4-Nitrophenyl 5-O-trans-feruloyl-a-L-arabinofuranoside is a high purity, enyzme substrate that is used in the diagnosis of phenylketonuria. It is also used to detect nitrophenols in environmental samples. This product has been shown to be a very good ligand for use in fluorescence and chemiluminescence studies. It can be used as a chromogenic substrate for the detection of enzymes such as oxidases and peroxidases. 4-Nitrophenyl 5-O-trans-feruloyl-a-L-arabinofuranoside has been shown to be a suitable bioluminescent substrate for the study of luciferase activity.