Synchronous Fluorescence Spectroscopy Research Articles

Eco-Friendly Synchronous Spectrofluorimetric Determination of Imipenem, Cilastatin, and Relebactam; Application to Market Formulations and Biological Fluids; Greenness Assessment.

The proposed study introduces a rapid, sensitive, and simple synchronous spectrofluorimetric technique for simultaneous quantification of relebactam, cilastatin, and imipenem in marketed pharmaceutical forms and biological fluids. Using synchronous fluorescence spectroscopy at Δ λ = 110nm, cilastatin was detected at 360nm. Fourier Self-Deconvolution was subsequently applied to the spectrum to estimate relebactam and imipenem at 430nm and 470nm, respectively after detection of cilastatin at 360nm ensuring no cross-interference. The pH was adjusted to 8.0 using 2.0 mL of alkaline borate buffer. This approach allowed for the precise quantification of relebactam, cilastatin, and imipenem through ranges of 50-400 ng mL- 1, 20-500 ng mL- 1, and 50-500 ng mL- 1 respectively. The lower detection and quantitation limits were 9.9 and 29.7 ng mL- 1 for REL, 4.5 and 13.6 ng mL- 1 for CIL and 5.5 and 16.5 ng mL- 1 for IMP. The proposed method was successfully applied for the determination of studied drugs in their pharmaceutical formulations with a high degree of accuracy and without interference from common excipients. This approach allowed for the precise quantification of relebactam, cilastatin, and imipenem through ranges of 50-400 ng mL- 1, 20-500 ng mL- 1, and 50-500 ng mL- 1, respectively. The proposed method was rigorously validated according to ICH guidelines. Furthermore, the method's environmental impact was assessed using Eco-scale and Green Analytical Procedure Index (GAPI) techniques.

Identification of Goat Milk Adulterated with Cow Milk Based on Total Synchronous Fluorescence Spectroscopy Combined with CNN

Identification of Goat Milk Adulterated with Cow Milk Based on Total Synchronous Fluorescence Spectroscopy Combined with CNN

Spectroscopic and Molecular Docking Studies on the Influence of Inulin on the Interaction of Sophoricoside with Whey Protein Concentrate

The influence of inulin on the interaction of sophoricoside (Sop) with whey protein concentrate (WPC) was investigated using various spectroscopic methods, including fluorescence spectroscopy (intrinsic fluorescence, synchronous fluorescence, and three-dimensional fluorescence), ultraviolet-visible (UV–Vis) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, and molecular docking. Sop was found to quench the intrinsic fluorescence of WPC by a static mechanism, both with and without the addition of inulin, and to enhance the antioxidant capacity of the protein. The addition of inulin slightly increased the binding distance between WPC and Sop, while reducing the number of binding sites from two to one. Non-covalent interactions, predominantly van der Waals forces and hydrogen bonding, were maintained between Sop and the protein. Synchronous fluorescence spectroscopy revealed that Sop prevents the exposure of hydrophobic groups on tryptophan residues, leading to increased surface hydrophilicity of the WPC complex. This aligns with the decreased protein surface hydrophobicity measured by 8-Anilino-1-naphthalenesulfonic acid (ANS) binding assays. With inulin, the overall hydrophobicity of the protein was lower than in the system without inulin, suggesting that both inulin and Sop improve the solubility of WPC. Three-dimensional fluorescence spectral analysis showed a reduction in fluorescence intensity and a red shift in the presence of both Sop and inulin. FTIR spectroscopy indicated a slight increase in the secondary structure ordering of WPC following the addition of both Sop and inulin, suggesting structural stabilization under heating conditions. Molecular docking highlighted the potential for hydrogen bond formation between Sop and WPC.

Investigation on the interaction mechanism of trilobatin with pepsin and trypsin by multi-spectroscopic and molecular docking methods

