Geschmack ist vorhersagbar: Mit FlavorMiner. FlavorMiner heißt das Tool, das IPB-Chemiker und Partner aus Kolumbien jüngst entwickelt haben. Das Programm kann, basierend auf maschinellem Lernen (KI), anhand der…
Seit Februar 2021 bietet Wolfgang Brandt, ehemaliger Leiter der Arbeitsgruppe Computerchemie am IPB, sein Citizen Science-Projekt zur Pilzbestimmung an. Dafür hat er in regelmäßigen Abständen öffentliche Vorträge zur Vielfalt…
Moura, P. H. B.; Porzel, A.; Nunes, R. M.; Baratto, L. C.; Wessjohann, L. A.; Martins, R. C. C.; Leal, I. C. R.;Antioxidant capacity and fragmentation features of
C‐glycoside isoflavones by high‐resolution electrospray ionization tandem mass spectrometry using collision‐induced and high‐energy collisional dissociation techniquesJ. Mass Spectrom.56e4793(2021)DOI: 10.1002/jms.4793
The rapid annotation and identification by mass spectrometry techniques
of flavonoids remains a challenge, due to their structural diversity and
the limited availability of reference standards. This study applies a
workflow to characterize two isoflavonoids, the orobol-C-glycosides
analogs, using high-energy collisional dissociation (HCD)- and
collision-induced dissociation (CID)-type fragmentation patterns, and
also to evaluate the antioxidant effects of these compounds by ferric
reducing antioxidant power (FRAP), 2,2′-azino-bis(3-ethylbenzothiazolin
acid) 6-sulfonic acid (ABTS), and 2,2-diphenyl-1-picrylhydrazyl (DPPH)
methods. By the CID-type fragmentation, in positive mode and at all
high-resolution mass spectrometry (HRMS) multiple stage, there were
shown differences in the annotation of the compounds, mainly concerning
some ratios of relative abundance. At CID-MS2 20 eV, the compounds could be efficiently characterized, because they present distinct base peaks [M + H]+ and [M + H–H2O]+ for the orobol-8-C- and orobol-6-C-glycoside, respectively. Similarly, by the HCD-type fragmentation, in HRMS2 stage, differences between orobol analogs in both mode of ionization were observed. However, the HR HCD-MS2 at 80 eV, in positive mode, generated more ions and each isomer presented different base peaks ions, [0,2X]+ for the orobol-8-C-glycoside and [0,3X]+ for the orobol-6-C-glycoside. By the DPPH, the 8-C-derivative
showed a very close value compared with the standard rutin and, in the
ABTS method, a higher radical-scavenging activity. In both methods, the
EC50 of orobol-8-C-glycoside was almost twice better compared with orobol-6-C-glycoside. In FRAP, both C-glycosides showed a good capacity as Fe+3
reducing agents. We could realize that combined MS techniques,
highlighting the positive mode of ionization, can be used to evaluate
the isoflavones analogs being useful to differentiate between the
isomeric flavones; therefore, these data are important to mass
spectrometry dereplication studies become more efficient.
Publikation
Schmidt, J.; Kuck, D.; Franke, K.; Sultani, H.; Laub, A.; Wessjohann, L. A.;The unusual fragmentation of long-chain feruloyl esters under negative ion electrospray conditionsJ. Mass Spectrom.54549-556(2019)DOI: 10.1002/jms.4357
Long‐chain ferulic acid esters, such as eicosyl ferulate (1), show a complex and analytically valuable fragmentation behavior under negative‐ion electrospay collision‐induced dissociation ((‐)‐ESI‐CID) mass spectrometry, as studied by use of a high‐resolution (Orbitrap) mass spectrometer. In a strong contrast to the very simple fragmentation of the [M + H]+ ion, which is discussed briefly, the deprotonated molecule, [M ‐ H]‐, exhibits a rich secondary fragmentation chemistry. It first loses a methyl radical (MS2) and the ortho‐quinoid [M ‐ H ‐ Me]‐• radical anion thus formed then dissociates by loss of an extended series of neutral radicals, CnH2n+1• (n = 0‐16) from the long alkyl chain, in competition with the expulsion of CO and CO2 (MS3). The further fragmentation (MS4) of the [M ‐ H ‐ Me ‐ C3H7]‐ ion, discussed as an example, and the highly specific losses of alkyl radicals from the [M ‐ H ‐ Me ‐ CO]‐• and [M ‐ H ‐ Me ‐ CO2]‐• ions provide some mechanistic and structural insights.
Publikation
Schüler, J.-A.; Neumann, S.; Müller-Hannemann, M.; Brandt, W.;ChemFrag: Chemically meaningful annotation of fragment ion mass spectraJ. Mass Spectrom.531104-1115(2018)DOI: 10.1002/jms.4278
Identification and structural determination of small molecules by mass spectrometry is an important step in chemistry and biochemistry. However, the chemically realistic annotation of a fragment ion spectrum can be a difficult challenge. We developed ChemFrag, for the detection of fragmentation pathways and the annotation of fragment ions with chemically reasonable structures. ChemFrag combines a quantum chemical with a rule‐based approach. For different doping substances as test instances, ChemFrag correctly annotates fragment ions. In most cases, the predicted fragments are chemically more realistic than those from purely combinatorial approaches, or approaches based on machine learning. The annotation generated by ChemFrag often coincides with spectra that have been manually annotated by experts. This is a major advance in peak annotation and allows a more precise automatic interpretation of mass spectra.
Publikation
Jablonická, V.; Ziegler, J.; Vatehová, Z.; Lišková, D.; Heilmann, I.; Obložinský, M.; Heilmann, M.;Inhibition of phospholipases influences the metabolism of wound-induced benzylisoquinoline alkaloids in Papaver somniferum L.J. Plant Physiol.2231-8(2018)DOI: 10.1016/j.jplph.2018.01.007
Benzylisoquinoline alkaloids (BIAs) are important secondary plant metabolites and include medicinally relevant drugs, such as morphine or codeine. As the de novo synthesis of BIA backbones is (still) unfeasible, to date the opium poppy plant Papaver somniferum L. represents the main source of BIAs. The formation of BIAs is induced in poppy plants by stress conditions, such as wounding or salt treatment; however, the details about regulatory processes controlling BIA formation in opium poppy are not well studied. Environmental stresses, such as wounding or salinization, are transduced in plants by phospholipid-based signaling pathways, which involve different classes of phospholipases. Here we investigate whether pharmacological inhibition of phospholipase A2 (PLA2, inhibited by aristolochic acid (AA)) or phospholipase D (PLD; inhibited by 5-fluoro-2-indolyl des-chlorohalopemide (FIPI)) in poppy plants influences wound-induced BIA accumulation and the expression of key biosynthetic genes. We show that inhibition of PLA2 results in increased morphinan biosynthesis concomitant with reduced production of BIAs of the papaverine branch, whereas inhibition of PLD results in increased production of BIAs of the noscapine branch. The data suggest that phospholipid-dependent signaling pathways contribute to the activation of morphine biosynthesis at the expense of the production of other BIAs in poppy plants. A better understanding of the effectors and the principles of regulation of alkaloid biosynthesis might be the basis for the future genetic modification of opium poppy to optimize BIA production.