can't read?
4-Nitrophenyl butyrate is a substrate for esterase, and lipase enzyme. Hydrolysis of 4-nitrophenyl butyrate by these enzymes releases the chromophore, 4-nitrophenolate which is spectrophotometrically analysed at 415 nm.
N 8789 (OTTO) 4-Nitrophenyl butyrate, ≥98% Cas 2635-84-9 - used as a substrate for esterase activity in monocyte-derived macrophage cell line in response to polyethylene.