Synergistic cytotoxicity and in vitro antioxidant activity of hederagenin and its glycoside from quinoa.

Although a series of studies confirm the bioactivities of hederagenin and its glycosides, their synergistic effects and potential mechanisms are still worthy of further exploration. This work investigated the synergistic cytotoxicity and in vitro antioxidant activity of hederagenin and hederagenin 28-O-ß-d-glucopyranoside (28-Glc-hederagenin). Hederagenin and 28-Glc-hederagenin inhibited HeLa cell growth and their combination further strengthened this effect. The combination of hederagenin and 28-Glc-hederagenin significantly increased the rate of apoptotic cells, suggesting the presence of a synergistic effect between the two substances. This combination also enhanced in vitro antioxidant activity compared with individual treatments. A network pharmacology and molecular docking-based approach was performed to explore the underlying mechanisms of hederagenin and 28-Glc-hederagenin against cervical cancer and oxidant damage. This work identified 18 related Kyoto Encyclopedia of Genes and Genome pathways, 202 related biological process terms, 17 related CC terms, and 35 related molecular function terms and then revealed 30 nodes and 196 edges. Subsequently, two highly connected clusters and the top four targets were identified. Molecular docking showed potent binding affinity of hederagenin and 28-Glc-hederagenin toward core targets associated with both cervical cancer and oxidant damage. This work may provide scientific basis for the combined use of hederagenin and its glycosides as dietary supplements.

Quantitative analysis of erythromycin, its major metabolite and clarithromycin in chicken tissues and eggs via QuEChERS extraction coupled with ultrahigh-performance liquid chromatography-tandem mass spectrometry.

A simple, rapid and novel method involving ultrahigh-performance liquid chromatography-electrospray ionization tandem triple quadrupole mass spectrometry (UHPLC-ESI-MS/MS) was developed to simultaneously detect erythromycin, its major metabolite and clarithromycin in chicken tissues (muscle, liver and kidney) and eggs (whole egg, albumen and yolk). Samples were extracted using acetonitrile-water (80:20, v/v), and a Cleanert MAS-Q cartridge was used to perform quick, easy, cheap, effective, rugged, and safe (QuEChERS) purification. The average recoveries were 87.78-104.22 %, and the corresponding intraday and interday relative standard deviations were less than 7.10 %. The decision limits and detection capabilities of the chicken tissues and eggs were 2.15-105.21 µg/kg and 2.26-110.42 µg/kg, respectively. For chicken tissues and eggs, the limits of detection and limits of quantification were 0.5 µg/kg and 2.0 µg/kg, respectively. The proposed method was successfully employed to analyse real samples, demonstrating its applicability.

Formation mechanism, environmental sensitivity and functional characteristics of succinylated ovalbumin/ε-polylysine electrostatic complexes: The roles of succinylation modification and ε-polylysine combination.

Biocomplex materials formed by oppositely charged biopolymers (proteins) tend to be sensitive to environmental conditions and may lose part functional properties of original proteins, and one of the approaches to address these weaknesses is protein modification. This study established an electrostatic composite system using succinylated ovalbumin (SOVA) and ε-polylysine (ε-PL) and investigated the impact of varying degrees of succinylation and ε-PL addition on microstructure, environmental responsiveness and functional properties. Molecular docking illustrated that the most favorable binding conformation was that ε-PL binds to OVA groove, which was contributed by the multi­hydrogen bonding and hydrophobic interactions. Transmission electron microscopy observed that SOVA/ε-PL had a compact spherical structure with 100 nm. High-degree succinylation reduced complex sensitivity to heat, ionic strength, and pH changes. ε-PL improved the gel strength and antibacterial properties of SOVA. The study suggests possible uses of SOVA/ε-PL complex as multifunctional protein complex systems in the field of food additives.

Involvement of the Keap1-Nrf2-ARE pathway in the antioxidant activity of sinomenine.

