Molecular networking connects mass spectra of molecules based on the similarity of their fragmentation patterns. However, during ionization, molecules commonly form multiple ion species with different fragmentation behavior. As a result, the fragmentation spectra of these ion species often remain unconnected in tandem mass spectrometry-based molecular networks, leading to redundant and disconnected sub-networks of the same compound classes. To overcome this bottleneck, we develop Ion Identity Molecular Networking (IIMN) that integrates chromatographic peak shape correlation analysis into molecular networks to connect and collapse different ion species of the same molecule. The new feature relationships improve network connectivity for structurally related molecules, can be used to reveal unknown ion-ligand complexes, enhance annotation within molecular networks, and facilitate the expansion of spectral reference libraries. IIMN is integrated into various open source feature finding tools and the GNPS environment. Moreover, IIMN-based spectral libraries with a broad coverage of ion species are publicly available.

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General conceptualization 48 RS, DP, LFN, MW, PCD conceptualized the idea of IIMN and its integration into GNPS and 49 feature-finding software tools 50 RS, DP, LFN, PCD wrote the manuscript 51 RS, BA, FH, HUH conceptualized the MZmine feature grouping workflow 52 UK, HH provided discussion and feedback on IIMN and the MZmine workflow 53 Development 54 RS developed the IIMN modules in MZmine and the MS 2 spectral library generation modules 55 MW, RS developed the "supplementary edges" format in the FBMN workflow to enable IIMN 56 MW programmed the IIMN workflow on GNPS 57 RS, MW developed the direct submission of MZmine data to run IIMN on GNPS 58 JR, MGA developed the XCMS/CAMERA IIMN integration in R 59 HT developed the MS-DIAL FBMN and IIMN integration 60 KD developed the MS 2 spectral merge function into the export modules for FBMN, IIMN, and 61 SIRIUS, which was coordinated by SB 62 TP, AK provided feedback and help for the development and integration of IIMN in MZmine 63

The occurrence of glucose-derived β-carboline alkaloids tangutorid E (Tan E) and tangutorid F (Tan F) as well as their dehydroxy-derivatives (DH-Tan E/F) was investigated in a broad variety of foodstuffs by LC–MS/MS-based stable isotope dilution analysis (SIDA). For that purpose, the target compounds and their 13C6-stable isotope-labeled analogues were synthesized from l-tryptophan and (13C6-)d-glucose and used to develop a rapid LC–MS/MS–SIDA method. After validation for several food matrices, the method was applied to the analysis of these β-carbolines in 80 food items. Quantitative amounts were detected in 46.3, 50.0, and 42.5% of the samples regarding Tan E, Tan F, and DH-Tan E/F, respectively, with corresponding ranges of 0.01–6.75, 0.01–5.07, and 0.01–0.75 mg/kg; the highest amounts were found in processed tomato products. A combination of the obtained occurrence data in foods with average food consumption data led to the calculation of rough estimates for the chronic daily intake of those alkaloids, yielding values of 0.44, 0.36, and 0.13 μg/kg body weight/day for Tan E, Tan F, and DH-Tan E/F, respectively. Evidently, the consumption of processed tomato-based products accounts for the majority of the total daily intake of the investigated β-carbolines; the potential bioactivities of Tan E, Tan F, and DH-Tan E/F have yet to be investigated.

In the course of gaining new insights into the secondary metabolite profile of various Stachybotrys strains, in particular concerning triprenyl phenol-like compounds, so far, unknown metabolites with analogous structural features were discovered. Three novel meroterpenoids containing a chromene ring moiety, namely stachybotrychromenes A–C, were isolated from solid culture of the filamentous fungus Stachybotrys chartarum DSMZ 12880 (chemotype S). Their structures were elucidated by means of comprehensive spectroscopic analysis (1D and 2D NMR, ESI-HRMS, and CD) as well as by comparison with spectroscopic data of structural analogues described in literature. Stachybotrychromenes A and B exhibited moderate cytotoxic effects on HepG2 cells after 24 h with corresponding IC50 values of 73.7 and 28.2 μM, respectively. Stachybotrychromene C showed no significant cytotoxic activity up to 100 μM. Moreover, it is noteworthy that stachybotrychromenes A–C are produced not only by S. chartarum chemotype S but also S. chartarum chemotype A and Stachybotrys chlorohalonata.Electronic supplementary materialThe online version of this article (10.1007/s12550-018-0312-7) contains supplementary material, which is available to authorized users.