-D-glucopyranoside substrate, 1.0 mg mL^-1 of Fast Blue B salt solution and 10 min as incubation time. Applying this methodology, coupled to HPTLC-MS and ultra-high-performance liquid chromatography (UHPLC)-diode array detector (DAD)-MS/MS, it was possible for the first time to detect and identify three AGIs in cherimoya peel and seeds. Compounds were tentatively assigned as phenolamides (phenylethyl cinnamides): N-trans-feruloyl tyramine (m/z 314 [M+H]⁺; UV λ_max 293 and 316 nm), N-trans-p-coumaroyl tyramine (m/z 284 [M+H]⁺; UV λ_max 296 nm) and N-trans-feruloyl phenethylamine (m/z 298 [M+H]⁺; UV λ_max 288 nm). To the best of our knowledge, the presence of latter compound is reported for the first time in cherimoya.

Automated piezoelectric spraying of biological and enzymatic assays for effect-directed analysis of planar chromatograms

Bioanalytical questions are more and more solved by bioassays directly in situ the planar separation. If compared to chemical derivatization in situ, several reagent applications on the same chromatogram make the workflow for enzymatic and biological assays more complex. Hence, if compared to piezoelectric spraying of chemical derivatization reagents, an assay transfer to the piezoelectric spraying technique was much more challenging. Important aspects were investigated, i.e., plate pre-wetting, spraying nozzle type and applied volumes for microorganism suspension as well as enzyme and substrate-chromogenic solutions. Finally, with the newly developed piezoelectric spraying procedures for the application of biological (Aliivibrio fischeri) and enzymatic (acetyl- and butyrylcholinesterase) assays, several obstacles of the state-of-the-art automated immersion were avoided such as the (1) required high volumes of solutions, (2) tailing of highly water-soluble zones upon slow plate withdrawal, (3) zone distortion or shift observed after previous buffer salt applications or long/slow immersion times/speeds, (4) gradual inactivation of the enzyme solution along with its ongoing re-use, and (5) lack of covering the whole plate surface. The benchmarking of both techniques also showed that simplicity remains the key argument for immersion. As proof of concept, piezoelectrically sprayed autograms were compared with those of immersion, by taking the example of Peganum harmala (P. h.) seed extract. The plate background and thus homogeneity of the applied solutions were found to be almost comparable. Three bands among the pronounced fluorescent bands were responsible for the most antibacterial activity of P. h. seed extract in the A. fischeri bioassay and were also inhibiting the AChE. These AChE and three further BChE inhibitors were detected, whereby the AChE inhibition was twice as strong as the BChE inhibition. By their in situ HRMS spectra, the active zones in the P. h. seed extract were assigned to be the AChE-inhibiting β-carboline alkaloids, harmine, harmaline and ruine, as well as the BChE-inhibiting quinazoline alkaloids, vasicine and deoxyvasicine, and the β-carboline alkaloid harmol. For the first time, the found inhibitors were calculated equivalently to the well-known ChE-inhibitor physostigmine, and thus, piezoelectric spraying was proven to be suited for quantifications.

HPTLC-FLD-SERS as a facile and reliable screening tool: Exemplarily shown with tyramine in cheese

The serious cytotoxicity of tyramine attracted marked attention as it induced necrosis of human intestinal cells. This paper presented a novel and facile high performance thin-layer chromatography (HPTLC) method tailored for screening tyramine in cheese. Separation was performed on glass backed silica gel plates, using methanol/ethyl acetate/ ammonia (6/4/1 v/v/v) as the mobile phase. Special efforts were focused on optimizing conditions (substrate preparation, laser wavelength, salt types and concentrations) of surface enhanced Raman spectroscopy (SERS) measurements directly on plates after derivatization, which enabled molecule-specific identification of targeted bands. In parallel, fluorescent densitometry (FLD) scanning at 380</400 nm offered satisfactory quantitative performances (LOD 9 ng/zone, LOQ 17 ng/zone, linearity 0.9996 and %RSD 6.7). Including a quick extraction/cleanup step, the established method was successfully validated with different cheese samples, both qualitatively (straightforward confirmation) and quantitatively (recovery rates from 83.7 to 108.5%). Beyond this application, HPTLC-FLD-SERS provided a new horizon in fast and reliable screening of sophisticated samples like food and herb drugs, striking an excellent balance between specificity, sensitivity and simplicity.