Sinomenine is a pure alkaloid isolated from Sinomenium acutum. This study is aimed to investigate the critical role of the nuclear factor erythroid 2-related factor 2 (Nrf2)-kelch-like ECH-associated protein-1(Keap1)-antioxidant response element (ARE) antioxidative signaling pathway in protecting sinomenine against H2O2-induced oxidative injury. Cytotoxicity and antioxidant experiments to initially determine the protective effects of sinomenine show that sinomenine has no effect on the decreased cell viability and presents similar potency in scavenging all three free radicals. The binding affinity between sinomenine and Keap1 was determined via fluorescence polarization assay, with IC50 of 13.52 µM. Quantum chemical calculation and theoretical simulation illustrated that sinomenine located into the Nrf2-binding site of Keap1 via hydrophobic and hydrogen interactions, showing high stability and binding affinity. On the basis of the stable binding of sinomenine with Keap1, sinomenine efficiently induced nuclear translocation of Nrf2, and increased in ARE activity in a concentration-dependent manner. Quantitative polymerase chain reaction provided further evidences that sinomenine-induced protection upregulated ARE-dependent genes, such as NAD(P)H quinone oxidoreductase 1, hemeoxygenase-1, and glutamate-cysteine ligase modifier subunit. Western blot confirmed that sinomenine increased the expressions of these antioxidative enzymes. Taken together, in vitro and in silico evaluations demonstrate that sinomenine inhibits the binding of Keap1 to Nrf2, promotes the nuclear accumulation of Nrf2 and thus leads to the upregulated expressions of Nrf2-dependent antioxidative genes. Our findings also highlight the use of sinomenine for pharmacological or therapeutic regulation of the Nrf2-Keap1-ARE system, which is a novel strategy to prevent the progression of oxidative injury.

Phytosterols in rice bran and their health benefits.

With the continuous technological innovation in the high-value utilization of rice bran byproducts, rice bran oil retains a higher concentration of beneficial components such as a well-balanced composition of fatty acids and abundant phytosterols. This makes it a highly nutritious and healthy vegetable oil. This review provides an overview of the advancements made in separating, purifying, and processing phytosterols in rice bran oil. The review also introduces techniques for assessing the stability of rice bran oil. Moreover, the review emphasizes the nutritional value of phytosterols found in rice bran oil, highlighting their various health benefits, including their anticancer, anti-inflammatory, anti-allergic, antibacterial, cholesterol-lowering, skin-protective, anti-obesity, anti-diabetic, neuroprotective, gastroprotective, and immune-enhancing effects. Attaining a comprehensive understanding of the research progress made in phytosterols derived from rice bran oil can offer valuable guidance for the efficient utilization of rice bran.

In vitro and in silico perspectives on the activation of antioxidant responsive element by citrus-derived flavonoids.

Introduction: Oxidative stress plays an essential role in the pathogenesis of chronic diseases. Disrupting the Keap1-Nrf2 pathway by binding Keap1 is identified as a potential strategy to prevent oxidative stress-related chronic diseases. Therefore, of special interest is the utilization of dietary antioxidations from citrus, including narirutin, naringenin, hesperetin, hesperidin, naringin, neohesperidin dihydrochalcone, neohesperidin, and nobiletin, has been exploited as a prospective way to treat or prevent several human pathologies as Keap1-Nrf2 inhibitors for modulation of antioxidant properties. Methods: To probe into the structural foundation of the molecular identification of citrus-derived antioxidations, we calculated the antioxidant responsive element activation ability of citrus-derived flavonoids after binding with Keap1. Also, the quantum chemistry properties and binding mode were performed theoretically with frontier molecular orbitals, molecular electrostatic potential analysis, molecular docking, and absorption, distribution, metabolism, excretion (ADME) calculation. Results and discussion: Experimental findings combining computational assays revealed that the tested citrus-derived flavonoids can be grouped into strong agonists and weak agonists. The citrus-derived antioxidations were well housed in the bound zone of Keap1 via stable hydrogen bonding and hydrophobic interaction. Eventually, three of eight antioxidations were identified after ADME and physicochemical evaluations. The citrus-derived flavonoids were identified as potential dietary antioxidants of the Keap1-Nrf2 interaction, and can be used to improve oxidative stress-related chronic diseases.

