8HQ-Gal

8HQ-Gal (8-Hydroxyquinolyl-β-D-galactopyranoside, CAS 110379-84-8) is a chromogenic substrate designed for β-galactosidase (EC 3.2.1.23) detection, where enzymatic hydrolysis cleaves the β-glycosidic linkage to release 8-hydroxyquinoline, which undergoes metal-catalyzed oxidation to form a brown insoluble precipitate, providing clear visual identification of enzyme-positive colonies, plaques, or tissues in microbiological and molecular biology applications. With molecular formula C15H17NO6 (MW 307.30 g/mol), this white to off-white solid features β-D-galactopyranose O-linked at C1 to the 8-hydroxyquinoline aglycone, exhibiting good stability at neutral pH until hydrolyzed by E. coli lacZ (α-complementation strains) or mammalian lysosomal β-galactosidases, yielding the fluorescent/chelating 8-HQ product that coordinates with trace metals (Fe³⁺, Cu²⁺) in media to produce the characteristic brown polymeric pigment localized to enzyme sources. Unlike X-Gal’s blue indigo, 8HQ-Gal’s brown coloration offers orthogonal contrast for multiplexing with other indolyl substrates, supporting dual-reporter screening (lacZ/GUS) and high-density transformation plates where color differentiation prevents misidentification. Used at 50-150 μg/mL with IPTG, it enables recombinant selection (white/brown colonies) in cloning workflows, while its metal-dependence allows modulation via chelators (EDTA) for background control. Applications extend to lysosomal storage disorder diagnostics (GM1-gangliosidosis), bacterial β-Gal profiling in probiotics, and histochemical staining orthogonal to GFP fluorescence, with the 8-HQ release enabling secondary fluorescence assays (Ex/Em ~370/525 nm).

Appearance

• White to off-white crystalline powder.
• Hydrolysis yields brown insoluble precipitate.

Source

• Glycosylation synthesis: protected β-D-galactopyranosyl donor + 8-hydroxyquinoline.
• Commercial research grade (Molecular Depot, Glentham).

Molecular Weight and Structure

• Formula: C15H17NO6; MW 307.30 g/mol.
• (2R,3R,4S,5R,6S)-2-(hydroxymethyl)-6-(quinolin-8-yloxy)oxane-3,4,5-triol.​

Sugar Specificity

• Selective β-D-galactopyranoside for β-galactosidases.
• Minimal cross-reactivity with glucosidases.​

Biological Activity

• Chromogenic β-Gal reporter; metal-dependent brown product.
• Sensitivity equivalent to X-Gal analogs.​

Purity and Microbial Contamination

• ≥98% (HPLC); biochemical grade.
• Synthetic; non-sterile.​

Identity and Quality Control

• ¹H-NMR confirmed β-anomer; InChI verified.
• Brown precipitate post-β-Gal incubation.​

Shelf Life and Storage

• 2+ years -20°C desiccated; DMSO soluble.
• Light/metal-protected.​

Applications

• β-Gal colony screening; lacZ multiplexing.
• Lysosomal diagnostics, histochemistry.​

Key Characteristics

• Brown color orthogonal to X-Gal blue; metal-modulatable.
• Fluorescent 8-HQ secondary readout.​

Citation Links

• https://pubchem.ncbi.nlm.nih.gov/compound/9879604​
• https://moleculardepot.com/product/8-hydroxyquinoline-β-d-galactopyranoside​
• https://www.creative-enzymes.com/product/8hydroxyquinolinebdgalactopyranoside_8591.html​
• https://www.chemicalbook.com/ChemicalProductProperty_IN_CB2138073.htm​
• https://www.benchchem.com/product/b38060​
• https://pubchem.ncbi.nlm.nih.gov/summary/summary.cgi?sid=354349811​
• https://www.chemimpex.com/products/21421​
• https://cymitquimica.com/products/54-BIB6069/113079-84-8​
• https://www.glentham.com/en/products/product/GC9186/​
• https://www.benchchem.com/jp/product/b038060