Broad range chemical profiling of natural deep eutectic solvent extracts using a high performance thin layer chromatography-based method

Natural deep eutectic solvents (NADES) made mainly with abundant primary metabolites are being increasingly applied in green chemistry. The advantages of NADES as green solvents have led to their use in novel green products for the food, cosmetics and pharma markets. However, one of the main difficulties encountered in the development of novel products and their quality control arises from their low vapour pressure and high viscosity. These features create the need for the development of new analytical methods suited to this type of sample. In this study, such a method was developed and applied to analyse the efficiency of a diverse set of NADES for the extraction of compounds of interest from two model plants, Ginkgo biloba and Panax ginseng. The method uses high-performance thin-layer chromatography (HPTLC) coupled with multivariate data analysis (MVDA). It was successfully applied to the comparative quali- and quantitative analysis of very chemically diverse metabolites (e.g., phenolics, terpenoids, phenolic acids and saponins) that are present in the extracts obtained from the plants using six different NADES. The composition of each NADES was a combination of two or three compounds mixed in defined molar ratios; malic acid-choline chloride (1:1), malic acid-glucose (1:1), choline chloride-glucose (5:2), malic acid-proline (1:1), glucose-fructose-sucrose (1:1:1) and glycerol-proline-sucrose (9:4:1). Of these mixtures, malic acid-choline chloride (1:1) and glycerol-proline-sucrose (1:1:1) for G. biloba leaves, and malic acid-choline chloride (1:1) and malic acid-glucose (1:1) for P. ginseng leaves and stems showed the highest yields of the target compounds. Interestingly, none of the NADES extracted ginkgolic acids as much as the conventional organic solvents. As these compounds are considered to be toxic, the fact that these NADES produce virtually ginkgolic acid-free extracts is extremely useful. The effect of adding different volumes of water to the most efficient NADES was also evaluated and the results revealed that there is a great influence exerted by the water content, with maximum yields of ginkgolides, phenolics and ginsenosides being obtained with approximately 20% water (w/w).

Phytochemical study of Illicium angustisepalum and its biological activities

Sixteen compounds, including two new natural products (1 and 2), were obtained from the twigs of Illicium angustisepalum. The structures were elucidated based on NMR, MS, IR data and optical rotation values. Compounds 4, 5, 6 and 8 displayed moderate antibacterial activities against clinical isolates; compounds 4, 5, 8, 9 and 15 protected neural cells against oxidative stress; and compounds 10 and 14 exhibited anti-acetylcholinesterase activity.

Direct Coupling of HPTLC with MALDI-TOF MS for Qualitative Detection of Flavonoids on Phytochemical Fingerprints

INTRODUCTION

Thin layer chromatographic fingerprints of plant raw materials and extracts for food and pharma applications often focus on phenol carbonic acids and flavonoids. The visual detection and comparison of Rf values of applied reference substances only renders limited phytochemical information. Recently, direct coupling of TLC with MALDI-TOF MS has been successfully applied for analysis of biologically relevant compounds such as lipids. The mass analysis of low molecular weight TLC or HPTLC fingerprints of flavonoids has, to our knowledge, not yet been investigated.

OBJECTIVES

In this study, the feasibility of direct coupling of HPTLC with UV-MALDI-TOF MS for determination of molecular mass of the ubiquitously present flavonol glycoside, rutin, and flavone glycoside, luteolin-7-O-glucoside, as well as their corresponding aglycones, quercetin and luteolin, is demonstrated.

METHODOLOGY

HPTLC plate suitable for combination with a MALDI MS adapter was used for chromatographic separation of compounds of interest. After separation, the plate was sprayed with 2,5 dihydroxybenzoic acid as a MALDI matrix using an automated spraying device. After drying, the developed chromatograms were scanned by UV-MALDI-TOF MS in positive mode with a spatial resolution of 0.2 mm.

