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Due to the lack of other treatment options, a rebirth of polymyxins is urgently required. Colistin (also called polymyxin E) and polymyxin B are the only two examples of this antibiotic class that were effectively employed in such critical situations. In the present work, both of the two studied medications were quantified via a simple, green, and non-extracting spectrophotometric approach based on the formation of ion-pair complexes with Erythrosine B. Without using any organic solvents, the pink color of the created complexes was detected at wavelength = 558 nm. To achieve the highest intensity of absorbance, optimum conditions were established by the screening of many experimental factors such as pH, buffer volume, the volume of Erythrosine B, and the time consumed to undergo the reaction. For Colistin and Polymyxin B respectively, Beer-Lambert's law was observed at the concentration ranges of 1–6, 1–9 µg mL− 1. The technique was approved and validated following ICH recommendations. Lastly, the suggested approach has been successfully implemented to quantify the cited medications colorimetrically, for the first time, in their parenteral dosage forms with excellent recoveries. Also, Content uniformity testing was implemented. [ABSTRACT FROM AUTHOR]

Resistant biofilms formed by Staphylococcus aureus on medical devices pose a constant medical threat. A promising alternative to tackle this problem is photodynamic inactivation (PDI). This study focuses on a polyurethane (PU) material with an antimicrobial surface consisting of a composite based on silicate, polycation, and erythrosine B (EryB). The composite was characterized using X-ray diffraction and spectroscopy methods. Anti-biofilm effectiveness was determined after PDI by calculation of CFU mL−1. The liquid PU precursors penetrated a thin silicate film resulting in effective binding of the PU/silicate composite and the PU bulk phases. The incorporation of EryB into the composite matrix did not significantly alter the spectral properties or photoactivity of the dye. A green LED lamp and laser were used for PDI, while irradiation was performed for different periods. Preliminary experiments with EryB solutions on planktonic cells and biofilms optimized the conditions for PDI on the nanocomposite materials. Significant eradication of S. aureus biofilm on the composite surface was achieved by irradiation with an LED lamp and laser for 1.5 h and 10 min, respectively, resulting in a 10,000-fold reduction in biofilm growth. These results demonstrate potential for the development of antimicrobial polymer surfaces for modification of medical materials and devices. [ABSTRACT FROM AUTHOR]

Abstract Due to the lack of other treatment options, a rebirth of polymyxins is urgently required. Colistin (also called polymyxin E) and polymyxin B are the only two examples of this antibiotic class that were effectively employed in such critical situations. In the present work, both of the two studied medications were quantified via a simple, green, and non-extracting spectrophotometric approach based on the formation of ion-pair complexes with Erythrosine B. Without using any organic solvents, the pink color of the created complexes was detected at wavelength = 558 nm. To achieve the highest intensity of absorbance, optimum conditions were established by the screening of many experimental factors such as pH, buffer volume, the volume of Erythrosine B, and the time consumed to undergo the reaction. For Colistin and Polymyxin B respectively, Beer-Lambert’s law was observed at the concentration ranges of 1–6, 1–9 µg mL− 1. The technique was approved and validated following ICH recommendations. Lastly, the suggested approach has been successfully implemented to quantify the cited medications colorimetrically, for the first time, in their parenteral dosage forms with excellent recoveries. Also, Content uniformity testing was implemented.

A recently developed antipsychotic drug, lurasidone, was determined using a simple, sensitive, and eco‐friendly spectrofluorimetric approach. The suggested approach was based on the quantifiable quenching impact of lurasidone on the inherent fluorescence of erythrosine B in an acidic environment employing a Teorell–Stenhagen buffer (pH 4). Following excitation at 530 nm, the quenching of erythrosine B fluorescence was monitored at 552 nm. The system variables were systematically optimized to enhance the formation of the lurasidone‐erythrosine B ion pair for analytical purposes. A linear calibration graph was built in the range of 20–600 ng mL−1 with 0.9998 as a coefficient of correlation. The quantitation and detection limits were 13.5 and 4.5 ng/mL, respectively. The analytical validity of the designed approach was assessed with respect to International Council on Harmonization (ICH) guiding principles. The proposed methodology was employed with high recoveries for assessing lurasidone in bulk powder and its therapeutic tablet dosage form. Additionally, the uniformity of tablet formulations was tested using the developed approach. Finally, the established approach was assessed for its greenness using various tools. [ABSTRACT FROM AUTHOR]

The visible light-assisted photocatalysis approach allows more sustainable and atom-economical C–H bond arylation processes. The polymer-based photocatalysts are an attractive choice because of their variable design and development feasibility as well as effective catalytic applications. In the present work, by following the basic principles of green chemistry, we have chosen an environmentally friendly and biologically suitable chemical i.e. Erythrosine B as a unit molecule for the generation of photocatalyst EP (C20H8O5S4). The generation of EP has been performed via a one-pot solvothermal reaction of Erythrosine B with sulfur powder. The structural analysis of the EP evidence the generation of an interesting example 2D-polymeric assembly where disulfide (–S–S–) units are acting as linkers and show high thermal stability up to 800 °C (39.9% left as a residue). The low optical band gap of 2.08 eV and electrochemical band gap of 2.09 eV favors its catalytic applicability. The catalytic investigation reveals excellent applicability of EP in C–H arylation (yield 98.5% & selectivity 99%). [ABSTRACT FROM AUTHOR]

This study introduces a practical and cost‐effective method for tracking diltiazem (DLZ) analytically. It utilizes a fluorimetric approach that relies on the modulation of fluorescence intensity of a dye called erythrosine B. Through a one‐pot experiment performed in an acidic environment, a complex is rapidly formed between DLZ and erythrosine B. By observing the decrease in erythrosine B emission, a linear calibration plot is established, enabling the detection and quantification of DLZ concentrations ranging from 40 to 850 ng/ml. The estimated limits of detection and quantitation were 10.5 and 32.1 ng/ml, respectively. The variables affecting the DLZ‐dye complex system were carefully adjusted. The validity of the approach was confirmed through a thorough evaluation based on the criteria set by ICH guidelines. The accuracy and precision of the methodology were evaluated, and the standard deviation and relative standard deviation were below 2. The strategy was successfully employed to analyze DLZ in tablets and capsules, and no significant variation between the proposed and reported methods as the values of the estimated t‐test and F‐test at five determinations were below 2.306 and 6.338, respectively. Notably, the method adheres to the principle of green chemistry by utilizing distilled water as the dispersing medium. [ABSTRACT FROM AUTHOR]

