Binding Of Chlorogenic Acid Research Articles

Grafting chlorogenic acid enhanced the antioxidant activity of curdlan oligosaccharides and modulated gut microbiota

In this study, the effects of grafting chlorogenic acid (CA) on the antioxidant and probiotic activities of curdlan oligosaccharides (CDOS) were investigated. CDOS with degrees of polymerization of 3–6 was first obtained by degradation of curdlan with hydrogen peroxide and then grafted with CA using a free radical-mediated method under an ultrasonication-assisted Fenton system. The thermal stability and antioxidant ability of CDOS were enhanced after grafting with CA. In vitro fermentation, supplementation of CDOS-CA stimulated the proliferation of Prevotella and Faecalibacterium while inhibiting the growth of harmful microbiota. Notably, the concentration of total short-chain fatty acids and the relative abundance of beneficial bacteria markedly increased after fermentation of CDOS-CA, indicating that CA grafting could improve the probiotic activity of CDOS. Overall, the covalent binding of CDOS and CA could enhance the antioxidant and probiotic activities of CDOS, suggesting potential improvements in gastrointestinal and colonic health.

Exploring the Interactions of Soybean 7S Globulin with Gallic Acid, Chlorogenic Acid and (-)-Epigallocatechin Gallate.

In this study, the noncovalent interaction mechanisms between soybean 7S globulin and three polyphenols (gallic acid (GA), chlorogenic acid (CA) and (-)-epigallocatechin gallate (EGCG)) were explored and compared using various techniques. Fluorescence experiments showed that GA and EGCG had strong static quenching effects on 7S fluorescence, and that of CA was the result of multiple mechanisms. The interactions caused changes to the secondary and tertiary structure of 7S, and the surface hydrophobicity was decreased. Thermodynamic experiments showed that the combinations of polyphenols with 7S were exothermic processes. Hydrogen bonds and van der Waals forces were the primary driving forces promoting the binding of EGCG and CA to 7S. The combination of GA was mainly affected by electrostatic interaction. The results showed that the structure and molecular weight of polyphenols play an important role in their interactions. This work is helpful for developing products containing polyphenols and soybean protein.

Physicochemical and Functional Changes in Lotus Root Polysaccharide Associated with Noncovalent Binding of Polyphenols

To promote the functional applications of lotus root polysaccharides (LRPs), the effects of noncovalent polyphenol binding on their physicochemical properties, as well as antioxidant and immunomodulatory activities, were investigated. Ferulic acid (FA) and chlorogenic acid (CHA) were spontaneously bound to the LRP to prepare the complexes LRP-FA1, LRP-FA2, LRP-FA3, LRP-CHA1, LRP-CHA2 and LRP-CHA3, and their mass ratios of polyphenol to LRP were, respectively, 121.57, 61.18, 34.79, 2359.58, 1276.71 and 545.08 mg/g. Using the physical mixture of the LRP and polyphenols as a control, the noncovalent interaction between them in the complexes was confirmed by ultraviolet and Fourier-transform infrared spectroscopy. The interaction increased their average molecular weights by 1.11~2.27 times compared to the LRP. The polyphenols enhanced the antioxidant capacity and macrophage-stimulating activity of the LRP depending on their binding amount. Particularly, the DPPH radical scavenging activity and FRAP antioxidant ability were positively related to the FA binding amount but negatively related to the CHA binding amount. The NO production of the macrophages stimulated by the LRP was inhibited by the co-incubation with free polyphenols; however, the inhibition was eliminated by the noncovalent binding. The complexes could stimulate the NO production and tumor necrosis factor-α secretion more effectively than the LRP. The noncovalent binding of polyphenols may be an innovative strategy for the structural and functional modification of natural polysaccharides.