Pepsin and trypsin are noteworthy for the digestion of proteins in the human body. Trilobatin is a dihydrochalone that has anti-obesity, antioxidant, and anti-diabetes functions. The interaction of trilobatin and pepsin or trypsin is not currently being explored. Therefore, in this research multiple methods involving fluorescence spectroscopy, synchronous fluorescence spectroscopy, ultraviolet–visible (UV–Vis) spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, circular dichroism (CD) and molecular docking were employed for studying the interaction between trilobatin and pepsin or trypsin. During the interaction between trilobatin and pepsin or trypsin, the quenching type was static quenching and a single binding site existed. The binding constants (Ka) values were 2.177 and 3.028 × 104 L/mol in trilobatin-pepsin and trilobatin-trypsin system at 298 K, respectively. However, the presense of metal ions (Zn2+, Ca2+ and K+) decreased the binding of trilobatin to pepsin and trypsin. The complex between trilobatin and pepsin was generated typically through hydrogen bonding and van der Waals force (ΔH° < 0 and ΔS° < 0), in comparison the complex between trilobatin and trypsin was established chiefly through hydrogen bond and hydrophobic force (ΔH° > 0 and ΔS° > 0). The data from UV–Vis, synchronous fluorescence, FT-IR and CD spectra indicated that trilobatin reduced the hydrophobicity of Tyrosine (Tyr) residues of pepsin and trypsin. Furthermore, trilobatin altered the secondary structures of pepsin and trypsin. Meanwhile, trilobatin changed the conformation of pepsin and trypsin so that the viscosity of the interaction systems decreased with increased of trilobatin concentration. The molecular docking modeling identified that the trilobatin interacted with amino acid residues around pepsin and trypsin. This work consistently showed the interaction between trilobatin and pepsin or trypsin, in addition to offering valuable information for the application of trilobatin.

Preparation of cellulose nano crystals from cinnamon stick, curcumin delivery and interaction with human hemoglobin protein: A novel view of the oxygenation hemoglobin

Curcumin (Cur), a natural phenolic compound, exhibits promising therapeutic properties including anti-cancer and anti-inflammatory effects. However, its limited bioavailability hinders its efficacy when administered alone. To address this challenge, this study explores the use of cellulose nano crystals (CNCs) derived from cinnamon stick via acid hydrolysis as carriers for Cur. The CNCs were thoroughly characterized, and Cur was successfully bound to them. Structural and morphological analyses of the CNCs-Cur complex were investigated applying Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). Interaction studies between hemoglobin and the CNCs-Cur complex were carried out using various fluorescence spectroscopic techniques. Fluorescence spectroscopy revealed hemoglobin fluorescence quenching by the CNCs-Cur complex, with Stern-Volmer constants determined at different temperatures indicating static mechanism for the quenching. Synchronous fluorescence spectroscopy provided insights into the molecular micro-environment surrounding chromophores, and the distance between the CNCs-Cur complex and hemoglobin fluorophores was calculated using Forster's non-radioactive energy transfer theory (FRET), yielding a distance of less than 7 nm. Circular dichroism (CD) analysis indicated structural changes in hemoglobin upon the interaction with CNCs-Cur, while oxygenation techniques were employed to investigate oxygen binding, release, and transfer in hemoglobin. This comprehensive investigation sheds light on the potential of CNCs as effective carriers for curcumin, offering valuable insights into their interaction with biological molecules.

Antibacterial Efficacy of Tryptophan Coordinated Silver Nanoparticles Against E. coli: Spectroscopic and Microscopic Evaluation of Bacterial Cell Death.

The capability of conventional fluorescence spectroscopy and right-angled synchronous fluorescence spectroscopy (SFS) was evaluated to quantify the antibacterial potential of chemically synthesized Tryptophan coordinated silver nanoparticles (Ag-TrpNPs). Silver nanoparticles have gained significant importance as a material of interest due to their diverse assemblies in the nanoscale range and their potent antibacterial activity. But due to toxicity of silver nanoparticles there is a dire need to coordinate these materials with some biocompatible and biodegradable molecules. The study has been focused on chemical synthesis of functional fluorescence nanomaterials based on Tryptophan molecules coordinated with silver nanoparticles (Ag-TrpNPs). The antibacterial activity of Ag-TrpNPs was assessed in bacteria due to their functional characteristics such as tuneability, biocompatibility, and bioavailability. We employed optical characterization techniques such as Ultraviolet-visible spectroscopy, dynamic light scattering (DLS), scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), fluorescence spectroscopy, and confocal microscopy to ensure the particles formation in aqueous suspension. DLS analysis confirmed the hydrodynamic size of the nanoparticles of approximately 100nm. SEM images revealed the spherical morphology and size distribution of the Ag-TrpNPs. Escherichia coli bacterial strains were used to assess the antibacterial efficacy of the Ag-TrpNPs using fluorescence spectroscopy and imaging. Initially, the agar well plate method was employed to evaluate the antimicrobial activity of the Ag-TrpNPs. The significant zones of inhibition of size 37mm at 500µg/mL and 27mm at 15.5µg/mL were reported which indicated the efficiency of Ag-TrpNPs from higher to lower concentration. Conventional and synchronous fluorescence spectra provided evidence of bacterial cell death in aqueous suspensions to ensure the interaction of Ag-TrpNPs with E. coli bacteria at different times and concentrations. SEM was employed to investigate the interaction mechanism between Ag-TrpNPs and bacterial cells. The images revealed cell wall disintegration, leading to the leakage of cellular contents, and eventually cell death occurred.

