X-β-L-Fuc 

X-β-L-Fuc (5-Bromo-4-chloro-3-indolyl-β-L-fucopyranoside, CAS 125280-49-9) is a synthetic chromogenic substrate designed for selective detection of β-L-fucosidase (EC 3.2.1.51) enzymes, cleaving to release a halogenated indoxyl aglycone that spontaneously dimerizes and oxidizes, forming an insoluble intense blue dibromo-dichloro-indigo precipitate for unambiguous visualization of enzyme-positive colonies, plaques, or tissues. With molecular formula C14H15BrClNO6 (MW 392.63 g/mol), this white crystalline compound features β-L-fucopyranose (6-deoxy-L-galactose) O-glycosidically linked at C1 to the 3-hydroxy position of 5-bromo-4-chloro-1H-indol-3-ol, exhibiting high stability until hydrolyzed by bacterial β-fucosidases from Bacteroides, Bifidobacterium species, and human lysosomal α-L-fucosidase (after epimerization considerations), yielding >1000-fold localized color amplification detectable by eye without instrumentation. The L-fucose configuration distinguishes it from α-L-Fuc substrates used in blood group FucT screening, supporting functional assays in microbiome studies (fucosidase-mediated HMO degradation), fucosidosis diagnostics (FUCA1 deficiency), and directed evolution of glycoside hydrolases (GH29/95 families). Incorporated into chromogenic media at 50-200 μM, it identifies fucosidase-positive probiotics and pathogens in dairy/gut samples, while the membrane-impermeant indigo enables histochemical mapping in fixed tissues and quantitative plaque assays orthogonal to X-Gal/X-Glc systems.

Appearance

• White crystalline powder.
• Hydrolysis produces deep blue insoluble precipitate.

Source

• Koenigs-Knorr synthesis: protected β-L-fucopyranosyl halide + bromochloroindol-3-ol.
• Specialty glycobiology suppliers (Hepattack 99%).

Molecular Weight and Structure

• Formula: C14H15BrClNO6; MW 392.63 g/mol.
• (2S,3S,4R,5R,6S)-2-(5-bromo-4-chloro-1H-indol-3-yloxy)-6-methyloxane-3,4,5-triol.

Sugar Specificity

• Selective β-L-fucopyranoside for β-L-fucosidases (GH29).
• Minimal cross-reactivity with α-fucosidases.

Biological Activity

• Chromogenic fucosidase reporter; non-toxic.
• Enzyme-localized blue product formation.

Purity and Microbial Contamination

• 99% (Hepattack vacuum foil packaging).
• Synthetic; non-sterile research grade.

Identity and Quality Control

• CAS-confirmed 125280-49-9; molecular weight verified.
• Characteristic blue hydrolysis product.

Shelf Life and Storage

• Stable vacuum-sealed; store desiccated -20°C.
• Long shelf life in foil packaging.

Applications

• β-L-Fucosidase chromogenic media; fucosidosis diagnostics.
• Microbiome HMO degradation assays.

Key Characteristics

• L-Fucose specific; eye-readable blue colonies.
• High purity (99%); vacuum packaged.

Citation Links

• https://www.hepattack.com (product image specs)
• https://cymitquimica.com/cas/125280-49-9/ (CAS data)
• https://pubchem.ncbi.nlm.nih.gov/compound/125280-49-9
• https://www.sigmaaldrich.com (indolyl fucoside catalog)
• https://www.tcichemicals.com (haloindolyl glycosides)
• https://www.biosynth.com (chromogenic fucosides)
• https://www.medchemexpress.com (enzyme substrates)
• https://www.glentham.com (microbiology reagents)
• https://www.chemicalbook.com/CASEN_125280-49-9.htm
• https://www.rpicorp.com (glycobiology tools)