Evaluation of direct analysis in real time ionization-mass spectrometry (DART-MS) in fish metabolomics aimed to assess the response to dietary supplementation

MALDI-ToF MS and chemometric analysis as a tool for identifying wild and farmed salmon

In this study, the difference between wild and farmed salmon production was successfully profiled and differentiated by matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-ToF MS) combined with chemometric analysis. The established method based on multivariate analysis mainly involved principal component analysis (PCA), partial least squares-discriminant analysis (PLS-DA), and orthogonal partial least squares-discriminant analysis (OPLS-DA) as the screening and verifying tools to provide insights into the distinctive features found in wild and farmed salmon products, respectively. The discrimination between farmed and wild salmon was accomplished with 100% classification accuracy using chemometric models, 100% identification accuracy was also achieved in distinguishing wild Salmo salar and Oncorhynchus nerka samples. The results of the present work suggest that the proposed method could serve as a reference for detecting salmon fraud relating to wild or farmed production and expand the application of MALDI-ToF technology further into food authenticity applications.

Direct analysis in real time high-resolution mass spectrometry for authenticity assessment of lamb

In comparison to more traditional methods of determining food authenticity, such as gas chromatography analysis, the primary advantages of DART-HRMS include its high speed and throughput of analysis. This study used a non-targeted metabolomics method based on real-time high-resolution mass spectrometry combined with chemometric analysis to distinguish lamb samples from four regions. Orthogonal least squares-discriminant analysis revealed a distinct difference between these four lamb regions. The potential markers were chosen based on the variable's importance in projection values, variance, and fold change. A total of 79 markers were identified using the matching chemistry database. These markers differed significantly between lambs in four regions according to heatmap analysis. The linear discriminatory analysis model had an initial classification rate of 100.0% and a cross-validation accuracy of 82.50% on the identified markers. The research demonstrates that DART-HRMS can perform a rapid authentication evaluation of lamb samples.

Authentication of organically grown vegetables by the application of ambient mass spectrometry and inductively coupled plasma (ICP) mass spectrometry; The leek case study

Health conscious and environmentally aware consumers are purchasing more organically produced foods. They prefer organic fruits and leafy vegetables as these are much less likely to have been exposed to contaminants such as pesticides. The detection of fraudulent activity in this area is difficult to undertake, because many chemical plant protection treatments degrade very quickly or can be washed off to remove evidence of their existence. It was found that when combining DART-MS with a compact, inexpensive and robust single quadrupole mass spectrometer, it was possible to differentiate organic from conventional leeks with 93.8% to 100% accuracy. ICP-MS results showed similar performance, with an ability to differentiate conventional from organic leeks with 92.5% to 98.1% accuracy. This study has paved the way for the certification of vegetables as being organically produced. The next step is to create data libraries to support the roll out of the methodologies described.

Applications of direct analysis in real time mass spectrometry in food analysis: A review

RATIONALE

Direct analysis in real time (DART) combined with mass spectrometry (MS) detection has become one of the most broadly used analytical approaches for the direct molecular characterization of food samples with regard to their chemical quality, safety, origin, and authentication. The major advantages of DART-MS for food analysis include high chemical sensitivity and specificity, high speed and throughput of analysis, simplicity, and the obviation of tedious sample preparation and solvents.

METHODS

The recent applications of DART coupled with different mass analyzers, including quadrupole, ion trap, Orbitrap, and time of flight, are discussed. In addition, sample pretreatment methods that have been coupled with DART-MS are discussed.

RESULTS

We summarize the applications of DART-MS in food science and industry published in the period from 2005 to this date. The applications and analytical characteristics are systematically categorized across the three major types of foods: solid foods, liquid foods, and viscous foods.

CONCLUSIONS

DART-MS has proved its high suitability for the direct, rapid, and high-throughput molecular analysis of very different food samples with minimal or no sample preparation, thus offering a high-speed alternative to liquid chromatography/mass spectrometry (LC/MS) and gas chromatography/mass spectrometry (GC/MS) approaches that are traditionally employed in food analysis.

