Used as a substrate in enzymatic assays, particularly for detecting esterase and lipase activity. When hydrolyzed by these enzymes, it releases 2-nitrophenol, which is yellow and can be measured spectrophotometrically at around 400–420 nm. This color change allows for easy monitoring of enzyme activity in laboratory settings. Commonly applied in diagnostic tests and biochemical research to quantify enzyme concentration or inhibition. Also utilized in screening microorganisms for esterase production in microbiology studies.