Background: Acinetobacter baumannii, a nosocomial pathogen, poses a major public health problem due to generating resistance to several antimicrobial agents. Antimicrobial photodynamic inactivation (APDI) employs a nontoxic dye as a photosensitizer (PS) and light to produce reactive oxygen species that destroy bacterial cells. The intracellular concentration of PS could be affected by factors such as the function of efflux pumps to emit PS from the cytosol. Objective: To evaluate the augmentation effect of an efflux pump inhibitor, verapamil, three multidrug-resistant A. baumannii were subjected to APDI by erythrosine B (EB). Methods and results: The combination of EB and verapamil along with irradiation at 530 nm induced a lethal effect and more than 3 log colony-forming unit reduction to all A. baumannii strains in planktonic state. In contrast, EB and irradiation alone could produce only a sublethal effect on two of the strains. Conclusions: These data suggest that verapamil increases the intracellular concentration of EB, which potentiates the lethal efficacy of APDI. Verapamil could be applied with EB and green light to improve their antimicrobial efficacy against A. baumannii-localized infections. [ABSTRACT FROM AUTHOR]

In an acidic buffered solution, erythrosine B can react with amiodarone to form an association complex, which not only generates great enhancement in resonance Rayleigh scattering (RRS) spectrum of erythrosine B at 346.5 nm but also results in quenching of fluorescence spectra of erythrosine B at λemission = 550.4 nm/λexcitation = 528.5 nm. In addition, the formed erythrosine B–amiodarone complex produces a new absorbance peak at 555 nm. The spectral characteristics of the RRS, absorbance, and fluorescence spectra, as well as the optimum analytical conditions, were studied and investigated. As a result, new spectroscopic methods were developed to determine amiodarone by utilizing erythrosine B as a probe. Moreover, the ICH guidelines were used to validate the developed RRS, photometric, and fluorimetric methods. The enhancements in the absorbance and the RRS intensity and the decrease in the fluorescence intensity of the used probe were proportional to the concentration of amiodarone in ranges of 2.5–20.0, 0.2–2.5, and 0.25–1.75 μg/mL, respectively. Furthermore, limit of detection values were 0.52 ng/mL for the spectrophotometric method, 0.051 μg/mL for the RRS method, and 0.075 μg/mL for the fluorimetric method. Moreover, with good recoveries, the developed spectroscopic procedures were applied to analyze amiodarone in its commercial tablets. [ABSTRACT FROM AUTHOR]

Ambroxol hydrochloride (AMX) and guaifenesin (GFN) are approved drugs utilized to treat coughs through their potent mucolytic and expectorant properties. Due to their massive, combined administration in many illnesses, there is a persistent need for their concurrent estimation in different pharmaceutical formulations. Two sensitive, environmentally friendly spectrofluorimetric methods were developed. AMX was determined using the first method (I) without interference from GFN. This method depends on the quenching of Erythrosine B (EB) native fluorescence at 552 nm after excitation at 527 nm due to the formation of a non‐fluorescent AMX‐EB ion‐pair complex in Britton–Robinson buffer (BRB) solution pH (3.5). The concentration plot is linear over the 0.25–5.0 μg/mL range, with a mean percent found value of 99.74%. Method (II) depends on measuring the native fluorescence of aqueous GFN solution at two analytical wavelengths, either 300 or 600 nm, after excitation at 274 nm. Relative fluorescence intensity (RFI)–concentration plots are linear over the ranges of 0.02–0.5 and 0.1–2.0 μg/ml, with mean percent found at 99.96% and 99.91% at dual wavelengths, respectively. The proposed methods were successfully applied to assay both drugs in raw materials and different single and combined pharmaceutical formulations. These methods have been thoroughly validated following International Committee on Harmonisation (ICH) guidelines. National Environmental Methods Index, Analytical Eco‐Scale, and Green Analytical Procedure Index were used to prove greenness, thereby enhancing their applicability. The proposed techniques provide straightforward, precise, and cost‐effective solutions for routine formulation analysis in quality control laboratories. [ABSTRACT FROM AUTHOR]

Resistant biofilms formed by Staphylococcus aureus on medical devices pose a constant medical threat. A promising alternative to tackle this problem is photodynamic inactivation (PDI). This study focuses on a polyurethane (PU) material with an antimicrobial surface consisting of a composite based on silicate, polycation, and erythrosine B (EryB). The composite was characterized using X-ray diffraction and spectroscopy methods. Anti-biofilm effectiveness was determined after PDI by calculation of CFU mL−1. The liquid PU precursors penetrated a thin silicate film resulting in effective binding of the PU/silicate composite and the PU bulk phases. The incorporation of EryB into the composite matrix did not significantly alter the spectral properties or photoactivity of the dye. A green LED lamp and laser were used for PDI, while irradiation was performed for different periods. Preliminary experiments with EryB solutions on planktonic cells and biofilms optimized the conditions for PDI on the nanocomposite materials. Significant eradication of S. aureus biofilm on the composite surface was achieved by irradiation with an LED lamp and laser for 1.5 h and 10 min, respectively, resulting in a 10,000-fold reduction in biofilm growth. These results demonstrate potential for the development of antimicrobial polymer surfaces for modification of medical materials and devices.

In this study, the chitosan boric acid (Ch‐B) composite has been prepared and characterized with sophisticated analytical techniques such as FT‐IR, SEM, and EDX. The prepared Ch‐B adsorbent was applied for the adsorption of erythrosine B (EB) dye from water samples under the optimized parameters of pH, adsorbent dosage, time, and temperature. Results shows that the Ch‐B adsorbent removes 96.5% of EB dye at pH 5, using 0.05 g of adsorbent. The adsorption equilibrium data have been subject to the Langmuir, Freundlich, and D‐R adsorption equilibrium models, which demonstrates that the Freundlich model was the best fit with good correlation coefficient value (R2 = 0.991), while energy E (9.18 KJ·mol−1) calculated from D‐R model suggested that the physical adsorption nature of the adsorption. Beside this, the thermodynamic and kinetic experiments were performed to check the feasibility and adsorption mechanism of EB‐dye onto Ch‐B adsorbent, which shows that the adsorption is endothermic (∆H = 0.124) and spontaneous in nature due to the negative values of Gibbs free energy (i.e., ∆G KJ·mol−1 = −13.01, −17.06, and −17.60). The kinetic models show that the adsorption equilibrium is best fitted with pseudo second order kinetic model due to good correlation coefficient (R2 = 0.99). Moreover, the interaction phenomenon between adsorbent and adsorbate was analyzed through DFT calculations. [ABSTRACT FROM AUTHOR]

