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International audience

International audience

International audience

Apple is a very important agricultural plant, and globally cultivated fruit tree. For its protection against pathogens, pesticides are commonly used, which poses a heavy burden on the environment. Therefore alternative methods of crop protection are being widely explored, some of them focusing on the stimulation of the plant’s immune defense (e.g. development of resistant genotypes, use of plant resistant inducers). In this respect, the induced formation of protective plant metabolites (phytoalexins) represents the most interesting strategy. Phytoalexins are monitored mostly by liquid chromatography coupled with mass spectrometry (LC-MS). For phenolic phytoalexins, matrix free laser desorption ionization (LDI) may provide a promising supplement or alternative, particularly as many phenols exhibit close structural similarities to commercial matrices used in matrix assisted laser desorption ionization (MALDI). Contrary to LC-MS, LDI-MS can be performed without time consuming sample preparation or chromatographic method optimization and is not limited to specific solvents.

The présent invention relates to a novel bithiophenic matrix for spécifie détection of alkaloids by MALDI-TOF mass spectrometry; La présente invention concerne une nouvelle matrice bithiophénique pour la détection spécifique des alcaloïdes par spectrométrie de masse de type MALDI-TOF

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

International audience

International audience

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 audience

International audience

International audience; 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 discussed

International audience

International audience; No abstract

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. Keywords: laser desorption ionization; mass spectrometry; secondary metabolites; MALDI; self-assembled monolayers

International audience; Notopterygiumroots (Qiang Huo) have been used in traditional Chinese medicine for treating colds, inflammatory diseases like rheumatoid arthritis, and as an analgesic. The anti-inflammatory activity of the roots ofNotopterygium incisumhas been evaluated by testing the inhibitory activity on nitric oxide production by inducible nitric oxide synthase. The apparent authenticity of the sample was checked by DNA sequence comparison. Using activity-guided isolation, different compounds were isolated and structurally characterized by means of NMR and mass spectroscopy. Eight polyacetylenes could be identified and were tested on their inhibitory activity on nitric oxide production in RAW 264.7 mouse macrophages using the Griess assay. Different 3-hydroxy allyl polyacetylenes exhibited significant activity (IC50: 8-acetoxyfalcarinol, 20.1 µM; falcarindiol, 9.2 µM; 9-epoxyfalcarindiol, 8.8 µM; and crithmumdiol, 23.6 µM).

In the search for peroxisome proliferator-activated receptor gamma (PPARγ) active constituents from the roots and rhizomes of Notopterygium incisum, 11 new polyacetylene derivatives (1-11) were isolated. Their structures were elucidated by NMR and HRESIMS as new polyyne hybrid molecules of falcarindiol with sesquiterpenoid or phenylpropanoid moieties, named notoethers A-H (1-8) and notoincisols A-C (9-11), respectively. Notoincisol B (10) and notoincisol C (11) represent two new carbon skeletons. When tested for PPARγ activation in a luciferase reporter assay with HEK-293 cells, notoethers A-C (1-3), notoincisol A (9), and notoincisol B (10) showed promising agonistic activity (EC50 values of 1.7 to 2.3 μM). In addition, notoincisol A (9) exhibited inhibitory activity on NO production of stimulated RAW 264.7 macrophages.

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.; La présente invention se rapporte à (i) une méthode d'analyse de petites molécules pouvant avoir une masse < 800 Da, en particulier des alcaloïdes, ladite méthode étant généralement désignée sous le nom de MALDI-TOF-MS (ou spectrométrie de masse à temps de vol MALDI) qui est un acronyme pour méthode d'analyse par spectrométrie de masse à temps de vol à désorption/ionisation sous laser assistée par matrice, à (ii) une molécule de formule (I) et à son utilisation comme matrice dans une telle méthode d'analyse.

National audience

International audience; Peroxisome proliferator-activated receptor gamma (PPARγ) is a key regulator of glucose and lipid metabolism and therefore an important pharmacological target to combat metabolic diseases. Since the currently used full PPARγ agonists display serious side effects, identification of novel ligands, particularly partial agonists, is highly relevant. Searching for new active compounds, we investigated extracts of the underground parts ofNotopterygium incisum, a medicinal plant used in traditional Chinese medicine, and observed significant PPARγ activation using a PPARγ-driven luciferase reporter model. Activity-guided fractionation of the dichloromethane extract led to the isolation of six polyacetylenes, which displayed properties of selective partial PPARγ agonists in the luciferase reporter model. Since PPARγ activation by this class of compounds has so far not been reported, we have chosen the prototypical polyacetylene falcarindiol for further investigation. The effect of falcarindiol (10 µM) in the luciferase reporter model was blocked upon co-treatment with the PPARγ antagonist T0070907 (1 µM). Falcarindiol bound to the purified human PPARγ receptor with aKiof 3.07 µM.In silicodocking studies suggested a binding mode within the ligand binding site, where hydrogen bonds to Cys285 and Glu295 are predicted to be formed in addition to extensive hydrophobic interactions. Furthermore, falcarindiol further induced 3T3-L1 preadipocyte differentiation and enhanced the insulin-induced glucose uptake in differentiated 3T3-L1 adipocytes confirming effectiveness in cell models with endogenous PPARγ expression. In conclusion, we identified falcarindiol-type polyacetylenes as a novel class of natural partial PPARγ agonists, having potential to be further explored as pharmaceutical leads or dietary supplements.

International audience; Within the last 25 years, matrix-assisted laser desorption ionization (MALDI) has become a powerful analytical tool in mass spectrometry (MS). While the method has been successfully applied to characterize large organic molecules such as proteins, sugars and polymers, its utilization for small molecules (≤ 600 Da) is significantly impaired by the coformation of matrix ions. Reducing or eliminating matrix-related signals has been subject of many studies. Some of which propose the enhancement of so-called matrix suppression effects, while others suggest the replacement of matrix molecules by materials such as microporous silicon. Alternatively, the immobilization of matrix molecules by utilizing them as self-assembled monolayers (SAMs) has been discussed. In continuation of this research, the current manuscript focuses on the elucidation of ion formation processes occurring on the surface of light absorbing SAMs. Ion yields obtained by free and immobilized matrix molecules as well as those generated by matrix-free gold film-assisted laser desorption ionization (GF-LDI) were compared. Experiments showed that the formation of strong analyte signals essentially required the presence of free matrix molecules, while the immobilization of the latter severely impaired ionization. The observed effect inversely correlated with the surface coverage of SAMs determined by cyclic voltammetry (CV). Based on these findings, the MS signal generated on light absorbing SAMs could be used supplementary to CV for determining the surface coverage of light absorbing SAMs.