Hemp seed protein and chlorogenic acid complex: Effect of ultrasound modification on its structure and functional properties

In this study, the effects of ultrasound and chlorogenic acid (CA) on the structural and functional properties of hemp seed protein (HSP) was investigated. Compared with natural HSP, the UV–vis spectra intensity of ultrasound-treated HSP (UHSP) and UHSP-CA increased, the fluorescence spectra intensity decreased with a red shift in the maximum intensity peak. The results showed that ultrasound modification and complexation with CA unfolded the structure of HSP exposing its internal groups. Fluorescence quenching analysis showed that the best binding between UHSP and CA (binding constant 2.94 × 102 L/mol) was achieved at 450 W for 15 min of ultrasound treatment. In addition, the same ultrasound conditions minimized the particle size and surface roughness of UHSP and UHSP-CA. The solubility of UHSP and UHSP-CA increased by 23.3 and 38.7 %, the emulsifying activity index increased by 16.9 and 16.2 %, and the emulsion stability index increased by 20.9 and 20.8 %, respectively. These results indicated that appropriate ultrasound treatment and complexation with CA can significantly modify the structural and functional properties of HSP, improving its application value in the food field.

Effect of Cu2+ and Al3+ on the interaction of chlorogenic acid and caffeic acid with serum albumin

Despite the phenolic acids' health benefits, their interactions with proteins are still unclear. In this study, the interactions of Bovine Serum Albumin (BSA) with chlorogenic acid (CHA), caffeic acid (CA), and their Al3+, Cu2+ complexes were studied by using circular dichroism (CD) spectroscopy, fluorescence spectroscopy, and UV/Vis spectroscopy. It was found that esterification of carboxyl group of CA with quinic acid increased the binding affinities for BSA. After chelating with Cu2+ and Al3+, both CHA and CA exhibited high binding affinities for BSA. CHA could form CHA-Cu2 and CHA-Al2 complex with Cu2+ and Al3+. The result of CD spectroscopy demonstrated that the binding of CHA and Al3+ with BSA contributed to the folding of BSA secondary structure. In addition, with the presence of CHA, binding with Al3+ could also induce changes in BSA conformation. The binding sites of both CHA and CA were closed to Trp213.

Evaluation the binding of chlorogenic acid with bovine serum albumin: Spectroscopic methods, electrochemical and molecular docking

Chlorogenic acid(CGA) is the common active phenolic acid in Chinese medicinal materials such as honeysuckle and eucommia. It is a class of small molecules with multiple activities such as antioxidant, inhibiting cancer cells, lowering blood sugar and lowering blood pressure. In this paper, UV–vis spectroscopy, fluorescence spectroscopy, circular dichroism, molecular dynamics simulation and cyclic voltammetry (CV) electrochemical analysis were used to investigate the mechanism about interaction between CGA and BSA. Based on fluorescence quenching analysis, CGA quenched the inherent fluorescence of BSA remarkably through a static mechanism. The obtained value of binding constant (Kb = 5.75 × 105 L·mol−1) revealed a high binding affinity between CGA and BSA. The simulated molecular docking showed that hydrophobic force were also involved in the interaction between BSA and CGA. This paper also investigate the effect of temperature and metal ions on the binding of CGA and BSA. When the temperature increased, the binding of BSA and CGA was destroyed. Metal ions affect both the structure of BSA and the combination of BSA and CGA. By studying the mechanism of CGA interaction with BSA, we elucidated the storage and transport mechanism of CGA in vivo under simulated human environment and temperature conditions.

Structural Investigation of the Interaction Mechanism between Chlorogenic Acid and AMPA Receptor via In Silico Approaches.

