Aspartic acid

Eight amino acids including tyrosine, tryptophan, threonine, glutamic acid, aspartic acid, histidine, phenylalanine, and arginine (Sinopharm Chemical Reagent Co., Ltd., Shanghai, China) were added into a 30% methanol aqueous solution of azalomycin F (100 μM) to obtain a mixed solution by vortexing, according to the molar concentration ratio of azalomycin F to each amino acid of 1:8. Simultaneously, the 30% methanol aqueous solution that only contained 100 μM azalomycin F was prepared as a blank control for background subtraction. After being incubated in a water bath at 37 °C for 30 min, these solutions were analyzed by a TripTOF 5600+ mass spectrometry (AB Sciex, Framingham, MA, USA) with an electrospray ion resource, and the detailed parameters are shown in Table S3 for negative ionization modes.

Luhua soybean sauce, Haitian soy sauce, Qiaoxifu sauce, Luhua vinegar, Zilin mature vinegar, and Qiaoxifu vinegar were purchased from the RT-MART market (Qingdao, China). Aspartic acid and glucose were supplied by the Sinopharm Group Co., Ltd. (Shanghai, China). 3-(4, 5-Dimethylthiazol-2-yl)-2, 5-diphenyl-tetrazolium bromide (MTT) was purchased from Gibco-BRL (Bethesda, MD, USA).