Characterization of interaction property of multicomponents in Chinese Herb with protein by microdialysis combined with HPLC

Identifying ligands directly interacting with target protein in medicinal herbs by metabolomic analysis of T2-filtered HSQC spectra

A protocol for efficiently identifying ligands directly interacting with a target protein in complex extracts of medicinal herbs was proposed by combining an adapted 2D perfect-echo Carr-Purcell-Meiboom-Gill heteronuclear single quantum correlation (PE-CPMG HSQC) spectrum with metabolomic analysis. PE-CPMG HSQC can suppress the signal interference from the target protein, allowing more accurate peak quantification than conventional HSQC. Inspired from untargeted metabolomics, regions of interest (ROIs) are constructed and quantified for the mixture or complex extract samples with and without a target protein, and then a binding index (BI) of each ROI is determined. ROIs or corresponding peaks significantly perturbed by the presence of the target protein (BI ≥1.5) are detected as differential features, and potential binding ligands identified from the differential features can be equated with bioactive markers associated with the 'treatment' of the target protein. Quantifying ROI can inclusively report the ligand bindings to a target protein in fast, intermediate and slow exchange regimes on nuclear magnetic resonance (NMR) time scale. The approach was successfully implemented and identified Angoroside C, Cinnamic acid and Harpagoside from the extract of Scrophularia ningpoensis Hemsl. as ligands binding to peroxisome proliferator-activated receptor γ. The proposed 2D NMR-based approach saves excess steps for sample processing and has a higher chance of detecting the weaker ligands in the complex extracts of medicinal herbs. We expect that this approach can be applied as an alternative to mining the potential ligands binding to a variety of target proteins from traditional Chinese medicines and herbal extracts.

Screening techniques for the identification of bioactive compounds in natural products

Natural products (NPs) have a long history of clinical use and are rich source of bioactive compounds. The development of tools and techniques for identifying and analyzing NP bioactive compounds to ensure their quality and discover new drugs is thus very important and still in demand. Screening techniques have proven highly useful for screening and analyzing active components in complex mixtures, which rely on cell culture, dialysis, ultrafiltration, chromatographic methods and target molecule immobilization, using biological targets to identify the active compounds. The recent progress in biological screening techniques in the field of natural products is reviewed here. This includes a review on the strategy and application of the screening methods, their detailed description and discussion of their existing limitations of the different models along with prospective in future development of screening techniques.

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

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

Heterogeneous dimer peptide-conjugated polylysine dendrimer-Fe3O4 composite as a novel nanoscale molecular probe for early diagnosis and therapy in hepatocellular carcinoma

A novel nanoscale molecular probe is formulated in order to reduce toxicity and side effects of antitumor drug doxorubicin (DOX) in normal tissues and to enhance the detection sensitivity during early imaging diagnosis. The mechanism involves a specific targeting of Arg-Gly-Asp peptide (RGD)-GX1 heterogeneous dimer peptide-conjugated dendrigraft poly-l-lysine (DGL)-magnetic nanoparticle (MNP) composite by α_vβ₃-integrin/vasculature endothelium receptor-mediated synergetic effect. The physicochemical properties of the nanoprobe were characterized by using transmission electron microscope, Fourier transform infrared spectroscopy, X-ray diffraction, dynamic light scattering (DLS), and vibrating sample magnetometer. The average diameter of the resulting MNP-DGL-RGD-GX1-DOX nanoparticles (NPs) was ~150-160 nm by DLS under simulate physiological medium. In the present experimental system, the loading amount of DOX on NPs accounted for 414.4 mg/g for MNP-DGL-RGD-GX1-DOX. The results of cytotoxicity, flow cytometry, and cellular uptake consistently indicated that the MNP-DGL-RGD-GX1-DOX NPs were inclined to target HepG2 cells in selected three kinds of cells. In vitro exploration of molecular mechanism revealed that cell apoptosis was associated with the overexpression of Fas protein and the significant activation of caspase-3. In vivo magnetic resonance imaging and biodistribution study showed that the MNP-DGL-RGD-GX1-DOX formulation had high affinity to the tumor tissue, leading to more aggregation of NPs in the tumor. In vivo antitumor efficacy research verified that MNP-DGL-RGD-GX1-DOX NPs possessed significant antitumor activity and the tumor inhibitory rate reached 78.5%. These results suggested that NPs could be promising in application to early diagnosis and therapy in hepatocellular carcinoma as a specific nanoprobe.