Chlorogenic acid (CGA), an important metabolite in natural plant medicines such as honeysuckle and eucommia, has been shown to have potent antinociceptive effects. Nevertheless, the mechanism by which CGA relieves chronic pain remains unclear. α-amino-3-hydroxy-5-methyl-4-isooxazolpropionic acid receptor (AMPAR) is a major ionotropic glutamate receptor that mediates rapid excitatory synaptic transmission and its glutamate ionotropic receptor AMPA type subunit 1 (GluA1) plays a key role in nociceptive transmission. In this study, we used Western blot, surface plasmon resonance (SPR) assay, and the molecular simulation technologies to investigate the mechanism of interaction between CGA and AMPAR to relieve chronic pain. Our results indicate that the protein expression level of GluA1 showed a dependent decrease as the concentration of CGA increased (0, 50, 100, and 200 μM). The SPR assay demonstrates that CGA can directly bind to GluA1 (KD = 496 μM). Furthermore, CGA forms a stable binding interaction with GluA1, which is validated by molecular dynamics (MD) simulation. The binding free energy between CGA and GluA1 is −39.803 ± 14.772 kJ/mol, where van der Waals interaction and electrostatic interaction are the major contributors to the GluA1–CGA binding, and the key residues are identified (Val-32, Glu-33, Ala-36, Glu-37, Leu-48), which play a crucial role in the binding interaction. This study first reveals the structural basis of the stable interaction between CGA and GluA1 to form a binding complex for the relief of chronic pain. The research provides the structural basis to understand the treatment of chronic pain and is valuable to the design of novel drug molecules in the future.

Complexation of chlorogenic acid enhances the antiproliferative effect of lactoferrin to colon cancer cells

Lactoferrin (LF) shows good anticancer biological activity. Lactoferrin can combine with chlorogenic acid (CGA) in dairy drinks like milk coffee and milk tea. However, the nature and functional changes of LF after binding of CGA are not clear. The stability and binding properties of CGA on LF and its antiproliferative effect on colorectal cancer SW480 cells were investigated by spectroscopic and cell experiments. The results showed that CGA could stabilize LF solution by reducing particle size (below 90 nm) and increasing zeta potential (over 14 in the absolute value). With addition of CGA, the UV absorption peak of LF solution changed (from 287 nm shifted to 290 nm) and fluorescence quenching occurred at the same time. By molecular dynamics calculation, the binding site number of CGA to LF was between 2 and 3 sites. Negative Gibbs free energy of (△G = −25.75 ± 0.84) indicated that the interaction between LF and CGA can occur spontaneously and effectively. Cell viability and apoptosis test showed that CGA and LF inhibited the growth of colorectal cancer SW480 cells in a synergistic way. Most of cells were arrested at G0/G1 phase by the CGA-LF complex. We conclude that CGA can bind to LF to form a relatively stable complex under natural conditions, which increases their antiproliferative function on colorectal cancer cells.

Introduction of chlorogenic acid during extrusion affects the physicochemical properties and enzymatic hydrolysis of rice flour

To investigate how chlorogenic acid (CHA) affects the physicochemical properties and hydrolysis of rice flour during extrusion. CHA was extruded with rice flour through a twin-screw extruder at different concentrations (0–2.0%), and the physicochemical properties of the extrudates, including crystallinity, pasting properties and CHA binding, were characterized through X-ray diffraction, Fourier-transform infrared spectroscopy, Rapid Visco Analyzer and ultraviolet spectrophotometer. Particularly, starch hydrolysis and the release of CHA were also evaluated through enzymatic hydrolysis and high-performance liquid chromatography. Results indicated that the addition of CHA promoted the formation of V-type crystals and increased the orderliness of the complexes. The maximum binding amount of CHA in extrudates was 10.98 mg/g without any isomerization or degradation. Additionally, the rapidly digestive starch (RDS) decreased markedly (down to 41.28 ± 2.66%), and there was a pronounced increase in resistant starch (RS), which varied from 10.28 ± 2.62 to 31.16 ± 0.50% in different extrudates. Our results indicated that CHA yielded a negative effect on starch hydrolysis and might provide basic guidance for the application of CHA to healthy starchy food processing in the future.

