G2 s qtof

The derivatized samples were analyzed with an Agilent 7890A GC system (Agilent, Santa Clara, CA, USA) coupled to a quadrupole TOF mass spectrometer, G2-S QTOF (Waters Corporation, Manchester, UK), operating in APGC mode. The GC separation was performed using a fused silica DB5-MS capillary column (30m x 250μm I.D., 0.25μm film thickness; J&W Scientific, Folson, CA, USA). The initial GC oven temperature was 70°C. One min after injection, the GC oven temperature was increased with 15°C/min to 320°C and held for 4 min at 320°C. Splitless injections of 1 μL using a straight empty deactivated liner from Restek were carried out at 240°C. Helium was used as carrier gas at 2.0 mL/min. The interface temperature was set to 250°C using N₂ as auxiliary gas at 400 L/h, and cone gas at 150 L/h. The APCI corona pin was operated at 3.0 μA. The APGC source was operated in proton transfer mode by placing an uncapped vial with water (modifier) in a specially designed holder located in the source door (REF). The QTOF detection was operated in full-scan mode (m/z 50–650) with the resolution at ~20,000.

The assessment of (-)-5-demethoxygrandisin B at 100 ppm in methanol: H₂O (80:20) was conducted using a Xevo^® G2-S QTof coupled with an ACQUITY Ultra Performance LC™ system (Waters Corp., Milford, MA, USA). The ionization source was configured with a desolvation gas flow (N2) at 600 L/h and a desolvation temperature of 150 °C. The cone gas flow (N2) was set at 50 L/h, and the source temperature was maintained at 120 °C. Adjustments were made to the capillary and sampling cone voltages, setting them at 1.0 kV and 40 V, respectively. The data acquisition was executed utilizing MassLynx 4.1 software (Waters, Milford, USA) [19 (link),20 (link)]. NMR 1D (¹H and ¹³C) and 2D homonuclear-correlated spectroscopy (COSY ¹Hx¹H), HMBC, and HSQC analyses were acquired with a Bruker 400 spectrometer AscendTM (Rheinstetten, Germany) model at 400.15 MHz (¹H) and 100.62 MHz (¹³C). The chemical shifts were determined relative to CDCl₃ at 0 ppm. A total of 20 mg of (-)-5-demethoxygrandisin B was solubilized in 600 μL of CDCl₃. TopSpin 3.6.0 software was used for data control and processing. Thereby, the spectra were manually evaluated. The optical rotation of the (-)-5-demethoxygrandisin was measured on a Perkin–Elmer 341 polarimeter (Perkin–Elmer Inc., Waltham, MA, USA).