13c4 fumaric acid

¹³C₃-lactic acid, ¹³C₂-oxalic acid, ²H₃-sacrosine, ²H₈-valine, ¹³C₃-dihydroxyacetone, ²H₁₀-isoleucine, ¹³C₄-fumaric acid, ¹³C₄-malic acid, ²H₃-aspartic acid, ¹³C₅-glutamic acid, ¹³C₆-4-hydroxybenzoic acid, ²H₃-lauric acid, ¹³C₅-ribose, ¹³C₂-taurine, ²H₄-citric acid, ²H₇-ornithine, ¹³C₆-tyrosine, ¹³C₆-dopa, ²H₆-kynurenine, ²H₈-cystamine, and ¹³C₁₁-tryptophan were purchased from Cambridge Isotope Laboratories, Inc. (MA, USA). ²H₃-2-hydorxybutyric acid and 2-isopropylmalic acid were purchased from CDN isotopes (Quebec, CA) and Sigma Aldrich (Tokyo, Japan), respectively. The compounds were dissolved in methanol, as shown in Supplementary Table 3, and then the obtained solution was used as an extraction solution. A standard alkane series mixture (C7 to C33) and octafluoronaphthalene (OFN) were purchased from Restek Co. (PA, USA) and Shimadzu Co. (Kyoto, Japan), respectively. Methoxyamine hydrochloride and N-methyl-N-trimethylsilyl-trifluoroacetamide (MSTFA), which were used for the derivatization, were obtained from Sigma-Aldrich and GL Science (Tokyo, Japan), respectively.