Shilan Feng

Electrochemically reduced graphene oxide-based electrochemical sensor for the sensitive determination of ferulic acid in A. sinensis and biological samples

An electrochemically reduced graphene oxide (ERGO) modified glassy carbon electrode (GCE) was used as a new voltammetric sensor for the determination of ferulic acid (FA). The morphology and microstructure of the modified electrodes were characterized by scanning electron microscopy (SEM) and Raman spectroscopy analysis, and the electrochemical effective surface areas of the modified electrodes were also calculated by chronocoulometry method. Sensing properties of the electrochemical sensor were investigated by means of cyclic voltammetry (CV) and differential pulse voltammetry (DPV). It was found that ERGO was electrodeposited on the surface of GCE by using potentiostatic method. The proposed electrode exhibited electrocatalytic activity to the redox of FA because of excellent electrochemical properties of ERGO. The transfer electron number (n), electrode reaction rate constant (ks) and electron-transfer coefficient (α) were calculated as 1.12, 1.24s(-1), and 0.40, respectively. Under the optimized conditions, the oxidation peak current was proportional to FA concentration at 8.49 × 10(-8)mol L(-1) to 3.89 × 10(-5)mol L(-1) with detection limit of 2.06 × 10(-8)mol L(-1). This fabricated sensor also displayed acceptable reproducibility, long-term stability, and high selectivity with negligible interferences from common interfering species. The voltammetric sensor was successfully applied to detect FA in A. sinensis and biological samples with recovery values in the range of 99.91%-101.91%.

Structure and antioxidant activity study of sulfated acetamido-polysaccharide from Radix Hedysari

A new sulfated acetamido-heteropolysaccharide, HPS4-2A, was obtained by aqueous extraction followed by precipitation with ethanol and fractionation with DEAE column chromatography from Radix Hedysari. It was composed of rhamnose, arabinose, glucose, galactose and 2-acetamido-2-deoxy-d-galactose in the molar ratio of 10.09%:25.90%:25.90%:25.0%:12.30%. Elemental analysis indicated that HPS4-2A was a sulfated polysaccharide containing small amount of sulfate groups (1.87%). Partial acid hydrolysis, GC, GC-MS, 1D and 2D NMR spectroscopy analysis of the HPS4-2A revealed a predominance of glucose, galactose and 2-acetamido-2-deoxy-D-galactose linked in a highly-branched structure. The molecular weight of HPS4-2A was determined by HPSEC and HPSEC-MALLS. AFM study indicated that HPS4-2A took a highly branched conformation, which in consistent with the result studied by SEC-MALLS. Structural features of HPS4-2A were also investigated by SEM and TEM. Antioxidant assays demonstrated that HPS4-2A possessed of strong DPPH and hydroxyl radicals scavenging activities, suggesting that HPS4-2A could potentially be used as natural antioxidant.

Component analysis and structure identification of active substances for anti-gastric ulcer effects in Radix Astragali by liquid chromatography and tandem mass spectrometry

This study provided a comprehensive component analysis and structure identification of active substances for the anti-gastric ulcer effects of Radix Astragali. The data were generated by organically combining the results from in vivo pharmacodynamic experiments, a cell growth-promoting assay, structure identification, content determination, fingerprinting, and correlation analyses. The fingerprints from high-performance liquid chromatography coupled with a diode array detector (HPLC-DAD) and from HPLC coupled with evaporative light scattering detectors (ELSD) from 95% ethanol extracts of Radix Astragali (ERA) were determined using HPLC-DAD-ELSD. The structures of 16 compounds were identified using ultra-pressure liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS). The contents of these 16 compounds were simultaneously determined in a single run using HPLC-DAD-ELSD. The strength of the anti-ulceration effect of each of the 16 compounds was correlated to its content in the HPLC spectrum using gray relation statistics. The sequence of the contribution from each of the 16 compounds to the anti-gastric ulcer effect was determined. The results showed that ononin, astragalosideIII, and astragalosideIV contributed most to the observed anti-gastric ulcer effects and that these three compounds also exhibited strong growth-promoting effects in cultured GES-1 cells. The results of this study can be used to evaluate the quality of Radix Astragali and to provide a theoretical foundation for its further study.

