Recent applications of liquid chromatography-mass spectrometry in natural products bioanalysis

High-speed countercurrent chromatography with offline detection by electrospray mass spectrometry and nuclear magnetic resonance detection as a tool to resolve complex mixtures: A practical approach using Coffea arabica leaf extract

INTRODUCTION

Many secondary metabolites isolated from plants have been described in the literature owing to their important biological properties and possible pharmacological applications. However, the identification of compounds present in complex plant extracts has remained a great scientific challenge, is often laborious, and requires a long research time with high financial cost.

OBJECTIVES

The aim of this study was to develop a method that allows the identification of secondary metabolites in plant extracts with a high degree of confidence in a short period of time.

MATERIAL AND METHODS

In this study, an ethanolic extract of Coffea arabica leaves was used to validate the proposed method. Countercurrent chromatography was chosen as the initial step for extraction fractionation using gradient elution. Resulting fractions presented a variation of compounds concentrations, allowing for statistical total correlation spectroscopy (STOCSY) calculations between liquid chromatography coupled with high-resolution tandem mass spectrometry (LC-HRMS/MS) and NMR across fractions.

RESULTS

The proposed method allowed the identification of 57 compounds. Of the annotated compounds, 20 were previously described in the literature for the species and 37 were reported for the first time. Among the inedited compounds, we identified flavonoids, alkaloids, phenolic acids, coumarins, and terpenes.

CONCLUSION

The proposed method presents itself as a valid alternative for the study of complex extracts in an effective, fast, and reliable way that can be reproduced in the study of other extracts.

Paenibacillus polymyxa YLC1: a promising antagonistic strain for biocontrol of Pseudomonas syringae pv. actinidiae, causing kiwifruit bacterial canker

BACKGROUND

Kiwifruit bacterial canker (KBC) caused by Pseudomonas syringae pv. actinidiae (Psa) is the main limiting factor in the kiwifruit industry. This study aimed to identify bacterial strains with antagonistic activity against Psa, analyze antagonistically active substances and provide a new basis for the biological control of KBC.

RESULTS

A total of 142 microorganisms were isolated from the rhizosphere soil of asymptomatic kiwifruit. Among them, an antagonistic bacterial strain was identified as Paenibacillus polymyxa YLC1 by 16S rRNA sequencing. KBC control by strain YLC1 (85.4%) was comparable to copper hydroxide treatment (81.8%) under laboratory conditions and field testing. Active substances of strain YLC1 were identified by genetic sequence analysis using antiSMASH. Six biosynthetic active compound gene clusters were identified as encoding ester peptide synthesis, such as polymyxins. An active fraction was purified and identified as polymyxin B1 using chromatography, hydrogen nuclear magnetic resonance (NMR), and liquid chromatography-mass spectrometry. In addition, polymyxin B1 also was found significantly to suppress the expression of T3SS-related genes, but did not affect the growth of Psa at low concentrations.

CONCLUSION

In this study, a biocontrol strain P. polymyxa YLC1 obtained from kiwifruit rhizosphere soil exhibited excellent control effects on KBC in vitro and in field tests. Its active compound was identified as polymyxin B1, which inhibits a variety of pathogenic bacteria. We conclude that P. polymyxa YLC1 is a biocontrol strain with excellent prospects for development and application. © 2023 Society of Chemical Industry.

Extraction and characterization of phenolic compounds and their potential antioxidant activities

For thousands of years, plant has been widely applied in the medical area and is an important part of human diet. A high content of nutrients could be found in all kinds of plants, and the most outstanding group of nutrients that attracts scientists' attention is the high level of phenolic compounds. Due to the relationship between high phenolic compound content and high antioxidant capacity, plant extracts are expected to become a potential treatment for oxidation stress diseases including diabetes and cancer. However, according to the instability of phenolic compounds to light and oxygen, there are certain difficulties in the extraction of such compounds. But after many years of development, the extraction technology of phenolic compounds has been quite stable, and the only problem is how to obtain high-quality extracts with high efficiency. To further enhance the value of plant extracts, concentration and separation methods are often applied, and when detailed analysis is required, characterization methods including HPLC and LC/GC-MS will be applied to evaluate the number and type of phenolic compounds. A series of antioxidant assays are widely performed in numerous studies to test the antioxidant capacity of the plant extracts, which is also an important basis for evaluating value of extracts. This paper intends to provide a view of a variety of methods used in plants' phenolic compound extraction, separation, and characterization. Furthermore, this review presents the advantages and disadvantages of techniques involved in phenolic compound research and provides selected representative bibliographic examples.