Sunitinib is a tyrosine kinase inhibitor used for the treatment of renal cell carcinoma and gastrointestinal stromal tumors. In this study, two spectroscopic methods, spectrofluorometric and spectrophotometric, were utilized to quantify sunitinib in different matrices. In method I, the native fluorescence of erythrosine B was quenched by forming ion‐pair complex with increasing quantities of sunitinib. This approach was utilized for measuring sunitinib in its dosage forms and spiked plasma. After excitation at 528 nm, the quenching of fluorescence is linearly related to the concentration across the range of 0.05–0.5 μg mL−1 at 550 nm in Britton–Robinson buffer (pH 4.0), with a correlation value of 0.9999 and a high level of sensitivity with detection limit down to 10 ng mL−1. Method II relies on spectrophotometric measurements of the produced complex at 550 nm across a range of 0.5–10.0 μg mL−1, with good correlation value of 0.9999. This method has a detection limit down to 0.16 μg mL−1. The proposed methodologies were validated according to International Conference on Harmonization (ICH) guidelines with satisfactory results. The stoichiometry of the reaction was determined through the application of Job's method, while the mechanism of quenching was investigated by employing the Stern–Volmer plot. The designated methods were used to estimate sunitinib in its capsules and in spiked human plasma. Additionally, the statistical analysis of the data revealed no substantial differences when compared to previous reported spectroscopic method. Green assessment tools provide further details about the eco‐friendly nature of the methods. [ABSTRACT FROM AUTHOR]

Naftidrofuryl is a vasodilator medication used for treating cerebral and peripheral vascular diseases. In this study, two spectroscopical techniques, spectrofluorimetric and resonance Rayleigh scattering (RRS), were utilized to quantify naftidrofuryl in its pharmaceutical samples. The developed methodologies in this study rely on a facile process of forming an association complex between erythrosine B reagent and naftidrofuryl under acidic conditions. The fluorimetric assay is based on the ability of naftidrofuryl to quench and decrease the native fluorescence intensity of the reagent when measured at λemis. = 550 nm (λexcit. = 526 nm). Under similar reaction conditions, the RRS method relies on the observed amplification in the RRS spectrum of the reagent at a wavelength of 577 nm following its interaction with naftidrofuryl. The methods exhibited linearity within the ranges 0.2–1.6 μg/ml (r2 = 0.999) and 0.1–1.4 μg/ml (r2 = 0.9994), with limit of quantitation values of 0.146 and 0.099 μg/ml, and limit of detection values of 0.048 and 0.032 μg/ml, for the fluorometric and the RRS methods, respectively. Moreover, the quenching between the dye and naftidrofuryl was studied using Stern–Volmer analysis, and the methodologies were experimentally optimized and validated. Additionally, acceptable recoveries were achieved when the procedures were applied to determine naftidrofuryl in pharmaceutical samples. [ABSTRACT FROM AUTHOR]

A spectrofluorimetric approach that is sensitive, simple, validated, and cost‐effective has been proposed for the estimation of amlodipine (AML) and perindopril (PER) in their bulk powders, pharmaceutical formulations, and spiked human plasma. The recommended approach utilized the quantitative quenching effect of the two cited drugs on the fluorescence intensity of erythrosine B, as a result of complex binary reactions among each drug with erythrosine B at pH 3.5 (Teorell and Stenhagen buffer). The quenching of erythrosine B fluorescence was recorded at 554 nm after excitation at 527 nm. The calibration curve was detected in the range 0.25–3.0 μg ml−1, with a correlation coefficient of 0.9996 for AML, and 0.1–1.5 μg ml−1, with a correlation coefficient of 0.9996 for PER. The established spectrofluorimetric approach was validated for the estimation of the cited drugs with high sensitivity regarding International Council on Harmonization guidelines. Therefore, the established approach could be utilized for quality control of the cited drugs in their pharmaceutical formulations. [ABSTRACT FROM AUTHOR]

Erythrosine B (EB) is a xanthene dye widely used in many fields such as food, cosmetics and medicine. The interaction between EB and cetyltrimethylammonium bromide (CTAB) was investigated using spectrophotometry. The quantities of the quenching constant of Stern-Volmer, the number of binding sites and the binding constant were calculated for the EB-CTAB system. Liquid crystal-based sensing platform (LC) developed for ultrasensitive and unlabelled EB determination using an LC interface decorated with cationic surfactants. Nematic liquid crystals exposed to CTAB exhibited homeotropic binding, when EB was inserted into LC cells, and the inward arrangement was thus changed to a coplanar shape by electrostatic interaction between CTAB and EB. The sensor was developed based on LC which recognised EB at tracking level too low, up to 2.0 pM. The proposed LC-based sensing system is a quick, comfortable and easy approach for the determination of EB in unlabelled biological samples. [ABSTRACT FROM AUTHOR]

Novel, selective, facile, and precise spectroscopic approaches were validated to determine nilotinib hydrochloride, a tyrosine kinase inhibitor used to treat patients with chronic myeloid leukemia. These approaches depend on the reaction of the tertiary amine group of nilotinib with erythrosine B in the Britton–Robinson buffer at pH 4. Method I, depends on measuring the absorbance of the formed complex at 551 nm. The absorbance concentration plot showed linearity over the concentration range of 1.0 to 9.0 μg/ml. Method II, involved the measurement of the quenching of the native fluorescence of erythrosine B by adding nilotinib in an acidic medium. The fluorescence quenching of erythrosine B was measured at 549 nm after excitation at 528 nm. This approach showed excellent linearity in the concentration range of 0.04 to 0.7 μg/ml. The limit of detection values for Method I and Method II were 0.225 and 0.008 μg/ml, respectively, while the limit of quantitation values for Method I and Method II were 0.68 and 0.026 μg/ml, respectively. To get the optimal conditions, factors that may affect the formation of the ion‐pairing complex were thoroughly examined. The two approaches were carefully validated following the International Conference of Harmonization (ICH Q2R1) guidelines. Statistical assessment of the results achieved using the suggested and previously published comparison approaches showed no significant difference. The approaches were successful in determining nilotinib in a pharmaceutical dosage form as well as spiked human plasma samples. The eco‐friendly properties of the methods were evaluated by three different tools. [ABSTRACT FROM AUTHOR]

Atomoxetine hydrochloride (ATX) is a potent and non-stimulant drug which was approved for the treatment of attention-deficit hyperactivity disorder. Owing to its importance, two green, simple and validated spectrofluorimetric methods were developed for its sensitive assay in pure and capsule forms. The first method (Method I) relied on measuring the enhanced fluorescence of ATX by the use of sodium dodecyl sulfate in alkaline medium at λex 227 nm/λem 298 nm. The second method (Method II) involved complex formation of ATX with Erythrosine B (EB) in aqueous acidic solution resulting in quantitative quenching of the EB naive fluorescence. This complex was formed in the presence of Britton–Robinson buffer (pH 4.0). The difference in fluorescence intensity was measured at λex 527/λem550 nm. The calibration curves were linear through the ranges of 0.2–2.0 µg ml−1 for Method I, 0.2–4.0 µg ml−1 for Method II with good correlation coefficient (r = 0.9998) for both methods. The suggested methods were perfectly applied for determination of ATX in its commercial capsules and content uniformity test. The greenness of the proposed methods was confirmed by three different assessment tools and it was found that both methods were green, eco-friendly and environmentally safe.

