4-Methylhippuric acid is has been used as a biological marker to monitor xylene exposure. It can also be used in HPLC to determine the carboxylic acid concentration in urine, along with styrene and ethyl benzene.

4-Methylindole is an indole used as a reagent in chemical synthesis. It has been used in the synthesis of triazolobenzazepine derivatives, anti-cancer phosphonate analogs and color emitting or electroluminescent applications.

4-Methylumbelliferone is useful as an indicator in the determination of nitric acid. It is also useful in the kinetic investigation of enzyme activity. 4-Methylumbelliferone is fluorescent in alkaline solution.

4-Methylumbelliferyl alpha-L-idopyranosiduronic acid sodium salt is a carbohydrate acid and organic sodium salt applied as an indicator. It is the fluorogenic substrate used in assays of α-L-Iduronidase and iduronate-2-sulfatase for identifying Hurler syndrome, also called mucopolysaccharidosis type I (MPS I). The disorder is characterized by α -L iduronidase enzyme deficiency, resulting in the buildup of glucosaminoglycans. Tests measure the chemical products 4-MU-α-IdoA or fluorophate 4-MU emitted following the enzymatic action of 4-Methylumbelliferyl alpha-L-idopyranosiduronic acid sodium salt. The substance is a white crystalline powder and is soluble in ethanol, methanol and water.

4-Methylumbelliferyl caprylate is a fluorogenic substrate for esterase with C8 activity, yielding a blue fluorescent solution upon cleavage and is used for the identification of Salmonella spp. based on the detection of caprylate esterase.

4-Methylumbelliferyl cholin phosphate is a fluorogenic substrate.

4-Methylumbelliferyl nonanoate is a fluorogenic substrate for esterase yielding a blue fluorescent solution upon cleavage. It can be useful for identification of certain Salmonella species.

4-Methylumbelliferyl palmitate is used as a fluorogenic substrate for a subclass of esterases called lipase.

Lipase is an enzyme that assists in the hydrolysis of fats. They have a large role in digestion as well as dietary lipid transport.

Lysosomal acid lipase (LAL), in particular, is required for the hydrolysis of cholesterol esters which are then delivered into the lysosome. Deficiencies in LAL are primarily associated with two diseases: cholesteryl ester storage disease (CESD) and Wolman’s disease (WD). 4-Methylumbelliferyl palmitate has often been used as one of the lipase substrates in studies involving either of these diseases.

Sensitive fluorogenic substrate for fluorometric and UV-spectrophotometric assays of phosphatases.

4-Methylumbelliferyl phosphate (MUP) is a sensitive fluorogenic substrate for fluorometric and UV-spectrophotometric assays of phosphatase.

Phosphotase activity has long been studied due to its importance in cellular function. Upon dephosphorylation, MUP yields fluorescent 4-methylumelliferone (4-MU). This reaction has been used to spot PCR amplified products in ELISA and to classify bacteria.

More specifically, MUP can act as an indicator of C. perfringens because of its ability to detect phosphatase which is a highly specific indicator of C. perfringens.