Photobehaviour and in vitro binding strategy of natural drug, chlorogenic acid with DNA: A case of groove binding

Chlorogenic acid (CHA), a non-toxic natural drug exhibits a wide range of pharmacological potential including anti-diabetic and anti-carcinogenic activities. The molecular mechanism behind the interaction of CHA with DNA has not yet been addressed, while its pharmacological activities have been reported. The sensible DNA targeting protocol by phytochemicals like CHA not only offers an insight into the designing of more efficient drugs, but also leading the way towards the establishment of therapeutic agents for the regulation of gene expressions. This study unravelled the binding mode of CHA with calf thymus DNA (ct-DNA) through a series of spectroscopic, calorimetric, dye displacement and molecular docking analysis. The binding constants obtained from the fluorescence and the UV absorption experiments were consistently in the order of 103 Mol−1 with the renowned minor groove binders. The dye displacement studies using fluorophores conjugated ct-DNA systems confirmed the minor groove binding of CHA. The energetics of interactions explored from ITC revealed a spontaneous and enthalpy driven exothermic association. The CD and FTIR analysis provide specific evidences regarding the conformational alterations and the stability aspects of ct-DNA in the presence of CHA. The experimental data were further compared with supporting molecular docking analysis and hence our investigations confirmed that CHA binds in the minor groove of ct-DNA without causing significant structural alteration to the DNA. The information regarding CHA deduced from the current work disclosed better binding affinities and selectivity towards ct-DNA may be considered as a prime compound for the development of better drugs with therapeutic efficacy.

Effect of Covalent Interaction with Chlorogenic Acid on the Allergenic Capacity of Ovalbumin.

Ovalbumin (OVA) is a major allergen in avian egg white. Here, we investigated the conjugation of OVA and chlorogenic acid (CHA) to reduce the allergenic capacity of OVA. OVA-CHA conjugate was characterized by SDS-PAGE, MALDI-TOF-MS, differential scanning calorimetry, and multispectroscopic methods. Sites of the OVA-CHA conjugate were identified by LC-MS/MS. CHA possibly conjugated with Lys20 and Lys17 in OVA, which resulted in the unfolding of OVA. ELISA and Western blot assay indicated that the OVA-CHA conjugate reduced the IgE binding capacity of OVA. The results also indicated that the ability of the OVA-CHA conjugate to activate histamine release was reduced. The decreased allergenic capacity of OVA was attributed to changes in the protein structure. Moreover, the CHA binding site in OVA might directly shield the linear IgE epitope, thereby reducing the IgE binding ability. Also, the OVA-CHA conjugate showed high antioxidant activity. OVA conjugated with CHA may be a promising method of OVA hyposensitization.

Study on the binding of chlorogenic acid to pepsin by spectral and molecular docking

The interaction of pepsin with chlorogenic acid (CHA) was investigated using fluorescence, UV/vis spectroscopy and molecular modeling methods. Stern-Volmer analysis indicated that the fluorescence quenching of pepsin by CHA resulted from a static mechanism, and the binding constant was 1.1846 × 10(5) and 1.1587 × 10(5) L/mol at 288 and 310 K, respectively. The distance between donor (pepsin) and acceptor (CHA) was calculated to be 2.39 nm and the number of binding sites for CHA binding on pepsin was ~ 1. The results of synchronous fluorescence and three-dimensional fluorescence showed that binding of CHA to pepsin could induce conformational changes in pepsin. Molecular docking experiments found that CHA bonded with pepsin in the area of the hydrophobic cavity with Van der Waals' forces or hydrogen bonding interaction, which were consistent with the results obtained from the thermodynamic parameter analysis. Furthermore, the binding of CHA can inhibit pepsin activity in vitro.

Comparison of the binding affinity of chlorogenic acid with two serum albumins

Chlorogenic acid (CA) is a well-known ester of caffeic acid present in some food. It is also an active component in traditional Chinese medicines which are used to treat various diseases, but the molecular basis of CA is not clear. In the present work, the proton selective relaxation rate and the affinity index were used to investigate the interaction of CA with human serum albumin and bovine serum albumin under the same buffer conditions. The results indicated that the binding affinity of chlorogenic acid to BSA was stronger than that to HSA. The binding site of the ligand–protein complex was elucidated by molecular docking, and the specific interaction was observed from those hydrogen bonds formed by the ligand and active residues. Using a combination of TR-NOE detection, the optimal ligand conformation was illustrated. Further conformational analysis of the complex revealed that the ability of hydrogen bond formation by polar side chain residues in the binding site of BSA might contribute to the greater binding affinity. The results provide a better understanding of CA binding and should contribute towards the design of modifications of CA for therapeutic purposes.