Characterization of interaction property of multi-components in Gardenia jasminoides with aldose reductase by microdialysis combined with liquid chromatography coupled to mass spectrometry

RATIONALE

An application of microdialysis sampling for evaluation of the interaction property of small molecules to macromolecules is presented. Microdialysis combined with liquid chromatography coupled to quadrupole time-of-flight tandem mass spectrometry (LC/QTOF-MS/MS) was established for the purpose of screening of the multiple bioactive compounds in traditional Chinese medicines (TCMs).

METHODS

Microdialysis experiments were performed in vitro using a syringe pump and probes. Separation was achieved via liquid chromatography, and MS analysis was conducted by electrospray ionization quadrupole time-of-flight mass spectrometry in negative mode. The interaction property of compounds in TCMs with aldose reductase can be deduced from the comparison of the peak areas in chromatograms using a stable internal standard.

RESULTS

In this work, 23 compounds including iridoids, flavonoids, monoterpenoids, carotenoids and phenolic acids were identified by comparison with reference compounds, characteristic high-resolution mass spectrometry and the MS/MS fragmentations simultaneously. Binding degrees of 23 compounds in Gardenia jasminoides Eliis (G. jasminoide) with aldose reductase ranged from 13.91% to 66.25%. Also, microdialysis recoveries of 23 compounds in G. jasminoides were determined.

CONCLUSIONS

The Interaction properties of 23 compounds in G. jasminoides with aldose reductase were investigated and they are potential bioactive ingredients. Microdialysis coupled to LC/QTOF-MS/MS can be used for screening of bioactive multicomponents from TCMs with appropriate targets. Copyright © 2016 John Wiley & Sons, Ltd.

Surface charge-switchable polymeric magnetic nanoparticles for the controlled release of anticancer drug

We develop paclitaxel (PTX) and magnetic nanoparticles (MNPs) coencapsulated, surface charge-switchable, thermosensitive poly(d,l-lactic-co-glycolic acid)-l-lysine-d-galactose (PTX-MNP-PLGA-Lys-Gal) NPs for the controlled release of the anticancer drug. The novel dual signal-responsive nanovehicle is formulated to shield off target at pH 7.4 but bind avidly to tumor cells in acidity, alleviating toxicity and side effects of the drug to normal tissues. The mechanism involves pH-sensitive NPs surface charge switching by the deblocking process of galactose molecules followed by protonation of ε-NH2 in lysine residue at acidic pH. Magnetic hyperthermia under near infrared (NIR) irradiation induced the contraction of PTX-MNP-PLGA-Lys-Gal NPs and, in turn, triggered burst release of PTX. Transmission electron microscopy (TEM), fluorescence microscope analyses, Fourier transform infrared (FTIR), X-ray diffraction (XRD), vibrating sample magnetometer (VSM), dynamic light scattering (DLS), and ξ-potential analyses were performed to characterize physicochemical properties of the as-prepared NPs. The size range of the globule PTX-MNP-PLGA-Lys-Gal NPs after being prescreened was from 130 to 150 nm under simulated physiological medium. The high encapsulation efficiencies of MNPs and PTX were obtained, reaching 85 and 78 wt % for PTX-MNP-PLGA-Lys-Gal NPs, respectively. The tumor inhibitory rate of 78.8% reflected that the resulting NPs could be promising to treat cancer by specific binding and targeting release drug to tumor.