Rapid and simultaneous determination of ultratrace pefloxacin and fleroxacin residues in wastewater by Al3+ sensitized first derivative synchronous fluorescence spectrometry

In this study, a new first derivative synchronous fluorescence spectrometry (SFS) for the accurate and sensitive determination of pefloxacin (PFX) and fleroxacin (FLX) in wastewater was established. PFX and FLX were complexed with Al3+ to significantly enhance their fluorescence intensity. Because the conventional fluorescence spectra of PFX-Al3+ and FLX-Al3+ overlap significantly, the wavelength difference (Δλ = 155 nm) was chosen for SFS scanning to narrow spectral band. And the narrowed synchronous fluorescence spectra was subjected to first derivative processing. Finally, the zero intersections of the first derivative synchronous fluorescence spectra at 281.6 nm and 273.6 nm were chosen for the determination of PFX and FLX, cleverly used of spectral parameters to eliminate the serious interference between PFX-Al3+ and FLX-Al3+ and the interference of wastewater background. The limits of detection of PFX and FLX were 0.0086 ng·mL−1 and 0.0068 ng·mL−1 with linear ranges from 0.1–40 ng·mL−1 and 0.2–80 ng·mL−1, respectively. Recoveries of PFX and FLX in wastewater were 88.60 %–98.60 % and 90.00 %–95.60 %. The first derivative SFS established in this study used spectral separation instead of chromatographic separation, so that sample pretreatment was simple and the detection speed was fast. Compared the conventional method of HPLC, the test results of above two methods were close. And the new method had been successfully used for the determination of PFX and FLX residues in wastewater with good results. Therefore, the new first derivative SFS was expected to become a routine detection technology for PFX and FLX residues in wastewater and widely used.

Monitoring small-scale bioreactor studies for media development using polarized total synchronous fluorescence spectroscopy (pTSFS) and synchronous light scattering (SyLS)

Biopharmaceutical process development often involves the use of small-scale bioreactors (SSBR) for optimizing media formulations and process conditions during scale up to commercial scale production. Two key process parameters (CPP) used in SSBR studies are protein titre and viable cell density (VCD). Here, we explore the efficacy of parallel polarized total synchronous fluorescence spectroscopy (TSFS||) and Synchronous Light Scattering (SyLS||) to qualitatively monitor these CPPs and quantitatively predict titre and VCD for a large-scale cell culture media optimization SSBR study. The study involved 71 different media formulations (50+ components each), and the bioprocess was run for 13 days or more. Samples were extracted at set times (Day 0, 3, 9, and 13) and clarified by centrifugation. TSFS|| spectra showed significant emission changes along with increased light scatter over the course of the bioprocess. SyLS|| measurements strongly correlated with particle size data obtained from Dynamic Light Scattering but did not correlate well with VCD probably because of the centrifugation-based sample preparation. Statistical and principal component analysis (PCA) of the pTSFS data showed that spectral variation was greater between media formulations than due to the evolving bioprocess. This prevented the development of accurate global prediction models for media performance (e.g., predicting product titre at day 9 from media spectra measured at day 0). However, classification methods were successfully used to select media subsets with better quantitative prediction accuracy based on spectral similarities. A practical binary (high/low performance) classification model based on Support Vector Machines was generated for media formulation screening. Combining emission and scatter measurements with multivariate data analysis provides a more holistic, multi-attribute bioprocess monitoring method that minimizes the need to use different offline analytical methods. This methodology can be used to monitor process trajectories and deviations, and ultimately be used to predict bioprocess CPPs when implemented on production scale processes where there is much less compositional variation in the media. We believe this SSBR-pTSFS/SyLS approach will provide a valuable resource to develop the design/parameter space for in-process monitoring at production scale from early-stage process/media development studies.