This study explored the effect of erythrosine B (EB) as a photosensitizer in corn starch (CS) film and its physicochemical properties and photodynamic bacteriostatic ability against Staphylococcus aureus , Escherichia coli , and Salmonella both in vitro and inoculated on pork under the irradiation of D65 light-emitting diode (LED) (400-800 nm). The study revealed that the physiochemical properties of CS films: moisture content, water solubility, and water vapor transmission were improved with the addition of EB. In addition, the elasticity and the thermal stability of the film were enhanced. The results showed that the CS-EB films stimulated a maximum of 26.36 μg/mL hydrogen peroxide and 74.5 μg/g hydroxyl radical under irradiation. The CS composite films with a 5 % concentration of EB inhibited the bacterial growth by 4.7 Log CFU/mL in vitro after 30 min of illumination, and 2.4 Log CFU/mL on the pork samples under the same experimental condition. Moreover, the antibacterial ability was enhanced with the increase in EB concentration. Overall, the CS-EB composite films can inhibit the growth of bacteria through photodynamic inactivation and has the potential to become a new type of environmentally friendly packaging material. • Corn starch (CS) films incorporated with erythrosine B (EB) were prepared. • The physiochemical properties of CS-EB films were improved. • The photodynamic antibacterial mechanism of CS-EB films was confirmed. • The antibacterial effect was proportional to the dose of light and erythrosine B. [ABSTRACT FROM AUTHOR]

Kinetic investigation of the degradation of Erythrosine B (EB) by H2O2 and copper‐iron bimetallic nanoparticles was carried out spectrophotometrically. The degradation was carried out under the condition of sonication at 40°C. The co‐precipitation method was used for the fabrication of CuO/Fe2O3 (Cu‐Fe) in an alkaline solution and characterized by SEM, XRD, FTIR, TEM, EDS, and BET methods. In the absence of the Cu‐Fe, no degradation of EB by H2O2 was observed. The presence of Cu‐Fe resulted into the degradation of EB by H2O2. The kinetics of the degradation was studied under the conditions of variation of the amount of nanoparticles and at different concentrations of EB, H2O2, H+, surfactants (sodium dodecyl sulphate; SDS and cetyltrimethylammonium bromide; CTABr). The rate of reaction depends on the amount of Cu‐Fe and [H2O2]. The rate constant values gave the peaked like curve (with maximum value at pH 3) at different pH. The dye degradation decreased with the increase in presence of (SDS) and (CTABr). [ABSTRACT FROM AUTHOR]

[Display omitted] • Herrin, the first method for determination of Vilazodone was reported based on quenching mechanism. • The procedure does not include prolonged stages for sample preparation, extraction or chemical derivatization. • The suggested method has been effectively applied to confirm the content uniformity of medication tablets. • Furthermore, the greenness of the procedure was evaluated with metric tools. Vilazodone is a recently approved antidepressant medicine used for treating major depressive disorder. A simple, extremely sensitive, accurate and green spectrofluorimetric method was constructed for its determination through formation of ion-pair complex with erythrosine B. The formation of ion-pair complex lowers the dye's native fluorescence emission measured at 552 nm (λ ex = 530 nm). In terms of analysis, the system's parameters for producing the vilazodone-erythrosine B complex have been optimized. The reaction was carried out in Teorell-Stenhagen buffering solution (pH 4.6). The fluorescence emission intensity of the dye decreased linearly in the range of 20 – 600 ng mL−1 and the correlation coefficient was 0.9999. The quantitation and detection limit values were 18.5 and 6.1 ng mL−1, respectively. The proposed strategy has been validated according to the ICH criteria. The proposed technique was thoroughly employed for evaluating vilazodone in raw material and pharmaceutical tablet dosage form. Furthermore, it was also successfully used for content uniformity testing. Lastly, using four advanced tools namely the Eco-Scale, the National Environmental Method Index (NEMI), the Green Analytical Procedure Index (GAPI), and the Analytical Greenness metric approach (AGREE), the greenness of the established technique was evaluated. [ABSTRACT FROM AUTHOR]

• The DFT study on the adsorption of erythrosine B dye on Ca 2 C and Ti 2 C MXenes. • Our results revealed that the EB adsorption is endothermic and spontaneous in nature. • Binding energies revealed that our findings support the hard and soft acid-base principle. In this work, the Ca 2 C and Ti 2 C MXenes have been investigated for the adsorption of erythrosine B (EB) dye from wastewater using density functional theory (DFT) calculations. The thermodynamic studies were carried out to examine the feasibility of EB adsorption on the Ca 2 C and Ti 2 C MXenes. Our results revealed that the EB adsorption is endothermic and spontaneous in nature with the negative Gibbs free energy values. Moreover, the obtained binding energies for the EB/Ca 2 C and EB/Ti 2 C systems are −2.24 eV and −2.96 eV, respectively. Adsorption procedure and binding energies obtained for the EB/Ca 2 C and EB/Ti 2 C systems revealed that our findings support the hard and soft acid-base principle. We found that both Ca 2 C and Ti 2 C MXenes are effective adsorbents for the removal of the EB from wastewater. Our findings might be helpful for future studies toward the application of carbide MXene materials for removing wastewater pollutants. [ABSTRACT FROM AUTHOR]

