7-Amino-4-methylcoumarin (AMC, CAS 26093-31-2) is a heterocyclic organic compound belonging to the coumarin family. It is a pale yellow to yellow crystalline powder with a molecular formula of C10H9NO2. This compound is a key derivative of 4-methylumbelliferone, featuring an amino group at the 7-position, which significantly alters its photophysical properties compared to its parent molecule. Its primary and most significant application is in biochemistry and life sciences as a versatile fluorogenic substrate. AMC is widely used to assay the activity of various hydrolytic enzymes, particularly proteases (e.g., trypsin, chymotrypsin, caspases) and esterases. In these assays, AMC is conjugated to specific peptides or esters via its amino group. Enzymatic cleavage releases the free AMC, which exhibits strong blue fluorescence (excitation ~365 nm, emission ~445 nm), allowing for highly sensitive and quantitative measurement of enzyme activity. This makes it indispensable in drug discovery, apoptosis research, and diagnostic kit development. Beyond its role as a probe, 7-amino-4-methylcoumarin serves as a crucial synthetic building block for the preparation of more complex fluorescent dyes, laser dyes, and optical brightening agents. Its structure allows for further functionalization, enabling the tuning of fluorescence wavelength and intensity for specific applications in labeling and sensing.