The specific binding of chlorogenic acid to human serum albumin

Protein-Chlorogenic Acid Interactions: Mechanisms, Characteristics, and Potential Food Applications

The interactions between proteins and chlorogenic acid (CGA) have gained significant attention in recent years, not only as a promising approach to modify the structural and techno-functional properties of proteins but also to enhance their bioactive potential in food systems. These interactions can be divided into covalent (chemical or irreversible) and non-covalent (physical or reversible) linkages. Mechanistically, CGA forms covalent bonds with nucleophilic amino acid residues of proteins by alkaline, free radical, and enzymatic approaches, leading to changes in protein structure and functionality, such as solubility, emulsification properties, and antioxidant activity. In addition, the protein-CGA complexes can be obtained by hydrogen bonds, hydrophobic and electrostatic interactions, and van der Waals forces, each offering unique advantages and outcomes. This review highlights the mechanism of these interactions and their importance in modifying the structural, functional, nutritional, and physiological attributes of animal- and plant-based proteins. Moreover, the potential applications of these protein-CGA conjugates/complexes are explored in various food systems, such as beverages, films and coatings, emulsion-based delivery systems, and so on. Overall, this literature review provides an in-depth overview of protein-CGA interactions, offering valuable insights for future research to develop novel protein-based food and non-food products with improved nutritional and functional characteristics.

Spectroscopy and molecular simulation on the interaction of Nano-Kaempferol prepared by oil-in-water with two carrier proteins: An investigation of protein-protein interaction

In this work, the interaction of human serum albumin (HSA) and human holo-transferrin (HTF) with the prepared Nano-Kaempferol (Nano-KMP) through oil-in-water procedure was investigated in the form of binary and ternary systems by the utilization of different spectroscopy techniques along with molecular simulation and cancer cell experiments. According to fluorescence spectroscopy outcomes, Nano-KMP is capable of quenching both proteins as binary systems by a static mechanism, while in the form of (HSA-HTF) Nano-KMP as the ternary system, an unlinear Stern-Volmer plot was elucidated with the occurrence of both dynamic and static fluorescence quenching mechanisms in the binding interaction. In addition, the two acquired Ksv values in the ternary system signified the existence of two sets of binding sites with two different interaction behaviors. The binding constant values of HSA-Nano KMP, HTF-Nano-KMP, and (HSA-HTF) Nano-KMP complexes formation were (2.54 ± 0.03) × 104, (2.15 ± 0.02) × 104 and (1.43 ± 0.04) × 104M-1at the first set of binding sites and (4.68 ± 0.05) × 104 M-1 at the second set of binding sites, respectively. The data of thermodynamic parameters confirmed the major roles of hydrogen binding and van der Waals forces in the formation of HSA-Nano KMP and HTF-Nano KMP complexes. The thermodynamic parameter values of (HSA-HTF) Nano KMP revealed the dominance of hydrogen binding and van der Waals forces in the first set of binding sites and hydrophobic forces for the second set of binding sites. Resonance light scattering (RLS) analysis displayed the existence of a different interaction behavior for HSA-HTF complex in the presence of Nano-KMP as the ternary system. Moreover, circular dichroism (CD) technique affirmed the conformational changes of the secondary structure of proteins as binary and ternary systems. Molecular docking and molecular dynamics simulations (for 100 ns) were performed to investigate the mechanism of KMP binding to HSA, HTF, and HSA-HTF. Next to observing a concentration and time-dependent cytotoxicity, the down regulation of PI3K/AkT/mTOR pathway resulted in cell cycle arrest in SW480 cells.

Multispectroscopic and Computational Investigations on the Binding Mechanism of Dicaffeoylquinic Acids with Ovalbumin

Recently, studies on the interactions between ovalbumin (OVA) and polyphenols have received a great deal of interest. This study explored the conformational changes and the interaction mechanism of the binding between OVA and chlorogenic acid (CGA) isomers such as 3,4-dicaffeoylquinic acids (3,4-diCQA), 4,5-dicaffeoylquinic acids (4,5-diCQA), and 3,5-dicaffeoylquinic acids (3,5-diCQA) using multispectroscopic and in silico analyses. The emission spectra show that the diCQAs caused strong quenching of OVA fluorescence under different temperatures through a static quenching mechanism with hydrogen bond (H-bond) and van der Waals (vdW) interactions. The values of binding constants (OVA-3,4-diCQA = 6.123 × 10⁵, OVA-3,5-diCQA = 2.485 × 10⁵, OVA-4,5-diCQA = 4.698 × 10⁵ dm³ mol^-1 at 298 K) suggested that diCQAs had a strong binding affinity toward OVA, among which OVA-3,4-diCQA exhibits higher binding constant. The results of UV-vis absorption and synchronous fluorescence indicated that the binding of all three diCQAs to OVA induced conformational and micro-environmental changes in the protein. The findings of molecular modeling further validate the significant role of vdW force and H-bond interactions in ensuring the stable binding of OVA-diCQA complexes. Temperature-dependent molecular dynamics simulation studies allow estimation of the individual components that contribute to the total bound free energy value, which allows evaluation of the nature of the interactions involved. This research can provide information for future investigations on food proteins' physicochemical stability and CGA bioavailability in vitro or in vivo.

