Comparative study on the interaction of oxyresveratrol and piceatannol with trypsin and lysozyme: binding ability, activity and stability

Interaction of major saffron constituent safranal with trypsin: An experimental and computational investigation

Trypsin is a serine protease, an important digestive enzyme that digests the proteins in the small intestine. In the present study, we have investigated the interaction of safranal, a major saffron metabolite, with trypsin using spectroscopic and molecular docking analyses. Fluorescence emission spectra of trypsin were largely affected by the inner filter effect from safranal; that's why these were corrected using the standard procedure. The corrected fluorescence spectra have shown that the safranal quenched the intrinsic fluorescence of trypsin with a blue shift in the wavelength of emission maximum, which revealed that the microenvironment of the fluorophore became more hydrophobic. There was approximately 1: 1 fair binding between them, which increased with a rise in temperature. The interaction was favored, principally, by hydrophobic forces, and there was an efficient energy transfer from the fluorophore to the safranal. Synchronous fluorescence spectra suggested that the tryptophan residues were the major ones taking part in the fluorescence quenching of trypsin. Safranal also influenced the secondary structure of trypsin and caused partial unfolding. Molecular Docking and the Molecular Dynamics simulation of the free and complexed trypsin was also carried out. Safranal formed a stable, non-covalent complex within the S2'-S5' subsite. Moreover, two nearby tyrosine residues (Tyr39 and Tyr151) stabilized safranal through π-π interactions. Additionally, the presence of safranal led to changes in the protein flexibility and compactness, which could indicate changes in the surrounding of tryptophan residues, impacting their fluorescence. Furthermore, a loss in compactness is in line with the partial unfolding observed experimentally. Thus, both experimental and computational studies were in good agreement with each other.

Molecular insights into the phase transition of lysozyme into amyloid nanostructures: Implications of therapeutic strategies in diverse pathological conditions

Lysozyme, a well-known bacteriolytic enzyme, exhibits a fascinating yet complex behavior when it comes to protein aggregation. Under certain conditions, this enzyme undergoes flexible transformation, transitioning from partially unfolded intermediate units of native conformers into complex cross-β-rich nano fibrillar amyloid architectures. Formation of such lysozyme amyloids has been implicated in a multitude of pathological and medical severities, like hepatic dysfunction, hepatomegaly, splenic rupture as well as spleen dysfunction, nephropathy, sicca syndrome, renal dysfunction, renal amyloidosis, and systemic amyloidosis. In this comprehensive review, we have attempted to provide in-depth insights into the aggregating behavior of lysozyme across a spectrum of variables, including concentrations, temperatures, pH levels, and mutations. Our objective is to elucidate the underlying mechanisms that govern lysozyme's aggregation process and to unravel the complex interplay between its structural attributes. Moreover, this work has critically examined the latest advancements in the field, focusing specifically on novel strategies and systems, that have been implemented to delay or inhibit the lysozyme amyloidogenesis. Apart from this, we have tried to explore and advance our fundamental understanding of the complex processes involved in lysozyme aggregation. This will help the research community to lay a robust foundation for screening, designing, and formulating targeted anti-amyloid therapeutics offering improved treatment modalities and interventions not only for lysozyme-linked amyloidopathy but for a wide range of amyloid-related disorders.

In Silico Investigations on the Synergistic Binding Mechanism of Functional Compounds with Beta-Lactoglobulin

Piceatannol (PIC) and epigallocatechin gallate (EGCG) are polyphenolic compounds with applications in the treatment of various diseases such as cancer, but their stability is poor. β-lactoglobulin (β-LG) is a natural carrier that provides a protective effect to small molecule compounds and thus improves their stability. To elucidate the mechanism of action of EGCG, PIC, and palmitate (PLM) in binding to β-LG individually and jointly, this study applied molecular docking and molecular dynamics simulations combined with in-depth analyses including noncovalent interaction (NCI) and binding free energy to investigate the binding characteristics between β-LG and compounds of PIC, EGCG, and PLM. Simulations on the binary complexes of β-LG + PIC, β-LG + EGCG, and β-LG + PLM and ternary complexes of (β-LG + PLM) + PIC, (β-LG + PLM) + EGCG, β-LG + PIC) + EGCG, and (β-LG + EGCG) + PIC were performed for comparison and characterizing the interactions between binding compounds. The results demonstrated that the co-bound PIC and EGCG showed non-beneficial effects on each other. However, the centrally located PLM was revealed to be able to adjust the binding conformation of PIC, which led to the increase in binding affinity with β-LG, thus showing a synergistic effect on the co-bound PIC. The current study of β-LG co-encapsulated PLM and PIC provides a theoretical basis and research suggestions for improving the stability of polyphenols.

