4-Nitrophenyl b-D-xylotrioside is a chromogenic substrate that can be used to test for the presence of certain enzymes in food. This substrate is also used in enzyme assays and is a ligand for certain proteins. 4-Nitrophenyl b-D-xylotrioside is often used as a culture medium additive and has been shown to conjugate with glutathione reductase, cytochrome P450, and mycobacterium.