Interaction between olanzapine and human serum albumin and effect of metal ions, caffeine and flavonoids on the binding: A spectroscopic study

In this study, the binding of olanzapine (OLZ) to human serum albumin (HSA) and the influence of metal ions (Ca²⁺, Mg²⁺, Cu²⁺, Zn²⁺, Fe³⁺), caffeine (CAF) and flavonoids (diosmin (DIO), catechin (CAT), quercetin (QUE)), on their affinity, was investigated by fluorescence spectroscopy and UV-vis absorption spectroscopy. Fluorescence experiments suggest that OLZ quench the fluorescence of HSA through the mixed quenching mechanism and non-radiation energy transferring as a result of the HSA-OLZ complex formation. OLZ spontaneously bind in the site I on HSA, and according to thermodynamic parameters, the reaction was spontaneous and mainly driven by hydrogen bonds and van der Waals interactions. The presence of Mⁿ⁺ ions, CAF, DIO and CAT decreased binding affinity between OLZ and HSA which indicates that they could compete against OLZ in the site I. Contrary, in the presence of QUE the binding affinity of the HSA-OLZ system enhanced, which may be explained by conformational changes in HSA (non-competitive interference).

Phenolic content and potential bioactivity of apple juice as affected by thermal and ultrasound pasteurization

Thermal (T) and ultrasound (US) pasteurization processes were applied to apple juice and the phenolic compounds (TPC) were quantified before and after in vitro digestion by HPLC-DAD-ESI-MSⁿ, with their bioaccessibility ascertained. Digested samples were analysed for their inhibitory capacity against α-glucosidase. Since some of the compounds exhibit fluorescence, both steady state and time-resolved fluorescence methods were used to investigate the binding to a blood transport protein, human serum albumin (HSA). It was found that processing induced an increase in the TPC content, which was more pronounced when US was applied. In contrast, digestion reduced the TPC content, evening out the overall effect. Still T and US pasteurized juices exhibited a higher quantity of TPC upon digestion as compared to the raw sample. No correlation was found between the TPC content and α-glucosidase inhibition, as the T and US pasteurized juices showed the highest and lowest inhibitory capacities against the enzyme, respectively. This is indicative that other compounds, such as those formed upon thermal treatment, may be involved in the antidiabetic effect of apple juice. The fluorescence study showed that binding occurred to HSA, at slightly different rates for different species present in the US treated extract. Considering energy consumption, US pasteurization is the most power consuming treatment despite its shorter duration. Overall, no univocal indication on the best pasteurization process can be gathered. Thus, it is necessary to define the desired target in order to drive technological interventions by a customized approach.

Purification of chlorogenic acid from Heijingang potatoes and evaluation of its binding properties to recombinant human serum albumin

The aim of the present study was to purify the natural chlorogenic acid (CGA) monomer from Heijingang potatoes and investigate its interaction with recombinant human serum albumin (rHSA). The potato extract (PE) was purified using macroporous resins and solvent, and the CGA monomer was subsequently isolated using semipreparative liquid chromatography (SP-LC). The purity and structure of the CGA monomer was analyzed by high-performance liquid chromatography (HPLC) and nuclear magnetic resonance (NMR). The interaction between the CGA monomer and rHSA was studied using fluorescence spectroscopy and molecular docking. HPLC analysis indicates that the CGA monomer had a retention time of 5.368 min and a purity of 97.9%, the presence of which was confirmed by NMR. The molecular docking and fluorescence spectroscopy demonstrate that CGA had a static quenching effect on rHSA with one binding site, and the range of K values was 7.14 × 10³ to 1.56 × 10⁴ M^-1. This simple and efficient extract coupled with SP-LC has the potential for use in the extraction and purification of CGA in pilot or large-scale operations.

