High-resolution electrospray mass spectra (HR-ESI-MS) were recorded on a timsTOF Pro TIMS-QTOF-MS instrument (Bruker Daltonics GmbH, Bremen, Germany). The samples were dissolved in (e.g. MeOH) at a concentration of ca. 50 µg ml -1 and analysed via continuous flow injection (2 µL min -1 ). The mass spectrometer was operated in the positive (or negative) electrospray ionisation mode at 4'000 V (-4'000 V) capillary voltage and -500 V (500 V) endplate offset with a N2 nebuliser pressure of 0.4 bar and a dry gas flow of 4 L min -1 at 180°C. Mass spectra were acquired in a mass range from m/z 50 to 2'000 at ca. 20'000 resolution (m/z 622) and at 1.0 Hz rate. The mass analyser was calibrated between m/z 118 and 2'721 using an Agilent ESI-L lowconcentration tuning mix solution (Agilent, USA) at a resolution of 20'000, giving a mass accuracy below 2 ppm. All solvents used were purchased in the best LC-MS quality.