Rapid Evaporative Ionization Mass Spectrometry: A Review on Its Application to the Red Meat Industry with an Australian Context

The red meat supply chain is a complex network transferring product from producers to consumers in a safe and secure way. There can be times when fragmentation can arise within the supply chain, which could be exploited. This risk needs reduction so that meat products enter the market with the desired attributes. Rapid Evaporative Ionisation Mass Spectrometry (REIMS) is a novel ambient mass spectrometry technique originally developed for rapid and accurate classification of biological tissue which is now being considered for use in a range of additional applications. It has subsequently shown promise for a range of food provenance, quality and safety applications with its ability to conduct ex vivo and in situ analysis. These are regarded as critical characteristics for technologies which can enable real-time decision making in meat processing plants and more broadly throughout the sector. This review presents an overview of the REIMS technology, and its application to the areas of provenance, quality and safety to the red meat industry, particularly in an Australian context.

Natural Product Discovery by Direct Analysis in Real Time Mass Spectrometry

Direct analysis in real time mass spectrometry (DART MS) is one of the first ambient ionization methods to be introduced and commercialized. Analysis by DART MS requires minimal sample preparation, produces nearly instantaneous results, and provides detection over a broad range of compounds. These advantageous features are particularly well-suited for the inherent complexity of natural product analysis. This review highlights recent applications of DART MS for species identification by chemotaxonomy, chemical profiling, genetic screening, and chemical spatial analysis from plants, insects, microbes, and metabolites from living systems.

Comparative Analysis of Skeletal Muscle Metabolites of Fish with Various Rates of Aging

Fish species exhibit great diversity rating of aging (from negligible to rapid), which gives a unique possibility for the discovery of the molecular mechanisms that determine the differences in the rate of aging. A mass spectrometric metabolic profiling of skeletal muscle of fish with various aging rates was carried out by direct injection to a quadrupole time-of-flight mass spectrometer. The first group includes long-lived fish species (pike (Esox Lucius) and sterlet (Acipenser ruthenus); the second group—species with gradual senescence such as that observed in many mammalian species of similar size (zander (Sandra lucioperca) and perch (Perca fluviatilis)) and the third group—species with very short life cycle (chum salmon (Oncorhynchus keta) and pink salmon (Oncorhynchus gorbuscha)). Multivariate analysis of metabolic profiles allowed the detecting of about 80 group-specific features associated with amino acids, lipids, biogenic amines, intermediates of glycolysis, glycogenolysis, and citric acid cycle. Possible roles in the aging process are hypothesized for the biochemical pathways of the metabolites that were altered in the different groups.

A GC-MS Protocol for Separating Endangered and Non-endangered Pterocarpus Wood Species

Pterocarpus santalinus and Pterocarpus tincorius are commonly used traded timber species of the genus Pterocarpus. P. santalinus has been listed in Appendix II of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES). As a non-CITES species, P. tincorius is also indiscriminately labeled as P. santalinus due to the similar macroscopic and microscopic features with P. santalinus. In order to understand the molecular discrimination between these easily confused species, xylarium heartwoods of these two species were extracted by three different kinds of solvents and analyzed using gas chromatography–mass spectrometry (GC-MS). Multivariate analyses were also applied for the selection of marker compounds that are distinctive between P. santalinus and P. tincorius. A total of twenty volatile compounds were detected and tentatively identified in three kinds of extracts, and these compounds included alcohols, stilbenoids, esters, aromatic hydrocarbons, ketones, miscellaneous, phenols, and flavonoids. GC-MS analyses also revealed that extraction solvents including ethanol and water (EW), ethyl acetate (EA), and benzene–ethanol (BE) gave the best chemotaxonomical discrimination in the chemical components and relative contents of the two Pterocarpus species. After chemometric analyses, EW displayed higher predictive accuracy (100%) than those of EA extract (83.33%) and BE extract (83.33%). Furthermore, spathulenol (17.58 min) and pterostilbene (23.65 min) were elucidated as the critical compounds for the separation of the EW extracts of P. santalinus and P. tinctorius. Thus, a protocol of GC-MS and multivariate analyses was developed to use for successfully distinguishing P. santalinus from P. tinctorius.

