TXN and inflammatory bowel disease: Other components of postbiotic preparations with proven beneficial effects include bacterial enzymes, tryptophan derivatives such as melatonin, fermentation products such as lactic acid and isocaproic acid, and secondary metabolites (e.g., colipterins from E. coli and thioredoxins from S. boulardii), which have demonstrated immunomodulatory properties that contribute to beneficial effects against IBD, both in vitro and in vivo [70].