Interaction of calcineurin with its activator, chlorogenic acid revealed by spectroscopic methods

Chlorogenic acid (CHA) has been proved to be an activator of calcineurin (CN) in our previous research. In this study, the activation of single chain calcineurin (BA) by CHA, their interaction and concomitant changes in protein conformation were studied using fluorescence and Fourier transform infrared spectroscopy. Evidence is present that binding of CHA to CN is responsible for the stimulation of enzyme and results in structural changes. Aromatic residues reorient into new environments upon binding of CHA, the binding constant for the reaction was (2.76 ± 0.64) × 10 4 M −1 by one binding site, which indicated that CHA bound to BA statically and the change of secondary structure was mainly due to reduced α-helical content and increased β-turns. The results obtained in this study should be useful for understanding the molecular mechanisms underlying the interactions between CN and its activators.

Interaction of 3’-O-caffeoyl D-quinic acid with multisubunit protein helianthinin

Chlorogenic acid, 3’-O-caffeoyl D-quinic acid, is an inherent ligand present in Helianthus annuus L. The effect of pH on chlorogenic acid binding to helianthinin suggests that maximum binding occurs at pH 6·0. The protein-polyphenol complex precipitates as a function of time. The association constant of the binding of chlorogenic acid to helianthinin, determined by equilibrium dialysis, at 31°C has a value of 3·5 ± 0·1 × 104M–1 resulting in a ΔG value of – 6·32 ±0·12 kcal /mol. The association constant Ka is 1·0 ± 0·1 × 104M-1 as determined by ultraviolet difference spectral titration at 25°C with ΔGo of -5·46 ± 0·06 kcal/mol. From fluorescence spectral titration at 28°C, the Ka value is 1·38 ± 0·1 × 1 0 4M-1 resulting in a ΔG of – 5·70 ± 0·05 kcal/mol. The total number of binding sites on the protein are 420 ± 50 as calculated from equilibrium dialysis. Microcalorimetric data of the ligand-protein interaction at 23°C suggests mainly two classes of binding. The thermal denaturation temperature, Tm of the protein decreases from 76°C to 72°C at 1 × 10-3M chlorogenic acid concentration upon complexation. This suggests that the complexation destabilizes the protein. The effect of temperature on Ka of chlorogenic acid shows a nonlinear increase from 10·2°C to 45°C. Chemical modification of both lysyl and tryptophanyl residues of the protein decreases the strength of binding of chlorogenic acid. Lysine, tryptophan and tyrosine of protein are shown to be present at the binding site. Based on the above data, it is suggested that charge-transfer complexation and entropically driven hydrophobic interaction are the predominant forces that are responsible for binding of chlorogenic acid to the multisubunit protein, helianthinin.

Interaction of 3'-O-caffeoyl D-quinic acid with human serum albumin.

The interaction of chlorogenic acid (CGA) with human serum albumin (HSA) was studied from the view-point of thermodynamics and mechanism of binding at pH 6.0. The association constants (Ka) for the HSA-CGA interaction at 10, 25 and 40 degrees C were 6.0 x 10(4), 9.0 x 10(3) and 2 x 10(4) M-1, resulting in delta G of -6.21, -5.80, -6.32 kcal/mol, respectively. These high Ka-values showed that the interaction between CGA and HSA is strong, endothermic and entropically driven. Binding of chlorogenic acid induces conformational change in HSA as indicated by quenching of fluorescence emission intensity along with a red shift in the emission maxima from 338 to 350 nm. This suggested the involvement of the lone tryptophan residue in the region of binding. Far-ultraviolet circular dichroic data showed a decrease in the alpha-helical content of HSA from 56 to 50% upon binding of CGA. These data are also supported by the decrease in the apparent Tm of HSA by 4 degrees C upon binding of CGA causing destabilization of the HSA molecule. The kinetics of the interaction involves a single step in the binding, and the kinetic curve attains equilibrium within 180 +/- 5 s. Data on caffeic acid (CA) and quinic acid (QA), which are the hydrolysis products of the bidentate CGA molecule, indicate that CA interacts more strongly than CGA. CA binds with an association constant of 8 x 10(4) M-1 and with a maximum number of binding sites of four. Microcalorimetric investigation of the interaction of these ligands with HSA suggests that the strength of binding follows the order CA >> CGA >>> QA with a single class of binding sites. The effect of temperature on the binding of CGA to HSA showed that the interaction is dominated by hydrophobic forces and hydrogen bonding.