Generating globin-like reactivities in [human serum albumin-FeII(heme)] complex through N-donor ligand addition

Human serum albumin (HSA) has a strong binding affinity for heme b, forming a complex in a 1:1 ratio with the co-factor ([HSA-FeIIIheme]). This system displays spectroscopic and functional properties comparable to globins when chemical derivatives mimicking them are incorporated into the protein matrix. The aim of this study is to generate globin-like systems using [HSA-FeIIIheme] as a protein template and binding N-donor ligands (imidazole, Im; and 1-methylimidazole, 1-MeIm) to construct artificial [HSA-Fe(heme)-(N-donor)] complexes. Their electronic structure and binding thermodynamics are investigated using UV–vis and (synchronous) fluorescence spectroscopies, while ligand-protein interactions are visualized using docking simulations. The imidazole derivatives have a strong affinity for [HSA-FeIIIheme] (K ~ 104–106), where the spontaneous binding of Im and 1-MeIm are dominated by entropic and enthalpic effects, respectively. The reduced form of the [HSA-Fe(heme)-(N-donor)] complexes demonstrate nitrite reductase (NiR) activity similar to that observed in globins, but with significant differences in their rates. [HSA-FeIIheme-(1-MeIm)] reduces nitrite ~4× faster than the Im analogue, and ~ 30× faster than myoglobin (Mb). The enhanced NiR activity of [HSA-FeIIheme-(1-MeIm)] is a cumulative effect of several factors including a slightly expanded and more optimal heme binding pocket, nearby residues as possible proton sources, and a H-bonding interaction between 1-MeIm and residues Arg160 and Lys181 that may have a long-distance influence on the heme π electron density.

Bio-spectroscopic analysis of corneal structural alterations in dry eye disease: A study of collagen, co-enzymes, lipids, and proteins with emphasis on phytotherapy intervention

Dry eye disease (DED) stands as a prevalent cause for ophthalmology consultations, securing the third position following refractive errors and cataracts. Moreover, the likelihood of experiencing DED escalates with advancing age. In this experimental study corneal tissue alterations due to DED were investigated over different periods by applying both infrared and synchronous fluorescence spectroscopy. The potential effects of instillation of pomegranate and green tea water extracts as green-friendly treatment modalities were also evaluated. The obtained results collectively indicate that DED affects the OH bearing constituents (collagen, glycosaminoglycans, and proteoglycans) of cornea leading to changes in protein secondary structure and the collagen fibrils. Additionally, enhanced dehydrated environment, and reduced energetic/metabolic state, as indicated by co-enzymes, was observed. Phyto-therapeutic administration can contain these alterations with enhanced energetic/metabolic state and increased hydration environment. In conclusion, instillation of green tea extract can protect/restore the collagen fibrils and its potential effects, in general, exceeds that of pomegranate extract.

Applying fluorescence and 2D-correlation spectroscopy to elucidate changes in the chemical composition of DOM from soils with different vegetation types

ABSTRACT To understand the decomposition of the dissolved organic matter (DOM), four different soils (from grassland, spruce forest, oak forest, and agricultural land) were incubated at 15 °C, and the DOM changes were monitored using UV-Vis, synchronized fluorescence and 2D-correlation spectroscopy. The DOM fraction of the agricultural and grassland soils showed a significant increase in both SUVA values in the middle of the incubation ranging from an initial 3–5 L mg−1 m−1 to 40–50 L mg−1 m−1. Synchronous fluorescence spectroscopy revealed that at the beginning of incubation, on day 3, there was an increase in the proportion of low molecular-weight, readily biodegradable compounds (PLF, protein-like fluorescence), while from day 8 onwards, microbial degradation generated a large number of medium-molecular-weight molecules (MHLF, microbial humus-like fluorescence). At further sampling dates, the proportion of compounds of microbial origin decreased systematically, due to a decrease in microbial activity caused by the lack of substrate. 2D-correlation measurements revealed further details of the changes in the quality of DOM, revealing two distinct patterns in the DOM dynamics of the soils, the sequence MHLF→PLF being observed for grassland and arable land and PLF→HLF for forest soils, probably due to the different N supplies of the soils.

