Xinfeng Zhao

Screening the bioactive compounds in aqueous extract of Coptidis rhizoma which specifically bind to rabbit lung tissues β2-adrenoceptor using an affinity chromatographic selection method.

A receptor affinity chromatographic selection method was developed for screening the bioactive compounds binding to beta(2)-adrenoceptor (beta(2)-AR) in Coptidis rhizome. The bioactive compounds were analyzed by molecular recognition with a beta(2)-AR affinity column. The retention compounds eluted from the beta(2)-AR column were separated online with reverse-phase high-performance liquid chromatography by column switching technology, and identified by a coupled ion-trap mass spectrometer. Four compounds were screened as the bioactive compounds of Coptidis rhizome and identified as 2,9,10-trimethoxy-3-hydroxyl-protoberberine (jateorhizine), 2,3-methylenedioxy-9-methoxy-protoberberine, 2,3,9,10-tetramethoxy-protoberberine (palmatine) and 2,3-methylenedioxy-9,10-dimethoxy-protoberberine (berberine). The association constants of jatrorrhizine, palmatine and berberine to the beta(2)-AR were determined by the zonal elution method with standards. Berberine and palmatine had only one type of binding site on the immobilized beta(2)-AR. Their association constants were (2.28+/-0.11)x10(4)/M and (3.00+/-0.10)x10(4)/M, respectively. Jatrorrhizine had at least two type of binding sites on the immobilized beta(2)-AR, and the corresponding association constants were (2.20+/-0.09)x10(-4)/M and (6.78+/-0.001)x10(5)/M.

Comparison of zonal elution and nonlinear chromatography in determination of the interaction between seven drugs and immobilised β2-adrenoceptor

Zonal elution and nonlinear chromatography are two mainstream models for the determination of drug-protein interaction in affinity chromatography. This work intended to compare the results by zonal elution with that by nonlinear chromatography when it comes to the analysis of the interaction between seven drugs and immobilised β2-adrenoceptor (β2-AR). The results of the zonal elution showed that clorprenaline, clenbuterol, methoxyphenamine, salbutamol, terbutaline, tulobuterol and bambuterol have only one type of binding site on immobilised β2-AR, while nonlinear chromatography confirmed the existence of at least two types of binding sites between β2-AR and clorprenaline, clenbuterol and bambuterol. On these sites, both zonal elution and nonlinear chromatography presented the same rank order for the association constants of the seven drugs. Compared with the data from zonal elution, the association constants calculated using nonlinear chromatography gave a good linear response to the corresponding values by radio-ligand binding assay. The sampling efficiencies of nonlinear chromatography were clearly higher than zonal elution. Nonlinear chromatography will probably become a powerful alternative for the high throughput determination of drug-protein interaction.

Binding interactions between prazosin and α1A-adrenoceptor: investigation on the thermodynamic behaviors and the binding mechanism by high performance affinity chromatography

Although the association constant and the number of binding sites of prazosin to α1A-adrenoceptor were determined by high performance affinity chromatography (HPAC) in our previous work, the thermodynamic behaviors and the binding mechanism of the drug to immobilized α1A-adrenoceptor remained unclear. This work intended to address the issue by HPAC and molecular docking. The investigations involved the determination of association constants by frontal analysis at different temperatures, the calculation of enthalpy, entropy and free energy changes, the examination of mobile phase composition on the binding parameters and the site-directed molecular docking. The changes of enthalpy, entropy and free energy during the interaction were −20.79 kJ mol−1, −59.28 J mol−1 K−1 and −2.4 kJ mol−1, respectively. The binding of prazosin to α1A-adrenoceptor was an endothermic process with an increase in entropy. This reaction was mainly driven by hydrogen bonds. The ionic strength of the mobile phase provided a positive response to the values of association constants, while the power of hydrogen and the concentration of isopropyl in the mobile phase showed a negative trend. Ser203 and Ser192 in the fifth transmembrane segment of the receptor were the positions for the formation of hydrogen bonds. It is possible to utilize the immobilized receptor to determine the mechanism of drug–receptor interactions.

Binding of caffeic acid to human serum albumin by the retention data and frontal analysis

A new mathematical model and frontal analysis were used to characterize the binding behavior of caffeic acid to human serum albumin (HSA) based on high-performance affinity chromatography. The experiments were carried out by injecting various mole amounts of the drug onto an immobilized HSA column. They indicated that caffeic acid has only one type of binding site to HSA on which the association constant was 2.75 × 10(4) /m. The number of the binding site involving the interaction between caffeic acid and HSA was 69 nm. The data obtained by the frontal analysis appeared to present the same results for both the association constant and the number of binding sites. This new model based on the relationship between the mole amounts of injection and capacity factors assists understanding of drug-protein interaction. The proposed model also has the advantages of ligand saving and rapid operation.

