X-Neu5Ac Sodium Salt 

X-Neu5Ac Sodium Salt (5-Bromo-4-chloro-3-indolyl-α-N-acetylneuraminic acid sodium salt, CAS 160369-85-7), also known as X-NeuNAc, represents a chromogenic substrate engineered for selective detection of neuraminidase (sialidase, EC 3.2.1.18) enzymes through hydrolysis that liberates a halogenated indoxyl aglycone, which rapidly auto-oxidizes to form the intensely blue 5,5′-dibromo-4,4′-dichloro-indigo precipitate for unambiguous colony/plaque visualization. With molecular formula C19H21BrClN2NaO9 (MW 559.73 g/mol), this sialoside features N-acetylneuraminic acid (Neu5Ac, sialic acid) α2-glycosidically linked at C2 to 5-bromo-4-chloroindol-3-ol, exhibiting excellent substrate kinetics (Km = 0.89 mM) for viral/bacterial neuraminidases (influenza NA, Clostridium perfringens NanI) while demonstrating high stability absent enzyme, enabling plate-based screening without spontaneous background. The sodium salt confers water solubility (>5 mg/mL) for uniform agar incorporation (100-200 μM), supporting functional assays of sialidases in influenza virus subtyping, microbiome sialometabolism studies, and directed evolution libraries for engineered glycosidases. Upon cleavage, the membrane-impermeant indigo localizes enzyme activity, distinguishing neuraminidase-positive pathogens (blue colonies) from negatives within 24-48h, with applications extending to antiviral screening (oseltamivir resistance), lysosomal storage disorder diagnostics (sialidosis), and glycobiology research probing α2,3/α2,6 sialic acid linkage specificity in mammalian/viral systems.

Appearance

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

Source

• Chemoenzymatic synthesis: α-sialylation of bromochloroindol-3-ol using Neu5Ac donor.
• Commercial: MedChemExpress, Biosynth (≥98% HPLC).

Molecular Weight and Structure

• Formula: C19H21BrClN2NaO9; MW 559.73 g/mol.
• Sodium (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 viral/bacterial neuraminidases (NanH/I, NA).
• Resistant to mammalian CMP-Neu5Ac synthetases.​

Biological Activity

• Chromogenic sialidase reporter; Km 0.89 mM (C. perfringens).
• No spontaneous hydrolysis; enzyme-specific.​

Purity and Microbial Contamination

• ≥98% (HPLC/NMR); molecular biology grade.
• Synthetic; non-sterile.​

Identity and Quality Control

• ¹H-NMR (Neu5Ac H3ax ~1.8 ppm, indolyl H); HRMS m/z 538 [M-Na]+.
• Blue product formation post-neuraminidase incubation.​

Shelf Life and Storage

• 2 years -20°C desiccated; aqueous stable 1 month 4°C.
• Light-protected.​

Applications

• Neuraminidase screening (influenza, Clostridium); viral diagnostics.
• Sialidase library screening, microbiome functional assays.​

Key Characteristics

• Water-soluble Na salt; eye-readable blue colonies.
• High stability; α2-Neu5Ac specific.​

Citation Links

• https://pubchem.ncbi.nlm.nih.gov/compound/66577049​
• http://chemsynlab.com/en/product/160369-85-7.html​
• https://pubchem.ncbi.nlm.nih.gov/compound/X-NeuNAc​
• https://pubchem.ncbi.nlm.nih.gov/compound/160369-85-7​
• https://www.medchemexpress.com/X-Neu5Ac.html​
• https://www.chemicalbook.com/ChemicalProductProperty_EN_CB5443473.htm​
• https://pubchem.ncbi.nlm.nih.gov/compound/71307251 [ variant]
• https://www.targetmol.com/compound/X_Neu5Ac-sodium/21486​
• https://www.tcichemicals.com/IN/en/p/M3031 [ variant]
• https://www.biosynth.com/p/MC04391/1007117-62-5