Paper-based visualization of auramine O in food and drug samples with carbon dots-incorporated fluorescent microspheres as sensing element.

A paper-based assay for visualization of auramine O (AO) was for the first time established by using CFMs as a ratiometric fluorescent probe (RFP). The CFMs were melamine formaldehyde microspheres (MFMs) incorporated with carbon dots (CDs), where the CDs species as sensing units and MFMs as a signal amplification carrier. The proposed RFP can quantitatively measure AO content from 0.0 to 10.0 µM and exhibited an ultralow limit of detection (LOD, 15.7 nM). In particular, obvious luminescence color change of CFMs from blue to green was perceived with naked-eyes and therefore, a solution-based and a paper-based visualization platform were respectively proposed for on-site visual detection of AO with LODs of 1.15 µM and 0.83 µM, separately. Finally, those fluorescence methods were adopted in sensitively quantitative measurement of AO within various food and drug samples, providing new prospects for analysts and technical support in food quality monitoring.

Complexation of phycocyanin with hydroxypropyl-ß-cyclodextrin and its application in blue beer containing quinoa saponins as foaming agents.

Introduction: With the increasing importance attached to human health, the inclusion complex (IC) of phycocyanin (PC) into hydroxypropyl-ß-cyclodextrin (HP-ß-CD) have been devoted to developing the use of food preservation in this study. Methods: In this experiment, the IC of PC into HP-ß-CD was prepared by the freeze-drying method and characterized by OM, TEM, UV, FTIR and TG/DSC methods. Results and discussion: The spectroscopic features were evaluated by Ultraviolet-visible (UV-vis) spectroscopy and Fourier transform infrared spectroscopy (FT-IR) confirming that PC was located in the hydrophobic cavity of HP-ß-CD. Consistent with the structural properties, optical microscopy (OM) and Transmission electron microscope (TEM) observed that the addition of PC subjected the IC to an aggregation state with irregular lamellar structures. Stability assessment showed that pH, heat and light tolerance of PC significantly regulated and improved due to the PC/HP-ß-CD complexation. The formation of ICs was helpful to enhancing the antioxidant activity of PC. Molecular modeling suggested that the D-pyrrole ring and its associated C=C group of phycocyanin entered the HP-ß-CD cavity from the wider edge. On this basis, the development of blue beer with quinoa saponins as foaming agent and ICs as colorant was explored. The addition of quinoa saponins made the foam richer and more delicate without destroying the overall taste coordination of beer. Moreover, the protective effect of HP-ß-CD presents a positive impact on the stability of blue beer pigment. Hence, PC encapsulated into HP-ß-CD will be an impressive approach in food-related application of PC.

Exploring the binding mechanism and adverse toxic effects of chiral phenothrin to human serum albumin: Based on multi-spectroscopy, biochemical and computational approach.

To understand the binding mechanism of a mixture of chiral phenothrin with human serum albumin (HSA), we used multi-spectroscopy, including steady-state fluorescence spectroscopic titration, three-dimensional fluorescence spectroscopy, circular dichroism, and FTIR spectra to explore the precise interactions between the complex. Based on the modified Stern-Volmer equation, the binding constant (Ka) was calculated under three temperatures, which revealed that phenothrin interacts with HSA through a static quenching mechanism. The thermodynamic parameters including enthalpy change (ΔH) and entropy change (ΔS) were determined by fitting the experimental data with van't Hoff equation, which indicates that electrostatic force and hydrogen bonds dominate the interplay in the phenothrin-HSA complex. Circular dichroism and FTIR showed the addition of phenothrin changed the secondary structure of proteins, in which the α-helicity decreased from 52.37% in free HSA to 50.02%. The esterase-like activity was reduced with the increase of phenothrin concentration, which may be attributed to the perturbated senior structure of HSA. Competitive displacement experiments confirmed that phenothrin inserted into the subdomain IIA (site I) of HSA. Several computational approaches such as molecular docking, frontier molecular orbital analysis, and electrostatic potential analysis were utilized to probe into the binding mode of the phenothrin-HSA complex. The binding behaviors of the chiral phenothrin mixture differed during the complexation. In conclusion, both the experimental and theoretical investigations provide useful information for better understanding and reducing the potential deleterious effects of the chiral phenothrin mixture on human long-term physio-pathological status.