Accurate Identification of Bioactive Meliaceae Limonoids by UHPLC-MS/MS Based Structure-Fragment Relationships (SFRs)

Limonoids are bioactive plant specialized metabolites found in the Meliaceae family. The basic limonoids, i.e., azadiradione, epoxyazadiradione, and gedunin have been exploited for various bioactivities and therefore are the potential drug leads for tomorrow. However, their low abundance, structural similarity, and lack of adequate mass fragmentation data have hampered their accurate identification and quantification from various sources. In the present study, basic limonoids such as azadirone, azadiradione, epoxyazadiradione, and gedunin isolated from Neem were utilized for the synthesis of their derivatives and isotopologs. A total of 30 one compounds were used in this study among which five were isolated, two were biotransformed, and 24 were synthesized. Among the synthesized compounds nine are novel compounds including six deuterated analogs/isotopologs which are (1,3-²H)-1,2-dihydro-3β-hydroxyazadiradione (9), (1,3,16-²H)-1,2-dihydro-3β-16β-dihydroxyazadiradione (10), 3β-hydroxyazadiradione (11), 3β-16β-dihydroxyazadiradione (12), (3-²H)-3β-hydroxyazadiradione (13), (3,16-²H)-3β-16β-dihydroxyazadiradione (14), (1,3,7-²H)-1,2-dihydro-3β-hydroxy-7-deacetylazadiradione (15), 1,2,20,21,22,23-hexahydroazadiradione (17), and (1,3-²H)-1,2-dihydro-3β-hydroxygedunin (29). These limonoids along with their semisynthesized derivatives were subjected to ultra high performance liquid chromatography mass spectrometry (UHPLC-MS/MS) and the fragmentation pathway was established based on structure-fragment relationships (SFRs), utilizing high resolution MS/MS data. We have developed a most reliable and easily reproducible protocol describing in depth analysis of SFRs based on the structural modifications and synthesis of isotopologs. Also, the MS/MS fragment library of these basic limonoids generated in this study acts as a fingerprint for accurate identification and quantification of limonoids by MS/MS analysis in various plant tissue extracts, phytopharmaceutical formulations and biological samples.

Comprehensive evaluation on anti-inflammatory and anti-angiogenic activities in vitro of fourteen flavonoids from Daphne Genkwa based on the combination of efficacy coefficient method and principal component analysis

ETHNOPHARMACOLOGICAL RELEVANCE

Genkwa flos, as a traditional herb, is the dried flower buds of Daphne genkwa Sieb.et Zucc. It is used in traditional medicine for the treatment of cough, sore throats, edema.

AIM OF THE STUDY

The study aimed to explore a new mathematical method for multivariate evaluation, investigate the anti-inflammatory and anti-angiogenic activities of flavonoids in Daphne Genkwa under ex vivo conditions.

MATERIALS AND METHODS

The flavonoids monomers in Daphne Genkwa were separated by preparative liquid chromatography and identified by HPLC-ESI-ITMS. An in vitro inflammatory model of macrophage RAW264.7 induced by LPS and an angiogenesis model of human umbilical vein endothelial cells induced by TNF-α were established. Flavonoids were extracted and prepared for intervention to detect the amount of secretion after drug intervention to reflect the anti-inflammatory and anti-angiogenic activities of each component. In addition, a new mathematical method, which combined principal component analysis and efficacy coefficient method, was adopted in pharmacodynamic evaluation.

RESULTS

Fourteen flavonoids monomers were separated by preparative liquid chromatography and identified by HPLC-ESI-ITMS including H1 (hydroxygenkwanin-5-O-β-D-glucoside), H2 (apigenin-7-O-β-D-glucoside), H3 (kaempferol-3-O-β-D-glucoside), H4 (hydroxygenkwanin-5-O-β-D-primeveroside), H5 (apigenin-5-O-β-D-primeveroside), H6 (apigenin-7-O-β-D-glucuronide), H7 (luteolin-5-O-β-D-glucopyranoside), H8 (genkwain-5-O-β-D- glucoside), H9 (luteolin), H10 (Daphnodorin G), H11 (tiliroside), H12 (apigenin), H13 (3'- hydroxygenkwain) and H14 (genkwanin). We found that most of flavonoids down-regulated VCAM and MMP-3, while H1, H8, H9, H14 reduced VEGF and ICAM was only decreased by H14.

CONCLUSION

Genkwanin may be the most active anti-rheumatoid arthritis flavonoids in Daphne genkwa. Meanwhile, the new mathematical method used in the study provided a new direction for solving the problem of multi-index pharmacodynamic evaluation.