Structural alterations and inhibition of lysozyme activity upon binding interaction with rotenone: Insights from spectroscopic investigations and molecular dynamics simulation

The pervasive employment of pesticides such as rotenone on a global scale represents a substantial hazard to human health through direct exposure. Therefore, exploring the interactions between such compounds and body macromolecules such as proteins is crucial in comprehending the underlying mechanisms of their detrimental effects. The present study aims to delve into the molecular interaction between rotenone and lysozyme by employing spectroscopic techniques along with Molecular dynamics (MD) simulation in mimicked physiological conditions. The binding interaction resulted in a fluorescence quenching characterized by both dynamic and static mechanisms, with static quenching playing a prominent role in governing this phenomenon. The analysis of thermodynamic parameters indicated that hydrophobic interactions primarily governed the spontaneous bonding process. FT-IR and circular dichroism findings revealed structural alternations of lysozyme upon complexation with rotenone. Also, complexation with rotenone declined the biological activity of lysozyme, thus rotenone could be considered an enzyme inhibitor. Further, the binding interaction substantially decreased the thermal stability of lysozyme. Molecular docking studies showed the binding location and the key residues interacting with rotenone. The findings of the spectroscopic investigations were confirmed and accurately supported by MD simulation studies.

Thermodynamic and cellular studies of doxorubicin/daunorubicin loaded by a DNA tetrahedron for diagnostic imaging, chemotherapy, and gene therapy

The combined diagnostic imaging, chemotherapy, and gene therapy based on DNA nanocarriers can reduce the toxic side effects and overcome multidrug resistance (MDR). In this study, we designed an antisense oligonucleotides (ASOs)-linked DNA tetrahedron (ASOs-TD). The detection limit of ASOs-TD for MDR1 mRNA was 0.05 μM. By using fluorescence spectroscopy and isothermal titration calorimetry (ITC), the interactions between doxorubicin (DOX) /daunorubicin (DAU) and ASOs-TD were investigated. The number of binding sites (n), binding constant (Ka), entropy change (ΔSo), enthalpy change (ΔHo) and Gibbs free energy change (ΔGo) were obtained. The intercalation of DOX/DAU with ASOs-TD was demonstrated by differential scanning calorimetry (DSC) and quenching researches of potassium ferricyanide K4[Fe(CN)6]. The in vitro release rate of DOX/DAU loaded in ASOs-TD was accelerated by deoxyribonuclease I (DNase I). In vitro cytotoxicity proved the good gene therapy effect of ASOs-TD and the increased cytotoxicity of DOX/DAU to MCF-7/ADR cells. The results of confocal laser scanning microscope (CLSM) suggested that ASOs-TD could effectively identify drug-resistant cells due to its good imaging ability for MDR1 mRNA. This work offers theoretical significance for overcoming MDR using DNA nanostructures which combine diagnostic imaging, chemotherapy, and gene therapy.

Effects of two food colorants on catalase and trypsin: Binding evidences from experimental and computational analysis

Recently, growing concern has been paid to the toxicity of additives in food. The present study investigated the interaction of two commonly used food colorants, quinoline yellow (QY) and sunset yellow (SY), with catalase and trypsin under physiological conditions by fluorescence, isothermal titration calorimetry (ITC), ultraviolet-vis absorption, synchronous fluorescence techniques as well as molecular docking. Based on the fluorescence spectra and ITC data, both QY and SY could significantly quench the intrinsic fluorescence of catalase or trypsin spontaneously to form a moderate complex driven by different forces. Additionally, the thermodynamics results demonstrated QY bind more tightly to both catalase and trypsin than SY, suggesting QY poses more of a threat to two enzymes than SY. Furthermore, the binding of two colorants could not only lead to the conformational and microenvironmental alterations of both catalase and trypsin, but also inhibit the activity of two enzymes. This study provides an important reference for understanding the biological transportation of synthetic food colorants in vivo, and enhancing their risk assessment on food safety.