Complexation mechanism between 20(R, S)-ginsenoside Rh1 and serum albumin: Multi-spectroscopy, in vitro cytotoxicity, and in silico investigations.

As rare ginsenosides, 20(R, S)-ginsenoside Rh1 [20(R, S)-Rh1] are isomers and have been reported to exhibit multiple biological effects. However, the application of 20(R, S)-Rh1 is still limited due to their poor solubilities and low bioavailabilities. Here, the complexation mechanism between 20(R, S)-Rh1 and serum albumin (SA) was explored by a combination of multi-spectroscopy and in silico investigations. Results of spectra experiments showed that 20(R, S)-Rh1 could form complexes with bovine serum albumin (BSA) and quench its intrinsic fluorescence. In addition, the influence of BSA on the anti-cancer activity of 20(R, S)-Rh1 was also evaluated in A549 cells. The result of the MTT assay indicated that anti-cancer activity of 20(R, S)-Rh1 was enhanced when combined with BSA. The results of molecular docking and dynamics simulation demonstrated that the subtle structural differences of 20(R, S)-Rh1 at the 20-carbon atom may be responsible for their different binding capacities and binding stabilities with human serum albumin. The cytotoxicity assay for 20(R, S)-Rh1 alone and their complexes with BSA demonstrated the enhancement effect of BSA for inhibition of cell proliferation. In conclusion, this work provided insight into the complexation mechanism between 20(R, S)-Rh1 and SA. PRACTICAL APPLICATION: The complexation mechanism between 20(R, S)-ginsenoside Rh1 [20(R, S)-Rh1] and serum albumin (SA) was explored by a combination of multi-spectroscopy and in silico investigations in this work. The cytotoxicity assay for 20(R, S)-Rh1 alone and their complexes with bovine serum albumin (BSA) demonstrates the enhancement effect of BSA for inhibition of cell proliferation. Hence, this work provided insight into the complexation mechanism between 20(R, S)-Rh1 and SA.

Preparation, characterization, and evaluation of HP-ß-CD inclusion complex with alcohol extractives from star anise.

The active compounds in star anise alcohol extractives (SAAE) have potent bioactivity. However, their poor solubility and stability limit their applications. In this study, SAAE/hydroxypropyl-ß-cyclodextrin (HP-ß-CD) inclusion complexes were prepared as a strategy to overcome the abovementioned disadvantages. The phase solubility results indicated that the solubility of the inclusion complex was enhanced. Complexation was confirmed by complementary methods, including Fourier-transform infrared spectroscopy, nuclear magnetic resonance spectroscopy, scanning electron microscopy, and transmission electron microscopy, which proved to be extremely insightful for studying the inclusion formation phenomenon between SAAE and HP-ß-CD. Despite there being no apparent improvements in the antioxidant capacity and antimicrobial activity, the results of the stability studies presented higher thermal, volatile, and photostability after encapsulation. Further, molecular modeling was used to investigate the factors influencing complex formation and provide the most stable molecular conformation. Thus, based on the obtained results, this study strongly demonstrates the potential of the SAAE/HP-ß-CD inclusion complex in the food industry.

Theoretical and experimental investigation of sodium alginate composite films containing star anise ethanol extract/hydroxypropyl-ß-cyclodextrin inclusion complex.

