Salmon‑α‑Glc

Salmon‑α‑Glc (CAS 467214‑46‑6), systematically 6‑chloro‑3‑indolyl α‑D‑glucopyranoside, is a synthetic α‑D‑glucosidase‑specific chromogenic substrate in which a 6‑chloro‑3‑indoxyl aglycone is linked via an α‑glycosidic bond to D‑glucose. When hydrolyzed by α‑D‑glucosidase (EC 3.2.1.20) or related α‑glucoside‑cleaving enzymes, the indoxyl moiety is released and undergoes aerial oxidation to form an insoluble salmon‑colored indigo‑type precipitate, enabling clear visual detection of enzyme activity. This substrate is widely used in selective agar media to screen and identify α‑glucosidase‑positive microorganisms, and in enzyme‑kinetic assays for recombinant or purified α‑D‑glucosidases. The salmon‑pink dye provides good contrast against background pigmentation, especially in dense or mixed‑culture platings, improving sensitivity and ease of readout. It is compatible with standard microbiological media and biochemical buffers, and is supplied as a research‑use‑only, high‑purity reagent optimized for chromogenic solid‑medium and histochemical applications.

Appearance

• Off‑white to pale yellow crystalline or lyophilized powder.
• Fine, free‑flowing texture suitable for accurate weighing and dissolution in aqueous or mixed aqueous‑organic solvents (commonly used in methanol or DMF stock solutions).

Source / synthesis

• Synthetically produced by coupling 6‑chloro‑3‑indoxyl with α‑D‑glucose under glycosylation conditions to form the α‑D‑glucopyranoside derivative.
• Commercially manufactured by specialty enzyme‑substrate and biochemical suppliers (e.g., BioGlyco, Geneseq, Clinisciences, Biosynth) as a high‑purity, research‑grade reagent.

Molecular weight and structure

• Molecular formula: C14H16ClNO6\text{C}_{14}\text{H}_{16}\text{ClNO}_{6}C14H16ClNO6.
• Molecular weight: 329.73 g/mol.
• Structure: 6‑chloro‑1H‑indol‑3‑yl α‑D‑glucopyranoside, with an α‑glycosidic linkage between the indole C3‑O and the D‑glucose ring in the (2R,3R,4S,5S,6R) configuration.

Sugar specificity

• Specifically hydrolyzed by α‑D‑glucosidases (EC 3.2.1.20) and other α‑glucoside‑cleaving enzymes.
• Shows minimal cross‑reactivity with other α‑glycosidases (e.g., α‑galactosidase, α‑fucosidase) and β‑glycosidases under optimized assay conditions, providing high selectivity for α‑D‑glucosidases.

Biological activity

• Acts as a chromogenic reporter for α‑D‑glucosidase‑mediated hydrolysis of α‑D‑glucosyl linkages in glucosides, disaccharides, and oligosaccharides.
• Enzymatic cleavage yields 6‑chloro‑3‑indoxyl, which oxidizes and dimerizes into an insoluble salmon‑colored dye, enabling sensitive detection in bacterial colonies, enzyme assays, and histochemical preparations.

Purity and microbial contamination

• Typically supplied at ≥97% purity as determined by HPLC or similar analytical methods.
• Certificates of analysis from major suppliers indicate acceptable levels of residual solvents, heavy metals, and non‑sterile, low‑microbial contamination status suitable for microbiological and biochemical use.

Identity and quality control

• Identity confirmed by molecular formula, molecular weight, NMR, and/or HPLC, with reference to standard indolyl‑α‑D‑glucopyranoside spectra and chromatograms.
• Quality‑control procedures include checks for appearance, solubility, spectral characteristics, and performance in a defined α‑glucosidase activity assay system.

Shelf life and storage

• Shelf life is generally 12–24 months when stored as a dry powder at –20 °C in a tightly sealed container, protected from moisture and light.
• Aqueous or stock solutions should be prepared immediately before use or stored frozen for short periods to minimize degradation and nonspecific oxidation of the indoxyl moiety.

Application

• Screening and phenotypic differentiation of α‑D‑glucosidase‑producing microorganisms (e.g., yeasts and bacteria) on selective agar media.
• Enzyme‑activity assays for recombinant or purified α‑D‑glucosidases in solution or immobilized formats.
• Histological or cytochemical localization of α‑D‑glucosidase activity in tissue sections and cell preparations.

Key characteristics

• High sensitivity and low background due to formation of an insoluble salmon‑colored dye upon α‑D‑glucosidase hydrolysis.
• Defined α‑D‑glucopyranoside linkage providing selectivity for α‑D‑glucosidases over other glycosidases.
• Crystalline, stable powder with a known molecular formula and weight, suitable for quantitative enzyme assays and standardized media formulations.

Citations

• Geneseq – Salmon‑α‑Glc product page (CAS 467214‑46‑6, molecular formula C14H16ClNO6\text{C}_{14}\text{H}_{16}\text{ClNO}_{6}C14H16ClNO6, MW 329.73): http://geneseqtools.cn/en/product03_cid_214_pid_519.html
• BioGlyco – Chromogenic substrate 6‑chloro‑3‑indolyl α‑D‑glucopyranoside (Salmon‑α‑Glc) entry: https://www.bioglyco.com/chromogenic-substrate-6-chloro-3-indolyl-d-glucopyranoside-item-20183.html
• Biosynth – 6‑Chloro‑3‑indolyl‑α‑D‑glucopyranoside (CAS 467214‑46‑6) product page: https://www.biosynth.com/p/EC03263/467214-46-6-chloro-3-indolyl-a-d-glucopyranoside
• Clinisciences – 6‑chloro‑3‑indoxyl‑α‑D‑glucopyranoside (Salmon‑α‑Glc) chromogenic substrate description: https://www.clinisciences.com/en/other-products-186/6-chloro-3-indoxyl-alpha-d-glucopyranoside-1789006730.html
• ChemImpex – 6‑Chloro‑3‑indoxyl‑α‑D‑glucopyranoside product page (for handling and assay‑format reference): https://www.chemimpex.com/products/21034
• PMC – Structure of human lysosomal acid α‑glucosidase (GAA, enzyme‑substrate‑mechanism context): https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5653652/
• Glentham – 6‑Chloro‑3‑indolyl‑β‑D‑glucopyranoside (Salmon‑β‑Glc, isomer‑context and dye‑chemistry reference): https://www.glentham.com/en/products/product/GC3677/
• InalcoPharm – 5‑bromo‑4‑chloro‑3‑indolyl‑α‑D‑glucopyranoside document (for α‑glucoside substrate properties and assay concepts): https://www.inalcopharm.com/download_files/10_12215032040.pdf
• General enzyme‑substrate catalog (α‑glucosidase‑specific indolyl‑substrates overview): https://www.medchemexpress.com/ (search for “α‑glucosidase substrate” or “Salmon‑α‑Glc”)
• AMS journal – Substrate‑specificity and characterization paper for fungal glucosidases (enzyme‑context for α‑glucosidase substrates): https://journals.asm.org/doi/10.1128/AEM.64.10.3607-3614.1998