Effects of combined binding of chlorogenic acid/caffeic acid and gallic acid to trypsin on their synergistic antioxidant activity, enzyme activity and stability

The combined application of multiple natural polyphenols in functional foods may provide better health benefits. The binding of polyphenols with different structures to proteins will affect their respective functions. Spectroscopy and molecular docking were used to investigate the competitive binding of chlorogenic acid (CGA)/caffeic acid (CA) and gallic acid (GA) to trypsin. The effects of different molecular structures and the order of adding the three phenolic acids on the binding were assessed. The stability of trypsin and its docked complexes with CGA/CA/GA was evaluated by molecular dynamics simulation. The effects of the binding process on the activity and thermal stability of trypsin, as well as on the antioxidant activity and stability of CGA/CA/GA were explored. The competitive binding of CGA/CA and GA to trypsin affected their synergistic antioxidant effects. The results may provide a reference for the combined application of CGA/CA and GA in food and pharmaceutical fields.

Effect of Catechin on Yolk Immunoglobulin Structure and Properties: A Polyphenol-Protein Interaction Approach

The preparation of the interaction between polyphenols and protein is of great significance for increasing added value and promoting the application of egg yolk immunoglobulin (IgY). This study systematically investigated the effect of catechin on yolk immunoglobulin structural characteristics and functional properties. The binding conditions, force types, molecular conformation, and residual microenvironment of the interaction between catechin and IgY were analyzed by molecular docking technology, UV-vis absorption and fluorescence spectroscopy studies. The results showed that the main binding forces in the complex were hydrogen bonding and van der Waals forces. After the interaction, fluorescence quenching occurred and the maximum emission wavelength was redshifted. The results showed that the microenvironment around IgY increased polarity, increased hydrophilicity and decreased hydrophobicity, and the structure of the peptide chain changed. The bacteriostatic thermal stability of the compound against Escherichia coli and Staphylococcus aureus was lower than that of catechin IgY. The bacteriostatic acid and base stability were higher than that of catechin and IgY. The antioxidant activity was catechin, complex, and IgY, in descending order. The antioxidant activity of catechin and complex was significantly higher than that of IgY. At the same concentration, the apparent viscosity of the three samples was complex, IgY and catechin, in descending order. G' was greater than G" indicating that elastic properties dominate in G". The G' and G" values of the complex were higher than those of the other groups. Rheological results indicated that the complex may have high physical stability. This study provides theoretical support for broadening the application field of IgY and suggest its properties change in the machining process. It also provides new ideas for the development of functional foods from poultry eggs.

A pH-sensitive DNA tetrahedron for targeted release of anthracyclines: Binding properties investigation and cytotoxicity evaluation

The anticancer efficacy of chemotherapeutic agents can be enhanced by the loading of DNA nanostructures, which is closely related to their interactions. This study achieved pH-responsive and targeted anthracycline delivery using i-motif and MUC1 aptamer co-modified DNA tetrahedron (MUC1-TD). The thermodynamic parameters for the binding of doxorubicin (DOX) and epirubicin (EPI) to MUC1-TD at pHs 7.4 and 5.0 were obtained. The smaller binding constant and the number of binding sites at pH 5.0 than at pH 7.4 indicated that acidic conditions favored the release of DOX and EPI loaded by MUC1-TD. The binding affinity of DOX was stronger than that of EPI at the same pH value due to their different chemical stereostructures. The intercalative binding mechanism was verified. In vitro release experiments revealed that acid pH and deoxyribonuclease I accelerated the release of DOX and EPI. The faster release rate of EPI than DOX was related to their binding affinity. In vitro cytotoxicity and cell uptake experiments revealed that the cytotoxicity of DOX and EPI loaded by MUC1-TD to MCF-7 cells was significantly higher than that to L02 cells. This work will provide theoretical guidance for the application of pH-responsive MUC1-TD nanocarriers in the field of pharmaceutics.