RESULTS

All compounds studied were distinctly detected in MALDI-TOF mass spectra. This is particularly pertinent for the co-eluted aglycones luteolin and quercetin, which could not have been distinguished by the common visual HPTLC derivatisation and evaluation.

CONCLUSION

This study demonstrates the potential of MALDI-TOF MS for the analysis of low molecular weight fingerprints of flavonoids directly from their HPTLC chromatogram. Copyright © 2016 John Wiley & Sons, Ltd.

Production of cyathane type secondary metabolites by submerged cultures of Hericium erinaceus and evaluation of their antibacterial activity by direct bioautography

Background

Fungi of the phylum Basidiomycota are well-known to form a broad spectrum of biologically active secondary metabolites, especially low molecular weight compounds such as terpenoids. Hericium erinaceus produces various cyathane type diterpenoids including erinacines. However, no quantitative data and production kinetics have been reported on the biosynthesis of the erinacines C and P in submerged cultures. In the present study, the production of erinacine C was optimized, and the product formation kinetics as well as the antimicrobial activity were studied by high-performance liquid chromatography (HPLC), high-performance thin-layer chromatography (HPTLC) and direct bioautography.

Results

Oatmeal and Edamin^® K were identified to be crucial media components for an efficient production of erinacine C. The highest concentrations of erinacine C were obtained in the optimized culture medium on the 9^th culture day (approximately 260 mg L⁻¹). The production of erinacine P was strongly time dependent. The maximum concentration of erinacine P of 184 mg L⁻¹ was observed on the third culture day. Afterwards, the concentrations of erinacine P decreased while the concentrations of erinacine C steadily increased. Comparable results were obtained by HPTLC with UV detection and HPLC with diode-array detection (DAD) analyses. Direct bioautography allowed for an additional analysis of the antimicrobial activity of the secondary metabolites.

Conclusions

The C and N sources oatmeal and Edamin^® K induced the formation of erinacine C. Detailed product formation kinetics of the erinacines C and P have been reported for the first time. HPTLC combined with the Aliivibrio fischeri bioassay allowed for an instant detection of cyathane diterpenoids in crude extracts and for an evaluation of the antimicrobial activity of the secondary metabolites directly on the plate.

Electronic supplementary material

The online version of this article (doi:10.1186/s40694-015-0018-y) contains supplementary material, which is available to authorized users.

Thin Layer Chromatography-Autography-High Resolution Mass Spectrometry Analysis: Accelerating the Identification of Acetylcholinesterase Inhibitors

INTRODUCTION

The prevailing treatment for Alzheimer's disease is the use of acetylcholinesterase (AChE) inhibitors. Natural extracts are the principal source of AChE's inhibitors. However, their chemical complexity demands for simple, selective and rapid assays.

OBJECTIVE

To develop a strategy for identification of AChE inhibitors present in mixtures employing high resolution mass spectrometry (HRMS) and thin layer chromatography (TLC)-biological staining.

METHODOLOGY

The strategy uses an autographic assay based on the α-naphthyl acetate - fast blue B system for the detection of AChE activity. The immobilisation of AChE in agar allowed the extraction of the compounds for analysis by HRMS. Three TLC experiments employing different solvent systems were used in parallel and the mass spectra of the compounds extracted from the inhibition halos, were compared. The analysis was performed under MatLab environment.

RESULTS

The strategy was used to detect the presence of physostigmine in an extract of Brassica rapa L. spiked with the inhibitor. Similarly, caffeine was straightforwardly spotted as responsible for the inhibitory properties of an extract of Ilex paraguariensis Saint-Hilaire. Comparison of the HRMS profiles lead to the facile identification of the [M+H](+) and [M+Na](+) of the compounds responsible for the inhibition.

CONCLUSION

The proposed methodology, coupling TLC-AChE autography-HRMS, illustrates the feasibility of assigning molecular formulas of active compounds present in complex mixtures directly from autography. The new AChE agar-immobilised assay presented a more homogenous colour and a better definition than direct spraying methods, reducing the cost of the assay and improving its sensitivity.