Dimethyl sulfoxide d6

Anhydrous betaine (>97%) was purchased from Tokyo Chemical Industry (Tokyo, Japan). L(+)-tartaric acid (>99.5%), DL-malic acid (>99.5%) were supplied by Scharlab (Sentmenat, Spain). Citric acid monohydrate (>99.5%) was purchased from AppliChem GmbH (Darmstadt, Germany). Hydrochloric acid was purchased from Lach-Ner (Brno, Czech Republic). Methanol was purchased from Macron (Avantor, Gliwice, Poland). Dimethyl sulfoxide-d₆ was obtained from Euriso-Top (St. Aubin Cedex, France). Lactic acid (natural, ≥85%) and all other chemicals were obtained from Sigma Aldrich (St. Louis, MO, USA). Human colorectal adenocarcinoma cells (Caco-2, ACC 169) and human caucasian colon adenocarcinoma (HT29, ACC 299) were purchased from DSMZ (Braunschweig, Germany). Roswell Park Memorial Institute (RPMI) medium, fetal bovine serum (FBS), and penicillin–streptomycin (PS) solution were purchased from Corning (Corning, NY, USA). CellTiter 96^® AQueous One Solution Cell Proliferation Assay was purchased from Promega (Madison, WI, USA).

All commercially purchased materials were used as received. Ethylenediamine, guanosine 5′-monophosphate disodium salt and ruthenium(III) chloride hydrate were purchased from Fluorochem Ltd. (Hadfield, UK). L-histidine was purchased from Acros Organics (Geel, Belgium). Silver carbonate was purchased from Alfa Aesar (Heysham, UK). Ammonium hexafluorophosphate, citric acid, deuterium chloride (20 wt. % solution in D₂O), sodium deuteroxide (40 wt. % solution in D₂O), sodium phosphate dibasic heptahydrate, sodium sulfate, trimethylamine and 2,2,2-trifluoroethanesulfonyl chloride were purchased from Fisher Scientific (Loughborough, UK). Dichloromethane, ethanol and methanol were purchased from Honeywell (Morristown, NJ, USA). Diethyl ether was purchased from VWR (Lutterworth, UK). Chloroform-d, dimethylsulfoxide-d₆ and deuterium oxide were purchased from Eurisotop (Saint-Aubin, France).

Dried and cut leaflets (Lot 26094) and pods (Lot 22421) were obtained from Alfred Galke GmbH (Bad Grund, Germany). Retard tablets (Sennalax^®, Lot 2014211) were bought in a local pharmacy. SPE cartridges (Chromabond HR-XA, 85 µm, 3 mL/500 mg) and a 70 mL reservoir column were obtained from Macherey-Nagel GmbH (Düren, Germany), and cartridges for flash chromatography (Flashpure Ecoflex Silica SL 50 μm irregular 10 g, Lot 150317B) were ordered from Büchi (Flawil, Switzerland). Dimethyl sulfoxide-d₆ (99.80%, lot S1051, batch 0119E) for NMR spectroscopy was purchased from Eurisotop GmbH, Saarbrücken, Germany, and conventional 5 mm sample tubes were obtained from Rototec-Spintec GmbH, Griesheim, Germany. LCMS-grade acetonitrile, gradient-grade methanol, analytical-grade solvents, and TLC plates (silica gel 60 F254) were purchased from VWR International GmbH, Darmstadt, Germany. Hydrochloric acid (34%) and trifluoroacetic acid (TFA) were obtained from Carl Roth GmbH (Karlsruhe, Germany), acetic acid was purchased from Thermo Fisher Scientific Inc. (Waltham, MA, USA), and LCMS-grade formic acid was purchased from Merck (Darmstadt, Germany). Water was doubly distilled in-house.