Salmon‑Glc

Salmon‑Glc (CAS 159954‑28‑6), systematically 6‑chloro‑3‑indolyl β‑D‑glucopyranoside, is a synthetic β‑D‑glucosidase‑specific chromogenic substrate in which a 6‑chloro‑3‑indoxyl aglycone is linked via a β‑glycosidic bond to D‑glucose. When hydrolyzed by β‑D‑glucosidase (EC 3.2.1.21) or glucosidase‑containing systems, the indoxyl moiety is released and undergoes aerial oxidation to form an insoluble salmon‑pink indigo‑type precipitate, enabling clear visual detection of enzyme activity. This substrate is commonly used in selective agar media to screen and identify β‑glucosidase‑producing microorganisms, and in enzyme‑kinetic assays for recombinant or purified β‑D‑glucosidases. The salmon‑pink color provides good contrast against background pigmentation, especially in mixed‑culture systems or when used alongside other chromogenic dyes, improving sensitivity and ease of readout. Salmon‑Glc is compatible with standard microbiological media and biochemical buffers, and is supplied as a high‑purity, research‑use‑only reagent optimized for chromogenic solid‑medium 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.

Source / synthesis

• Synthetically produced by coupling 6‑chloro‑3‑indoxyl with β‑D‑glucose under glycosylation conditions to form the β‑D‑glucopyranoside derivative.
• Commercially manufactured by specialty carbohydrate and enzyme‑substrate suppliers (e.g., InalcoPharm, DC Fine Chemicals, Benchchem) as a high‑purity, research‑grade reagent.

Molecular weight and structure

• Molecular formula: C14H16ClNO6C14H16ClNO6.
• Molecular weight: 329.73–329.74 g/mol.
• Structure: 6‑chloro‑1H‑indol‑3‑yl β‑D‑glucopyranoside, with a β‑glycosidic linkage between the indole C3‑O and the D‑glucose ring.

Sugar specificity

• Specifically hydrolyzed by β‑D‑glucosidases (EC 3.2.1.21) and other β‑glucoside‑cleaving glycosidases.
• Shows minimal cross‑reactivity with other β‑glycosidases (e.g., β‑galactosidase, β‑glucuronidase) under optimized assay conditions, providing good selectivity for β‑glucosidases.

Biological activity

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

Purity and microbial contamination

• Typically supplied at ≥95–98% purity as determined by HPLC or similar analytical methods.
• Certificates of analysis from vendors 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 inferred from molecular formula, molecular weight, and spectral data (UV/Vis, NMR), with reference to analogous 6‑chloro‑3‑indolyl‑β‑D‑glucopyranoside data.
• Quality‑control procedures include checks for appearance, solubility, spectral characteristics, and performance in a defined β‑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 β‑D‑glucosidase‑producing microorganisms (e.g., yeasts and bacteria) on selective agar media.
• Enzyme‑activity assays for recombinant or purified β‑D‑glucosidases in solution or immobilized formats.
• Histological or cytochemical localization of β‑D‑glucosidase activity in tissue sections and cell preparations.

Key characteristics

• High sensitivity and low background due to formation of an insoluble salmon‑pink dye upon β‑D‑glucosidase hydrolysis.
• Defined β‑D‑glucopyranoside linkage providing selectivity for β‑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

• InalcoPharm – 6‑Chloro‑3‑Indolyl‑β‑D‑Glucopyranoside (Salmon‑Glc / Salmon‑Glucoside) product page: https://www.inalcopharm.com/cart.php?m=product_detail&p=19
• DC Fine Chemicals – 6‑Chloro‑3‑indolyl‑β‑D‑glucopyranoside (Salmon‑glucoside) entry: https://www.dcfinechemicals.com/en/products/carbohydrates/6-chloro-3-indolyl–d-glucopyranoside-detail/
• Benchchem – 6‑Chloro‑3‑indolyl‑β‑D‑glucopyranoside (CAS 159954‑28‑6) product information: https://www.benchchem.com/product/B1143134
• PubChem – 6‑Chloro‑3‑indolyl‑β‑D‑glucopyranoside (chromogenic glucosidase‑substrate class): https://pubchem.ncbi.nlm.nih.gov/compound/6-Chloro-3-indolyl-beta-D-glucopyranoside (search for “6‑chloro‑3‑indolyl‑β‑D‑glucopyranoside”)
• ChemicalBook – 6‑Chloro‑3‑indolyl‑β‑D‑galactopyranoside (Salmon‑Gal / Rose‑Gal) data page (for dye‑chemistry and 6‑chloro‑3‑indolyl core properties): https://www.chemicalbook.com/ChemicalProductProperty_EN_CB1278754.htm
• SRL Chem – 6‑Chloro‑3‑indoxyl‑α‑D‑glucopyranoside (Salmon‑α‑D‑Glc) product page (for 6‑chloro‑3‑indolyl‑α‑glucoside structure and handling reference): https://www.srlchem.com/product/details/25/89432/6-Chloro-3-Indoxyl-a-D-Glucopyranoside-Salmon-a-D-Glc-extrapure-98
• ACS Chemical Biology – alkaloid‑biosynthetic glucosidase‑substrate‑specificity paper (β‑glucosidase context): https://pubs.acs.org/doi/10.1021/cb200267w
• Enzyme‑substrate catalog (β‑glucosidase and 6‑chloro‑3‑indolyl‑based substrates overview): https://www.medchemexpress.com/ (search for “β‑glucosidase substrate” or “Salmon‑Glc”)
• PubChem – 6‑Chloro‑3‑indolyl‑β‑D‑galactopyranoside data page (for 6‑chloro‑3‑indolyl‑β‑D‑hexoside dye‑chemistry reference): https://pubchem.ncbi.nlm.nih.gov/compound/6-Chloro-3-indolyl-beta-D-galactopyranoside
• General carbohydrate‑substrate catalog (DC Fine Chemicals enzyme‑substrate list): https://www.dcfinechemicals.com/en/ (search for “6‑Chloro‑3‑indolyl‑β‑D‑glucopyranoside” or “Salmon‑glucoside”)