Laser Desorption Ionization and Related Methods for the Detection of Small Molecules

In recent years metabolomic profiling and dereplication have become important tools in the field of natural products’ (NPs) research and quality control. These experiments are mainly based on methods such as high-performance liquid chromatography coupled with mass spectrometry (HPLC-MS) as well as 1H and 13C nuclear magnetic resonance spectroscopy (NMR) (El-Elimat, T., et al. J. Nat. Prod. 2013, 76, 1709–1716; Williams, R.B., et al. Org. Biomol. Chem. 2015, 39, 9957–9962). On the other hand matrix assisted matrix laser desorption ionization (MALDI) and matrix free laser desorption ionization (LDI) are hardly discussed in this context. This lecture will highlight some recent advances in both methods such as the development of selective MALDI matrices for the detection of alkaloids in complex mixtures but also the matrix free LDI of NPs. Many NPs exhibit close structural similarities to MALDI matrices and can be directly ionized by LDI (Schinkovitz, A., et al. J. Mass Spectrom. 2015, 50 , 270–274 ; Le-Pogam, P., et al. Anal. Chem. 2015, 87, 10421–10428). The effect is observed for a large variety of different compounds belonging to various chemical families, such as flavonoids, coumarins, tocopherols, and alkaloids, some of which could even be detected from crude extracts. Eventually the concept of selective signal enhancement by multi-wavelength laser irradiation targeting absorption maxima of selected analytes will be discusse

Usnic acid and its versatility as MALDI matrix

No abstrac

New Developments of Laser Desorption Ionization Mass Spectrometry in Natural Products Research

Mass spectrometry (MS) represents an indispensable tool for the structural identification of natural products (NPs) and is one of the major focus areas of analytical chemistry research. The technique has long been used to obtain molecular weights and further molecular formulae. In the past, former ionization sources such as electronic impact (EI) limited MS analysis to predominately volatile, polar, and thermostable compounds. However, the development of soft ionization techniques such as electrospray ionization (ESI), atmospheric pressure chemical ionization (APCI), and laser desorption/ionization (LDI) have gradually extended the scope of MS analysis to a much wider range of chemical entities. Moreover, the hyphenation of liquid and gas chromatography with MS (LC‐MS, GC‐MS) has provided a most powerful tool for the analysis of complex mixtures and NPs. In fact, LC‐MS is often considered as a method of first choice particularly when studying complex mixtures of small molecules. On the other hand, recent developments in matrix‐assisted laser desorption/ionization (MALDI) and LDI may provide useful supplements and potential alternatives to this approach. Both methods share similar, though slightly different ionization mechanisms. While MALDI uses small molecules comprising strong UV chromophores (matrices) to transfer laser energy to the sample material, LDI targets compounds that can be directly ionized by laser irradiation without any matrix support. Moreover, certain compounds showing LDI properties may also work as MALDI matrices. With regard to NPs research, MALDI and LDI may help overcoming certain limitations encountered in LC‐MS such as the indispensable use of buffer solutions when analyzing alkaloids. Moreover, as (MA)LDI hardly requires any sample conditioning, analysis time can be significantly shortened. With all this in mind, the subsequent article will highlight some interesting MALDI and LDI applications, which focus on the detection of NPs in complex mixtures. This includes the use of specifically adapted matrices for the selective detection of alkaloids (i), the study of the inherent LDI and matrix properties of phenolic compounds (ii) as well of evaluation on the reproducibility of LDI signal patterns (iii). Eventually, a statistical approach toward LDI profiling, which may provide a future tool for quality control of large sample batches will be presented (iv)

A Novel Matrix Molecule for the Selective Detection of Alkaloids in MALDI

National audienc

Natural products as potential leads for treating infectious and lifestyle diseases. Phytochemical characterization of active extracts and compounds by methods of LC-MS, quantitative 1H NMR and laser desorption ionization MS/ Recherche de produits d’origin

Depuis très longtemps les produits naturels (NPs), connus pour montrer une grande diversité d\u27activités biologiques, sont fréquemment utilisés comme modèles pour la création de nouveaux médicaments. Dans le présent travail des NPs Provenant de plantes, de bryophytes ou de lichens et qui présentent Des activités antimycobactériennes, antioxydants et cytotoxiques seront décrits. Considérant que la bioactivité observée est parfois associée aux effets synergiques existants entres plusieurs composés, que ceux-ci soient des impuretés ou des produits de dégradation des principes actifs, différentes méthodes permettant l’évaluation de la pureté d’un échantillon (CPG, CLHP, qRMN 1H) seront comparées. Parmi les NPs, les alcaloïdes représentent de plus un très important groupe de composés démontrant différentes propriétés pharmacologiques très marquées. Dans le domaine des analyses par spectrométrie de masse, une méthode spécifiquement adaptée pour la détection des alcaloïdes par désorption-ionisation laser assistée par matrice (MALDI), utilisant une nouvelle molécule sélective (MT3P), sera ainsi présenté

Biological and Chemical Profiling of Natural Products Approaches, Pitfalls and Targeted Strategies

Présentation invitée dans le cadre d’un programme d’échange ECOS-NORD. Fait a "El Centro de Investigacion Cientifica de Yucaran A.C." Merida, Mexique le 28.4.2017.National audienc

New Developments of Laser Desorption Ionization Mass Spectrometry in Plant Analysis

The structural identification of natural products is one of the major focus areas of analytical chemistry research. Mass spectrometry (MS) has long been used to obtain molecular weights and further molecular formulae. In the past, former ionization sources such as electronic impact unfortunately limited MS analysis to predominately volatile, polar, and thermostable compounds. However, recent developments in soft ionization techniques such as electrospray ionization (ESI), atmospheric pressure chemical ionization (APCI), or laser desorption/ionization (LDI) have gradually extended MS analysis to a much wide range of chemical structures. As far as small natural compounds are concerned, LDI sources are still seldom used because of specific technical limitations. Indeed, the photoionization process of LDI is generally assisted by a matrix, which is a small molecule carrying strong UV chromophore. The process is then called matrix‐assisted laser desorption/ionization (MALDI) process. MALDI ionization therefore induces the formation of numerous matrix ions that commonly appear in the range 0–600 Da, and consequently interfere with molecular ions originating from many natural products. For this reason, the correct signal assignment is highly impaired in the critical region of interest. As LDI and MALDI are not only soft ionization processes but also quite sensitive techniques yielding high resolution spectra when coupled to a time‐of‐flight (TOF) analyzer, different attempts have been made to adapt these techniques for the analysis of natural products. Three of them will be more specifically discussed in this chapter: (i) LDI on neat gold surfaces obtained by physical vapor diffusion (PVD), (ii) desorption/ionization on self‐assembled monolayer surfaces (DIAMS), and (iii) the use of specific matrices for the selective detection of alkaloids

Chemical Profiling of Natural Products by Matrix Assisted and Matrix Free Laser Desorption Ionization

International audienc

Analysis of complex phenolic mixtures by matrix free laser desorption ionization

The presentation highlights matrix free laser desorption ionization as a versatile tool for the characterization of complex mixtures of phenolic compounds

New Use for a Compound as a Matrix in the Specific Detection, Identification and/or Quantification of Alkaloids by MALDI-TOF Mass Spectrometry

The present invention relates to (i) a method of analysing small molecules that may have a mass of < 800 Da, in particular alkaloids, said method being generally referred to as MALDI-TOF-MS (or MALDI Time-of-Flight MAss Spectrometry) which is an acronym for a method of analysis by matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry, to (ii) a molecule according to formula (I) and to the use thereof as a matrix in such an analysis method