Effect of chemical modification of sunflower 11 S protein on the binding of chlorogenic acid

Binding of chlorogenic acid by sunflower 11S protein and succinylated and N-ethylmaleimide-treated protein was measured at pH 4.0 in 0.1M acetate buffer. Succinylation reduced binding, whereas N-ethylmaleimide treatment did not. Analysis of the binding data showed that succinylation reduced the number of binding sites without affecting the binding affinity. N-Ethylmaleimide treatment reduced neither the number of binding sites nor the binding affinity. Succinylation dissociated the 11S protein, whereas N-ethylmaleimide treatment did not. The secondary structure of N-ethylmaleimide-treated protein was different from that of the unmodified protein.

Binding of chlorogenic acid by the isolated polyphenol-free 11 S protein of sunflower (Helianthus annuus) seed

By use of a published method for the isolation of the 11S protein of sunflower seed in a homogeneous form, a procedure has been outlined for obtaining polyphenol-free 11S protein. Neither the gel filtration nor the PAGE pattern of the protein was affected by the method of polyphenol removal. The near-and farultraviolet circular dichroism spectrum of the protein was nearly the same as that of the protein containing polyphenols. Binding of chlorogenic acid by the polyphenol-free 11S protein of sunflower seed has been measured as a function of pH, salt concentration, and temperature. Increase in pH or salt concentration decreased the binding. Binding at 45 °C was less than at 30 °C; it was completely abolished at 55 °C. Addition of Na2S03 (0.01 M), dioxane (4%), or urea (8 M) to the buffer abolished the binding. Analysis of the binding data by Scatchard equation and Hill equation showed that binding affinity was not affected by pH or salt, but the maximum number of binding sites was reduced. Decreasing the pH dissociated the 11S protein to lower molecular weight proteins. This effect was reversed by the addition of NaCl or Na2S03.

Changes in free and bound chlorogenic acid and in polyphenoloxidase activity during the industrial processing of sunflower seeds (Short communication)

AbstractThe discolouration of sunflower protein isolates which impairs their food use is brought about by the covalent binding of protein with the products of chlorogenic acid (CA) oxidation 1, 21 which proceeds both under the action of polyphenoloxidase (PPO) at pH values near the neutral and by a nonenzymatic way at alkaline pH [3]. The presence of PPO in sunflower seeds was established [4, 5]. Although its activity decreases during oil processing [4, 5], moistening and increased temperature favour the enzymatic oxidation of CA and its coupling with protein. As a result the obtained cake may become unsuitable for food protein isolation. The decrease of free CA (extracted by aqueous ethanol) during the heating of moistened sunflower seeds was described [6]. It was attributed to the thermal decomposition of CA. These results do not exclude the covalent binding of CA with protein.The determination of both free and bound CA was applied in this work to follow the changes of CA during the processing of sunflower seeds. The decrease of PPO activity was assessed simultaneously and the relationship between these two processes was discussed.

Sunflower protein isolates chromaticity Part 2. Effect of chlorogenic acid binding on the chromaticity and available lysine content

Sunflower protein isolates chromaticity Part 2. Effect of chlorogenic acid binding on the chromaticity and available lysine content