Study on the interaction between active components from traditional Chinese medicine and plasma proteins

Traditional Chinese medicine (TCM), as a unique form of natural medicine, has been used in Chinese traditional therapeutic systems over two thousand years. Active components in Chinese herbal medicine are the material basis for the prevention and treatment of diseases. Research on drug-protein binding is one of the important contents in the study of early stage clinical pharmacokinetics of drugs. Plasma protein binding study has far-reaching influence on the pharmacokinetics and pharmacodynamics of drugs and helps to understand the basic rule of drug effects. It is important to study the binding characteristics of the active components in Chinese herbal medicine with plasma proteins for the medical science and modernization of TCM. This review summarizes the common analytical methods which are used to study the active herbal components-protein binding and gives the examples to illustrate their application. Rules and influence factors of the binding between different types of active herbal components and plasma proteins are summarized in the end. Finally, a suggestion on choosing the suitable technique for different types of active herbal components is provided, and the prospect of the drug-protein binding used in the area of TCM research is also discussed.

Probing the interaction of cephalosporin with bovine serum albumin: A structural and comparative perspective

Cephalosporins belong the largest class of antibiotics used in the treatment of a wide range of infectious diseases caused by susceptible organisms. In the present study, we chose two typical antibiotics cefalexin/cefixime based on their structure, and investigated the interaction of cephalexin/cefixime with bovine serum albumin (BSA) using UV-vis absorption spectra, fluorescence spectroscopy, circular dichroism (CD) spectroscopy and molecular modeling approaches. Spectroscopic experiments revealed the formation of a BSA - cefalexin/cefixime complex. The binding parameters calculated using a modified Stern - Volmer method and the Scatchard method reached 10³ -10⁴  L·mol^-1 . Thermodynamic parameter studies revealed that binding characteristics by negative enthalpy and positive entropy changes, and electrostatic interactions play a major role. Site marker competitive displacement experiments and molecular modeling approaches demonstrated that cefalexin and cefixime bind with appropriate affinity to site I (subdomain IIA) of BSA. Furthermore, synchronous fluorescence spectra, CD spectra and molecular modeling results indicated that the secondary structure of BSA was changed in the presence of cefalexin and cefixime. Additionally, the effects of metal ions on the BSA - cefalexin/cefixime system were also assessed.

Interaction between Mimic Lipid Membranes and Acylated and Nonacylated Cyanidin and Its Bioactivity

We investigated the effects of acylated cyanidin-3-O-β-(6″-O-E-p-coumaroyl-sambubioside)-5-O-β-glucoside (C3-cs-5G) and nonacylated cyanidin, cyanidin-3,5-di-O-β-glucoside (C3,5G) and cyanidin-3-O-β-glucoside (C3G), on cell-mimic membranes (MM) that reflected the membrane lipid composition of tumor cells. The relationship between structural derivatives of cyanidin (Cy-d), membrane interactivity, their antioxidant activity, and interaction with albumin were characterized. Studies showed that Cy-d caused an increase in packing order mainly in the hydrophilic region of the membranes. Cy-d have shown high antioxidant activity against liposome oxidation induced by AAPH and ability to bind to albumin through a static quenching mechanism. The results showed that glycosylation number and the presence of aromatic acid attached to sugars affected the membrane properties, according to the sequence C3-cs-5G > C3,5G > C3G. It can be stated that Cy-d in the process of interaction with MM caused a rigidifying effect, which is fundamental for understanding their anticancer and antioxidant activity and is one of the possible pharmaceutical mechanisms.

Biological Activity of Japanese Quince Extract and Its Interactions with Lipids, Erythrocyte Membrane, and Human Albumin

The aim of the study was to determine in vitro biological activity of fruit ethanol extract from Chaenomeles speciosa (Sweet) Nakai (Japanese quince, JQ) and its important constituents (−)-epicatechin (EC) and chlorogenic acid (CA). The study also investigated the structural changes in phosphatidylcholine (PC) liposomes, dipalmitoylphosphatidylcholine liposomes, and erythrocyte membranes (RBC) induced by the extract. It was found that the extract effectively inhibits oxidation of RBC, induced by 2,2′-azobis (2-amidinopropane) dihydrochloride (AAPH), and PC liposomes, induced by UVB radiation and AAPH. Furthermore, JQ extract to a significant degree inhibited the activity of the enzymes COX-1 and COX-2, involved in inflammatory reactions. The extract has more than 2 times greater activity in relation to COX-2 than COX-1 (selectivity ratio 0.48). JQ extract stimulated growth of the beneficial intestinal bacteria Lactobacillus casei and Lactobacillus plantarum. In the fluorimetric method by means of the probes Laurdan, DPH and TMA-DPH, and ¹H-NMR, we examined the structural changes induced by JQ and its EC and CA components. The results show that JQ and its components induce a considerable increase of the packing order of the polar heads of lipids with a slight decrease in mobility of the acyl chains. Lipid membrane rigidification could hinder the diffusion of free radicals, resulting in inhibition of oxidative damage induced by physicochemical agents. JQ extract has the ability to quench the intrinsic fluorescence of human serum albumin through static quenching. This report thus could be of huge significance in the food industry, pharmacology, and clinical medicine.