An environmentally sustainable synchronous spectrofluorimetric method coupled with second derivative signal processing for simultaneous determination of velpatasvir and simeprevir in pharmaceutical and plasma samples

Velpatasvir and simeprevir are two direct acting antivirals that are often used in combination with sofosbuvir to treat HCV infections. Herein, an environmentally benign spectrofluorimetric method was developed for simultaneous quantification of velpatasvir and simeprevir in pharmaceutical and plasma samples. To address the issue of overlapping fluorescence spectra presented by these compounds, this method integrates synchronous fluorescence and second-derivative spectroscopy. By employing the second derivative of the synchronous fluorescence spectra measured at Δλ of 140 nm, the accurate determination of velpatasvir at 400 nm and simeprevir at 426 nm was achieved without any interference. Different experimental parameters affecting the synchronous fluorescence of the studied drugs were carefully optimized. The plots of second-derivative amplitudes against concentrations showed linearity in the range of 5–400 ng/mL for velpatasvir and 80–800 ng/mL for simeprevir. The method was very sensitive, with lower detection limits of 1.11 ng/mL and 25.40 ng/mL, and quantification limits of 3.36 ng/mL and 76.96 ng/mL for velpatasvir and simeprevir, respectively.The method was effectively used to determine velpatasvir and simeprevir simultaneously in their pure forms, pharmaceutical dosage forms, and human plasma with no interference. The suggested technique was additionally evaluated for its eco-friendliness through the utilization of the Analytical GREEnness (AGREE) and Green Analytical Procedure Index (GAPI) evaluation metrics, revealing that the method is indeed sustainable.

Individual mono and co-interactions of butylated hydroxytoluene and its metabolite with pepsin: Multi-pronged research strategies

In this study, the interactions between butylated hydroxytoluene (BHT) and its metabolite 2,6-Di-tert-butyl-p-benzoquinone (BHT-Q) with pepsin (PEP) were explored using multispectral measurements and computer prediction techniques. UV–vis absorption spectra, fluorescence lifetime, and Stern-Volmer quenching analysis showed static fluorescence quenching of PEP by BHT/BHT-Q. Negative thermodynamic parameters indicated that the spontaneous formation of complexes was primarily driven by van der Waals (vdW) forces and hydrogen bonds (HB). Synchronous fluorescence and circular dichroism spectroscopy revealed conformational changes induced by BHT/BHT-Q on PEP. Furthermore, BHT and BHT-Q inhibited PEP's enzymatic activity, while PEP suppressed their antioxidant activity. Interestingly, BHT-Q weakened BHT's binding strength to PEP, affecting the enzyme inhibition rate. Computer predictions highlighted the integral role of hydrophobic interactions. Moreover, BHT and BHT-Q exhibited different effects on the stability and compactness of PEP, the residue environment of PEP became more flexible or rigid in the presence of BHT and BHT-Q. Changes in the hydrophobic solvent accessible surface area (SASA) elucidated that the microenvironment of hydrophobic residues of PEP was changed after binding with BHT and BHT-Q. Ultimately, BHT's stronger binding affinity to PEP than BHT-Q was attributed mainly to its larger negative surface area, facilitating interactions with more amino acid residues.

Non-Invasive Endometrial Cancer Screening through Urinary Fluorescent Metabolome Profile Monitoring and Machine Learning Algorithms.

Endometrial cancer is becoming increasingly common, highlighting the need for improved diagnostic methods that are both effective and non-invasive. This study investigates the use of urinary fluorescence spectroscopy as a potential diagnostic tool for endometrial cancer. Urine samples were collected from endometrial cancer patients (n = 77), patients with benign uterine tumors (n = 23), and control gynecological patients attending regular checkups or follow-ups (n = 96). These samples were analyzed using synchronous fluorescence spectroscopy to measure the total fluorescent metabolome profile, and specific fluorescence ratios were created to differentiate between control, benign, and malignant samples. These spectral markers demonstrated potential clinical applicability with AUC as high as 80%. Partial Least Squares Discriminant Analysis (PLS-DA) was employed to reduce data dimensionality and enhance class separation. Additionally, machine learning models, including Random Forest (RF), Logistic Regression (LR), Support Vector Machine (SVM), and Stochastic Gradient Descent (SGD), were utilized to distinguish between controls and endometrial cancer patients. PLS-DA achieved an overall accuracy of 79% and an AUC of 90%. These promising results indicate that urinary fluorescence spectroscopy, combined with advanced machine learning models, has the potential to revolutionize endometrial cancer diagnostics, offering a rapid, accurate, and non-invasive alternative to current methods.