Biological Fingerprinting of Herbal Samples by Means of Liquid Chromatography

Biological chromatographic fingerprinting is a relatively new concept in the quality control of herbal samples. Originally it has been developed with the application of HPLC, and recently herbal samples' biological profiles have been obtained by means of thin-layer chromatography (TLC). This paper summarizes the application of liquid chromatographic techniques for the purpose of biological fingerprint analysis (BFA) of complex herbal samples. In case of biological TLC fingerprint, which is a relatively novel solution, perspectives of its further development are outlined in more detail. Apart from already published data, some novel results are also shown and briefly discussed. The paper aims at drawing scientists' attention to the unique solutions offered by biological fingerprint construction.

Bioactivity-based liquid chromatography-coupled electrospray ionization tandem ion trap/time of flight mass spectrometry for β₂AR agonist identification in alkaloidal extract of Alstonia scholaris

Although chromatographic fingerprinting combined with chemometrics, is a rational method for the quality control of traditional Chinese medicine (TCM), chemometrics cannot fully explore the relationship between chemical information and the efficacy of the potential activity. In the present work, a cell-based β₂ adrenergic receptor (β₂AR) agonist functional evaluation model coupled with high-performance liquid chromatography was developed to screen the potential β₂AR agonist components in the alkaloidal extract of Alstonia scholaris leaves. Using a liquid chromatography with ion trap time-of-flight mass spectrometry (LCMS-IT-TOF) system, the potential bioactive compounds in the prescription were identified and deduced based on the mass spectrometric fragmentation patterns, tandem mass spectrometry (MS/MS) data, and relevant literature. Several new β₂AR agonists of indole alkaloids were successfully found, and their activities were confirmed through an in vivo relaxant test on guinea pig tracheal muscles. The developed method is rapid and reliable compared with conventional fingerprinting and showed high sensitivity and resolution for the identification of β₂AR agonists in TCM prescriptions. This strategy clearly demonstrates that bioactivity-integrated fingerprinting is a powerful tool not only in screening and identifying potential lead compounds and in determining the therapeutic material basis of Chinese herbal prescriptions, but also in supplying suitable chemical markers for their quality control.

Analysis of the interactions of multicomponents in Cornus officinalis Sieb. et Zucc. with human serum albumin using on-line dialysis coupled with HPLC

Interactions of three iridoid glycosides extracted from Cornus officinalis Sieb. et Zucc. (CIG) with protein were simultaneously explored by on-line dialysis sampling coupled with high-performance liquid chromatography (DS-HPLC). Three main compounds in CIG were unequivocally identified as loganin, sweroside and cornuside by comparing their t(R), MS data and UV spectra with those of reference compounds. Dialysis recoveries and quantitative characteristics of DS-HPLC for three iridoid glycosides were determined. Recoveries of dialysis sampling ranged from 73.9 to 91.7% with the RSD below 3.0%. Based on the determination of concentrations before and after interaction with human serum albumin (HSA), the binding parameters of loganin, sweroside and cornuside with HSA were obtained and the binding mechanisms were investigated.

Ligand fishing with functionalized magnetic nanoparticles coupled with mass spectrometry for herbal medicine analysis: ligand fishing for herbal medicine analysis

