Salmon‑GlcA Sodium Salt 

Salmon‑GlcA Sodium Salt (CAS 216971‑56‑1), systematically 6‑chloro‑3‑indolyl β‑D‑glucuronide sodium salt, is a synthetic β‑D‑glucuronidase‑specific chromogenic substrate in which a 6‑chloro‑3‑indoxyl aglycone is linked via a β‑glycosidic bond to β‑D‑glucuronic acid and presented as the monosodium salt. When hydrolyzed by β‑D‑glucuronidase (EC 3.2.1.31) or GUS‑expressing systems, the indoxyl moiety is released and oxidizes to an insoluble salmon‑colored indigo‑type precipitate, enabling clear visual detection of enzyme activity. This sodium‑salt form is highly soluble in aqueous buffers and is commonly used in bacterial‑colony screening, GUS‑reporter assays, and histochemical staining of β‑glucuronidase activity in plants, tissues, and cell cultures. The salmon‑pink color provides good contrast with background pigmentation and can be combined with other chromogenic substrates (e.g., X‑Gal) for multiplex detection of different enzyme activities on the same plate. The compound is supplied as a high‑purity, research‑use‑only reagent compatible with standard microbiological and molecular‑biology buffers.

Appearance

• Off‑white to pale yellow crystalline or lyophilized powder.
• Free‑flowing solid suitable for preparation of aqueous stock solutions; typically soluble in water at concentrations up to about 1%.

Source / synthesis

• Synthetically produced by coupling 6‑chloro‑3‑indoxyl with β‑D‑glucuronic acid and then converting the acid form into the monosodium salt to enhance water solubility.
• Commercially manufactured by specialty enzyme‑substrate and biochemical suppliers (e.g., Glycosynth, Hepattack, Duchefa‑style vendors) as a high‑purity GUS‑assay reagent.

Molecular weight and structure

• Molecular formula: C14H13ClNO7⋅Na
• Molecular weight: 365.7 g/mol.
• Structure: 6‑chloro‑1H‑indol‑3‑yl β‑D‑glucopyranuronate monosodium salt, with a β‑glycosidic linkage between the indole C3‑O and the D‑glucuronic‑acid ring.

Sugar specificity

• Specifically hydrolyzed by β‑D‑glucuronidases (GUS, EC 3.2.1.31) and β‑glucuronide‑cleaving enzymes.
• Shows high selectivity over other β‑glycosidases, making it ideal for detection of β‑glucuronidase activity in bacteria, plant‑transformation systems, and histochemical applications.

Biological activity

• Acts as a chromogenic reporter for β‑glucuronidase‑mediated hydrolysis of β‑D‑glucuronosyl linkages in glucuronides and glycosaminoglycan‑derived substrates.
• Enzymatic cleavage releases 6‑chloro‑3‑indoxyl, which oxidizes and dimerizes into a salmon‑colored, water‑insoluble dye, enabling sensitive detection in bacterial colonies, plant‑tissue GUS assays, and histological preparations.

Purity and microbial contamination

• Typically supplied at ≥95–98% purity as determined by HPLC or equivalent methods.
• Product data sheets and SDS‑type entries indicate acceptable levels of residual solvents, heavy metals, and 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 standard indolyl‑β‑D‑glucuronide profiles.
• Quality‑control procedures include checks for appearance, solubility, and performance in a defined β‑glucuronidase assay (e.g., E. coli GUS⁺ colonies or plant GUS staining).

Shelf life and storage

• Shelf life is generally 12–24 months when stored as a dry powder at –20 °C in a tightly sealed, desiccated container, protected from moisture and light.
• Stock solutions in water or buffer 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 identification of β‑glucuronidase‑positive bacteria (e.g., certain E. coli strains) on selective agar media.
• GUS‑reporter assays for detection of β‑glucuronidase gene expression in bacterial, yeast, and plant systems.
• Histological and plant‑tissue localization of GUS activity in transgenic and reporter‑gene experiments.

Key characteristics

• High sensitivity and low background due to formation of an insoluble salmon‑colored dye upon β‑glucuronidase hydrolysis.
• Defined β‑D‑glucuronide linkage with a sodium counterion, providing improved water solubility over free‑acid forms.
• Crystalline, stable powder with a known molecular formula and weight, suitable for quantitative GUS assays and standardized media formulations.

Citations

• ChemicalBook – 6‑Chloro‑3‑indolyl‑β‑D‑glucuronide sodium salt (CAS 216971‑56‑1): https://www.chemicalbook.com/ChemicalProductProperty_US_CB71092616.aspx
• Glycosynth – 6‑Chloro‑3‑indolyl‑β‑D‑glucuronide sodium salt entry: https://www.glycosynth.co.uk/det/71/6-Chloro-3-indolyl-beta-D-glucuronide-sodium-salt/
• Hepattack – Salmon‑GlcA Sodium Salt product page (CAS 216971‑56‑1, formula, MW): https://www.hepattack.com/en/product03_cid_214_pid_524.html
• NextSSDS – 6‑Chloro‑3‑indolyl‑β‑D‑glucuronide sodium salt substance data: https://nextsds.com/substances/216971-56-1-6-chloro-3-indolyl-beta-d-gluconoride-sodium-salt
• India‑based 6‑chloro‑3‑indolyl‑β‑D‑glucuronide sodium salt supplier listing (purity 98%, bulk packages): https://www.chemicalbook.com/Manufacturers-india/6-chloro-3-indolyl-beta-d-gluconoride-sodium-salt.htm
• MedChemExpress – 6‑Chloro‑3‑indolyl‑β‑D‑glucuronide cyclohexylammonium salt (closely related Salmon‑GlcA‑type GUS substrate for dye‑color and assay‑format reference): https://www.medchemexpress.com/6-chloro-3-indolyl-%CE%B2-d-glucuronide-cyclohexylammonium.html
• Duchefa Biochemie – Salmon‑XGlcA cyclohexylammonium salt (for GUS‑reporter and multiplex‑staining context, e.g., with X‑Gal): https://www.duchefa-biochemie.com/product/details/number/S1407
• β‑Glucuronidase‑substrate review or application note (for GUS‑assay‑design references – search vendor or journal sites via https://www.medchemexpress.com/ for “GUS substrate” or “β‑glucuronidase substrate”)
• General glycosidase‑substrate catalog (6‑chloro‑3‑indolyl‑β‑D‑glucuronide and sodium‑salt options overview): https://www.chemicalbook.com/
• Enzyme‑substrate database (indolyl‑type β‑glucuronidase substrates for GUS‑applications context): https://www.medchemexpress.com/ (search for “β‑glucuronidase substrate” or “Salmon‑GlcA”)