Distribution of Metabolites in Root Barks of Seven Tree Peony Cultivars for Quality Assessment Using NMR-based Metabolomics

Abstract Objective To determine the distribution of metabolites in the root barks of different tree peony cultivars for quality assessment. Methods Seven tree peony phenotypic cultivars with different colors were systematically analyzed using NMR-based metabolomics. Results A total of 16 metabolites from their methanol extracts were simultaneously identified and quantified, including one primary metabolite (sucrose) and 15 secondary ones (acetophenones, phenolics, monoterpene glycosides, flavonoids, and unsaturated fatty acids). The quantitative data indicated that sucrose (90-180 mg/g) and acetophenones (15-100 mg/g), and non-phenolics, monoterpene glycosides, flavonoids, and unsaturated fatty acids (2-15 mg/g) were the major metabolites in these tree peony cultivars. The significantly increasing levels of paeonoside with bioactivity were observed in “Xiangyu”, “Wujinyaohui”, “Roufurong”, “Yaohuang”, “Zhaofen”, “Doulű”, and “Yingrihong” in order. Opposite trends in the levels of paeonoside and paeonol were observed in “Xiangyu” and “Yingrihong”, suggesting that the changes of the secondary metabolites in plants were influenced by primary metabolites, such as sucrose/glucose, and the different physiological processes occurred in different tree peony cultivars. Conclusion “Yingrihong” with red flower has the highest medicine quality whereas “Xiangyu” with white flower has the worst one based on the content of paeonoside.

Binding mechanism of nine N-phenylpiperazine derivatives and α1A-adrenoceptor using site-directed molecular docking and high performance affinity chromatography

N-Phenylpiperazine derivatives are widely used as clinical drugs for fighting diseases related to the cardiovascular system by mediating the signal pathway of α1-adrenoceptor. The binding mechanism of nine N-phenylpiperazine derivatives to α1A-adrenoceptor was explored using molecular docking and high performance affinity chromatography. The methodology involved homology modelling of the three dimensional structure of α1A-adrenoceptor, predication of the binding behaviors using LIBDOCK and investigation of the thermodynamic behaviors of the binding by frontal analysis. Molecular docking results showed that Asp106, Gln177, Ser188, Ser192 and Phe193 of the receptor were the main binding sites for the nine N-phenylpiperazine derivatives binding to α1A-adrenoceptor. The binding was driven by formation of hydrogen bonds and electrostatic forces. The affinity of these derivatives for the receptor depended on the functional groups of an ionizable piperazine, hydrogen bond acceptor and hydrophobic moiety in the ligand structures. Frontal analysis indicated that the association constants of these compounds for the receptor were determined by their structural deviations in the above-mentioned functional groups. Thermodynamic studies presented negative enthalpy and Gibbs free energy changes with a positive entropy change, providing proof that the binding of the derivatives to α1A-adrenoceptor was mainly driven by electrostatic forces. This result was in line with the binding mechanism predicted by molecular docking. It is possible to explore the binding mechanism of drug candidates specifically binding to α1A-adrenoceptor using receptor chromatography.

Confirming therapeutic target of protopine using immobilized β2-adrenoceptor coupled with site-directed molecular docking and the target-drug interaction by frontal analysis and injection amount–dependent method

Drug‐protein interaction analysis is pregnant in designing new leads during drug discovery. We prepared the stationary phase containing immobilized β2‐adrenoceptor (β2‐AR) by linkage of the receptor on macroporous silica gel surface through N,N′‐carbonyldiimidazole method. The stationary phase was applied in identifying antiasthmatic target of protopine guided by the prediction of site‐directed molecular docking. Subsequent application of immobilized β2‐AR in exploring the binding of protopine to the receptor was realized by frontal analysis and injection amount–dependent method. The association constants of protopine to β2‐AR by the 2 methods were (1.00 ± 0.06) × 105M−1 and (1.52 ± 0.14) × 104M−1. The numbers of binding sites were (1.23 ± 0.07) × 10−7M and (9.09 ± 0.06) × 10−7M, respectively. These results indicated that β2‐AR is the specific target for therapeutic action of protopine in vivo. The target‐drug binding occurred on Ser169 in crystal structure of the receptor. Compared with frontal analysis, injection amount–dependent method is advantageous to drug saving, improvement of sampling efficiency, and performing speed. It has grave potential in high‐throughput drug‐receptor interaction analysis.