The chemical composition of herbal medicines is very complex, and their therapeutic effects are determined by multi-components with sophisticated synergistic and/or suppressive actions. Therefore, quality control of herbal medicines has been a formidable challenge. In this work, we describe a fast analytical method that can be used for quality assessment of herbal medicines. The method is based on ligand fishing using human-serum-albumin-functionalized magnetic nanoparticles (HSA-MNPs) and mass spectrometry. To demonstrate the applicability of the proposed method, eight samples of Dioscorea panthaica were analyzed. The sampled plants were of both wild and cultivated origins. They grew at different geographical locations and were harvested at different times. The ligands bound to HSA-MNPs were isolated from the plant extracts and detected by using direct infusion electrospray ionization mass spectrometry (DI-ESI-MS). Chemical identity has been confirmed for five of the ligands isolated. From more than 15 peaks in the ESI-MS spectrum, 11 common peaks were selected for calculating the correlation coefficient and cosine ratio. The values of correlation coefficient and cosine ratio were >0.9824 and >0.9988, respectively, for all the samples tested. The results indicated a high level of similarity among the eight D. panthaica samples. Compared with chromatographic fingerprint analysis, the proposed HSA-MNP-based DI-ESI-MS/MS approach was not only fast and easy to carry out but also biological-activity-oriented, promising a more effective data interpretation and thus reliable assessment conclusions.

Recent analytical approaches in quality control of traditional Chinese medicines--a review

Traditional Chinese medicines (TCMs) are gaining more and more attention all over the world, due to their specific theory and long historical clinical practice. But the uncontrollable quality is a bottleneck for its modernization and globalization. This paper reviewed the recent analytical methods in the quality control of TCMs, including screening strategies of bioactive markers from TCMs through biochromatographic methods, the traditional chromatographic methods, DNA methods, as well as the spectroscopic methods, including FT-IR, NIR and NMR. The comprehensive methods, such as fingerprint and multi-component quantification are emphasized; hyphenated techniques, like HPLC-MS, GC-MS, CE-MS, LC-NMR, chemometric methods, and combination of chemical and biological methods, such as biofingerprint, metabolic fingerprint are now more and more widely used in TCMs. In a few word, the analysis and quality control of TCMs are moving towards an integrative and comprehensive direction, in order to better address the inherent holistic nature of TCMs.

Determination of sweroside in rat plasma and bile for oral bioavailability and hepatobiliary excretion

Sweroside is an active ingredient of iridoid glycoside isolated from the flower buds of Lonicera japonica THUNB. A quantitative HPLC-UV method was developed for monitoring sweroside in rat plasma, urine, feces and bile. The method was successfully applied for a basic pharmacokinetic study. The obtained data of pharmacokinetics were applied to evaluate the oral bioavailabilities of sweroside and the active ingredients of purified herbal extracts (IGEs-1). The absolute bioavailability was estimated to F(sweroside) 0.31% and F(IGEs-1) 0.67%. The majority of sweroside excreted to feces revealed one reason of the low oral bioavailability. The values of F(IGEs-1) much higher than that of F(sweroside) reveals that ingredients in IGEs-1 such as loganin, secoxyloganin and some phenolic acids may promote the absorption of sweroside. The study of hepatobiliary excretion was achieved by an in vivo microdialysis sampling method after intravenous administration of sweroside. The percentage of accumulation of free form sweroside in bile duct was 31.2+/-7.2% of the total dosage. It may be one reason why sweroside possesses strong hepatoprotective effect.

Preparation, characterization, and evaluation of liposomal ferulic acid in vitro and in vivo

In the present study, various gradients were evaluated for efficient loading of weak acid into liposomes. Several salt gradients showed efficient loading of ferulic acid (FA) into liposomes and the optimized conditions were established in calcium acetate gradient method to obtain 80.2 +/- 5.2% entrapment efficiency (EE). Unilamellar vesicles were observed in micrographs and liposomal FA showed good stability. 80% of FA was released from liposomes within 5 h in vitro. There is a novel finding in this study: that drugs could be entrapped with a high solubility in the intraliposomal buffer in contrast to the low solubility in the extraliposomal buffer. The results of body distribution in rats indicated that liposomes could improve the body distribution of FA. For FA liposome, the concentration of FA in brain was two-fold higher than that of free FA. Liposomal FA was a promising approach to improve the body distribution of FA.