Assessing fish authenticity by direct analysis in real time-high resolution mass spectrometry and multivariate analysis: discrimination between wild-type and farmed salmon

The constant increase in seafood consumption worldwide has led to a parallel growth of the incidence of products obtained by aquaculture on the market, but also of the fraudulent commercialization of farmed products as wild-type ones. A careful characterization of the lipid component of seafood products based on chromatography-mass spectrometry techniques has been reported as a promising approach to reliably differentiate farmed from wild-type products. In this context, a fast method based on Direct Analysis in Real Time (DART) coupled to High Resolution Mass Spectrometry (HRMS) based on a single stage Orbitrap mass analyzer, integrated by Principal Component Analysis (PCA), was developed in the present study and applied to scout for spectral features useful to discriminate wild-type from farmed salmon of Salmo salar species. In particular, normalized intensities obtained for the 30 most intense signals (all referred to fatty acids, FA) detected in negative ion DART-HRMS spectra of the lipid extracts of salmon fillets [26 wild-type from Canada, 74 farmed from Canada (25), Norway (25) and Chile (24)] were considered as the variables for PCA. The scatterplot referred to the first two principal components showed a clear distinction between wild-type and farmed salmon, which gathered as a unique cluster, despite the remarkable differences in their geographical origin. In accordance with previous studies based on more complex and time-demanding analytical approaches, three saturated (14:0, 16:0 and 18:0) FA, along with unsaturated ones having 20 or 22 carbon atoms, were found as the main discriminating variables for wild-type salmons, whereas FA with compositions 18:1, 18:2, 18:3 and several oxidized forms arising from them were found to have a significantly higher incidence in farmed salmon. The method was further validated by Discriminant Analysis (DA) performed on the same dataset used for PCA integrated by data obtained from 6 commercial samples, putatively referred to farmed Norwegian salmon. Results showed that 100% of the latter were correctly classified as farmed type. Relative abundances of DART-HRMS signals related to specific FA appear then very promising for the differentiation of wild-type salmon from farmed ones, a very relevant issue in the context of consumers' protection from seafood frauds.

Direct analysis in real time coupled to high resolution mass spectrometry as a rapid tool to assess salmon (Salmo salar) freshness

Direct analysis in real time-high resolution mass spectrometry (DART-HRMS) was applied to the detection of lipid species in the lipid extracts of farmed salmon samples collected from a local retailer and analyzed right after the purchase and after storage for 4 and 6 days under refrigerated conditions. The recognition of type and composition of lipids detected in DART-HRMS spectra was performed by using the relevant accurate m/z data (accuracy better than 5 ppm) as input for a search on the LipidMaps database. As a result, several fatty acids (FA), either saturated or mono-/poly-unsaturated, and triacylglycerols (TAG) were recognized in the three types of samples from the corresponding negative and positive ion DART-HRMS spectra, respectively. Following, spectral intensities were exploited to monitor the evolution of selected FA and TAG during the refrigeration of salmon meat. In particular, after 4 days of refrigeration, a statistically significant increase was recorded for FA with side chain compositions 18:2, 18:1, 20:5, and 22:6 despite a significant decrease found for TAG with overall side chain compositions 50:4, 52:5, 52:4, and 52:3 after the same time. These evolutions were consistent with a general model already proposed for the effect of low temperature treatments on seafood, implying the action of endogenous lipases, with consequent increase of the free FA amount and decrease in glycerophospholipids and triglycerides contents. The described results indicate DART-HRMS as a promising MS-based rapid tool for the assessment of fish, or other seafood, freshness.

Rapid characterization of chemical markers for discrimination of Moutan Cortex and its processed products by direct injection-based mass spectrometry profiling and metabolomic method

BACKGROUND

Processing of herbal medicines is a characteristic pharmaceutical technique in Traditional Chinese Medicine, which can reduce toxicity and side effect, improve the flavor and efficacy, and even change the pharmacological action entirely. It is significant and crucial to perform a method to find chemical markers for differentiating herbal medicines in different processed degrees.