Two facile spectroscopic methodologies were designed for estimating trospium chloride (TPM) in raw material and tablets with high operational reliability and selectivity. The methods were based on using erythrosine B (EB) as a spectroscopic tool for ion‐pair complex formation with the drug. In a mild acidic medium of Britton Robinson buffer (pH 4.0), the ionized hydroxyl group in the reagent interacted with the ionized amine in the studied drug. Method I was based on the spectrophotometric measuring of the absorbance of the reaction product at 557 nm. Method II was based on spectrofluorimetric measurement of the quenching effect of TPM on the inherent fluorescence of EB at 550 nm (λex. = 528 nm). The two methods showed linearity through ranges 1.0–10.0 and 0.5–10.0 μg/ml for Methods I and II, respectively. The suggested methods were exploited for analyzing TPM in Trospamexin® tablets and showed good applicability. The designed systems were validated as per International Conference on Harmonization guidelines. Experimental conditions were modulated to obtain the best sensitivities. The quenching mechanism was investigated and the quenching constant was computed relying on the Stern–Volmer equation. Environmental impact was appraised using novel metric green tools, GABI, and AGREE. The suggested systems excelled over other reported methods in terms of greenness, sensitivity, and cost–effectiveness. [ABSTRACT FROM AUTHOR]

In the present study, two drugs for treating acromegaly are investigated which are either synthetic growth hormone inhibiting hormone (GHIH) or dopamine receptor agonist. Octreotide (OCT) and bromocriptine (BCT) were quantified with a quick, simple, and sensitive spectrophotometric approach in their authentic forms and commercial dosage forms. This approach was based upon formation of ion pair complex between erythrosine B and investigated drugs in an aqueous buffered solution. For OCT determination the higher sensitivity was obtained using ΔA at 525 nm. On the other hand, BCT was estimated using the absorbance at 556 nm. Under optimal conditions for the reaction, construction of calibration curves were performed within concentration range of 0.4-4 µg ml -1 for OCT and 1-9 µg ml -1 for BCT with with low detection limits (0.094 and 0.235 µg ml -1 ) and low quantitation limits (0.29 and 0.71 µg ml -1 ) for OCT and BCT respectively. The developed approach was assessed for linearity, accuracy, precision, limits of detection, and limits of quantitation in compliance with ICH validation recommendations. The suggested approaches demonstrated good linearity, as evidenced by determination coefficients (r 2 ) of 0.999 with a slope 0.14 for OCT and 0.9989 with a slope 0.06 for BCT. Additionally, the environmental friendliness of the investigated method was assessed with some of the recent green analytical chemistry metrics., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Herein, two new facile methods were examined for varenicline determination using erythrosine. The latter is a food additive that has been recently investigated as a fluorescent dye for the determination of drugs. In the first method, the fluorescence of erythrosine B was quenched quantitatively by increasing the concentration of varenicline through ion-pair complex formation. This linear response was a basis for the spectrofluorimetric method used for varenicline quantitation in pure and dosage forms. The quenching is correlated with the concentration linearly over the range of 0.4–4.0 µg ml−1 at 550 nm after excitation at 528 nm with a correlation coefficient of 0.9993. Different parameters were investigated to reach the optimal conditions with the highest sensitivity and repeatability. The second method is depending on measuring the formed complex by spectrophotometry at 550 nm over the range of 1.0–10.0 µg ml−1 with an excellent correlation coefficient of 0.9999. The suggested methods were validated consistently with ICH guidelines, with acceptable results. The procedures were used to test the uniformity of content of Champix tablets. By comparing with the previous spectroscopic method, there was no significant difference as revealed from the calculated Student t-test and variance ratio F-test values.

The present study investigates the removal of Erythrosine B (EB), a neurotoxin and carcinogenic dye from aqueous system using Prosopisspicigera L. wood (PsLw) carbon-iron oxide composite. The adsorbent is well characterized by Fourier Transform Infra Red spectroscopy (FTIR), Scanning Electron Microscope (SEM) for surface morphology, Brunauer-Emmett-Teller nitrogen adsorption method (BET)/methylene blue method for surface area determination and potentiometric methods for surface charge (pHzpc) determination. The removal capacity of the adsorbent has been evaluated by batch method under varying pH, contact time, adsorbate initial concentrations, and in the presence of other ions. The Langmuir maximum adsorption capacity is found to be 487.8 mg/g at pH = 2.0 for an initial concentration of 250 mg/L. The adsorption follows pseudo second order kinetics and fits to Langmuir isotherm. The adsorption is thermodynamically spontaneous and exothermic in nature. Pore diffusion and mass transfer studies are performed. Column mode analysis is applied in the process for industrial applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • Two spectroscopic methods were reported for olanzapine assay using erythrosine B as a probe. • The procedure does not include complex steps in sample preparation, extraction or heating. • The suggested methods were applied to analyze tablets formulation and spiked human plasma. • Moreover, the greenness of the procedures was confirmed with two analytical metric tools. In this work, the xanthene dye, erythrosine B, was employed as a probe for the determination of olanzapine using two fast and highly simple analytical approaches. The assay was based on the formation of a binary complex between the drug and erythrosine B in a slightly acidic aqueous buffered solution. In the first method, the absorbance of the formed product was monitored at 558 nm. The reaction stoichiometry was investigated, and the stability constant of the formed complex was estimated. The linear range of the method that obeyed Beer's law was in the concentration range of 0.6–8.0 µg/ml. The calculated detection and quantitation limits were 0.2 and 0.6 µg/mL. Upon adding the drug solution to erythrosine B, the native fluorescence of the dye was quenched and monitored at 550 nm after excitation at 528 nm. Thus, the fluorescence quenching was utilized as the quantitative signal in the spectrofluorimetric approach. The extent of quenching in the fluorescence intensity was rectilinear with the drug concentration in a range of 0.1–2.5 µg/ml with a detection limit of 0.032 µg/ml. Both approaches were analytically validated based on the guiding rules of the ICH with acceptable results, and were utilized efficiently in the analysis of olanzapine in commercial tablets containing the cited drug. In addition, owing to its high sensitivity and selectivity, the spectrofluorimetric method was applied for drug analysis in spiked human plasma with satisfactory % recoveries. Finally, the greenness of the methods was confirmed using eco-score scale and Analytical Green Evaluation metrics. [ABSTRACT FROM AUTHOR]

A recently developed antipsychotic drug, lurasidone, was determined using a simple, sensitive, and eco-friendly spectrofluorimetric approach. The suggested approach was based on the quantifiable quenching impact of lurasidone on the inherent fluorescence of erythrosine B in an acidic environment employing a Teorell-Stenhagen buffer (pH 4). Following excitation at 530 nm, the quenching of erythrosine B fluorescence was monitored at 552 nm. The system variables were systematically optimized to enhance the formation of the lurasidone-erythrosine B ion pair for analytical purposes. A linear calibration graph was built in the range of 20-600 ng mL -1 with 0.9998 as a coefficient of correlation. The quantitation and detection limits were 13.5 and 4.5 ng/mL, respectively. The analytical validity of the designed approach was assessed with respect to International Council on Harmonization (ICH) guiding principles. The proposed methodology was employed with high recoveries for assessing lurasidone in bulk powder and its therapeutic tablet dosage form. Additionally, the uniformity of tablet formulations was tested using the developed approach. Finally, the established approach was assessed for its greenness using various tools., (© 2024 John Wiley & Sons Ltd.)

