Resorufin ethyl ether,

7-Ethoxy-3H-phenoxazin-3-one; 7-O-Ethoxyresorufin

Resorufin ethyl ether is a fluorescent substrate that is used to measure the activity of cytochrome P450 enzymes. It can be used in vitro to study the effects of drugs on enzyme activities and in vivo to study liver lesions. Resorufin ethyl ether is also used as a model system for studying synchronous fluorescence, which is the emission of light by two or more substances at the same time. The nitrogen atoms in resorufin ethyl ether can be substituted with other atoms such as magnesium or zinc, which will affect its activity and fluorescence properties. Resorufin ethyl ether binds to cytochrome P450 enzymes and therefore inhibits their activity. This inhibition is reversible, and it can be reversed by adding a substance that competes with the substrate for binding sites on the enzyme.