Synchronous Fluorescence Spectroscopy as a Green Method for the Prediction of Antioxidant Activity in Wine Brandy and Sweet Wine

Synchronous Fluorescence Spectroscopy as a Green Method for the Prediction of Antioxidant Activity in Wine Brandy and Sweet Wine

Differentiating Nylon Samples with Visually Indistinguishable Fluorescence Using Principal Component Analysis and Common Dimension Partial Least Squares Linear Discriminant Analysis with Synchronous Fluorescence Spectroscopy.

Fluorescence spectroscopy is an attractive candidate for analyzing samples of nylon. Impurities within the polymers formed during the synthesis and processing of nylons give rise to the observed fluorescence, allowing for nylons to be analyzed based on their impurities. Nylons from the same source are expected to display similar fluorescence profiles, and nylons with different fluorescence are expected to be from different sources. This paper investigates an important case where different nylons displayed similar fluorescence, preventing easy discrimination. Samples of Nylon 6 and Nylon 6/12 had visually indistinguishable excitation-emission matrices (EEM), excitation spectra, fluorescence spectra, and synchronous fluorescence spectra at larger Δλ. By collecting synchronous fluorescence spectra at smaller Δλ, additional features in the fluorescence profiles were identified that allowed for some discrimination between the two nylons. Combining the EEM and synchronous fluorescence data with chemometric algorithms provided a clearer differentiation between the two nylons. parallel factor analysis, principal component analysis, and common dimension partial least squares (ComDim-PLS) showed two distinct clusters in the data, with ComDim-PLS providing the greatest distinction between the clusters. The loadings revealed the variables of interest to the ComDim-PLS were the 400 nm and 335 nm bands for all synchronous fluorescence spectra, the 460 nm and 310 nm bands for the Δλ = 20 nm and Δλ = 30 nm synchronous fluorescence spectra, and the 440 nm band for the Δλ = 20 nm synchronous fluorescence spectra. The linear discriminant analysis performed with the PLS data yielded a classification accuracy of 95% with the EEM data and 100% with the synchronous fluorescence data, displaying the power of this technique to differentiate two different nylons with visually indistinguishable fluorescence spectra.

Eco-friendly second derivative synchronous fluorescence spectroscopic method for simultaneous determination of rosuvastatin and ezetimibe in pharmaceutical capsules

The fixed dose combination of Rosuvastatin and ezetimibe has recently received approval from the FDA for the treatment of elevated levels of low-density lipoprotein cholesterol in adults. Herein, an eco-friendly and highly sensitive spectrofluorimetric method was developed and validated for simultaneous determination of rosuvastatin and ezetimibe in commercial capsules. The developed method involved synchronous fluorescence spectroscopy combined with second derivative spectroscopy to resolve the overlapping fluorescence spectra of rosuvastatin and ezetimibe. The studied drugs were measured in synchronous mode at Δλ of 40 and their recorded synchronous fluorescence spectra were derivatized into second-order spectra, enabling the selective quantification of rosuvastatin and ezetimibe at 370 nm and 312 nm, respectively. Optimization studies regarding to the influence of buffer pH, incorporation of surfactant, choice of diluting solvent, and synchronous Δλ were carried out. The method was validated using the validation characteristics listed in ICH Q2(R1). The calibration curves displayed satisfactory linear relationships across the calibration range of 0.1–2 µg/mL for rosuvastatin and 0.05–3 µg/mL for ezetimibe. The methodology demonstrated robustness to minor modifications in the procedural parameters and selectivity in quantifying the studied drugs in synthetic mixed solutions and commercial capsules without interference. Furthermore, the level of environmental friendliness and sustainability of the suggested spectrofluorimetric approach was assessed in relation to two previously documented methodologies utilizing the AGREE metric. The findings indicated that the suggested method demonstrated a notably superior level of sustainability in comparison to the documented methods.

The interaction between resveratrol and catalase was studied by multispectral method and molecular docking simulation