This study introduces a practical and cost-effective method for tracking diltiazem (DLZ) analytically. It utilizes a fluorimetric approach that relies on the modulation of fluorescence intensity of a dye called erythrosine B. Through a one-pot experiment performed in an acidic environment, a complex is rapidly formed between DLZ and erythrosine B. By observing the decrease in erythrosine B emission, a linear calibration plot is established, enabling the detection and quantification of DLZ concentrations ranging from 40 to 850 ng/ml. The estimated limits of detection and quantitation were 10.5 and 32.1 ng/ml, respectively. The variables affecting the DLZ-dye complex system were carefully adjusted. The validity of the approach was confirmed through a thorough evaluation based on the criteria set by ICH guidelines. The accuracy and precision of the methodology were evaluated, and the standard deviation and relative standard deviation were below 2. The strategy was successfully employed to analyze DLZ in tablets and capsules, and no significant variation between the proposed and reported methods as the values of the estimated t-test and F-test at five determinations were below 2.306 and 6.338, respectively. Notably, the method adheres to the principle of green chemistry by utilizing distilled water as the dispersing medium., (© 2024 John Wiley & Sons Ltd.)

In an acidic buffered solution, erythrosine B can react with amiodarone to form an association complex, which not only generates great enhancement in resonance Rayleigh scattering (RRS) spectrum of erythrosine B at 346.5 nm but also results in quenching of fluorescence spectra of erythrosine B at λ emission  = 550.4 nm/λ excitation  = 528.5 nm. In addition, the formed erythrosine B-amiodarone complex produces a new absorbance peak at 555 nm. The spectral characteristics of the RRS, absorbance, and fluorescence spectra, as well as the optimum analytical conditions, were studied and investigated. As a result, new spectroscopic methods were developed to determine amiodarone by utilizing erythrosine B as a probe. Moreover, the ICH guidelines were used to validate the developed RRS, photometric, and fluorimetric methods. The enhancements in the absorbance and the RRS intensity and the decrease in the fluorescence intensity of the used probe were proportional to the concentration of amiodarone in ranges of 2.5-20.0, 0.2-2.5, and 0.25-1.75 μg/mL, respectively. Furthermore, limit of detection values were 0.52 ng/mL for the spectrophotometric method, 0.051 μg/mL for the RRS method, and 0.075 μg/mL for the fluorimetric method. Moreover, with good recoveries, the developed spectroscopic procedures were applied to analyze amiodarone in its commercial tablets., (© 2024 John Wiley & Sons Ltd.)

Ambroxol hydrochloride (AMX) and guaifenesin (GFN) are approved drugs utilized to treat coughs through their potent mucolytic and expectorant properties. Due to their massive, combined administration in many illnesses, there is a persistent need for their concurrent estimation in different pharmaceutical formulations. Two sensitive, environmentally friendly spectrofluorimetric methods were developed. AMX was determined using the first method (I) without interference from GFN. This method depends on the quenching of Erythrosine B (EB) native fluorescence at 552 nm after excitation at 527 nm due to the formation of a non-fluorescent AMX-EB ion-pair complex in Britton-Robinson buffer (BRB) solution pH (3.5). The concentration plot is linear over the 0.25-5.0 μg/mL range, with a mean percent found value of 99.74%. Method (II) depends on measuring the native fluorescence of aqueous GFN solution at two analytical wavelengths, either 300 or 600 nm, after excitation at 274 nm. Relative fluorescence intensity (RFI)-concentration plots are linear over the ranges of 0.02-0.5 and 0.1-2.0 μg/ml, with mean percent found at 99.96% and 99.91% at dual wavelengths, respectively. The proposed methods were successfully applied to assay both drugs in raw materials and different single and combined pharmaceutical formulations. These methods have been thoroughly validated following International Committee on Harmonisation (ICH) guidelines. National Environmental Methods Index, Analytical Eco-Scale, and Green Analytical Procedure Index were used to prove greenness, thereby enhancing their applicability. The proposed techniques provide straightforward, precise, and cost-effective solutions for routine formulation analysis in quality control laboratories., (© 2024 John Wiley & Sons Ltd.)

Abstract The ability of Rhizopus arrhizus biomass for the removal of dye erythrosine B from aqueous solution was explored. The dye removal capacity of the biomass was evaluated by conducting batch tests using various parameters, viz. effect of pH, biomass dosage, contact time, modified biomasses and initial dye concentrations. The adsorption process followed a pseudo-second-order kinetic model suggesting chemisorption might be the rate-limiting step. The equilibrium process was found to be in good agreement with Langmuir adsorption isotherm, and maximum adsorption capacities of 355.9 mg/g and 363.6 mg/g were achieved with both waste and acid-treated fresh biomass, respectively. Graphical abstract

Cell viability is a critical indicator for assessing culture quality in microalgae cultivation for biorefinery and bioremediation. Fluorescent dyes that distinguish viable from nonviable cells can enable viability quantification based on the percentage of live cells. However, fluorescence analysis using the typical flow cytometry method is costly and impractical for industrial applications. To address this, we developed new microplate assays utilizing fluorescein diacetate as a live cell stain and erythrosine B as a dead cell stain. These assays provide a low-cost, simple, and reliable method of assessing cell viability. The proposed microplate assays were successfully applied to monitor the viability of the microalgae Dunaliella viridis under carbon and nitrogen limitation stresses and demonstrated good agreement with flow cytometry measurements. We conducted a systematic investigation of the effects of dye concentration, incubation time, and background fluorescence on the microplate assays' performance. Further, we provide a comprehensive review of commonly used fluorescent dyes for microalgae staining, discuss strategies to enhance assay performance, and offer recommendations for dye selection and protocol development. This study presents a comprehensive new method for microplate-based viability analysis, providing valuable insights for future microalgae viability assessments and applications.

