Pyrogallol Red

• CAS: 32638-88-3
• Catalog Number: ACM32638883-2
• Category: Main Products
• Molecular Weight: 400.36
• Molecular Formula: C19H12O8S
• Description: Alfa Chemistry offers Pyrogallol Red products for various research purposes. Please contact us by email if you do not find the specification you are looking for on this page.
• Synonyms: Pyrogallolsulfonephthalein
• IUPAC Name: 1,1-dioxospiro[2,1ж╦6-benzoxathiole-3,9'-xanthene]-3',4',5',6'-tetrol
• SMILES: C1=CC=C2C(=C1)C3(C4=C(C(=C(C=C4)O)O)OC5=C3C=CC(=C5O)O)OS2(=O)=O
• InChI: InChI=1S/C19H12O8S/c20-12-7-5-10-17(15(12)22)26-18-11(6-8-13(21)16(18)23)19(10)9-3-1-2-4-14(9)28(24,25)27-19/h1-8,20-23H
• InChI Key: KUQNCHZOCSYKOR-UHFFFAOYSA-N
• Melting Point: ≥300 °C (lit.)
• Appearance: Dark red to Brown powder to crystal
• Application: Applications of xanthene dyes involve optical materials and organic dyes for medical diagnosis research. Several characteristic features of xanthene dyes are large absorption and luminescence, excellent light resistance, low toxicity in-vivo, and relatively high solubility in water.
• Absorbance: (E1%1cm) min. 850(pH 8.0 buffer sol., 539.0 to 543.0 nm)
• Absorption Wavelength: (max.) 541(pH 8.0 buffer sol.) nm
• Complexity: 690
• Condition To Avoid: Hygroscopic
• Covalently-Bonded Unit Count: 1
• EC Number: 251-134-3
• Exact Mass: 400.025289g/mol
• Features And Benefits: Both cationic and anionic xanthene dyes are known to be efficient fluorescent dyes. Functional groups on the xanthene moiety control their fluorescent colors.
• Formal Charge: 0
• H-Bond Acceptor: 8
• H-Bond Donor: 4
• Heavy Atom Count: 28
• MDL Number: MFCD00005046
• Monoisotopic Mass: 400.025289g/mol
• Packaging: 25g
• Physical State: (20 deg.C) Solid
• Pubchem SID: 87574743
• Rotatable Bond Count: 0
• Storage Conditions: Store under inert gas
• XLogP3: 2.1

Case Study

Study on the Improved Pyrogallol Red-Molybdate Method for Determining Total Urinary Protein

Orsonneau, Jean-Luc, et al. Clinical Chemistry 35.11 (1989): 2233-2236

This study improved the pyrogallol red-molybdate (PRM) method for total urinary protein determination by adding sodium dodecyl sulfate (SDS) and adapted it to the Cobas Bio centrifugal analyzer. The original PRM method showed unequal reactivity to different proteins, with 30% lower sensitivity for gamma globulins than albumin. By optimizing the SDS concentration to 25 mg/L in the PRM reagent, the chromogenicity of human gamma globulins was adjusted to match that of albumin-sensitivity for gamma globulins increased by 25% while only a 7% loss in albumin sensitivity was observed. The modified method (PRM-SDS) had a detection limit of 35 mg/L and a linear range up to 2.00 g/L, with a linear regression equation of y=1.021x - 0.022 g/L (r=0.999). Assays of 206 urine samples showed good correlation with the reference method (gel filtration + modified biuret reaction) with r=0.951. Within-run CVs ranged from 1.48% to 9.26%, and between-run CVs were 7.18% to 12.5%. The normal range for 24-hour urinary protein excretion in 65 healthy adults was 40-180 mg. These studies demonstrate that the PRM-SDS method is simple, rapid, sensitive, and cost-effective, with equal reactivity to major urinary proteins, making it suitable for routine clinical use.
The in vitro performance of the PRM-SDS method was verified through systematic experiments. Human serum albumin, gamma globulins, and other standard proteins were used to evaluate reactivity. Urine samples from patients and healthy adults were assayed, with precision assessed by repeated measurements of urine samples and controls. Accuracy was determined by comparing with the reference method and calculating analytical recovery (mean 97.7%). The Cobas Bio centrifugal analyzer was set with specific parameters: 5 μL sample volume, 350 μL reagent volume, incubation at 37°C for 3 minutes, and detection at 600 nm. SDS was added to the PRM reagent to unfold polypeptide chains and expose additional basic amino acid groups, balancing the binding competition between pyrogallol red and SDS at pH 2.5. Light-chain proteins (lambda and kappa types) showed improved reactivity with the PRM-SDS reagent compared to the unmodified PRM method.