The aim of this study is to prepare composite films incorporated with star anise ethanol extract (SAEE)/hydroxypropyl-ß-cyclodextrin (HP-ß-CD) inclusion complex. The effects of sodium alginate concentration on mechanical properties of films are tested. Sodium alginate, SAEE, and SAEE/HP-ß-CD inclusion complex-based composite films are characterized in terms of UV-visible spectroscopy, microstructure characterizations, including transmission electron microscopy, scanning electronic microscopy, Fourier transform infrared, and 1 H NMR analysis, and molecular modeling calculations. With various stoichiometries, the complexes of sodium alginate/SAEE/HP-ß-CD are compared through both theoretical and experimental analyses. Molecular simulations are applied to predict the possible orientations of SAEE inside the HP-ß-CD cavity and the optimal stoichiometry of the complex formation. According to the simulation, the system of sodium alginate/SAEE (or SAEE/HP-ß-CD inclusion complex) in a 3:1 stoichiometry reaches the lowest total energy and achieves a balance in complex system. In addition, the composite films can maintain high-content vitamin C and reduce weight loss rate of fresh-cut Chinese yam. In conclusion, coinciding with the experimental results, the molecular modeling successfully calculates the reasonable molecular structure and molecular behavior of sodium alginate/SAEE/HP-ß-CD inclusion complex. The composite films in this study have the potential to be used for food packaging applications. PRACTICAL APPLICATION: In this paper, we present composite films incorporated with star anise ethanol extract (SAEE)/hydroxypropyl-ß-cyclodextrin (HP-ß-CD) inclusion complex for the use of fresh-cut Chinese yam preservation. The present study demonstrates a successful application of molecular modeling to predict the geometry of the final complex. It can serve as a powerful tool to calculate the energy of association between inclusion complex and sodium alginate molecules.

Computational and experimental characterization of estrogenic activities of 20(S, R)-protopanaxadiol and 20(S, R)-protopanaxatriol.

BACKGROUND: As the main metabolites of ginsenosides, 20(S, R)-protopanaxadiol [PPD(S, R)] and 20(S, R)-protopanaxatriol [PPT(S, R)] are the structural basis response to a series of pharmacological effects of their parent components. Although the estrogenicity of several ginsenosides has been confirmed, however, the underlying mechanisms of their estrogenic effects are still largely unclear. In this work, PPD(S, R) and PPT(S, R) were assessed for their ability to bind and activate human estrogen receptor α (hERα) by a combination of in vitro and in silico analysis. METHODS: The recombinant hERα ligand-binding domain (hERα-LBD) was expressed in E. coli strain. The direct binding interactions of ginsenosides with hERα-LBD and their ERα agonistic potency were investigated by fluorescence polarization and reporter gene assays, respectively. Then, molecular dynamics simulations were carried out to simulate the binding modes between ginsenosides and hERα-LBD to reveal the structural basis for their agonist activities toward receptor. RESULTS: Fluorescence polarization assay revealed that PPD(S, R) and PPT(S, R) could bind to hERα-LBD with moderate affinities. In the dual luciferase reporter assay using transiently transfected MCF-7 cells, PPD(S, R) and PPT(S, R) acted as agonists of hERα. Molecular docking results showed that these ginsenosides adopted an agonist conformation in the flexible hydrophobic ligand-binding pocket. The stereostructure of C-20 hydroxyl group and the presence of C-6 hydroxyl group exerted significant influence on the hydrogen bond network and steric hindrance, respectively. CONCLUSION: This work may provide insight into the chemical and pharmacological screening of novel therapeutic agents from ginsenosides.

Interactions of bisphenol diglycidyl ethers with estrogen receptors α: Fluorescence polarization, reporter gene, and molecular modeling investigations.

Based on human estrogen receptor α ligand binding domain (hERα-LBD) as recognition element, a fluorescence polarization assay was developed for the determination of bisphenol A diglycidyl ether (BADGE), bisphenol F diglycidyl ether (BFDGE), and their derivatives. Fluorescence polarization assay showed that BADGE, BFDGE and their derivatives exhibited dose-dependent binding to the receptor protein. The results of reporter gene assay indicated that all the tested bisphenol diglycidyl ethers show no agonistic activities, but some of them exhibit anti-estrogenic activities toward ERα. All the tested bisphenol diglycidyl ethers fitted into the hydrophobic binding pocket and adopted the conformation that resembled 4-hydroxytamoxifen, a selective antagonist of ERα. Quantitative structure-activity relationship analysis showed that the binding potencies of bisphenol diglycidyl ethers with hERα-LBD might be structure-dependent. This work may provide insight into the in silico screening of ER ligands from unsuspected chemicals.