Quantitative analysis of costunolide and dehydrocostuslactone in rat plasma by ultraperformance liquid chromatography-electrospray ionization-mass spectrometry.

Costunolide and dehydrocostuslactone are well-known sesquiterpene lactones contained in many plants used as popular herbs, such as Saussurea lappa and Laurus novocanariensis, and have been considered as potential candidates for the treatment of various types of tumor. In the present work, a sensitive UPLC-MS/MS for the quantification of costunolide and dehydrocostuslactone in biological matrices has been developed. The method is based on protein precipitation with acetonitrile followed by isocratic ultraperformance liquid chromatographic separation using methanol-formic acid (0.1% in water; 70:30, v/v) mobile phase. Detection was performed by ESI mass spectrometry in MRM mode with the precursor-to-product ion transitions m/z 233-187 and m/z 231-185, respectively. The calibration curves of analytes showed good linearity within the established range 0.19-760  ng/mL for costunolide and 0.23-908  ng/mL for dehydrocostuslactone. The lower limits of quantification of costunolide and dehydrocostuslactone were found to be 0.19 and 0.23  ng/mL, respectively. The intra-day and inter-day presicions of this method for the entire validation were less than coefficient of variation of 7% and the accuracy was within ±8% (relative error). The mean extraction recoveries were 73.8 and 75.3%, respectively. The method was found to be precise, accurate and specific during the study, and was successfully used to analyze the pharmacokinetics of costunolide and dehydrocostuslactone.

Ultrasensitive Detection of Ferulic Acid Using Poly(diallyldimethylammonium chloride) Functionalized Graphene-Based Electrochemical Sensor

The electrochemical redox of ferulic acid (FA) was investigated systematically by cyclic voltammetry (CV) with a poly(diallyldimethylammonium chloride) functionalized graphene-modified glassy carbon electrode (PDDA-G/GCE) as a working electrode. A simple and sensitive differential pulse voltammetry (DPV) technique was proposed for the direct quantitative determination of FA in Angelica sinensis and spiked human urine samples for the first time. The dependence of the intensities of currents and potentials on nature of the supporting electrolyte, pH, scan rate, and concentration was investigated. Under optimal conditions, the proposed sensor exhibited excellent electrochemical sensitivity to FA, and the oxidation peak current was proportional to FA concentration in the range of 8.95 × 10−8 M ~5.29 × 10−5 M, with a relatively low detection limit of 4.42 × 10−8 M. This fabricated sensor also displayed acceptable reproducibility, long-term stability, and high selectivity with negligible interferences from common interfering species. Besides, it was applied to detect FA in Angelica sinensis and biological samples with satisfactory results, making it a potential alternative tool for the quantitative detection of FA in pharmaceutical analysis.

Study on pharmacokinetics and tissue distribution of pteryxin in mice by ultra-pressure liquid chromatography with tandem mass spectrometry.

Pteryxin is a coumarin compound naturally occurring in the roots of Radix Peucedani, a commonly used as traditional Chinese medicine for the treatment of certain respiratory diseases and hypertension. An UPLC-MS/MS method was established to quantify pteryxin in mouse plasma and tissue homogenates. Isoimperatorin was used as internal standard (IS). The method was based on protein precipitation with methanol for sample preparation. Pteryxin and IS were separated using a UPLC™ BEH C₁₈ column and eluted with a mobile phase consisting of methanol and water (70:30, v/v) at a flow-rate of 0.2 mL/min. MS/MS detection was carried out by monitoring the fragmentation of m/z 409.3-287.2 for pteryxin and m/z 271.3-185.2 for IS on a triple-quadrupole mass spectrometer. The total run time was only 6 min. The results showed that it had good linearity over a wide concentration range (r > 0.999), and pteryxin was rapidly distributed and then eliminated from mouse plasma (t(½) =1.463 h). The major distribution tissues of pteryxin in mice were liver, and pteryxin was enabled to cross the blood-brain barrier owing to its low polarity. There was no long-term accumulation of pteryxin in mouse tissues.

