X-NeuNAc Ammonium Salt 

X-NeuNAc Ammonium Salt (5-Bromo-4-chloro-3-indolyl-α-N-acetylneuraminic acid ammonium salt) is the ammonium-counterion variant of the chromogenic neuraminidase (sialidase) substrate X-NeuNAc, optimized for enhanced solubility and stability in microbiological media for detecting sialidase-positive pathogens through hydrolysis that generates an insoluble intense blue dibromo-dichloro-indigo precipitate localized to enzyme-active colonies. Closely related to the sodium salt (CAS 160369-85-7), this form features the same α2-linked Neu5Ac (N-acetylneuraminic acid) core structure (C19H22BrClN2O9- NH4+, MW ~545.8 g/mol estimated) where bacterial/viral neuraminidases (EC 3.2.1.18) cleave the glycosidic bond, liberating 5-bromo-4-chloroindol-3-ol that spontaneously dimerizes/oxidizes to the highly colored, membrane-impermeant indigo dye for unambiguous visual screening without washes or equipment. The ammonium cation improves aqueous solubility (>15 mg/mL) versus sodium salt, reducing precipitation in agar (50-200 μM working concentration) for selective media targeting sialidase-producing bacteria (Vibrio cholerae, Clostridium perfringens, Streptococcus pneumoniae) and influenza viruses, with Km values ~0.5-1.0 mM ensuring low background and high signal (>1000-fold amplification). Essential for food safety (Vibrio detection in seafood), clinical diagnostics (pneumococcal meningitis), and glycobiology research screening sialidase inhibitors (oseltamivir analogs), it provides permanent archival staining orthogonal to fluorogenic MUNANA/MUANeu5Ac, supporting directed evolution of engineered sialidases and microbiome sialometabolism profiling with quantitative colony counts.

Appearance

• White to pale off-white crystalline powder.
• Hydrolysis yields deep blue insoluble precipitate.​

Source

• Chemoenzymatic α-sialylation of bromochloroindol-3-ol, ammonium salt precipitation.
• Specialty suppliers for glycobiology reagents.​

Molecular Weight and Structure

• Formula: C19H26BrClN3O9 (estimated); MW ~545.8 g/mol.
• Ammonium (2S,4S,5R,6R)-5-acetamido-2-[(5-bromo-4-chloro-1H-indol-3-yl)oxy]-4-hydroxy-6-[(1R,2R)-1,2,3-trihydroxypropyl]oxane-2-carboxylate.​

Sugar Specificity

• α2-Neu5Ac selective for bacterial/viral neuraminidases (NanA/I/H).
• High linkage specificity; resistant to mammalian sialidases.​

Biological Activity

• Chromogenic sialidase substrate; Km ~0.8 mM (viral NA).
• Enzyme-specific; minimal auto-hydrolysis.​

Purity and Microbial Contamination

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

Identity and Quality Control

• NMR/HRMS verified; solubility >15 mg/mL H2O.
• Blue product post-neuraminidase confirmation.​

Shelf Life and Storage

• 2+ years -20°C desiccated; aqueous stable weeks at 4°C.
• Light/moisture protected.​

Applications

• Sialidase chromogenic media (Vibrio, Clostridium detection).
• Antiviral screening, glycobiology enzyme assays.​

Key Characteristics

• Superior solubility vs. Na salt; eye-readable blue colonies.
• Stable in media; α2-Neu5Ac specific.​

Citation Links

• https://www.chemicalbook.com/ChemicalProductProperty_EN_CB820216122.htm​
• https://pubchem.ncbi.nlm.nih.gov/compound/160369-85-7​
• https://pubchem.ncbi.nlm.nih.gov/compound/66577049​
• http://chemsynlab.com/en/product/160369-85-7.html​
• https://www.medchemexpress.com/X-Neu5Ac.html​
• https://pubchem.ncbi.nlm.nih.gov/compound/X-NeuNAc​
• https://www.chemicalbook.com/ChemicalProductProperty_EN_CB5443473.htm​
• https://cdn.caymanchem.com/cdn/insert/24206.pdf​
• https://pubchem.ncbi.nlm.nih.gov/compound/71307251 [ variant]
• https://www.targetmol.com/compound/X_Neu5Ac-sodium/21486