Novel ORAC Methodology Based on Pyrogallol Red for Evaluating Antioxidant Reactivity

López-Alarcón, C., et al. Free Radical Research 40.9 (2006): 979-985

This study developed a simple oxygen radical absorbance capacity (ORAC) methodology using Pyrogallol Red (PGR) as the target molecule to evaluate the radical scavenging capacity of pure antioxidants and complex mixtures, with peroxyl radicals generated by 2,2'-azo-bis(2-amidinopropane)dihydrochloride (AAPH). PGR is a colored reagent that undergoes absorbance bleaching upon oxidation by peroxyl radicals, which can be monitored at 540 nm using a UV-visible spectrophotometer. The method was validated with pure compounds (quercetin, kaempferol, gallic acid, etc.) and complex mixtures (red wine, white wine, black tea extract). Results showed that ORAC values obtained with PGR (ORAC-PGR) were strongly correlated with the reactivity of tested compounds (r=0.936), unlike traditional ORAC methods using fluorescein (FL) or phycoerythrin (PE) that are influenced by stoichiometric factors. Quercetin exhibited the highest ORAC-PGR (11.5±0.4) and reactivity ratio (k₁/k_Trolox=27), while gallic acid also showed high ORAC-PGR (11.1±0.7). For complex mixtures, red wine had an ORAC-PGR equivalent to 42,400±900 μM Trolox, nearly 10 times higher than white wine (3900±300 μM Trolox), and black tea extract had an ORAC-PGR of 52,900±1700 μM Trolox. These studies demonstrate that the PGR-based ORAC methodology is simple, relies on visible spectroscopy, and provides accurate evaluation of antioxidant reactivity, making it suitable for both pure compounds and complex mixtures.
The in vitro antioxidant evaluation using the PGR-based ORAC method was conducted through controlled experiments. Stock solutions of PGR (1×10⁻⁴ M) and FL (1×10⁻⁵ M) were prepared daily in 75 mM phosphate buffer (pH 7.4). Reaction mixtures contained AAPH (10 mM), PGR (5 μM), and test samples (pure compounds or complex mixtures) in phosphate buffer, incubated at 37°C. Absorbance changes of PGR were recorded at 540 nm, and fluorescence changes of FL (excitation 493 nm, emission 515 nm) were measured for comparison. ORAC values were calculated by integrating the area under the curve (AUC) up to 80% probe consumption, with Trolox as the reference standard. For complex mixtures, red wine was diluted 1:10 with buffer, white wine was used undiluted, and black tea extract was prepared by extracting ground dry leaves with acetone/water (50:50, v:v) followed by centrifugation. All experiments were performed in triplicate to ensure reproducibility.

Study on the Oxidation Mechanism of Pyrogallol Red Induced by Free Radicals and Reactive Oxidant Species

Atala, E., et al. The Journal of Physical Chemistry B 117.16 (2013): 4870-4879

This study investigated the oxidation mechanism of Pyrogallol Red (PGR) induced by various free radicals and reactive oxidant species (RS), including peroxyl radicals (ROO·), peroxynitrite (ONOO⁻), nitrogen dioxide (NO₂), and hypochlorite (HOCl), using spectroscopic, electrochemical, and chromatographic techniques. PGR, with a characteristic absorption peak at 540 nm at pH 7.4, undergoes irreversible oxidation upon reaction with RS, accompanied by a decrease in 540 nm absorption and formation of a new peak at 390 nm with an isosbestic point at 445 nm. HPLC-MS analysis identified the oxidation product as a quinone derivative (m/z=433), with no formation of peroxides or chlorinated compounds confirmed by FOX assay and oxygen consumption experiments. Cyclic voltammetry showed PGR undergoes two-electron oxidation: initial formation of a phenoxy radical from the deprotonated enolate at carbon 3, followed by a second charge transfer to form the ortho-quinone. Spectroelectrochemical studies confirmed that electrochemical oxidation of PGR produces the same spectral changes as RS-induced oxidation, with reaction rates dependent on pH (highest at pH 7.0, k=0.526 cm s⁻¹). These studies demonstrate that PGR is oxidized to a single quinone derivative by diverse RS via a consistent mechanism, supporting its utility as a reliable probe for evaluating antioxidant capacity.
The in vitro oxidation of PGR was studied through controlled experiments with different RS. PGR solutions (5-30 μM) were prepared in 75 mM phosphate buffer (pH 7.4) and reacted with RS (AAPH for ROO·, synthesized peroxynitrite, NO₂ from copper-nitric acid reaction, and HOCl). UV-visible spectra were recorded at 37 °C to monitor absorbance changes. Electrochemical experiments used cyclic voltammetry (GC electrode) and spectroelectrochemistry (ITO electrode) in deaerated 100 mM phosphate buffer. HPLC-DAD-MS analyses were performed with C18 columns to separate and identify products, with mobile phases optimized for PGR and its oxidation derivatives. Hydroperoxide formation was quantified by FOX assay, and nitrogen dioxide concentration was determined via Griess assay. All experiments were conducted in triplicate to ensure reproducibility, with pH-dependent studies confirming the dominant reactive species as the PGR dianion at physiological pH.