In this research, we delved into the interaction mechanism between Resveratrol (RES) and Catalase (CAT) utilizing a suite of advanced analytical techniques, including multispectral analysis and molecular docking simulation. A comprehensive assessment of their binding characteristics, modalities, distances, and the subsequent impact on CAT's secondary structure was conducted through fluorescence spectroscopy, ultraviolet spectroscopy, circular dichroism, three-dimensional fluorescence spectroscopy, synchronous fluorescence spectroscopy, and molecular docking simulation. By employing the Stern-Volmer equation to determine KSV and Kq values, Our findings indicate that the RES-CAT interaction results in static fluorescence quenching, By conducting experiments, the binding constant KA and the number of binding sites n for CAT and RES were determined, with the number of binding sites n being close to 1, indicating the presence of a specific binding site between CAT and RES. Parameters at 298 K. The negative values of ΔH and ΔS suggest that van der Waals forces and hydrogen bonding are predominant in mediating the interaction between CAT and RES. The negativity of ΔG indicates the spontaneity of the reaction. The Fӧrster resonance energy transfer theory calculation revealed a binding distance of 4.917 nm, substantiating the occurrence of non-radiative energy transfer between RES and CAT. Furthermore, the UV-VIS absorption spectrum, synchronous fluorescence spectrum, three-dimensional fluorescence spectrum, and circular dichroism analyses collectively demonstrated that RES induces alterations in CAT's secondary structure, augmenting the polarity around tryptophan (Trp) residues, reducing hydrophobic interactions, and bolstering hydrophilicity. This work offers novel insights into the antioxidant mechanisms of resveratrol within biological systems and holds significant theoretical and practical implications for the medical application and development of resveratrol.

Characterization of fused aromatic multirings in lignin via synchronous fluorescence spectroscopy and catalytic hydro-depolymerization

The structural analysis of lignin is highly significant in practical terms. We investigated the presence of fused aromatic multirings (FARs) distinct from conventional phenylpropane units in seven lignin types using synchronous fluorescence spectroscopy (SFS) and quantified their relative proportions. Our findings reveal that FARs are present in all lignin samples, primarily composed of 2–6 rings. The relative distribution of FARs in lignin is ranked as follows: 2 rings > 1 ring > 4 rings > 3 rings > 6 rings > 5 rings. The relative contents of these FARs (1–6 rings) exhibit slight variations across all lignin samples. Notably, FARs with 2 rings are the highest at 35 %−53 %, while those with 5 and 6 rings are the lowest, collectively accounting for less than 1.37 %. Moreover, the relative contents of FARs with 1 and 2–6 rings range approximately 24 %−32 % and 68 %−76 %, respectively. Furthermore, the catalytic hydro-depolymerization of lignin was performed and the experimental results demonstrate that the hydro-liquefied oil from lignin contains aromatic compounds with 1–7 rings, and the relative contents of aromatic compounds with 1 ring and 2–7 rings in the oil are 29 % and 71 %, respectively, which is consistent with that of lignin SFS. These findings are also consistent with the existing literature and experimental results. This study offers an explanation for the low yields observed in current depolymerization processes targeting small molecules within lignin and establishes a theoretical foundation for achieving high yields in the preparation of multiring aromatic hydrocarbons.

Effect of the presence of berberine/curcumin on the binding of limonin to human serum albumin and antitumor activity in vitro

The competition among drugs for binding to plasma proteins is regarded as a pharmacokinetic drug interaction. Competition between antitumor agents and other drugs for plasma protein binding can alter the free concentration of the drug, potentially impacting its efficacy and increasing the risk of toxic side effects. Through a range of spectroscopic techniques, this study examined the interaction between limonin and human serum albumin (HSA) in the context of berberine (Ber) and curcumin (Cur) under physiological conditions to clarify the binding mechanisms of binary and ternary systems at the molecular level. As demonstrated by fluorescence quenching experiments, Static quenching was identified as the mechanism of interaction between HSA and limonin. The results of site competition experiments indicated that the binding site between limonin and HSA was site I, a result further supported by molecular docking simulations. Through the use of thermodynamic data calculations, it was determined that limonin forms a stable complex with HSA by establishing hydrogen bonds and van der Waals forces. Circular dichroism (CD) spectroscopy, three-dimensional (3D) fluorescence spectroscopy, and synchronous fluorescence spectroscopy (SFS) employed to validate the notion that limonin perturbed the microenvironment of amino acids and induced conformational changes in HSA. What’s more, the presence of Ber or Cur was found to have further modified the alterations observed in the interaction between the original HSA-limonin binary system. In vitro cellular experiments showed that interaction with HSA reduced the antitumor activity of limonin. In contrast, adding Ber or Cur increased the inhibition rate of tumor cells. The coexistence of both Ber and Cur significantly diminished limonin’s binding affinity to HSA. The current investigation enhances comprehension regarding the binding characteristics and interaction mechanisms involving limonin, Ber, Cur, and HSA. It explores the potential of HSA as a versatile drug carrier and furnishes theoretical underpinnings for co-administrative strategies.