Analysis of interaction property of bioactive components in Flos Lonicerae Japonicae with protein by microdialysis coupled with HPLC-DAD-MS

Interaction of the Flos Lonicerae Japonicae (FLJ) with protein was studied by microdialysis coupled with HPLC-DAD-MS. Eight compounds were identified by comparing their t(R), UV data and MS data with reference compounds. Microdialysis recoveries and binding degrees of compounds in FLJ with bovine serum albumin (BSA) were determined. Recoveries of microdialysis sampling ranged from 51.3 to 73.2% with relative standard deviation (RSD) below 3.1%, and the binding degrees of those compounds to BSA ranged from 4.8 to 61.2 (0.3 mM BSA) and from 11.1 to 76.2% (0.6 mM BSA), respectively. The results showed that the binding properties of compounds in FLJ were influenced by pH. Furthermore, the binding degrees of five reference compounds were determined separately under the same conditions, the binding degrees of chlorogenic acid, luteolin-3-O-glucoside and 4,5-di-O-caffeoyl quinic acid was lower in FLJ than in single compound solution, on the contrary the binding degree of caffeic acid and rutin was higher in FLJ, which indicated that a significant effects of the interaction of compounds with each other on their binding degrees to BSA. The results showed that there were ten compounds had interaction with BSA, eight of them were the proven active compounds, and the other two compounds had similar binding degree with the proven active compounds, so the ten compounds might possess potential activities.

Screening and identification of permeable components in a combined prescription of Danggui Buxue decoction using a liposome equilibrium dialysis system followed by HPLC and LC-MS

A new method, i.e., liposome equilibrium dialysis followed by HPLC and LC-MS analysis, has been developed for the screening of permeable components in combined prescriptions of Danggui Buxue decoction (CPDBD). Multiple permeable components were simultaneously predicted by comparison of chromatograms of CPDBD extract before and after interaction with liposome membranes. A diode-array detector (DAD) and an evaporative light scattering detector (ELSD) were used, and the permeable compounds were identified by comparison with the available reference compounds and confirmed by on-line LC-MS. About fifteen compounds in a CPDBD extract were found to interact with liposome membranes. They were identified as calycosin-7-O-beta-D-glucoside (1), senkyunolide I or H (2), ononin (3), (6alphaR,11alphaR)-9,10-dimethoxypterocarpan-3-O-beta-D-glucoside (4), (3R)-2'-hydroxy-3',4'-dimethoxyisoflavan-7-O-beta-D-glucoside (5), calycosin (6), astragaloside IV (7), isoastragaloside II (8), formononetin (9), (6alphaR, 11alphaR),-3-hydroxy-9,10-dimethoxypterocarpan (10), (3R)-7,2'-dihydroxy-3',4'-dimethoxyisoflavan (11), astragaloside I (12), isoastragaloside I (13), E-ligustilide (14), and Z-ligustilide (15), respectively. Among all permeable components, 1, 3, 6, and 9 (flavonoids), 2, 14, and 15 (phthalides), and 7 (saponins) have been considered as major bioactive components in CPDBD. Therefore, this new method appears useful as a first step in the screening of bioactive components in natural products including Traditional Chinese Medicines (TCMs).

Comparative studies of the interaction between ferulic acid and bovine serum albumin by ACE and surface plasmon resonance

Affinity capillary electrophoresis (ACE) was used to study the interaction between ferulic acid (FA) and BSA. The interaction between FA and BSA was facilitated by injecting FA into a BSA-containing running buffer. Both mobility ratio and mobility shift assays were performed to deduce the binding constant (K(b)). However, the K(b )value obtained with the mobility ratio assay was only approximately 20% of that extracted from the mobility shift assay. The former assay yielded a K(b) value (5.6 +/- 0.4 x 10(4) M(-1)), which compares well with the result obtained with surface plasmon resonance (SPR) (5.1 +/- 0.6 x 10(4) M(-1)). The discrepancy between the mobility ratio and mobility shift assays suggests that the data extrapolation from the mobility ratio should be more reliable for cases when both changes in the EOF and viscosity of the running buffer are important. The work demonstrates that ACE, a solution-based technique, and SPR, a technique addressing interfacial processes, are highly complementary to each other and the comparative studies are confirmatory and allow binding constants to be accurately determined.