Pyrogallol Red as a Target Molecule for Evaluating Antioxidant Reactivity Against Peroxyl Radicals

López-Alarcón, Camilo, et al. Free Radical Research 39.7 (2005): 729-736

This study established a competitive method to evaluate the reactivity of antioxidants using Pyrogallol Red (PGR) as the target molecule and 2,2'-azo-bis-(2-amidinopropane) dihydrochloride (AAPH) as the peroxyl radical source. PGR, with a strong absorption peak at 540 nm, undergoes bleaching upon oxidation by peroxyl radicals, which can be monitored by UV-visible spectroscopy. The method was validated with 10 polyphenols and ascorbic acid (AA), with experiments conducted in phosphate buffer/ethanol (70:30, pH 7.0) at 37°C. Results showed that PGR consumption followed zero-order kinetics at concentrations ≥30 μM, and Stern-Volmer like plots of R⁰/R (ratio of PGR consumption rate without/with antioxidant) against antioxidant concentration were linear. The reactivity of polyphenols followed the order: quercetin (relative rate constant vs. Trolox = 4.3) > gallic acid (1.9) > Trolox (1.0) > kaempferol (0.3). AA showed a distinct induction time, indicating strong radical scavenging ability. Red wine, a complex antioxidant mixture, dose-dependently inhibited PGR bleaching, with a Trolox equivalent of 16 μM. These studies demonstrate that PGR is a suitable target molecule for evaluating the reactivity of highly reactive antioxidants, offering simplicity, sensitivity, and compatibility with both pure compounds and complex mixtures.
The in vitro evaluation of antioxidant reactivity using PGR was conducted through controlled kinetic experiments. Stock solutions of PGR (1 mM) and antioxidants were prepared freshly, and reaction mixtures contained AAPH (10 mM), PGR (60 μM), and test antioxidants. PGR bleaching was monitored by measuring absorbance at 540 nm over time, with the initial rate of consumption calculated to determine R⁰/R. For zero-order kinetics analysis, PGR concentration was maintained at ≥30 μM to ensure most peroxyl radicals reacted with PGR. The effect of complex mixtures was tested by adding red wine aliquots to the reaction system. Kinetic data were analyzed using Stern-Volmer like plots, and relative rate constants were derived by comparing slopes with Trolox as the reference. All experiments were performed in triplicate, with an isosbestic point at 435 nm confirming stable product formation without intermediate accumulation.

Custom Q&A

What is the molecular formula of Pyrogallol Red?

The molecular formula of Pyrogallol Red is C19H12O8S.

What are the synonyms of Pyrogallol Red?

The synonyms of Pyrogallol Red are Pyrogallolsulfonephthalein and 3',4',5',6'-Tetrahydroxyspiro[benzo[c][1,2]oxathiole-3,9'-xanthene] 1,1-dioxide.

What is the molecular weight of Pyrogallol Red?

The molecular weight of Pyrogallol Red is 400.4 g/mol.

When was Pyrogallol Red created?

Pyrogallol Red was created on August 8, 2005.

What is the IUPAC name of Pyrogallol Red?

The IUPAC name of Pyrogallol Red is 1,1-dioxospiro[2,1λ6-benzoxathiole-3,9'-xanthene]-3',4',5',6'-tetrol.

What is the InChI code of Pyrogallol Red?

The InChI code of Pyrogallol Red is InChI=1S/C19H12O8S/c20-12-7-5-10-17(15(12)22)26-18-11(6-8-13(21)16(18)23)19(10)9-3-1-2-4-14(9)28(24,25)27-19/h1-8,20-23H.

What is the InChIKey of Pyrogallol Red?

The InChIKey of Pyrogallol Red is KUQNCHZOCSYKOR-UHFFFAOYSA-N.

What is the CAS number of Pyrogallol Red?

The CAS number of Pyrogallol Red is 32638-88-3.

What is the hydrogen bond donor count of Pyrogallol Red?

The hydrogen bond donor count of Pyrogallol Red is 4.

What is the heavy atom count of Pyrogallol Red?

The heavy atom count of Pyrogallol Red is 28.