Stable isotope labeled amino acid mix

Short-chain and medium-chain fatty acid standards including formic acid, propionic acid, isobutyric acid, butyric acid, isovaleric acid, valeric acid, hexanoic acid, isocaproic acid, and n-heptanoic acid were purchased from Sigma–Aldrich (St. Louis, MO, USA). Phenolic compound standards including protocatechuic acid, 3,4-Dihydroxyphenyl ethanol, 3,4-dihydroxyphenylacetic acid, gallic acid, caffeic acid, isoferulic acid, urolithin A, trans-resveratrol, equol, daidzein, homovanillic acid sulfate, genistein, naringenin, phloretin, kaempferol, epicatechin, catechin, enterolactone, quercetin, hesperetin, epigallocatechin, isorhamnetin, myricetin, chlorogenic acid, roseoflavin, phlorizin, epicatechin gallate, epigallocatechin gallate, quercetin 3-D-galacoside, and rutin were purchased from Cayman company (Ann Arbor, MI, USA). The stable isotope-labeled amino acid mix (20 AA U-13C, 97–99%; U-15N, 97–99%) was purchased from Cambridge Isotope Laboratories (Tewksbury, MA, USA). HPLC-MS-grade acetonitrile, ammonium acetate, formic acid, and acetic acid were purchased from Fisher Scientific (Pittsburgh, PA, USA).

Free fatty acid standards including propionic acid, isobutyric acid, butyric acid, 2-methyl-butyric acid, isovaleric acid, valeric acid, hexanoic acid, and isocaproic acid were purchased from Sigma–Aldrich (St. Louis, MO, USA). Phenolic compound standards including protocatechuic acid, 3,4-dihydroxyphenyl ethanol, 3,4-dihydroxyphenylacetic acid, gallic acid, caffeic acid, isoferulic acid, urolithin A, trans-resveratrol, equol, daidzein, homovanillic acid sulfate, genistein, naringenin, phloretin, kaempferol, epicatechin, catechin, enterolactone, quercetin, hesperetin, epigallocatechin, isorhamnetin, myricetin, chlorogenic acid, roseoflavin, phlorizin, epicatechin gallate, epigallocatechin gallate, quercetin 3-D-galacoside, and rutin,were purchased from Cayman company (Ann Arbor, MI, USA). The stable isotope-labeled amino acid mix (20 AA U-13C, 97–99%; U-15N, 97–99%) was purchased from Cambridge Isotope Laboratories (Tewksbury, MA, USA). HPLC-MS-grade acetonitrile, ammonium acetate, formic acid, and acetic acid were purchased from Fisher Scientific (Pittsburgh, PA, USA).