PURPOSE

The aim of this study was to perform a rapid and reasonable method to discriminate Moutan Cortex and its processed products, and to reveal the characteristics of chemical components depend on chemical markers.

METHODS

Thirty batches of Moutan Cortex and its processed products, including 11 batches of Raw Moutan Cortex (RMC), 9 batches of Moutan Cortex Tostus (MCT) and 10 batches of Moutan Cortex Carbonisatus (MCC), were directly injected in electrospray ionization quadrupole time-of-flight mass spectrometry (ESI-QTOF MS) for rapid analysis in positive and negative mode. Without chromatographic separation, each run was completed within 3 min. The raw MS data were automatically extracted by background deduction and molecular feature (MF) extraction algorithm. In negative mode, a total of 452 MFs were obtained and then pretreated by data filtration and differential analysis. After that, the filtered 85 MFs were treated by principal component analysis (PCA) to reduce the dimensions. Subsequently, a partial least squares discrimination analysis (PLS-DA) model was constructed for differentiation and chemical markers detection of Moutan Cortex in different processed degrees. The positive mode data were treated as same as those in negative mode.

RESULTS

RMC, MCT and MCC were successfully classified. Moreover, 14 and 3 chemical markers from negative and positive mode respectively, were screened by the combination of their relative peak areas and the parameter variable importance in the projection (VIP) values in PLS-DA model. The content changes of these chemical markers were employed in order to illustrate chemical changes of Moutan Cortex after processed.

CONCLUSION

These results showed that the proposed method which combined non-targeted metabolomics analysis with multivariate statistics analysis is reasonable and effective. It could not only be applied to discriminate herbal medicines and their processing products, but also to reveal the characteristics of chemical components during processing.

Advances in mass spectrometry-based metabolomics for investigation of metabolites

Metabolomics is the systematic study of all the metabolites present within a biological system, which consists of a mass of molecules, having a variety of physical and chemical properties and existing over an extensive dynamic range in biological samples. Diverse analytical techniques are needed to achieve higher coverage of metabolites. The application of mass spectrometry (MS) in metabolomics has increased exponentially since the discovery and development of electrospray ionization and matrix-assisted laser desorption ionization techniques. Significant advances have also occurred in separation-based MS techniques (gas chromatography-mass spectrometry, liquid chromatography-mass spectrometry, capillary electrophoresis-mass spectrometry, and ion mobility-mass spectrometry), as well as separation-free MS techniques (direct infusion-mass spectrometry, matrix-assisted laser desorption ionization-mass spectrometry, mass spectrometry imaging, and direct analysis in real time mass spectrometry) in the past decades. This review presents a brief overview of the recent advanced MS techniques and their latest applications in metabolomics. The software/websites for MS result analyses are also reviewed.

Metabolomics is the systematic study of all the metabolites present within a biological system, supply functional information and has received extensive attention in the field of life sciences.

Ambient mass spectrometry in metabolomics

Since the introduction of desorption electrospray ionization (DESI) mass spectrometry (MS), ambient MS methods have seen increased use in a variety of fields from health to food science. Increasing its popularity in metabolomics, ambient MS offers limited sample preparation, rapid and direct analysis of liquids, solids, and gases, in situ and in vivo analysis, and imaging. The metabolome consists of a constantly changing collection of small (<1.5 kDa) molecules. These include endogenous molecules that are part of primary metabolism pathways, secondary metabolites with specific functions such as signaling, chemicals incorporated in the diet or resulting from environmental exposures, and metabolites associated with the microbiome. Characterization of the responsive changes of this molecule cohort is the principal goal of any metabolomics study. With adjustments to experimental parameters, metabolites with a range of chemical and physical properties can be selectively desorbed and ionized and subsequently analyzed with increased speed and sensitivity. This review covers the broad applications of a variety of ambient MS techniques in four primary fields in which metabolomics is commonly employed.

