Oxylipin standards and internal standards

LC-MS grade acetonitrile (ACN), methanol (MeOH), n-hexane, ethyl acetate, and methyl formate were purchased from Fisher Scientific (Schwerte, Germany). Dulbecco’s modified Eagle’s medium (DMEM), fetal bovine serum (FBS), and all other cell culture reagents were purchased from Biochrom/Merck (Berlin, Germany). Oxylipin standards and internal standards were either purchased from Cayman Chemicals (local distributor: Biomol, Hamburg, Germany) or synthesized in-house as described in the Electronic Supplementary Material (ESM). Acetic acid (HAc) LC-MS grade, formic acid (FA) LC-MS grade, N-(3-dimethylaminopropyl)-N′-ethylcarbodiimide hydrochloride (EDC), N,N-dimethylformamide (DMF), human blood serum, and all other chemicals were acquired from Sigma-Aldrich (Steinheim, Germany). Human blood plasma and second-pool human blood serum were purchased from BioIVT (West Sussex, UK). Caco-2 cells were obtained from the German Collection of Microorganisms and Cell Cultures (DSMZ, Braunschweig, Germany). Finally, AMPP and ²H₅-AMPP were synthesized as described before [42 (link)] (for details see ESM).