3 indolepropionic acid

Formic acid (HPLC grade) was purchased from Dikma Technologies Inc. (Lake Forest, CA, USA). Ultra-pure water was obtained from Hangzhou Wahaha Group Co., Ltd. (Zhejiang, China). Methanol (HPLC grade), acetonitrile (HPLC grade), chloroform (HPLC grade), isopropanol (HPLC grade), Tween, pCPA, serotonin hydrochloride, 5-hydroxyindoleacetate, kynurenine, kynurenate, 3-hydroxykynurenine, phenylalanine, tyrosine, sodium hippurate hydrate, creatinine, guanosine, hypoxanthine, 3-indolepropionic acid, citrate, oxoglutarate, succinate, xanthine, uric acid and indoxyl sulfate potassium salt were purchased from Sigma-Aldrich (St. Louis, MO, USA). T-AOC assay kit with Ferric Reducing Ability of Plasma (FRAP) method, SOD assay kit, total GPx assay Kit and lipid peroxidantion MDA assay kit were purchased from Beyotime Institute of Biotechnology (Jiangsu, China). CAT assay kit and reactive oxygen species assay kit were obtained from Nanjing Jiancheng Bioengineering Institute (Jiangsu, China).

The reference standards of uric acid, deoxycytidine, 3-indolepropionic acid and lysophosphatidylcholines (C16:0 LPC, C18:0 LPC, C18:1 LPC) were supplied by Sigma Corporation (St. Louis, MO, USA). Phenylalanine, tryptophan, tyrosine, proline and serine were supplied by Tianjin Bodi Chemical Co., Ltd. (Tianjin, China). Creatine, betaine, taurine, carnitine, creatinine, hippuric acid, citrate and α-ketoglutaric acid were supplied by Sinopharm Chemcial Reagent Co. Ltd (Shanghai, China). Cholic acid was purchased from the National Institutes for Food and Drug Control (Beijing, China). Fluoxetine was provided by Lilly S.A. (Spain, France). Acetonitrile and formic acid of HPLC grade were purchased from Dikma Corporation (Richmond Hill, NY, USA). Water was purified by redistillation and filtered through 0.22 μm membrane filter before use. NaCsI was obtained from Sigma-Aldrich (MO, USA). All other chemicals were of analytical grade.