4-Methylumbelliferone

Technical Specifications

Product Description & Scientific Applications

4-Methylumbelliferone (4-MU), 7-hydroxy-4-methylcoumarin, is a hydroxycoumarin fluorophore whose phenolic OH is weakly acidic, with a pKa of 7.8. Because this pKa is relatively high, the fluorescent anion only partially dissociates under the near-neutral conditions (pH 6–6.5) at which many enzymes are most active.

Excited-state proton transfer. In the excited state 4-MU undergoes proton transfer, and neutral, anionic and tautomeric prototropic forms can be identified, so its emission depends on pH and on the local water environment.

Fluorogenic enzyme substrates. Its most established use is as the fluorogenic leaving group of enzyme substrates: 4-methylumbelliferyl glycosides, sulfate and phosphate esters are cleaved by the corresponding hydrolases to release 4-MU, whose ionised phenol is strongly fluorescent, giving a sensitive readout of enzyme activity. 4-Methylumbelliferyl sulfate (MUS) is the common fluorogenic substrate for aryl sulfatases, and 4-MU-releasing substrates are standard indicators of enzymatic activity for detecting microorganisms and pathogens.

Hyaluronan-synthesis inhibition. 4-MU is also an inhibitor of hyaluronan synthesis, demonstrated in human skin fibroblasts and in group C Streptococcus. On this basis it is used in drug-discovery research as a hyaluronan-synthesis-inhibitor tool to study hyaluronan-dependent disease biology across oncology, inflammation and autoimmunity.

Coumarin scaffold. 4-MU also serves as a coumarin scaffold from which derivatives are synthesised and evaluated in anticancer research.

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