Metabolic study of paeoniflorin and total paeony glucosides from Paeoniae Radix Rubra in rats by high-performance liquid chromatography coupled with sequential mass spectrometry.

A clear understanding of the metabolism of Traditional Chinese Medicines is extremely important in their rational clinical application and effective material foundation research. A novel and reliable strategy was performed to find more metabolites of paeoniflorin, determine the metabolites of total paeony glucosides (TPG) by means of determining those metabolites of paeoniflorin, and compare the metabolism differences between paeoniflorin and TPG by intragastric administration. This strategy was characterized as follows. Firstly, the rats were divided into two groups (the paeoniflorin group and the TPG group) to find differences in metabolism mechanisms between paeoniflorin and TPG. Secondly, UPLC-FT-ICR MS and UPLC-Q-TOF MS2 were applied to obtain accurate molecular weight and structural information, respectively. Thirdly, the metabolites were tentatively identified by a combination of data-processing methods including mass defect screening, characteristic neutral loss screening and product ion screening. Finally, a comparative study was employed in the metabolism of paeoniflorin and TPG. Based on the strategy, 18 metabolites of paeoniflorin (including four new compounds) and 11 metabolites of TPG (including two new compounds) were identified. In all of the identified metabolites of paeoniflorin, two metabolites in rat plasma, four metabolites in rat urine and six metabolites in rat feces were found for the first time after paeoniflorin administration. The results indicate that hydrolyzation of the ester bond and glucosidic band and conjugation with glucuronide were the major metabolic pathways of paeoniflorin. The metabolites of paeoniflorin and TPG in rat plasma, urine and feces have been detected for the first time after intragastric administration. The results may contribute to a better understanding of the metabolism mechanism and provide a scientific rationale for researching the material basis of paeoniflorin and TPG in vivo.

Effects of different metal ions on the fluorescence of CdSe/ZnS quantum dots capped with various thiolate ligands.

In this report, we systematically studied the effects of different metal ions on the fluorescence of common thiolate ligand capped quantum dots. Generally, heavy metal ions exhibited much more significant fluorescence quenching. Also, the coordination capability and steric hindrance of the ligand jointly affect the quenching efficiency.

Studies on the metabolism of paeoniflorin in human intestinal microflora by high performance liquid chromatography/electrospray ionization/Fourier transform ion cyclotron resonance mass spectrometry and quadrupole time-of-flight mass spectrometry.

In this study, a high performance liquid chromatography/electrospray ionization/Fourier transform ion cyclotron resonance mass spectrometry and quadrupole time-of-flight mass spectrometry (HPLC-ESI-FT-ICR MS and HPLC-ESI-QTOF MS2) based on chemical profiling method was established to study the metabolites of paeoniflorin in human intestinal microflora (HIM). By virtue of the high resolution, high speed of HPLC and the accurate mass measurement of FT-ICR MS and QTOF MS2, 31 metabolites in methyl tert-butyl ether (MTBE) layer were detected, and the structures of 16 metabolites were identified. Among them, 13 metabolites (including two new compounds) were found for the first time in HIM transformation in vitro. The results indicated that metabolic pathways of paeoniflorin in HIM contained extensive metabolic reactions. The hydrolysis, oxidization and conjugation were major metabolic pathways, and the glycosidic linkage, ester bond, benzene ring and pinane of the structure were metabolic sites. These results would contribute to better understanding the metabolic mechanism of paeoniflorin, thereby to in-depth study and development of paeoniflorin in medicine.

[Determination of sedative and ß-receptor hormone residues in feed by ultra high performance liquid chromatography-tandem mass spectrometry].

An analysis and detection method for eight sedatives and fifteen ß-receptor hormones in feed was established by ultra high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). The sample was extracted with acetonitrile-1% (v/v) trichloroacetic acid aqueous solution (7:3, v/v), and purified by cationic solid phase extraction column. The extracts were separated on an Agilent Zorbax Eclipse Plus C18 chromatographic column (100 mm×3.0 mm, 1.8 µm) and then quantified via internal standard method. The results showed that the linear relationships of the 23 targets were good in the range of 2.0-200.0 µg/L (r2> 0.99). The average recoveries of the targets spiked in the matrix of feed samples were within 75.1%-102.4% in three spiked levels of 5.0, 10, 50 µg/kg, and the relative standard deviations (RSDs) were within 4.3%-14.3% (n=6). This method with high purification efficiency and extensive scope of application can be applied to screening and detecting sedatives and ß -receptor hormones in feed.

Probing the binding reaction of cytarabine to human serum albumin using multispectroscopic techniques with the aid of molecular docking.

Cytarabine is a kind of chemotherapy medication. In the present study, the molecular interaction between cytarabine and human serum albumin (HSA) was investigated via fluorescence, UV-vis absorption, circular dichroism (CD) spectroscopy and molecular docking method under simulative physiological conditions. It was found that cytarabine could effectively quench the intrinsic fluorescence of HSA through a static quenching process. The apparent binding constants between drug and HSA at 288, 293 and 298K were estimated to be in the order of 103L·mol-1. The thermodynamic parameters ΔH°, ΔG°and ΔS° were calculated, in which the negative ΔG°suggested that the binding of cytarabine to HSA was spontaneous, moreover the negative ΔS°and negative ΔH°revealed that van der Waals force and hydrogen bonds were the major forces to stabilize the protein-cytarabine (1:1) complex. The competitive binding experiments showed that the primary binding site of cytarabine was located in the site I (subdomain IIA) of HSA. In addition, the binding distance was calculated to be 3.4nm according to the Förster no-radiation energy transfer theory. The analysis of CD and three-dimensional (3D) fluorescence spectra demonstrated that the binding of drug to HSA induced some conformational changes in HSA. The molecular docking study also led to the same conclusion obtained from the spectral results.

Study on the interaction of paeoniflorin with human serum albumin (HSA) by spectroscopic and molecular docking techniques.

The interaction of paeoniflorin with human serum albumin (HSA) was investigated using fluorescence, UV-vis absorption, circular dichroism (CD) spectra and molecular docking techniques under simulative physiological conditions. The results clarified that the fluorescence quenching of HSA by paeoniflorin was a static quenching process and energy transfer as a result of a newly formed complex (1:1). Paeoniflorin spontaneously bound to HSA in site I (subdomain IIA), which was primarily driven by hydrophobic forces and hydrogen bonds (ΔH° = - 9.98 kJ mol-1, ΔS° = 28.18 J mol-1 K-1). The binding constant was calculated to be 1.909 × 103 L mol-1 at 288 K and it decreased with the increase of the temperature. The binding distance was estimated to be 1.74 nm at 288 K, showing the occurrence of fluorescence energy transfer. The results of CD and three-dimensional fluorescence spectra showed that paeoniflorin induced the conformational changes of HSA. Meanwhile, the study of molecular docking also indicated that paeoniflorin could bind to the site I of HSA mainly by hydrophobic and hydrogen bond interactions.