Analysis of interaction property of bioactive components in Danggui Buxue Decoction with protein by microdialysis coupled with HPLC–DAD–MS

Interaction of a commonly used combined prescription of Danggui Buxue Decoction (CPDBD) with protein was studied by microdialysis coupled with HPLC-DAD-MS. Nine compounds in CPDBD were unequivocally identified by comparing with their t(R), MS data and UV spectra with those of reference compounds, and simultaneously quantified. Microdialysis recoveries and binding degrees of 20 compounds in CPDBD with bovine serum albumin (BSA) were determined. Recoveries of microdialysis sampling ranged from 66.9 to 91.5% with RSD below 3.0%, and the binding degrees of those to BSA ranged from 6.3 to 59.8% (0.3mM BSA) and from 6.9 to 86.6% (0.6mM BSA). The results were determined at pH 7.4 and the influence of different pH value was investigated. Furthermore, the binding degrees of eight reference compounds were determined separately under the same conditions, indicating a significant effect of the interaction of compounds with each other on their binding degrees to BSA. By comparing their binding degrees with BSA with those of proven active compounds in CPDBD, i.e. chlorogenic acid (3), ferulic acid (6), ononin (12) and calycosin (16), other five compounds were found to possess potential activities, which were tentatively identified as calycosin-7-O-beta-D-glucoside-6-O-malonate (9), senkyunolide I or H (10), formononetin-7-O-beta-D-glucoside-6-O-malonate (17), and two unknown compounds.

Combining high-performance liquid chromatography with on-line microdialysis sampling for the simultaneous determination of ascorbyl glucoside, kojic acid, and niacinamide in bleaching cosmetics

We have used on-line microdialysis sampling coupled with high-performance liquid chromatography and UV-vis detection to simultaneously determine the contents of ascorbyl glucoside (AA-2G), kojic acid (KA), and niacinamide (VitB(3)) in commercial bleaching cosmetics. Our results indicate that AA-2G, KA, and VitB(3) separated well within 4.5 min on a reverse-phase Hypersil Fluophase PFP column when eluting with 0.020 M phosphate buffer solution in 40% (v/v) methanol at pH 5.5. The calibration curves were linear over the ranges 0.068-304, 0.071-284, and 0.024-488 microg mL(-1) for AA-2G, KA, and VitB(3), respectively, with correlation coefficients for the linear regression analyses falling within the range 0.9982-0.9999. The detection limits for AA-2G, KA, and VitB(3) were 0.01, 0.01, and 0.007 microg mL(-1), respectively. The detection wavelength was robust when the levels of the analytes in the samples were high (0.1-2%). The analytes were all detected using ultraviolet light (254 nm). The compounds diffuse through the membrane more readily when KA and VitB(3) are in their molecular forms and AA-2G is ionized. The recoveries were in the range 92-106% with good reproducibility (R.S.D.=3.9-8.7%). We used this procedure to assay six commercially available bleaching cosmetics; our results confirmed not only the precision of the method but also the claims made on the labels of the cosmetics. This approach provides a very simple means to determine the contents of AA-2G, KA, and VitB(3) in various dosages in bleaching cosmetics.

