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Stool samples (100mg) were extracted by solvent mixture 1 (1.2 mL for stool samples, acetonitrile: water, 1:1, vol/vol) and solvent mixture 2 (0.7 mL for stool samples, acetonitrile: methanol, 1:3, vol/vol). After 5 min of sonication and centrifugation each, the aliquot (160 µL) was transferred to a new vial and concentrated to complete dryness using a speed vacuum concentrator (SCANVAC, Seoul, South Korea). The dried sample was re-constituted with 70% ACN (acetonitrile) (70 µL) for mass-spectrometric analysis. , Serum samples (100 µL) were extracted by solvent mixture (3.9 mL, methanol: acetonitrile: water, 3:3:2, vol/vol/vol). After 5 min of sonication and centrifugation each, the aliquot (160 µL) was transferred to a new vial and concentrated to complete dryness using a speed vacuum concentrator (SCANVAC, Seoul, South Korea). The dried sample was re-constituted with 70% ACN (acetonitrile) (70 µL) for mass-spectrometric analysis. , Liver sample (100 mg) were extracted by solvent mixture 1 (1.1 mL for liver samples, acetonitrile: water, 1:1, vol/vol) and solvent mixture 2 (0.6 mL for liver samples, acetonitrile: methanol, 1:3, vol/vol). After 5 min of sonication and centrifugation each, the aliquot (160 µL) was transferred to a new vial and concentrated to complete dryness using a speed vacuum concentrator (SCANVAC, Seoul, South Korea). The dried sample was re-constituted with 70% ACN (acetonitrile) (70 µL) for mass-spectrometric analysis. , Cecum samples (100 mg) were extracted by solvent mixture 1 (1.2 mL for cecum samples, acetonitrile: water, 1:1, vol/vol) and solvent mixture 2 (0.7 mL for cecum samples, acetonitrile: methanol, 1:3, vol/vol)

Samples were chromatographically separated by an UltiMate-3000 UPLC system (Thermo Fisher Scientific, Waltham, MA, USA) equipped with 150 × 2.1  mm UPLC BEH 1.7-µm C18 column (Waters, Milford, MA, USA) and 5.0 mm × 2.1 mm UPLC BEH 1.7-µm C18 VanGuard Pre-Column (Waters, Milford, MA, USA). The mobile phase consisted of solvent A (water with 0.1% formic acid) and solvent B (100% acetonitrile with 0.1% formic acid). The flow rate was set to 300 µL/min, and the gradient of solvent B was programmed as follows: 0–2 min, 3%; 2–11 min, 3%–100%; 11–12 min, 100%; 12–15 min, 3%.

Mass-spectrometry was conducted in polarity-switching ionization mode using Q-Exactive plus Orbitrap (Thermo Fisher Scientific, Waltham, MA, USA) with a heated electrospray ionization probe. Full mass spectrum (MS) scan was operated in the range of 70–1,000 m/z (resolution: 70,000 FWHM at m/z = 200) with automatic gain control target of 1e6 ions and maximum injection time of 100 ms.