Sunitinib is a tyrosine kinase inhibitor used for the treatment of renal cell carcinoma and gastrointestinal stromal tumors. In this study, two spectroscopic methods, spectrofluorometric and spectrophotometric, were utilized to quantify sunitinib in different matrices. In method I, the native fluorescence of erythrosine B was quenched by forming ion-pair complex with increasing quantities of sunitinib. This approach was utilized for measuring sunitinib in its dosage forms and spiked plasma. After excitation at 528 nm, the quenching of fluorescence is linearly related to the concentration across the range of 0.05-0.5 μg mL -1 at 550 nm in Britton-Robinson buffer (pH 4.0), with a correlation value of 0.9999 and a high level of sensitivity with detection limit down to 10 ng mL -1 . Method II relies on spectrophotometric measurements of the produced complex at 550 nm across a range of 0.5-10.0 μg mL -1 , with good correlation value of 0.9999. This method has a detection limit down to 0.16 μg mL -1 . The proposed methodologies were validated according to International Conference on Harmonization (ICH) guidelines with satisfactory results. The stoichiometry of the reaction was determined through the application of Job's method, while the mechanism of quenching was investigated by employing the Stern-Volmer plot. The designated methods were used to estimate sunitinib in its capsules and in spiked human plasma. Additionally, the statistical analysis of the data revealed no substantial differences when compared to previous reported spectroscopic method. Green assessment tools provide further details about the eco-friendly nature of the methods., (© 2023 John Wiley & Sons Ltd.)

A highly sensitive and selective method of high performance liquid chromatography (HPLC) combined with resonance Rayleigh scattering (RRS) spectra was developed for the detection of three antihistamine drugs, including pyrilamine (PY), carbinoxamine (CAR) and tripelennamine (TRI). The three antihistamines were separated by a C18 column. The mobile phase contained 25% acetonitrile (ACN) and 75% phosphate buffered solution (pH 3.2) with the flow rate of 0.4 ml min−1. In medium of Britton–Robinson (BR) buffer solution (pH 4.6), the PY, CAR and TRI separated by HPLC and then reacted with Erythrosine B (EryB), forming 1:1 ion‐association complexes, which led to significant signal enhancement of RRS spectra. The RRS spectra was detected at the wavelength λex=λem = 370 nm. The calibration curves of PY, CAR and TRI were linear in the range from 0.02 to 25 μg ml−1, and the detection limit [signal‐to‐noise ratio (S/N) = 3] were 3.38, 4.48 and 5.50 ng ml−1, respectively. In addition, under the optimum experiment condition, the reaction mechanism and the reasons for RRS enhancement were investigated in this work. The developed method was applied to the simultaneous detection of three antihistamines in water samples with satisfying results. [ABSTRACT FROM AUTHOR]

Naftidrofuryl is a vasodilator medication used for treating cerebral and peripheral vascular diseases. In this study, two spectroscopical techniques, spectrofluorimetric and resonance Rayleigh scattering (RRS), were utilized to quantify naftidrofuryl in its pharmaceutical samples. The developed methodologies in this study rely on a facile process of forming an association complex between erythrosine B reagent and naftidrofuryl under acidic conditions. The fluorimetric assay is based on the ability of naftidrofuryl to quench and decrease the native fluorescence intensity of the reagent when measured at λ emis . = 550 nm ( λ excit . = 526 nm). Under similar reaction conditions, the RRS method relies on the observed amplification in the RRS spectrum of the reagent at a wavelength of 577 nm following its interaction with naftidrofuryl. The methods exhibited linearity within the ranges 0.2-1.6 μg/ml (r 2  = 0.999) and 0.1-1.4 μg/ml (r 2  = 0.9994), with limit of quantitation values of 0.146 and 0.099 μg/ml, and limit of detection values of 0.048 and 0.032 μg/ml, for the fluorometric and the RRS methods, respectively. Moreover, the quenching between the dye and naftidrofuryl was studied using Stern-Volmer analysis, and the methodologies were experimentally optimized and validated. Additionally, acceptable recoveries were achieved when the procedures were applied to determine naftidrofuryl in pharmaceutical samples., (© 2023 John Wiley & Sons Ltd.)

A spectrofluorimetric approach that is sensitive, simple, validated, and cost-effective has been proposed for the estimation of amlodipine (AML) and perindopril (PER) in their bulk powders, pharmaceutical formulations, and spiked human plasma. The recommended approach utilized the quantitative quenching effect of the two cited drugs on the fluorescence intensity of erythrosine B, as a result of complex binary reactions among each drug with erythrosine B at pH 3.5 (Teorell and Stenhagen buffer). The quenching of erythrosine B fluorescence was recorded at 554 nm after excitation at 527 nm. The calibration curve was detected in the range 0.25-3.0 μg ml -1 , with a correlation coefficient of 0.9996 for AML, and 0.1-1.5 μg ml -1 , with a correlation coefficient of 0.9996 for PER. The established spectrofluorimetric approach was validated for the estimation of the cited drugs with high sensitivity regarding International Council on Harmonization guidelines. Therefore, the established approach could be utilized for quality control of the cited drugs in their pharmaceutical formulations., (© 2023 John Wiley & Sons Ltd.)

Abstract: We report the synthesis of thiopyran derivatives under photosensitized conditions. This method is of interest for its reaction mechanism and is a novel synthetic route to heterocycles. [ABSTRACT FROM AUTHOR]

A highly sensitive resonance Rayleigh scattering (RRS) method for the determination of chitosan (CTS) was developed. In the pH 3.8 Britton-Robinson buffer solution, CTS interacted with erythrosine B (Ery B) to form an ion-association complex of [Ery B-CTS] which increased the RRS intensity of the system. With the addition of polyvinyl alcohol (PVA), the RRS intensity was significantly enhanced, and the RRS intensity of the reagent blank( I 0 ) dramatically decreased. The enhanced RRS intensity (Δ I ) was linearly proportional to the concentration of chitosan. Taking the medium molecular weight chitosan as the representative, the linear range of the method was 5.0–100.0 ng/mL and the detection limit (DL) was 0.47 ng/mL. The effect of the molecular weight of CTS on its accurate quantification was studied. Furthermore the dispersion and stability mechanism of PVA was discussed. Accordingly this assay was applied to detect the concentration of CTS in health products with satisfactory results. [ABSTRACT FROM AUTHOR]