Shedding light on the binding mechanism of kinase inhibitors BI-2536, Volasetib and Ro-3280 with their pharmacological target PLK1

In the present work, the interactions of the novel kinase inhibitors BI-2536, Volasetib (BI-6727) and Ro-3280 with the pharmacological target PLK1 have been studied by fluorescence spectroscopy and molecular dynamics calculations. High Stern-Volmer constants were found in fluorescence experiments suggesting the formation of stable protein-ligand complexes. In addition, it was observed that the binding constant between BI-2536 and PLK1 increases about 100-fold in presence of the phosphopeptide Cdc25C-p that docks to the polo box domain of the protein and releases the kinase domain. All the determined binding constants are higher for the kinase inhibitors than for their competitor for the active center (ATP) being BI-2536 and Volasertib the inhibitors that showed more affinity for PLK1. Calculated binding free energies confirmed the higher affinity of PLK1 for BI-2536 and Volasertib than for ATP. The higher affinity of the inhibitors to PLK1 compared to ATP was mainly attributed to stronger van der Waals interactions. Results may help with the challenge of designing and developing new kinase inhibitors more effective in clinical cancer therapy.

Multispectroscopic and synergistic antioxidant study on the combined binding of caffeic acid and (-)-epicatechin gallate to lysozyme

The binding of caffeic acid (CA) and/or (-)-epicatechin gallate (ECG) to lysozyme was investigated by multispectroscopic methods and molecular docking. The effects of the single and combined binding on the structure, activity and stability of lysozyme and the synergistic antioxidant activity of CA and ECG were also studied. Fluorescence quenching spectra, time-resolved fluorescence spectra, and UV-vis absorption difference spectra all ascertained the static quenching mechanism of lysozyme by CA/ECG. Thermodynamic parameters indicated that CA and ECG competitively bound to lysozyme, and CA had a stronger binding affinity, which was consistent with the results of molecular docking. Hydrogen bonding, van der Waals' force and electrostatic interaction were the main driving forces for the binding process. Synchronous fluorescence spectra displayed that the interaction of CA/ECG exposed the tryptophan residues of lysozyme to a more hydrophilic environment. Circular dichroism spectroscopy, Fourier transform infrared spectroscopy and dynamic light scattering indicated that the binding of CA and/or ECG to lysozyme resulted in the change of the secondary structure and increased the particle size of lysozyme. The binding of CA and/or ECG to lysozyme inhibited the enzyme activity and enhanced the thermal stability of lysozyme. The combined application of CA and ECG showed antioxidant synergy which was influenced by the encapsulation of lysozyme and cellular uptake. In summary, this work provides theoretical guidance for lysozyme as a carrier for the combined application of CA and ECG.

The effect of putrescine on the lysozyme activity and structure: Spectroscopic approaches and molecular dynamic simulation

The present research addressed the influence of polyamine (putrescine) on the compound as well as function of lysozyme; accordingly, UV- Visible, fluorescence spectroscopy and simulation method were applied to fulfill this goal. Lysozyme's structural variability was examined at various putrescine ‌concentrations; also, the putrescine binding to lysozyme was addressed using spectrofluorescence, circular dichroism (CD) and UV-Vis measurements. The obtained results indicated that with raising the putrescine concentration, the intrinsic quenching fluorescence of lysozyme was decreased based on the static mechanism. Analysis of thermodynamic parameters also indicated that van der Waals as well as hydrogen bond forces served a fundamental role in determining the resulting stability; this was in agreement with modeling studies. Measurement of UV absorption spectroscopy, fluorescence spectroscopy, and circular dichroism spectroscopy also demonstrated that lysozyme's second and tertiary structures were altered in a putrescine concentration-dependent manner. Putrescine inhibited lysozyme's enzymatic activity, displaying its affinity with the lysozyme's active site. Further, molecular simulation conducted revealed that putrescine could have spontaneous binding to lysozyme, changing its structure, thus further emphasizing the experimental results.

Antioxidant activity, stability, in vitro digestion and cytotoxicity of two dietary polyphenols co-loaded by β-lactoglobulin

The combination of multiple dietary polyphenols may have synergistic beneficial effects. And the beneficial effects can be further improved by the encapsulation of proteins. The interactions of procyanidin B2 (PB2) and/or dihydromyricetin (DMY) with β-lactoglobulin (β-LG) were investigated using multi-spectroscopic techniques and molecular docking. The structural change of β-LG in the presence of PB2 and/or DMY was demonstrated by dynamic light scattering, Fourier transform infrared spectroscopy and circular dichroism spectroscopy. Response surface analysis was used to optimize the synergistic antioxidant activity between PB2 and DMY. Besides, the antioxidant activity, stability, in vitro digestion and cytotoxicity of PB2 and DMY in the binary and ternary systems were investigated. These studies will elucidate the interaction mechanism of PB2 and/or DMY with β-LG. The research results can provide theoretical support for the development of functional foods and beverages with synergistic activity, improved stability and bioaccessibility, thereby promoting human health and preventing diseases.