Multi-Residue Method for the Analysis of Stilbene Estrogens in Milk.

The rapid analysis of stilbene estrogens is crucially important in the environment, food and health sectors, but quantitation of lower detection limit for stilbene estrogens persists as a severe challenge. We herein described a homologous and sensitive fluorescence polarization (FP) assay based on estrogen receptor α ligand binding domain (ER-LBD) to monitor stilbene estrogens in milk. Under optimal conditions, the half maximal inhibitory concentrations (IC50) of the FP assay were 9.27 nM, 12.94 nM, and 22.38 nM for hexestrol, dienestrol and diethylstilbestrol, respectively. And the corresponding limits of detection (LOD) values were 2.94 nM, 2.89 nM, and 3.12 nM. Finally, the assay was applied to determine the stilbenes in milk samples where the mean recoveries ranged from 95.76% to 112.78% and the coefficients of variation (CV) below 12.00%. Furtherly, we have focused our study on high cross-reactivity phenomena by using two in silico approaches, including molecular docking analysis and topology analysis. Overall, docking results show that several residues in the hydrophobic pocket produce hydrophobic interactions with the tested drug molecules, which contribute to the stability of their binding. In this paper, we conclude that the FP method is suitable for the rapid detection of stilbenes in milk samples, requiring no expensive analytical equipment or time-consuming sample preparation. This work offers a practical approach that applies bioscience technology in food safety testing and improves analytical speed and laboratory efficiency.

Estrogen receptor-based multi-residue screening of bisphenol compounds in urine.

Human exposure to bisphenol compounds (BPs) has been implicated in the development of several chronic diseases. Instead of exploiting the traditional methods for determination of BPs, this work confirms that the human estrogen receptor α ligand binding domain (hERα-LBD) is a powerful recognition element that can be used to monitor multi-residue of BPs in urine samples by fluorescence polarization (FP) assay. Test parameters were optimized for the best performance. Under the optimal conditions, the IC50 values of BPs are in the range of 0.04-1.61 µg mL-1 . Recovery experiments were then performed to assess the accuracy and precision of the established method. The results detected by FP assay show good agreements with that of liquid chromatography-tandem mass spectrometry method with a fit of R2  = 0.9372 and 0.9640 for BPE and BPAP, respectively. A computational methodology, ligand-based pharmacophore model, was also employed to further explore the broad-specific of tested compounds. It was found that the two hydrogen bond acceptor features and one hydrophobic aliphatic feature were essential for the corresponding cross-reactivity results from the FP assay. All these results suggest that the established method can be successfully applied to monitor the occurrence of BPs in urine.

In vitro and in silico perspectives on estrogenicity of tanshinones from Salvia miltiorrhiza.

This work aims to investigate the structure-activity relationship for binding and activation of human estrogen receptor α ligand binding domain (hERα-LBD) with tanshinones by a combination of in vitro and in silico approaches. The recombinant hERα-LBD was expressed in E. coli strain. The direct binding interactions of tanshinones with hERα-LBD and their ERα agonistic potency were investigated by fluorescence polarization (FP) and reporter gene assays, respectively. FP assay suggested that the tested tanshinones can bind to hERα-LBD as affinity ligands. Tanshinones acted as agonists of hERα as demonstrated by transactivation of estrogen response element (ERE) in transiently transfected MCF-7 cells and by molecular docking of these compounds into the hydrophobic binding pocket of hERα-LBD. Interestingly, comparison of the calculated binding energies versus Connolly solvent-excluded volume and experimental binding affinities showed a good correlation. This work may provide insight into chemical and pharmacological characterization of novel bioactive compounds from Salvia miltiorrhiza.

Estrogen receptor-based fluorescence polarization assay for bisphenol analogues and molecular modeling study of their complexation mechanism.