Recent applications of ion mobility spectrometry in natural product research

Ion mobility spectrometry (IMS) is a rapid separation technique capable of extracting complementary structural information to chromatography and mass spectrometry (MS). IMS, especially in combination with MS, has experienced inordinate growth in recent years as an analytical technique, and elicited intense interest in many research fields. In natural product analysis, IMS shows promise as an additional tool to enhance the performance of analytical methods used to identify promising drug candidates. Potential benefits of the incorporation of IMS into analytical workflows currently used in natural product analysis include the discrimination of structurally similar secondary metabolites, improving the quality of mass spectral data, and the use of mobility-derived collision cross-section (CCS) values as an additional identification criterion in targeted and untargeted analyses. This review aims to provide an overview of the application of IMS to natural product analysis over the last six years. Instrumental aspects and the fundamental background of IMS will be briefly covered, and recent applications of the technique for natural product analysis will be discussed to demonstrate the utility of the technique in this field.

Compensate for or Minimize Matrix Effects? Strategies for Overcoming Matrix Effects in Liquid Chromatography-Mass Spectrometry Technique: A Tutorial Review

In recent decades, mass spectrometry techniques, particularly when combined with separation methods such as high-performance liquid chromatography, have become increasingly important in pharmaceutical, bio-analytical, environmental, and food science applications because they afford high selectivity and sensitivity. However, mass spectrometry has limitations due to the matrix effects (ME), which can be particularly marked in complex mixes, when the analyte co-elutes together with other molecules, altering analysis results quantitatively. This may be detrimental during method validation, negatively affecting reproducibility, linearity, selectivity, accuracy, and sensitivity. Starting from literature and own experience, this review intends to provide a simple guideline for selecting the best operative conditions to overcome matrix effects in LC-MS techniques, to obtain the best result in the shortest time. The proposed methodology can be of benefit in different sectors, such as pharmaceutical, bio-analytical, environmental, and food sciences. Depending on the required sensitivity, analysts may minimize or compensate for ME. When sensitivity is crucial, analysis must try to minimize ME by adjusting MS parameters, chromatographic conditions, or optimizing clean-up. On the contrary, to compensate for ME analysts should have recourse to calibration approaches depending on the availability of blank matrix. When blank matrices are available, calibration can occur through isotope labeled internal standards and matrix matched calibration standards; conversely, when blank matrices are not available, calibration can be performed through isotope labeled internal standards, background subtraction, or surrogate matrices. In any case, an adjusting of MS parameters, chromatographic conditions, or a clean-up are necessary.

Recent (2000-2015) developments in the analysis of minor unknown natural products based on characteristic fragment information using LC-MS

Liquid chromatography-Mass Spectrometry (LC-MS) has been widely used in natural product analysis. Global detection and identification of nontargeted components are desirable in natural product research, for example, in quality control of Chinese herbal medicine. Nontargeted components analysis continues to expand to exciting life science application domains such as metabonomics. With this background, the present review summarizes recent developments in the analysis of minor unknown natural products using LC-MS and mainly focuses on the determination of the molecular formulae, selection of precursor ions, and characteristic fragmentation patterns of the known compounds. This review consists of three parts. Firstly, the methods used to determine unique molecular formula of unknown compounds such as accurate mass measurements, MSⁿ spectra, or relative isotopic abundance information, are introduced. Secondly, the methods improving signal-to-noise ratio of MS/MS spectra by manual-MS/MS or workflow targeting-only signals were elucidated; pure precursor ions can be selected by changing the precursor ion isolated window. Lastly, characteristic fragmentation patterns such as Retro-Diels-Alder (RDA), McLafferty rearrangements, "internal residue loss," and so on, occurring in the molecular ions of natural products are summarized. Classical application of characteristic fragmentation patterns in identifying unknown compounds in extracts and relevant fragmentation mechanisms are presented (RDA reactions occurring readily in the molecular ions of flavanones or isoflavanones, McLafferty-type fragmentation reactions of some natural products such as epipolythiodioxopiperazines; fragmentation by "internal residue loss" possibly involving ion-neutral complex intermediates). © 2016 Wiley Periodicals, Inc. Mass Spec Rev 37:202-216, 2018.