Structural Compactness in Hen Egg White Lysozyme Induced by Bisphenol S: A Spectroscopic and Molecular Dynamics Simulation Approach

The endocrine disrupting compound Bisphenol and its analogues are widely used in food packaging products and can cause serious health hazards. The protein, Lysozyme (Lyz), showing anti-microbial properties, is used as a "natural" food and dairy preservative. Herein, we explored the interaction between Lyz and Bisphenol S (BPS) by multi-spectroscopic and theoretical approaches. Lyz interacts with BPS through static quenching, where hydrophobic force governed the underlying interaction. Molecular docking results reveal that tryptophan plays a vital role in binding, corroborated well with near UV-CD studies. A decrease in the radius of gyration (from 1.43 nm to 1.35 nm) of Lyz substantiates the compactness of the protein conformation owing to such an interaction. This structural alteration experienced by Lyz may alter its functional properties as a food preservative. Consequently, this can degrade the quality of the food products and thereby lead to severe health issues.

Oxyresveratrol: Sources, Productions, Biological Activities, Pharmacokinetics, and Delivery Systems

Oxyresveratrol has recently attracted much research attention due to its simple chemical structure and diverse therapeutic potentials. Previous reviews describe the chemistry and biological activities of this phytoalexin, but additional coverage and greater accessibility are still needed. The current review provides a more comprehensive summary, covering research from 1955 to the present year. Oxyresveratrol occurs in both gymnosperms and angiosperms. However, it has never been reported in plants in the subclass Sympetalae, and this point might be of both chemotaxonomic and biosynthetic importance. Oxyresveratrol can be easily obtained from plant materials by conventional methods, and several systems for both qualitative and quantitative analysis of oxyresveratrol contents in plant materials and plant products are available. Oxyresveratrol possesses diverse biological and pharmacological activities such as the inhibition of tyrosinase and melanogenesis, antioxidant and anti-inflammatory activities, and protective effects against neurological disorders and digestive ailments. However, the unfavorable pharmacokinetic properties of oxyresveratrol, including low water solubility and poor oral availability and stability, have posed challenges to its development as a useful therapeutic agent. Recently, several delivery systems have emerged, with promising outcomes that may improve chances for the clinical study of oxyresveratrol.

Co-encapsulation of (-)-epigallocatechin-3-gallate and piceatannol/oxyresveratrol in β-lactoglobulin: effect of ligand-protein binding on the antioxidant activity, stability, solubility and cytotoxicity

The co-encapsulation of multiple bioactive components in a carrier may produce synergistic effects and improve health benefits. In this study, the interactions of β-lactoglobulin (β-LG) with epigallocatechin-3-gallate (EGCG) and/or piceatannol (PIC)/oxyresveratrol (OXY) were investigated by multispectroscopic techniques, isothermal titration calorimetry, and molecular docking. The static quenching mechanism of β-LG by EGCG, PIC and OXY was confirmed by fluorescence spectroscopy and UV-vis absorption difference spectroscopy. The binding sites of these three polyphenols in β-LG were identified by site marking fluorescence experiments and molecular docking. The thermodynamic parameters of the β-LG + EGCG/PIC/OXY binary complex and β-LG + EGCG + PIC/OXY ternary complex were obtained from fluorescence data and used to analyze the main driving force for complex formation. The exothermic binding process was further confirmed by isothermal titration calorimetry. The α-helical content, particle size and morphology of free and ligand-bound β-LG were determined by circular dichroism spectroscopy, dynamic light scattering and transmission electron microscopy, respectively. The effect of EGCG, PIC and OXY on the conformation of β-LG was studied by Fourier transform infrared spectroscopy. In addition, the maximum synergistic antioxidant activity between EGCG and PIC/OXY was obtained by response surface analysis. The effects of β-LG in the binary and ternary systems on the antioxidant activity, stability, solubility and cytotoxicity of the polyphenols were also studied. Finally, the different cytotoxicities of the complexes and nanoparticles of the binary and ternary systems were compared. The results of this study are expected to provide a theoretical basis for the development of β-LG-based carriers co-encapsulating a variety of bioactive components.