A fluorescence polarization (FP) assay based on estrogen receptor was developed for the determination of bisphenol compounds (BPs). The human estrogen receptor α ligand binding domain (hERα-LBD) and coumestrol were employed as recognition element and fluorescent probe, respectively. Competitive displacement of tracer from receptor suggested that BPs exhibited dose-dependent binding to hERα-LBD. In order to elucidate the structural basis for the interaction between BPs and hERα-LBD, molecular dynamics simulations were performed to explore their complexation mechanism. The docked bisphenol compounds adopted agonist/antagonist conformations with varying positions and orientations in the hydrophobic binding pocket, depending on their structural characteristics of bridging moieties. Interestingly, the calculated binding energies were generally correlated with the experimentally measured affinities, indicating a potential advantage of the molecular modeling approach in predicting the binding potencies of putative ligands. Considering that the real samples may contain more than one BP, the established FP assay can potentially be used as a pre-screening method to determine the total amounts of bisphenol compounds.

Quantitative structure-activity relationship for estrogenic flavonoids from Psoralea corylifolia.

A combination of in vitro and in silico approaches was employed to investigate the estrogenic activities of flavonoid compounds from Psoralea corylifolia. In order to develop fluorescence polarization (FP) assay for flavonoids, a soluble recombinant protein human estrogen receptor α ligand binding domain (hERα-LBD) was produced in Escherichia coli strain. The competition binding experiment was performed by using coumestrol (CS) as a tracer. The result of FP assay suggested that the tested flavonoids can bind to hERα-LBD as affinity ligands, except for corylin. Then, molecular modeling was conducted to explore the binding modes between hERα-LBD and flavonoids. All the tested compounds fit into the hydrophobic binding pocket of hERα-LBD. The hydrophobic and hydrogen-bonding interactions are dominant forces to stabilize the flavonoids-hERα-LBD binding. It can be speculated from molecular docking study that the hydroxyl groups and prenyl group are essential for flavonoid compounds to possess estrogenic activities. Both methylation of hydroxyl group and cyclization of prenyl group significantly diminish the estrogenic potency of flavonoids. Furthermore, quantitative structure-activity relationship (QSAR) analysis was performed by the calculated binding energies of flavonoids coupled with their determined binding affinities. Comparison between the docking scores and the pIC50 values yields an R-squared value of 0.9722, indicating that the estrogenic potency of flavonoids is structure-dependent. In conclusion, molecular docking can potentially be applied for predicting the receptor-binding properties of undescribed compounds based on their molecular structure.

Estrogenic properties of coumarins and meroterpene from the fruits of Cullen corylifolium: Experimental and computational studies.

Coumarins and meroterpene from the fruits of Cullen corylifolium were evaluated for their ability to bind and activate human estrogen receptor α (hERα) by a combination of in vitro studies and molecular dynamics simulations. The recombinant hERα ligand binding domain (hERα-LBD) was produced in BL21 (DE3)pLysS and the fluorescence polarization (FP) assay was performed to determine the binding affinities of coumarins and meroterpene with receptor protein. These compounds displayed distinct binding potency toward hERα-LBD, generally increased with their increasing molecular length and Connolly solvent-excluded volume (CSEV). In an estrogen response element-luciferase (ERE-Luc) reporter gene assay, coumarins and meroterpene acted as agonists of human estrogen receptor α. Subsequently, molecular docking was conducted to elucidate the molecular mechanism behind their agonistic activities. Coumarins and meroterpene adopted an agonist conformation within the cavity of hERα-LBD. The hydrophobic and hydrogen-bonding interactions were dominant forces to stabilize their binding. The structure-activity relationship analysis suggested that the presence of hydroxyl groups and prenyl group were crucial for possessing estrogenic activities. Comparison of the calculated binding energies with the determined binding affinities yielded a good correlation (R2 = 0.9727). In conclusion, molecular modeling techniques can potentially be applied for in silico screening of selective estrogen receptor modulators (SERMs) from undescribed compounds.