Compounds isolated from Eriobotrya deflexa leaves protect against ultraviolet radiation B-induced photoaging in human fibroblasts

Ultraviolet (UV) irradiation leads to skin photoaging because of the upregulation of matrix metalloproteinase (MMP)-1 and downregulation of type I collagen and tissue inhibitor of metalloproteinase (TIMP)-1. Eriobotrya deflexa (Hemsl.) Nakai (Rosaceae) is a flowering plant endemic to Taiwan, and its leaves have been used as an expectorant and in antitussive folk remedy. Our previous studies have demonstrated that an E. deflexa leaf extract functions as a free radical scavenger. The current evaluated the antiphotoaging effect of partitioned fractions and specific compounds from the leaves of E. deflexa by using bioguided isolation, compound identification, and biological activity testing with UVB-irradiated human fibroblasts (WS-1 cells). E. deflexa leaves were extracted with 95% ethanol and then partitioned using a sequential treatment of n-hexane, ethyl acetate, and n-butanol (n-BuOH). The bioactive n-BuOH fraction was used for isolation and purification through chromatography. The compounds were identified by analyzing their physical and spectroscopic properties. We identified eight compounds from this fraction; of these compounds, 3-O-α-l-rhamnopyranosyl-(1‴→6″)-β-d-galactopyranoside (1), hyperin (2), afzelin (5), and cryptochlorogenic acid methyl ester (7) were isolated from E. deflexa for the first time, and they exhibited MMP-1 inhibition activity. The IC₅₀ values were 96.5, 89.5, 93.4, and 92.8μM for 1, 2, 5, and 7, respectively. These compounds also enhanced the expression of procollagen type I, and TIMP-1 and hyperin (2) were found to be most effective with IC₅₀ values of 56.7 and 70.3μM, respectively. Hyperin (2) could reduce intracellular reactive oxygen species production in UVB-irradiated WS-1 cells, with the corresponding IC₅₀ value being 80.7μM. Liquid chromatography triple-quadrupole mass spectrometry was used for the quantitative and chemical fingerprint analysis of active compounds. Quercetin 3-O-α-l-rhamnopyranosyl-(1‴→6″)-β-d-galactopyranoside (1), hyperin (2), afzelin (5), and cryptochlorogenic acid methyl ester (7) constituted 24.2±3.9, 5.5±1.0, 3.4±0.3, and 67.1±8.1mg/g of dry weight in the active n-BuOH fraction, respectively. Our results demonstrate that the extract and the isolated active compounds from E. deflexa leaves possess the potential for protection against skin photoaging.

Characterization and stability studies of bioactive compounds and food matrices as evidence in support of health claims

The characterization and stability evaluation of food and food constituents (chemical active ingredient/microorganism) for which nutrition or health claims want to be requested are essential for the success of an application to EFSA. This work reviews the requirements that must be fulfilled for a full characterization of the active substance, comprising origin, elaboration, or extraction method, and chemical/microbiological composition, using validated analytical methods. The review focuses not only on establishing the specifications of the final active ingredient or food but also on ensuring homogeneity between batches. In addition, the article discusses the methodologies and conditions of the stability studies that need to be performed on food and food constituents to verify that the relevant compounds--chemical and microbiological active ingredients--will get to the consumer in the intended state and concentration to accomplish the claimed health effect over shelf life.

Tailoring and recycling of deep eutectic solvents as sustainable and efficient extraction media

The present study demonstrates that deep eutectic solvents (DESs) with the highest extractability can be designed by combining effective DES components from screening diverse DESs. The extraction of polar ginseng saponins from white ginseng was used as a way to demonstrate the tuneability as well as recyclability of DESs. A newly designed ternary DES (GPS-5) composed of glycerol, l-proline, and sucrose at 9:4:1 was used as a sustainable and efficient extraction medium. Based on the anti-tumor activity on HCT-116 cancer cells, it was confirmed that GPS-5 was merely an extraction solvent with no influence of the bioactivity of the ginsenosides extracted. Excellent recovery of the extracted saponins was easily achieved through solid-phase extraction (SPE). Recycling of the DES was accomplished by simple freeze-drying of the washed solutions from the SPE. The extraction efficiencies of the DESs recycled once, twice, and thrice were 92%, 85%, and 83% of that of the freshly synthesized solvent.