Enhancement of the binding affinity of methylene blue to site I in human serum albumin by cupric and ferric ions

In this work, the binding characteristics of methylene blue (MB) to human serum albumin (HSA) and the influence of Cu(2+) and Fe(3+) on the binding affinity of MB to HSA were investigated using fluorescence, absorption, circular dichroism (CD) spectroscopy and molecular modelling. The results of competitive binding experiments using the site probes ketoprofen and ibuprofen as specific markers suggested that MB was located in site I within sub-domain IIA of HSA. The molecular modelling results agreed with the results of competitive site marker experiments and the results of CD spectra indicated that the interaction between MB and HSA caused the conformational changes in HSA. The binding affinity of MB to HSA was enhanced but to a different extent in the presence of Cu(2+) and Fe(3+), respectively, which indicated that the influence of different metal ions varied. Enhancement of the binding affinity of MB to HSA in the presence of Cu(2+) is due to the formation of Cu(2+)-HSA complex leading to the conformational changes in HSA, whereas in the presence of Fe(3+), enhancement of the binding affinity is due to the greater stability of the Fe(3+)-HSA-MB complex compared with the MB-HSA complex.

Use of nucleic acids anchor system to reveal apoferritin modification by cadmium telluride nanoparticles

The aim of this study was to synthesize cadmium telluride nanoparticles (CdTe NPs) modified apoferritin, and examine if apoferritin is able to accommodate CdTe NPs.

Promising antioxidant and anticancer (human breast cancer) oxidovanadium(IV) complex of chlorogenic acid. Synthesis, characterization and spectroscopic examination on the transport mechanism with bovine serum albumin

A new chlorogenate oxidovanadium complex (Na[VO(chlorog)(H2O)3].4H2O) was synthesized by using Schlenk methodology in the course of a reaction at inert atmosphere in which deprotonated chlorogenic acid ligand binds to oxidovanadium(IV) in a reaction experiment controlled via EPR technique and based in a species distribution diagram. The compound was characterized by FTIR, EPR, UV-visible and diffuse reflectance spectroscopies and thermogravimetric, differential thermal and elemental analyses. The ligand and the complex were tested for their antioxidant effects on DPPH (1,1-diphenyl-2-picrylhydrazyl radical), ABTS(+) (radical cation of 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt), O2(-), OH and ROO radicals and their cytotoxic activity on different cancer cell lines (SKBR3, T47D and MDAMB231) and primary human mammary epithelial cells. The complex behaved as good antioxidant agent with strongest inhibitory effects on O2(-), OH and ROO radicals and exhibited selective cytotoxicity against SKBR3 cancer cell line. Albumin interaction experiments denoted high affinity toward the complex and its calculated binding constant was indicative of a strong binding to the protein. Based on this study, it is hypothesized that Na[VO(chlorog)(H2O)3].4H2O would be a promising candidate for further evaluation as an antioxidant and anticancer agent.

Exploring the site-selective binding of jatrorrhizine to human serum albumin: spectroscopic and molecular modeling approaches

This paper exploring the site-selective binding of jatrorrhizine to human serum albumin (HSA) under physiological conditions (pH=7.4). The investigation was carried out using fluorescence spectroscopy, UV-vis spectroscopy, and molecular modeling. The results of fluorescence quenching and UV-vis absorption spectra experiments indicated the formation of the complex of HSA-jatrorrhizine. Binding parameters calculating from Stern-Volmer method and Scatchard method were calculated at 298, 304 and 310 K, with the corresponding thermodynamic parameters ΔG, ΔH and ΔS as well. Binding parameters calculating from Stern-Volmer method and Scatchard method showed that jatrorrhizine bind to HSA with the binding affinities of the order 10(4) L mol(-1). The thermodynamic parameters studies revealed that the binding was characterized by negative enthalpy and positive entropy changes and the electrostatic interactions play a major role for jatrorrhizine-HSA association. Site marker competitive displacement experiments and molecular modeling calculation demonstrating that jatrorrhizine is mainly located within the hydrophobic pocket of the subdomain IIIA of HSA. Furthermore, the synchronous fluorescence spectra suggested that the association between jatrorrhizine and HSA changed molecular conformation of HSA.