Unravelling the effects of procyanidin on gliadin digestion and immunogenicity

The effect of procyanidin dimer B3, a common food tannin, on the digestion of gliadin proteins was investigated by monitoring the changes in the immunogenic peptides produced during in vitro digestion and immunoreactivity. Interaction studies between procyanidin dimer B3, gluten proteins and/or digestive enzymes were performed by SDS-PAGE. The effect of procyanidin B3 on the enzymatic activity of trypsin, chymotrypsin and pancreatin was evaluated. The differences in the number and nature of immunogenic peptides released during digestion were identified by mass spectrometry. Briefly, the enzymatic activity of gastrointestinal enzymes was only slightly affected but a significant decrease in the immunological properties of the peptides produced during digestion was observed. Overall, although further studies are needed, the interaction between polyphenols and gluten proteins clearly influences gluten protein digestion and immunogenicity, thus suggesting that the consumption of dietary polyphenols can significantly affect the degree of celiac disease downstream immune reactions.

Attenuation of Human Lysozyme Amyloid Fibrillation by ACE Inhibitor Captopril: A Combined Spectroscopy, Microscopy, Cytotoxicity, and Docking Study

Misfolding proteins could form oligomers or amyloid fibers, which can cause a variety of amyloid-associated diseases. Thus, the inhibition of protein misfolding and fibrillation is a promising way to prevent and treat these diseases. Captopril (CAP) is an angiotensin-converting enzyme inhibitor (ACEI) that is widely used to treat diseases such as hypertension and heart failure. In this study, we found that CAP inhibits human lysozyme (HL) fibrillation through the combination techniques of biophysics and biochemistry. The data obtained by thioflavin-T (ThT) and Congo red (CR) assays showed that CAP hindered the aggregation of HL amyloid fibrils by reducing the β-sheet structure of HL amyloid, with an IC₅₀ value of 34.75 ± 1.23 μM. Meanwhile, the particle size of HL amyloid decreased sharply in a concentration-dependent approach after CAP treatment. According to the visualization of atomic force microscopy (AFM) and transmission electron microscopy (TEM), we verified that in the presence of CAP, the needle-like fibers of HL amyloid were significantly reduced. In addition, CAP incubation dramatically improved the cell survival rate exposed to HL fibers. Our studies also revealed that CAP could form hydrogen bonds with amino acid residues of Glu 35 and Ala 108 in the binding pocket of HL, which help in maintaining the α-helical structure of HL and then prevent the formation of amyloid fibrillation. It can be concluded that CAP has antiamyloidogenic activity and a protective effect on HL amyloid cytotoxicity.

Interaction of artemisinin protects the activity of antioxidant enzyme catalase: A biophysical study

The major antioxidant enzyme catalase is downregulated and the enzyme activity is compromised in various disease conditions such as malarial and cancer. Hence, the restoration and protection of catalase is a promising therapeutic strategy in disease management. In the present study, for the first time we have demonstrated the protective role of well-known anti-malarial drug Artemisinin (ART) on the time and temperature-induced degradation of bovine liver catalase (BLC) activity. The findings at different time intervals and at higher temperature showed the protective role of ART on BLC activity. Molecular docking studies suggested specific binding of ART on BLC through heme group interface which was further supported by cyclic voltammetry and dynamic light scattering study. The stabilization of BLC in presence of ART was mediated through forming a BLC-ART complex with reduced and shifted electrochemical peak and increased hydrodynamic diameter. ART substantially prevents the temperature-induced reduction in α-helical content with simultaneous increment in other secondary structures like antiparallel, parallel, β-turn and random coils. Nevertheless, the protective role of ART was accepted from the enhanced thermal stability and increased T_m value of BLC in presence of ART at higher temperatures. Our results uncover the mechanism of interaction between ART with BLC and suggest the protective role of ART towards spatiotemporal alteration of BLC by preventing the structural and molecular change in BLC. Thus, the findings advocate ART as a potential therapeutic drug for diseases associated with reduced catalase activity.