Rapid Fingerprint Analysis of Plant Extracts for Ellagitannins, Gallic Acid, and Quinic Acid Derivatives and Quercetin-, Kaempferol- and Myricetin-Based Flavonol Glycosides by UPLC-QqQ-MS/MS

This paper describes the development of a rapid method with ultraperformance liquid chromatography-triple-quadrupole mass spectrometry that can specifically measure group-specific fingerprints from plant extracts for the following polyphenol groups: (1) ellagitannins, (2) gallic acid derivatives, (3) quinic acid derivatives, (4) quercetin-based flavonol glycosides, (5) kaempferol-based flavonol glycosides, and (6) myricetin-based flavonol glycosides. In addition, the method records simultaneously diode array and full scan mass spectrometry data that can be used to later characterize and quantify the main individual polyphenols if necessary. All of this is achieved within the 10 min period of analysis, which makes the presented method a significant addition to the chemistry tools currently available for the rapid analysis of complex polyphenol mixtures from plant extracts.

Metabolite profile of marine-derived endophytic Streptomyces sundarbansensis WR1L1S8 by liquid chromatography-mass spectrometry and evaluation of culture conditions on antibacterial activity and mycelial growth

AIMS

This study was designed to investigate whether culture conditions (media, seawater concentration and pH) could lead Streptomyces sundarbansensis strain (isolated from marine brown algae Fucus sp. collected from Algerian coastline) to produce bioactive secondary metabolites. The most favourable condition for the production of anti-MRSA compound 1 [2-hydroxy-5-((6-hydroxy-4-oxo-4H-pyran-2-yl)methyl)-2-propylchroman-4-one] was determined.

METHODS AND RESULTS

The profile of metabolites present in the crude extracts was carried out by HPLC analysis equipped with a diode array detector evaporative light scattering detection (DAD-ELSD) or online coupled to electrospray ionization-mass spectrometry (ESI-MS). Compound 1 was the most abundant secondary metabolite by culturing the strains on starch casein agar (SCA) medium in freshwater or 50% seawater at pH 7 or 9 using agar-state fermentation method.

CONCLUSIONS

The study has shown the efficiency of HPLC/ESI-MS technique in the analysis of polyketides produced by the strain under investigation. It was possible to establish the best culture conditions for obtaining the most bioactive compound 1, previously isolated by the same strain.

SIGNIFICANCE AND IMPACT OF THE STUDY

Marine algae-actinobacteria associations are a particularly promising renewable system for the production of new antibacterial metabolites. Based on the promising bioactivity of the chemically characterized compound 1, the analytical methodology here applied has resulted as an effective approach for establishing its optimized production.

Characterization of flavonoids and phenolic acids in Myrcia bella Cambess. using FIA-ESI-IT-MS(n) and HPLC-PAD-ESI-IT-MS combined with NMR

The leaves of Myrcia DC. ex Guill species are used in traditional medicine and are also exploited commercially as herbal drugs for the treatment of diabetes mellitus. The present work aimed to assess the qualitative and quantitative profiles of M. bella hydroalcoholic extract, due to these uses, since the existing legislation in Brazil determines that a standard method must be developed in order to be used for quality control of raw plant materials. The current study identified eleven known flavonoid-O-glycosides and six acylated flavonoid derivatives of myricetin and quercetin, together with two kaempferol glycosides and phenolic acids such as caffeic acid, ethil galate, gallic acid and quinic acid. In total, 24 constituents were characterized, by means of extensive preparative chromatographic analyses, along with MS and NMR techniques. An HPLC-PAD-ESI-IT-MS and FIA-ESI-IT-MS(n) method were developed for rapid identification of acylated flavonoids, flavonoid-O-glycosides derivatives of myricetin and quercetin and phenolic acids in the hydroalcoholic M. bella leaves extract. The FIA-ESI-IT-MS techinique is a powerful tool for direct and rapid identification of the constituents after isolation and NMR characterization. Thus, it could be used as an initial method for identification of authentic samples concerning quality control of Myrcia spp extracts.

HPLC-ESI-QTOF-MS as a powerful analytical tool for characterising phenolic compounds in olive-leaf extracts

INTRODUCTION

Olea europaea L. leaves may be considered a cheap, easily available natural source of phenolic compounds. In a previous study we evaluated the possibility of obtaining bioactive phenolic compounds from olive leaves by pressurised liquid extraction (PLE) for their use as natural anti-oxidants. The alimentary use of these kinds of extract makes comprehensive knowledge of their composition essential.

OBJECTIVE

To undertake a comprehensive characterisation of two olive-leaf extracts obtained by PLE using high-performance liquid chromatography coupled to electrospray ionisation and quadrupole time-of-flight mass spectrometry (HPLC-ESI-QTOF-MS).

METHOD

Olive leaves were extracted by PLE using ethanol and water as extraction solvents at 150°C and 200°C respectively. Separation was carried out in a HPLC system equipped with a C₁₈-column working in a gradient elution programme coupled to ESI-QTOF-MS operating in negative ion mode.

