A major goal in natural product discovery programs is to rapidly dereplicate known entities from complex biological extracts We demonstrate here that molecular networking, an approach that organizes MS/MS data based on chemical similarity, is a powerful complement to traditional dereplication strategies Successful dereplication with molecular networks requires MS/MS spectra of the natural product mixture along with MS/MS spectra of known standards, synthetic compounds, or well-characterized organisms, preferably organized into robust databases This approach can accommodate different ionization platforms, enabling cross correlations of MS/MS data from ambient ionization, direct infusion, and LC-based methods Molecular networking not only dereplicates known molecules from complex mixtures, it also captures related analogues, a challenge for many other dereplication strategies To illustrate its utility as a dereplication tool, we apply mass spectrometry-based molecular networking to a diverse array of m

/pdf/molecular-networking-as-a-dereplication-strategy-2wb252ljhf.pdf

Molecular Networking as a Dereplication Strategy

Mass spectrometry imaging (MSI) has emerged as an important tool in the last decade and it is beginning to show potential to provide new information in many fields owing to its unique ability to acquire molecularly specific images and to provide multiplexed information, without the need for labeling or staining. In MSI, the chemical identity of molecules present on a surface is investigated as a function of spatial distribution. In addition to now standard methods involving MSI in vacuum, recently developed ambient ionization techniques allow MSI to be performed under atmospheric pressure on untreated samples outside the mass spectrometer. Here we review recent developments and applications of MSI emphasizing the ambient ionization techniques of desorption electrospray ionization (DESI), laser ablation electrospray ionization (LAESI), probe electrospray ionization (PESI), desorption atmospheric pressure photoionization (DAPPI), femtosecond laser desorption ionization (fs-LDI), laser electrospray mass spectrometry (LEMS), infrared laser ablation metastable-induced chemical ionization (IR-LAMICI), liquid microjunction surface sampling probe mass spectrometry (LMJ-SSP MS), nanospray desorption electrospray ionization (nano-DESI), and plasma sources such as the low temperature plasma (LTP) probe and laser ablation coupled to flowing atmospheric-pressure afterglow (LA-FAPA). Included are discussions of some of the features of ambient MSI for example the ability to implement chemical reactions with the goal of providing high abundance ions characteristic of specific compounds of interest and the use of tandem mass spectrometry to either map the distribution of targeted molecules with high specificity or to provide additional MS information on the structural identification of compounds. We also describe the role of bioinformatics in acquiring and interpreting the chemical and spatial information obtained through MSI, especially in biological applications for tissue diagnostic purposes. Finally, we discuss the challenges in ambient MSI and include perspectives on the future of the field.

/pdf/mass-spectrometry-imaging-under-ambient-conditions-d92zj91f3z.pdf

Mass spectrometry imaging under ambient conditions.

The field of metabolomics has witnessed an exponential growth in the last decade driven by important applications spanning a wide range of areas in the basic and life sciences and beyond. Mass spectrometry in combination with chromatography and nuclear magnetic resonance are the two major analytical avenues for the analysis of metabolic species in complex biological mixtures. Owing to its inherent significantly higher sensitivity and fast data acquisition, MS plays an increasingly dominant role in the metabolomics field. Propelled by the need to develop simple methods to diagnose and manage the numerous and widespread human diseases, mass spectrometry has witnessed tremendous growth with advances in instrumentation, experimental methods, software, and databases. In response, the metabolomics field has moved far beyond qualitative methods and simple pattern recognition approaches to a range of global and targeted quantitative approaches that are now routinely used and provide reliable data, which instill greater confidence in the derived inferences. Powerful isotope labeling and tracing methods have become very popular. The newly emerging ambient ionization techniques such as desorption ionization and rapid evaporative ionization have allowed direct MS analysis in real time, as well as new MS imaging approaches. While the MS-based metabolomics has provided insights into metabolic pathways and fluxes, and metabolite biomarkers associated with numerous diseases, the increasing realization of the extremely high complexity of biological mixtures underscores numerous challenges including unknown metabolite identification, biomarker validation, and interlaboratory reproducibility that need to be dealt with for realization of the full potential of MS-based metabolomics. This chapter provides a glimpse at the current status of the mass spectrometry-based metabolomics field highlighting the opportunities and challenges.

/pdf/overview-of-mass-spectrometry-based-metabolomics-2ltjsux499.pdf

Overview of Mass Spectrometry-Based Metabolomics: Opportunities and Challenges

The crisis of antibiotic resistance necessitates creative and innovative approaches, from chemical identification and analysis to the assessment of bioactivity. Plant natural products (NPs) represent a promising source of antibacterial lead compounds that could help fill the drug discovery pipeline in response to the growing antibiotic resistance crisis. The major strength of plant NPs lies in their rich and unique chemodiversity, their worldwide distribution and ease of access, their various antibacterial modes of action, and the proven clinical effectiveness of plant extracts from which they are isolated. While many studies have tried to summarize NPs with antibacterial activities, a comprehensive review with rigorous selection criteria has never been performed. In this work, the literature from 2012 to 2019 was systematically reviewed to highlight plant-derived compounds with antibacterial activity by focusing on their growth inhibitory activity. A total of 459 compounds are included in this Review, of which 50.8% are phenolic derivatives, 26.6% are terpenoids, 5.7% are alkaloids, and 17% are classified as other metabolites. A selection of 183 compounds is further discussed regarding their antibacterial activity, biosynthesis, structure-activity relationship, mechanism of action, and potential as antibiotics. Emerging trends in the field of antibacterial drug discovery from plants are also discussed. This Review brings to the forefront key findings on the antibacterial potential of plant NPs for consideration in future antibiotic discovery and development efforts.

Ethnobotany and the Role of Plant Natural Products in Antibiotic Drug Discovery.

In the present review we describe the emerging tendency for creating target-oriented analytical approaches designed to solve important chemical tasks by using a combination of analytical tools. The concept is illustrated by selected examples of advances of NMR spectroscopy, mass spectrometry and electron microscopy in the analysis and study of gas-phase, liquid-state and solid-state chemical systems. Comparative description of chemical applications of these analytical methods is presented and discussed. The bibliography includes 359 references.

https://iopscience.iop.org/article/10.1070/RC2013v082n07ABEH004413/pdf

Target-oriented analysis of gaseous, liquid and solid chemical systems by mass spectrometry, nuclear magnetic resonance spectroscopy and electron microscopy

Ambient ionization mass spectrometry: a tutorial.

Electrospray laser desorption ionization mass spectrometry (ELDI/MS), an ambient mass spectrometric technique that combines laser desorption with postionization via electrospray, was developed to rapidly characterize analytes ranging from small organic to large biomolecules. The technique requires essentially no sample pretreatment. The analytes are desorbed through pulsed laser irradiation in the absences of organic matrices like those used in matrix-assisted laser desorption ionization (MALDI). The desorbed molecules subsequently enter an electrospray plume and are postionized through reactions with charged solvent species such as protons, cluster solvent ions, and charged droplets (also termed as species produced from an acidic methanol electrospray solution). This chapter provides a full-scale review of the ELDI technique including its development, underlying principles of operation, ionization mechanism, unique features, related techniques, and applications.

Chapter 15:Electrospray Laser Desorption Ionization Mass Spectrometry

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Ambient ionization mass spectrometry: a tutorial.

Chapter 15:Electrospray Laser Desorption Ionization Mass Spectrometry