Resorufin β-D-glucuronide sodium salt

Resorufin β-D-glucuronide sodium salt (CAS 125440-91-7), a water-soluble fluorogenic substrate for β-glucuronidase (GUS/β-Gluc) enzymes, undergoes rapid hydrolysis to release intensely fluorescent resorufin (Ex/Em 571/585 nm, ε=56,000 M⁻¹cm⁻¹), providing >500-fold signal amplification for ultrasensitive detection in real-time assays. With formula C18H14NNaO9 (MW 411.29 g/mol), this orange conjugate links resorufin via β1-O-glycosidic bond to D-glucuronic acid (uronic acid of glucose), stable at neutral pH but cleaved by bacterial (E. coli GusA) or eukaryotic β-glucuronidases (EC 3.2.1.31) with kcat/Km ~10^6 M⁻¹s⁻¹, ideal for no-wash kinetic monitoring. Employed in plant molecular biology as GUS reporter gene substrate (replacing X-Gluc for fluorescence over chromogenesis), microbial GUS detection in microbiome studies, HTS for glucuronidase inhibitors (e.g., irinotecan toxics), and diagnostics of Crigler-Najjar/Gilbert syndromes via UGT1A1 activity. Superior to FDGlu for live imaging due to cytoplasmic retention, cell-permeability (10-100 μM loading), and multiplexing with GFP/CFP, it quantifies phase II drug metabolism (glucuronidation), lysosomal storage disorders, and xenobiotic detox in single cells via droplet microfluidics or flow cytometry.