RESULTS

This analytical platform was able to detect 48 compounds and tentatively identify 31 different phenolic compounds in these extracts, including secoiridoids, simple phenols, flavonoids, cinnamic-acid derivatives and benzoic acids. Lucidumoside C was also identified for the first time in olive leaves.

CONCLUSION

The coupling of HPLC-ESI-QTOF-MS led to the in-depth characterisation of the olive-leaf extracts on the basis of mass accuracy, true isotopic pattern and tandem mass spectrometry (MS/MS) spectra. We may conclude therefore that this analytical tool is very valuable in the study of phenolic compounds in plant matrices.

Isolation and characterization of bioactive compounds from plant resources: the role of analysis in the ethnopharmacological approach

The phytochemical research based on ethnopharmacology is considered an effective approach in the discovery of novel chemicals entities with potential as drug leads. Plants/plant extracts/decoctions, used by folklore traditions for treating several diseases, represent a source of chemical entities but no information are available on their nature. Starting from this viewpoint, the aim of this review is to address natural-products chemists to the choice of the best methodologies, which include the combination of extraction/sample preparation tools and analytical techniques, for isolating and characterizing bioactive secondary metabolites from plants, as potential lead compounds in the drug discovery process. The work is distributed according to the different steps involved in the ethnopharmacological approach (extraction, sample preparation, biological screening, etc.), discussing the analytical techniques employed for the isolation and identification of compound/s responsible for the biological activity claimed in the traditional use (separation, spectroscopic, hyphenated techniques, etc.). Particular emphasis will be on herbal medicines applications and developments achieved from 2010 up to date.

Rapid Identification of unstable acyl glucoside flavonoids of Oxytropis racemosa Turcz by high-performance liquid chromatography-diode array detection-electrospray ionisation/multi-stage mass spectrometry

INTRODUCTION

Oxytropis racemosa Turcz is an important minority medicine that is used mainly to improve children's indigestion, especially in inner Mongolia and Tibet. Previous studies indicated that the characteristic constituents of this plant are acylated flavonoids.

OBJECTIVE

Rapidly identify the characteristic chemical constituents of O. racemosa by high-performance liquid chromatography-diode array detection-electrospray ionisation/multi-stage mass spectrometry (HPLC-DAD-ESI/MS(n) ) and suggest a useful method to control the quality of this medicinal plant.

METHODS

In the HPLC fingerprint, 32 flavonoids were tentatively identified by a detailed analysis of their mass spectra, UV spectra and retention times. Furthermore, 13 flavonoids were confirmed by comparison with previously isolated compounds obtained from O. racemosa.

RESULTS

In total, 32 flavonoids, including 13 flavonoids with 3-hydroxy-3-methylglutaric acid (HMG) moieties and four flavonoids with 3-malonyl moieties, were identified in the extract of O. racemosa. Among the compounds identified, 10 were characterised as new compounds for their particular acylated sugar moieties.

CONCLUSIONS

The method described is effective for obtaining a comprehensive phytochemical profile of plants containing unstable acylated flavonoids. The method is also useful for constructing the chromatographic fingerprint of the minority medicine -O. racemosa Turcz for quality control.

Bioassay-guided isolation of DPP-4 inhibitory fractions from extracts of submerged cultured of Inonotus obliquus

Inonotus obliquus is a medicinal mushroom used in Russian and Eastern European folk medicine for the treatment of gastrointestinal cancer, cardiovascular disease and diabetes. Previous studies in our laboratory have demonstrated that the mycelium powders of I. obliquus possess significant antihyperglycemic effects in a mouse model of diabetic disease induced by alloxan. However, the active ingredients of mycelium powders responsible for the diabetes activity have not been identified. This study aims to identify the active ingredients of I. obliquus mycelium powders by a bioassay-guided fractionation approach and explore the mechanism of action of these active ingredients by using a well-established DPP-4 (an important enzyme as a new therapeutic target for diabetes) inhibitory assay model. The results showed the chloroform extract of mycelium was potential inhibitory against DPP-4. Bioactivity guided fractionation led to the identification of 19 compounds using UPLC-Q-TOF-MS. Molecular docking between the compounds and DPP-4 revealed that compounds 5, 8, 9, 14, 15 may be the active components responsible for the DPP-4 inhibitory activity.

