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.

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.

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.

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.

Estrogenicity of halogenated bisphenol A: in vitro and in silico investigations.

The binding interactions of bisphenol A (BPA) and its halogenated derivatives (halogenated BPAs) to human estrogen receptor α ligand binding domain (hERα-LBD) was investigated using a combined in vitro and in silico approach. First, the recombinant hERα-LBD was prepared as a soluble protein in Escherichia coli BL21(DE3)pLysS. A native fluorescent phytoestrogen, coumestrol, was employed as tracer for the fluorescence polarization assay. The results of the in vitro binding assay showed that bisphenol compounds could bind to hERα-LBD as the affinity ligands. All the tested halogenated BPAs exhibited weaker receptor binding than BPA, which might be explained by the steric effect of substituents. Molecular docking studies elucidated that the halogenated BPAs adopted different conformations in the flexible hydrophobic ligand binding pocket (LBP), which is mainly dependent on their distinct halogenation patterns. The compounds with halogen substituents on the phenolic rings and on the bridging alkyl moiety acted as agonists and antagonists for hERα, respectively. Interestingly, all the compounds in the agonist conformation of hERα formed a hydrogen bond with His524, while the compounds in the antagonist conformation formed a hydrogen bond with Thr347. These docking results suggested a pivotal role of His524/Thr347 in maintaining the hERα structure in the biologically active agonist/antagonist conformation. Comparison of the calculated binding energies vs. experimental binding affinities yielded a good correlation, which might be applicable for the structure-based design of novel bisphenol compounds with reduced toxicities and for environmental risk assessment. In addition, based on hERα-LBD as a recognition element, the proposed fluorescence polarization assay may offer an alternative to chromatographic techniques for the multi-residue determination of bisphenol compounds.