Structural characterization and antioxidant activity of a heteropolysaccharide isolated from Hedysarum polybotrys

A water-soluble polysaccharide (HPS3aS) with a molecular mass of 1.22 × 104 Da was isolated from Hedysarum polybotrys using anion-exchange and gel-permeation chromatography. HPS3aS exhibits a globular-shaped conformation in 0.1 M NaNO3 by size exclusion chromatography with multi-angle laser light scattering (SEC-MALLS). The investigation of the structural features of this heteropolysaccharide through a combination of chemical and instrumental analyses revealed that the backbone of HPS3aS is composed of α-d-(1 → 4)-linked glucopyranose residues, which occasionally branched at O-6. The branches are composed of (1 → 4)-linked galactopyranose residues and terminated with glucopyranose residues. HPS3aS possesses good in vitro antioxidant activity, as evaluated by scavenging assays with 1,1-diphenyl-2-picrylhydrazyl, hydroxyl, and superoxide radicals, which suggests that HPS3aS could be a potential antioxidant.

Structural characterization and stimulating effect on osteoblast differentiation of a purified heteropolysaccharide isolated from Hedysarum polybotrys

Radix Hedysari polysaccharides (HPS) is the principal active fraction of Radix Hedysari (RH). The information about HPS3d, the main fraction of HPS3, and its effect on bone is still unknown. In the present study, the purified HPS3d was obtained by anion-exchange column. It consisted of 94.38% polysaccharide, 3.40% protein and 13.30% uronic acid. The molecular weight was measured to be 84.6kDa. The backbone consisted of galactopyranose and galacturonopyranose, and the side chains were composed of glucopyranose, rhamnopyranose and arabinofuranose. The FT-IR and elemental analysis showed that HPS3d was the sulfated polysaccharide. HPS3d upregulated alkaline phosphatase (ALP) activity and the expression of other osteogenic marker genes in osteoblast. In addition, HPS3d increased the expression and transcriptional activity of Runt-related transcription factor 2 (Runx-2) and Osterix, the two master genes of osteoblast differentiation. These findings suggest that HPS3d stimulates osteoblast differentiation by activation of Runx-2 and Osterix.

Determination of Light Toxic Compound Coumarin in Enrichment Angelica Pills and Angelica Sinensis by Ultra Performance Liquid Chromatography

An ultra performance liquid chromatography (UPLC) method was developed for the simultaneous determination of psoralen, xanthotoxin and bergapten in Enrichment angelica pills and Angelica sinensis. The samples were extracted with methanol. The target compounds were seperated on Waters ACQUITY BEH C-18 (100 mm x 2.10 mm 1.7 mu m), with a gradient acetonitrile-water solvent system at 30 degrees C, the flow rate was 0.45 mL/min, the detection wavelength was set at 245 nm and the injection volume was 3 mu L. Results showed the good linear ranges for psoralen, xanthotoxin and bergapten were within 2.34-67.4 mg/L, with correlation coefficients(r) of 0.9992-0.9996, the mean recoveries were in the range of 96.20%-102.42%, with the relative standard deviation of 1.5%-3.0%. The method is simple, rapid, accurate and reliable, and suitable for the determination of psoralen, xanthotoxin and bergapten.

Quantification of six bioactive compounds in Zhenqi Fuzheng preparation by high-performance liquid chromatography coupled with diode array detector and evaporative light scattering detector

A simple and accurate high-performance liquid chromatography (HPLC) coupled with diode array detector (DAD) and evaporative light scattering detector (ELSD) was established for the determination of six bioactive compounds in Zhenqi Fuzheng preparation (ZFP). The monitoring wavelengths were 254, 275 and 328 nm. Under the optimum conditions, good separation was achieved, and the assay was fully validated in respect of precision, repeatability and accuracy. The proposed method was successfully applied to quantify the six ingredients in 31 batches of ZFP samples and evaluate the variation by hierarchical cluster analysis (HCA), which demonstrated significant variations on the content of these compounds in the samples from different manufacturers with different preparation procedures. The developed HPLC method can be used as a valid analytical method to evaluate the intrinsic quality of this preparation.