Surface Modification of RGD-Liposomes for Selective Drug Delivery to Monocytes/Neutrophils in Brain

In the present study, RGD peptide was coupled with ferulic acid (FA) liposomes for binding to monocytes and neutrophils in peripheral blood for brain targeting in response to leukocyte recruitment. Cholesterol (Ch) was esterified with succinic anhydride to introduce a carboxylic end group (Ch-COOH). Soybean phosphatidylcholine, cholesterol and Ch-COOH were in a molar ratio of 1 : 0.23 : 0.05. FA was loaded into liposomes with 80.2+/-5.2% entrapment efficiency (EE) using a calcium acetate gradient method since it was difficult to load FA by other methods. RGD peptide was a novel compound coupled with Ch-COOH via carbodiimide and N-hydroxysulfosuccinimide. The results of the in vitro flow cytometric study showed that RGD conjugation liposomes (RGD-liposomes) could bind to monocytes/neutrophils efficiently. The rats were subjected to intrastriatal microinjections of 100 microl of human recombinant IL-1beta to produce brain inflammation and subsequently sacrificed after 15, 30, 60 and 120 min of administration of three formulations (FA solution, FA liposome, RGD-coated FA liposome). The body distribution results showed that RGD-liposomes could be directed to the target site, i.e. the brain, by cell selectivity in case of an inflammatory response. For RGD coated liposomes, the concentration of FA in brain was 6-fold higher than that of FA solution and 3-fold higher than that of uncoated liposomes. MTT assay and flow cytometry were used in the pharmacodynamic studies where it was found that FA liposomes exhibited greater antioxidant activity to FA solution on U937 cell.

Characterization of enantioselective binding of racemic natural tetrahydropalmatine to DNA by chromatographic methods

A racemate from natural product, tetrahydropalmatine (THP), was characterized on its enantioselective binding to DNA by the chromatographic methods including microdialysis/HPLC, centrifugal ultrifiltration/HPLC and immobilized DNA affinity chromatography. It was found that its (+)-enantiomer was preferential to binding on B-form duplex DNA including calf thymus DNA, AT and GC sequence oligo DNA, as well as triplex oligo DNA. The binding constants of the THP enantiomers to ct-DNA were determined with the methods of microdialysis/HPLC and frontal affinity chromatography. In addition, the DNA structural preference of either enantiomer was evaluated with the chromatographic methods.

Biological fingerprinting analysis of the interactome of a kinase inhibitor in human plasma by a chemiproteomic approach

In this study, a gel free chemiproteomic method based on chromatography was developed and applied for the biological fingerprinting analysis of complex biological system. p-Aminobenzamidine (ABA), an inhibitor of trypsin-like serine proteases, was immobilized for characterizing their interacting proteins in human plasma. By the proteomic analysis method, 214 proteins were identified with obvious affinity to the immobilized ABA. By searching the sequences of above proteins with consensus patterns of the two active sites, seven proteins belong to trypsin-like serine protease group were found. Based on the Gene Ontology annotation, the identified trypsin-like serine proteases have the function of catalytic activity and calcium ion binding, and are mainly involved in the biological process of blood coagulation. Eight more other proteins related to calcium ion binding and blood coagulation were found. Nearly all of these proteins cannot be identified by directly analyzing the plasma sample demonstrating the chemiproteomics a useful approach to characterize interacting proteins in the low abundance range.

Comprehensive two-dimensional HPLC to study the interaction of multiple components inRheum palmatum L. with HSA by coupling a silica-bonded HSA column to a silica monolithic ODS column

A mode of comprehensive 2-D LC was developed by coupling a silica-bonded HSA column to a silica monolithic ODS column. This system combined the affinity property of the HSA column and the high-speed separation ability of the monolithic ODS column. The affinity chromatography with HSA-immobilized stationary phase was applied to study the interaction of multiple components in traditional Chinese medicines (TCMs) with HSA according to their affinity to protein in the first dimension. Then the unresolved components retained on the HSA column were further separated on the silica monolithic ODS column in the second dimension. By hyphenating the 2-D separation system to diode array detector and MS detectors, the UV and molecular weight information of the separated compounds can also be obtained. The developed separation system was applied to analysis of the extract of Rheum palmatum L., a number of low-abundant components can be separated on a single peak from the HSA column after normalization of peak heights. Six compounds were preliminarily identified according to their UV and MS spectra. It showed that this system was very useful for biological fingerprinting analysis of the components in TCMs and natural products.