Screening bioactive compounds with multi-targets from Rhodiola crenulata by a single column containing co-immobilized beta2-adrenergic receptor and voltage dependent anion channel isoform 1

The pursuit of drugs having improved therapeutic efficacy necessitates increasing research on new assays for screening bioactive compounds with multi-targets. This work synthesized a chromatographic stationary phase containing co-immobilized beta2-adrenergic receptor (β2-AR) and voltage dependent anion channel isoform 1 (VDAC-1) to achieve such purpose. Specific ligands of the two receptors (e.g. salbutamol, methoxyphenamine, ATP and NADH) were utilized to characterize the specificity and bioactivity of the column. Validated application of the stationary phase was performed by screening multi-target compounds of Rhodiola crenulata using high performance affinity chromatography coupled with ESI-Q-TOF-MS. By zonal elution, we identified salidroside as a bioactive compound simultaneously binding to β2-AR and VDAC-1. The compound exhibited the binding sites of 1.0 × 10-7 and 4.0 × 10-7 M on the β2-AR and VDAC-1. On these sites, the association constants were calculated to be 3.3 × 104 and 1.0 × 104 M-1. Molecular docking indicated that the binding of salidroside to the two receptors occurred on Ser169 and Phe255of β2-AR, and the channel wall of VDAC-1. Taking together, we concluded that the column containing co-immobilized receptors has potential for screening bioactive compounds with multi-targets from complex matrices including traditional Chinese medicines.

Tanshinol borneol ester on nanostructured lipid carriers has longer brain and systemic effector retention and better antioxidant activity in vivo

Background Tanshinol borneol ester (DBZ) is a hybrid of danshensu (DSS) and borneol and has anti-ischemic activity in animals. However, its low water solubility and short half-life limit its clinical application. Methods We prepared polyethylene glycol (PEG)-modified and DBZ-loaded nanostructured lipid carriers (DBZ-PEG-NLC) and DBZ-NLC, and examined their physical characteristics, such as particle size, zeta potential, entrapment efficiency and drug loading. The in vitro stability and pharmacokinetics in rats as well as antioxidant activity of DBZ-PEG-NLC and DBZ-NLC in a C57BL/6 mouse model of ischemia/reperfusion-related brain injury were investigated. The levels of DBZ and its hydrolyzed DSS in rat plasma and brain microdialysates were determined by liquid chromatography–mass spectroscopy/mass spectroscopy analysis. Results We found that the mean particle size and entrapment efficacy of DBZ-PEG-NLC were similar to that of DBZ-NLC. The DBZ-PEG-NLC, like DBZ-NLC, released DBZ in a biphasic manner with initially burst release and then prolonged slow release in vitro. Intravenous injection of DBZ-PEG-NLC resulted in significantly higher levels and longer retention periods of DBZ and DSS in plasma and the brains than DBZ-NLC and DBZ in rats. Finally, treatment with DBZ-PEG-NLC achieved a better antioxidant activity than DBZ or DBZ-NLC in mouse model of ischemia/reperfusion by reducing the levels of brain malondialdehyde, but increasing the levels of brain superoxide dismutase and glutathione. Conclusion DBZ-PEG-NLC is a preferable option to deliver DBZ for sustainable release of DSS and borneol in vivo, and may serve as a promising drug for effective therapy of ischemic cardiovascular and cerebrovascular diseases.

Reliable Analysis of the Interaction between Specific Ligands and Immobilized Beta-2-Adrenoceptor by Adsorption Energy Distribution

Although a comparatively robust method, immobilized protein-based techniques have displayed limited precision and inconsistent results due to a lack of strategy for the accurate selection of drug adsorption models on the protein surface. We generated the adsorption data of three drugs on immobilized beta-2-adrenoceptor (β2-AR) by frontal affinity chromatography-mass spectrometry (FAC-MS) and site-specific competitive FAC-MS. Using adsorption energy distribution (AED) calculations, we achieved the best adsorption models for the binding of salbutamol, terbutaline, and pseudoephedrine to immobilized β2-AR. The Langmuir model proved to be desirable for describing the adsorptions of salbutamol and terbutaline on immobilized β2-AR, while the bi-Langmuir model was favorable to characterize the adsorption of pseudoephedrine on the receptor. Relying on the accurate determination of association constants, we presented an efficient approach for β2-AR ligand screening based on the loss of breakthrough time of an indicator drug caused by the inclusion of competitive drugs in the mobile phase. We concluded that the current strategy enables the reliable and accurate analysis of G protein-coupled receptor (GPCR)-drug interaction. The percentage change in the breakthrough time for drugs can provide useful information for estimating their binding affinity to the receptor. This approach builds a powerful platform for high-throughput ligand screening.