HybridSPE: A novel technique to reduce phospholipid-based matrix effect in LC-ESI-MS Bioanalysis

When complex biological materials are analyzed without an adequate sample preparation technique, MS signal and response undergo significant alteration and result in poor quantification and assay. This problem generally takes place due to the presence of several endogenous materials component in samples. One of the major causes of ion suppression in bioanalysis is the presence of phospholipids during LC-MS analysis. The phospholipid-based matrix effect was investigated with a commercially available electro spray ionization (ESI) source coupled with a triple quadrupole mass spectrometer. HybridSPE dramatically reduced the levels of residual phospholipids in biological samples, leading to significant reduction in matrix effects. This new procedure that combines the simplicity of precipitation with the selectivity of SPE allows obtaining much cleaner extracts than with conventional procedures. HybridSPE-precipitation procedure provides significant improvement in bioanalysis and a practical and fast way to ensure the avoidance of phospholipids-based matrix effects. The present review outlines the HybridSPE technique to minimize phospholipids-based matrix effects on LC–ESI-MS bioanalysis.

LC-MS/MS Identification of a Bromelain Peptide Biomarker from Ananas comosus Merr

Bromelain (Br) is a cysteine peptidase (GenBank AEH26024.1) from pineapple, with over 40 years of clinical use. The constituents mediating its anti-inflammatory activity are not thoroughly characterized and no peptide biomarker exists. Our objective is to characterize Br raw material and identify peptides in the plasma of Br treated mice. After SDS-PAGE in-gel digestion, Br (VN#3507; Middletown, CT, USA) peptides were analyzed via LC/MS/MS using 95% protein probability, 95% peptide probability, and a minimum peptide number = 5. Br spiked mouse plasma (1 ug/ul) and plasma from i.p. treated mice (12 mg/kg) were assessed using SRM. In Br raw material, we identified seven proteins: four proteases, one jacalin-like lectin, and two protease inhibitors. In Br spiked mouse plasma, six proteins (ananain, bromelain inhibitor, cysteine proteinase AN11, FB1035 precursor, FBSB precursor, and jacalin-like lectin) were identified. Using LC/MS/MS, we identified the unique peptide, DYGAVNEVK, derived from FB1035, in the plasma of i.p. Br treated mice. The spectral count of this peptide peaked at 6 hrs and was undetectable by 24 hrs. In this study, a novel Br peptide was identified in the plasma of treated mice for the first time. This Br peptide could serve as a biomarker to standardize the therapeutic dose and maximize clinical utility.

NMR and mass spectrometric characterization of vinblastine, vincristine and some new related impurities - part I

In the course of exploring the possibilities of developing a new, improved process at Gedeon Richter for the production of the "bisindole" alkaloids vinblastine (VLB) and vincristine (VCR), some novel VLB/VCR-related trace impurities were detected by analytical HPLC. Following isolation by preparative HPLC, a combination of 1D and 2D ultra high-field NMR and high-resolution (HR) (LC-)MS/MS studies allowed the structural identification and complete spectral characterization of several hitherto unpublished VLB/VCR-analogue impurities. Since the impurities could not be isolated in entirely pure forms and were available only in minute, mass-limited quantities, accessing the spectral information needed for their ab initio structure determination was met with various practical difficulties. Successful structure determination therefore relied heavily on the availability and use of detailed and definitive spectral data for both VLB and VCR. In particular, the utilization of detailed (1)H, (13)C, and (15)N NMR assignments as well as (1)H-(1)H, (1)H-(13)C and (1)H-(15)N spin-spin connectivities pertaining to different solvents for VLB/VCR base and sulphate salt was required. Although NMR studies on VLB base and other bisindoles were reported earlier in the literature, an NMR characterization of VLB and VCR under the above-mentioned circumstances and using ultra-high field instrumentation is either scarcely available or entirely lacking, therefore the necessary data had to be obtained in-house. Likewise, a modern tandem HR-ESI-MS/MS(n) fragmentation study of VLB and VCR has not been published yet. In the present paper we therefore give a thorough NMR and MS characterization of VLB and VCR specifically with a view to filling this void and to provide sufficiently extensive and solid reference data for the structural investigation of the aforementioned VLB/VCR impurities. Besides being scientifically relevant in its own right, the disclosed data should be useful for anyone interested in VLB/VCR-related molecules at a structural level.

