Monopotassium phosphate kh2po4

The 1D and 2D NMR spectra were recorded on a 600 MHz Varian NMR spectrometer (VNS-600, Palo Alto, CA, USA), operated using Bruker TopSpin software (Billerica, MA, USA), at the Core Research Support Center for Natural Products and Medical Materials (CRCNM). The acquired data were processed using MestReNova 12.0.3 software (Mestrelab Research SL, Santiago de Compostela, Spain). Analytical HPLC was conducted using a Shimadzu LC-20A system (Kyoto, Japan) equipped with a Shimadzu SPD-M20A photodiode array (PDA) detector (Kyoto, Japan) and an Alltech 3300 evaporative light scattering detector (ELSD, Essen, Germany), with a Phenomenex Luna 5 μm C₁₈ column (100 Å, 250 × 4.6 mm, 1 mL/min). Deuterated solvents, including 3-(trimethylsilyl)-1-propanesulfonic acid solution (DSS, an internal calibrant, 1 wt% in D₂O, 99.9 atom % D) and sodium deuteroxide solution (NaOD, 40 wt% in D₂O, 99.5 atom % D) for NMR experiments, as well as monopotassium phosphate (KH₂PO₄, ≥99.0%), were purchased from Sigma-Aldrich. Azelaic acid (98%), sebacic acid (98%), and glycerophosphocholine (choline alfoscerate, 98%) were obtained from AK Scientific. Choline sulfate (98%) and phosphocholine chloride calcium salt tetrahydrate (>98%) were purchased from Cambridge Isotope Laboratories and TCI Chemicals, respectively. All solvents were of ACS grade or better.

Deuterium oxide (D₂O, 99.9% atom D) including 0.05% 3-(trimethylsilyl) propionic-2,2,3,3-d₄ acid sodium salt (TSP), Deuterium oxide (D₂O, 99.9% atom D), and monopotassium phosphate (KH₂PO₄) were purchased from Sigma-Aldrich (St. Louis, MO, USA). Sodium deuteroxide solution (NaOD, 99.5% atom D; 40% in D₂O) was purchased from Cambridge Isotope Laboratories, Inc. (Andover, MA, USA).