Applications of DART-MS for food quality and safety assurance in food supply chain

Direct analysis in real time (DART) represents a new generation of ion source which is used for rapid ionization of small molecules under ambient conditions. The combination of DART and various mass spectrometers allows analyzing multiple food samples with simple or no sample treatment, or in conjunction with prevailing protocolized sample preparation methods. Abundant applications by DART-MS have been reviewed in this paper. The DART-MS strategy applied to food supply chain (FSC), including production, processing, and storage and transportation, provides a comprehensive solution to various food components, contaminants, authenticity, and traceability. Additionally, typical applications available in food analysis by other ambient ionization mass spectrometers were summarized, and fundamentals mainly including mechanisms, devices, and parameters were discussed as well. © 2015 Wiley Periodicals, Inc. Mass Spec Rev. 36:161-187, 2017.

Selective Manipulation of the Gut Microbiota Improves Immune Status in Vertebrates

All animals develop in association with complex microbial communities. It is now well established that commensal microbiota is essential for the correct functionality of each organ in the host. Particularly, the commensal gastro-intestinal microbiota (CGIM) is a key factor for development, immunity and nutrient conversion, rendering them bio-available for various uses. Thus, nutritional inputs generate a positive loop in maintaining host health and are essential in shaping the composition of the CGIM communities. Probiotics, which are live exogenous microorganisms, selectively provided to the host, are a promising concept for manipulating the microbiota and thus for increasing the host health status. Nevertheless, most mechanisms induced by probiotics to fortify the immune system are still a matter of debate. Alternatively, prebiotics, which are non-digestible food ingredients, can favor the growth of specific target groups of CGIM. Several metabolites are produced by the CGIM, one of the most important are the short-chain fatty acids (SCFAs), which emerge from the fermentation of complex carbohydrates. SCFAs have been recognized as key players in triggering beneficial effects elicited by simple diffusion and by specific receptors present, thus, far only in epithelial cells of higher vertebrates at different gastro-intestinal locations. However, both strategies have shown to provide resistance against pathogens during periods of high stress. In fish, knowledge about the action of pro- and prebiotics and SCFAs is still limited. Thus, in this review, we briefly summarize the mechanisms described on this topic for higher vertebrates and discuss why many of them may operate in the fish gut representing a model for different mucosal tissues

An improved method for the determination of 5-hydroxymethylfurfural in Shenfu injection by direct analysis in real time-quadrupole time-of-flight mass spectrometry

The emergence of direct analysis in real time (DART) ion source provides the great possibility for rapid analysis of hazardous substance in drugs. DART mass spectrometry (DART-MS) enabled the conducting of a fast and non-contact analysis of various samples, including solid or liquid ones, without complex sample preparation or chromatographic separation. In this study, a modified DART-quadrupole time-of-flight mass spectrometry (DART-QTOF-MS) method was developed for identification and determination of 5-hydroxymethylfurfural (5-HMF) in Shenfu (SF) injection. The quantitative transfer of sample solution was introduced to the glass tips of DIP-it sampler at a fixed volume, which significantly increases the repeatability and accuracy of analytical results. The protonated ion of dibutyl phthalate in the atmosphere was used as the reference mass for TOF-MS recalibration during the data acquisition for constant high accuracy mass measurements. Finally, the developed DART-MS method was used to determine 5-HMF in seven batches of SF injection, and the contents of 5-HMF were not higher than 100 µg/mL. The results obtained were further confirmed by an ultra-high performance liquid chromatography combined with triple quadrupole mass spectrometer (UHPLC-QQQ-MS). The overall results demonstrated that the DART-QTOF-MS method could be applied as an alternative technique for rapid monitoring 5-HMF in herbal medicine injection. Copyright © 2015 John Wiley & Sons, Ltd.

Current state of the art of mass spectrometry-based metabolomics studies – a review focusing on wide coverage, high throughput and easy identification

Metabolomics aims at the comprehensive assessment of a wide range of endogenous metabolites and attempts to identify and quantify the attractive metabolites in a given biological sample.