Recent advances in metabolite identification and quantitative bioanalysis by LC–Q-TOF MS

The need for rapid, sensitive and effective identification and quantitation of drugs and metabolites to accelerate drug discovery and development has given MS its central position in drug metabolism and pharmacokinetic research. This review attempts to orient the readers with respect to hybrid Q-TOF MS, which enables accurate mass measurement and generates information-rich datasets. The key properties of the Q-TOF MS system, including mass accuracy, resolution, scan speed and dynamic range, are herein discussed. Developments on tandem separation techniques (e.g., UHPLC® and ion mobility spectrometry), data acquisition and data-mining methods (e.g., mass defect, product/neutral loss, isotope pattern filters and background subtraction) that facilitate qualitative and quantitative analysis are then examined. The performance and versatility of LC–Q-TOF MS are thoroughly illustrated by its applications in metabolite identification and quantitative bioanalysis. Future perspectives are also discussed.

Extraction and isolation of phenolic compounds

Phenolic compounds constitute a major class of plant secondary metabolites that are widely distributed in the plant kingdom and show a large structural diversity. These compounds occur as aglycones or glycosides, as monomers or constituting highly polymerized structures, or as free or matrix-bound compounds. Furthermore, they are not uniformly distributed in the plant and their stability varies significantly. This greatly complicates their extraction and isolation processes, which means that a single standardized procedure cannot be recommended for all phenolics and/or plant materials; procedures have to be optimized depending on the nature of the sample and the target analytes, and also on the object of the study. In this chapter, the main techniques for sample preparation, and extraction and isolation of phenolic compounds have been reviewed-from classical solvent extraction procedures to more modern approaches, such as the use of molecularly imprinted polymers or counter-current chromatography.

Qualitative and quantitative determination of nine main active constituents in Pulsatilla cernua by high-performance liquid chromatography coupled to electrospray ionization tandem mass spectrometry

A novel qualitative and quantitative method using high-performance liquid chromatography coupled to electrospray ionization tandem mass spectrometry (HPLC-ESI-MS/MS) was developed for simultaneous determination of the nine major active constituents in Pulsatilla cernua (Thunb.) Bercht. et Opiz., namely anemoside A3 (1), anemoside B4 (2), 23-hydroxybetulinic acid (3), cirenshenoside S (4), pulsatilloside B (5), pulsatilloside C (6), oleanolic acid (7), ajugasterone C (8) and β-ecdysterone (9), respectively. A Sapphire C18 column (250 mm × 4.6 mm, 5 μm) and gradient elution were used during the analysis. The identification and quantification of the analytes were achieved on a hybrid quadrupole linear ion trap mass spectrometer. Multiple-reaction monitoring (MRM) scanning was employed for quantification with switching electrospray ion source polarity between positive and negative modes in a single run. All calibration curves showed good linearity (r(2) > 0.9948) within the test ranges. The intra and interday variations for nine analytes were less than 3.95 and 3.78%, respectively. The developed method was successfully applied to determine the investigated compounds in 15 batches of natural and cultured samples of P. cernua. The results indicated that the method was simple, rapid, specific and reliable, which is helpful to comprehensive evaluation of quality of P. cernua.

Structural characterization of flavonoid glycosides by multi-stage mass spectrometry

Flavonoids are secondary plant metabolites of great structural variety and high medicinal significance. The search for new chemical entities and the quality control of flavonoid containing natural products require easy-to-use but reliable and robust analytical methodologies. For structural elucidation of flavonoids and their glycosides, nuclear magnetic resonance (NMR) and mass spectroscopy (MS) are the generally used techniques. In phytochemical analyses, however, high amounts of flavonoids are difficult to isolate for NMR, thus low sample volume requiring MS based methods are emerging. This review summarizes and compares currently available methods for structural elucidation of flavonoids by LC-MS and LC-MS(n), and focuses on the identification options of unknown flavonoid glycosides in complex samples (e.g., plant extracts) with the emphasis on the differentiation of isomeric compounds.

Advanced separation methods of food anthocyanins, isoflavones and flavanols

In recent years, increasing knowledge of the positive health effects of food polyphenols has prompted the need to develop new separation techniques for their extraction, fractionation and analysis. This article provides an updated and exhaustive review of the application of counter-current chromatography, high performance liquid chromatography, capillary electrophoresis, and their hyphenation with mass spectrometry to the study of food polyphenols. Flavonoids constitute the largest class of polyphenols, widely spread in the plant kingdom and common in human diet which has been the most widely studied with respect to their antioxidant and biological activities. The main subgroups are anthocyanins, catechins, isoflavones, flavonols and flavones. They are reported to exhibit antioxidant, anti-carcinogenic, anti-inflammatory, anti-atherogenic, anti-thrombotic, and immune modulating functions, among others. Since red fruit anthocyanins, soy isoflavones and flavanols from grapes and teas are currently the most used phenolic compounds for producing new nutraceuticals and functional foods, this review is focused on these three flavonoid groups.