Erythrosine B is an important representative of the xanthene dye class, widely used in food, pharmaceutical and cosmetic industry. The local agriculture byproduct namely beans hulls was used to identify the interactions between the xanthene foods dye Erythrosine B with its components. The process was studied at natural solution pH (5.6) and a sorbent dosage of 20 g/L representing the favorable adsorption conditions established in the previous investigations. The amount of dye adsorbed was found to vary with initial dye concentration and contact time. The data obtained from Erythrosine B sorption onto beans hulls was interpreted using four types of kinetics models: Lagergren pseudo-firstorder, Ho's pseudo-second-order, Elovich and Weber and Morris intraparticle diffusion model. According to the values obtained for correlation coefficient (R2>0.99), the adsorption data fitted the pseudo-secondorder model. The two and three linear section with different slope (for concentration higher than 10 mg/L) was assigned to two/three interparticle diffusion steps occurring during the adsorption process of the dye. The rate of Erythrosine B uptake onto beans hulls was found to be controlled by intraparticle diffusion considering that at last one stage has negative intercept values for three (10 mg/L, 30 mg/L and 50 mg/L) of the five studied concentrations. [ABSTRACT FROM AUTHOR]

Erythrosine B dye has found applications as photosensitizers in photodynamic therapy, fluorescent probes in chemistry and biology. In this study, we have investigated the effect of nano-droplets, concentration and size on linear and nonlinear optical characteristics of Erythrosine B (EryB) by Z-Scan, UV-Vis spectroscopy and spectrofluorometer techniques. Two-photon absorption coefficient ( β) of EryB was measured using the Z-Scan technique at two molar ratios of water to AOT surfactant (W = 3 and 8) for two types of Oil (n-decane and n-heptane) and different nano-droplet concentrations as well as nonlinear refractive index ( n ) of EryB in bulk water. Our results showed that two-photon absorption coefficient ( β) was enhanced in nano-droplet as compared with bulk water. Moreover, the fluorescence peaks of EryB was enhanced by nano-droplets (microemulsion). The excited to ground state dipole moment ratio ( μ /μ ) was calculated through quantum-mechanical second order perturbation theory for different nano-droplet concentrations. The results indicated that μ /μ of EryB in bulk water is higher than that of in water nano-droplets. It is demonstrated that for the equal concentration of EryB in the microemulsion, the peak of fluorescence intensity varied by changing the concentration of nano-droplets. Moreover, the fluorescence peak intensity enhanced when the continuous phase of microemulsion changed from n-decane to n-heptane. [ABSTRACT FROM AUTHOR]

Erythrosine B (ErB) is a cherry pink food colorant and is widely used in foods, drugs, and cosmetics. Quinoline yellow (QY) is a chinophthalon derivative used in cosmetic compositions for application to the skin, lips, and/or body surface. Previously, ErB and QY synthetic dyes were found to induce DNA damage in HepG2 cells. The aim of this study was to investigate the molecular basis underlying the genotoxicity attributed to ErB and QY using the RT² Profiler polymerase chain reaction array and by analyzing the expression profile of 84 genes involved in cell cycle arrest, apoptosis, and DNA repair in HepG2 cells. ErB (70 mg/L) significantly decreased the expression of two genes (FENI and REVI) related to DNA base repair. One gene (LIGI) was down- regulated and 20 genes related to ATR/ATM signaling (ATR, RBBP8, RADI, CHEKI, CHEK2, TOPBI), nucleotide excision repair (ERCCI, XPA), base excision repair (FENI, MBD4), mismatch repair (MLHI, MSH3, TP73), double strand break repair (BLM), other DNA repair genes (BRIPI, FANCA, GADD45A, REVI), and apoptosis (BAX, PPPIRI5A) were significantly increased after treatment with QY (20 mg/L). In conclusion, our data suggest that the genotoxic mechanism of ErB and QY dyes involves the modulation of genes related to the DNA repair system and cell cycle. [ABSTRACT FROM AUTHOR]

An ultraviolet visible (UV-Vis) spectrophotometric and partial least squares (PLS) chemometric method was developed for the simultaneous determination of erythrosine B (red), Brilliant Blue, and tartrazine (yellow) dyes. A training set (n=64) was generated using a full factorial design and its accuracy was tested in a test set (n=13) using a Box-Behnken design. The test set garnered a root mean square error (RMSE) of 1.79×10-7 for blue, 4.59×10-7 for red, and 1.13×10-6 for yellow dyes. The relatively small RMSE suggests only a small difference between predicted versus measured concentrations, demonstrating the accuracy of our model. The relative error of prediction (REP) for the test set were 11.73%, 19.52%, 19.38%, for blue, red, and yellow dyes, respectively. A comparable overlay between the actual candy samples and their replicated synthetic spectra were also obtained indicating the model as a potentially accurate method for determining concentrations of dyes in food samples. [ABSTRACT FROM AUTHOR]

The spectroscopic studies of erythrosine B thin films manufactured by the spin coating technique have been presented. The spectra of infrared absorption allow characterization of vibrational modes for erythrosine B in powder form, pristine and UV irradiated thin films. The absorption spectra recorded in UV–vis–NIR for pristine films of erythrosine B display two main bands. UV irradiation on erythrosine B films decreased absorbance over the spectra. Indirect allowed transition with optical energy gap of 2.57 eV is observed in pristine films. UV irradiation introduced structural defects and decreased optical band gap. Some of the optical absorption parameters and their relation to UV irradiation times, namely molar extinction coefficient ( ε ), electronic dipole strength ( q 2 ), and oscillator strength ( f ), of the principal optical transitions have also been evaluated. [ABSTRACT FROM AUTHOR]

Formation of amyloid fibrils has been associated with at least 30 different protein aggregation diseases. The 129-residue polypeptide hen lysozyme, which is structurally homologous to human lysozyme, has been demonstrated to exhibit amyloid fibril-forming propensity in vitro . This study is aimed at exploring the influence of erythrosine B on the in vitro amyloid fibril formation of hen lysozyme at pH 2.0 and 55 °C using ThT binding assay, transmission electron microscopy, far-UV circular dichroism absorption spectroscopy, 1-anilinonaphthalene-8-sulfonic acid fluorescence spectroscopy, and synchronous fluorescence study. We found that lysozyme fibrillogenesis was dose-dependently suppressed by erythrosine B. In addition, our far-UV CD and ANS fluorescence data showed that, as compared with the untreated lysozyme control, the α-to-ß transition and exposure of hydrophobic clusters in lysozyme were reduced upon treatment with erythrosine B. Moreover, it could be inferred that the binding of erythrosine B occurred in the vicinity of the tryptophan residues. Finally, molecular docking and molecular dynamics simulations were further employed to gain some insights into the possible binding site(s) and interactions between lysozyme and erythrosine B. We believe the results obtained here may contribute to the development of potential strategies/approaches for the suppression of amyloid fibrillogenesis, which is implicated in amyloid pathology. [ABSTRACT FROM AUTHOR]