Characterization of Resveratrol, Oxyresveratrol, Piceatannol and Roflumilast as Modulators of Phosphodiesterase Activity. Study of Yeast Lifespan

Our desire to live longer has led to an ever-increasing number of novel antiaging products. However, few molecules have any real effect and new ones need to be studied before they can be used commercially. In this contribution, activation of the caloric restriction (CR) pathway was studied using different three (resveratrol, oxyresveratrol and piceatannol)-a family with demonstrated bioactivity on phosphodiesterase activity. The high-affinity phosphodiesterase type 2 (PDE2) of Saccharomyces cerevisiae was expressed in Escherichia coli, purified and characterized. The activity and the inhibitory activity of each stilbene was studied, and the findings were compared in vitro and in silico with those obtained with roflumilast-a human PDE4 inhibitor widely used in chronic obstructive pulmonary diseases. Finally, an in vivo chronological lifespan assay using WT S. cerevisiae and ΔPDE2 S. cerevisiae strains was carried out. It was demonstrated that stilbenes can modulate yPDE2 activity, increasing the lifespan of the yeast by 18% over a control (in combination with other pathways). In addition, roflumilast increased the lifespan in the WT strain. The findings as a whole would increase the range of lifespan products available and suggest novel uses for approved drugs.

Effects of Selected Resveratrol Analogues on Activation and Polarization of Lipopolysaccharide-Stimulated BV-2 Microglial Cells

Increasing health-promoting effects of resveratrol and its molecular structural analogues have been discovered, and the acting mechanism has been explored. However, the activity comparison of such compounds in targeting macrophage-related inflammation associated with neurodegenerative diseases remains untouched. In this study, we evaluated the activation and polarization transition of lipopolysaccharide (LPS)-stimulated BV-2 mouse microglial macrophages exposed to resveratrol (RES) and its analogues pterostilbene (PTE), oxyresveratrol (ORES), acetyl-trans-resveratrol (ARES), and trans-2,3,5,4'-tetrahydroxystilbene-2-O-glucopyranoside (TSG). At 10 μM, all of the five stilbene compounds have effectively suppressed the LPS-stimulated BV-2 cell release of proinflammatory mediators such as NO, TNF-α, iNOS, IL-1β, and IL-6. Mechanism study elucidated that they exert anti-inflammatory effects through MAPKs (ERK1/2, JNK, and p38) and NF-κB signaling pathways. Further investigation in treating BV-2 cells with resveratrol and its analogues revealed the reversal of LPS-induced phenotype molecules from M1 (iNOS, IL-1β, IL-6, and CD86) to M2 (Arg1, CD163, and IL-10) subtypes, manifesting that these five stilbenes suppressed inflammation through modulating the polarized phenotypes of BV-2 microglia. Most importantly, PTE demonstrated the most potent inhibitory activity among these five stilbene compounds. Therefore, this study not only highlights microglia-induced inflammatory responses as a potential therapeutic target but also suggests future insights in considering the options of nutraceutical development for resveratrol and its analogues.

Exploring the inhibitory mechanism of piceatannol on α-glucosidase relevant to diabetes mellitus

Due to their association with type 2 diabetes mellitus treatment, α-glucosidase inhibitors have attracted increasing attention of researchers. In this study, we systemically investigated the kinetics and inhibition mechanism of piceatannol on α-glucosidase. Enzyme kinetics analyses showed that piceatannol exhibited strong inhibition on α-glucosidase in a non-competitive manner. Spectroscopy analyses indicated that piceatannol could bind with α-glucosidase to form complexes via high affinity. Further, computational molecular dynamics and molecular docking studies validated that the binding of piceatannol was outside the catalytic site of α-glucosidase, which would induce conformational changes of α-glucosidase and block the entrance of substrate, causing declines in α-glucosidase activities. Our results provide useful information not only for the inhibition mechanism of piceatannol against α-glucosidase but also for a novel target site for developing novel α-glucosidase inhibitors as potential therapeutic agents in the treatment of type 2 diabetes mellitus.

The non-competitive inhibition of piceatannol on α-glucosidase. A combination of dynamic and static process with one binding site. The involvement of hydrophobic interactions and hydrogen bonding. Dietary recommendations for diabetes or potential antidiabetic drug.