Identification of metabolites in WZS‐miniature pig urine after oral administration of Danshen decoction by HPLC coupled with diode array detection with electrospray ionization tandem ion trap and time‐of‐flight mass spectrometry

Danshen (DS) is a widely used traditional Chinese medicine for treating cardiovascular and cerebrovascular diseases. A simple, rapid and sensitive method was developed for identification of the in vivo metabolites in urine of WZS‐miniature pigs after oral administration of DS decoction by HPLC coupled with diode array detection with electrospray ionization tandem ion trap and time‐of‐flight mass spectrometry. This method has been successfully applied to simultaneous identification of 50 compounds (including 11 new ones) in pig urine. In addition, one new compound, (3‐hydroxyphenyl) crylic acid glycine methyl ester (C1), along with eight known ones were first isolated by column chromatography and identified by spectroscopic means, including 1D/2DNMR and mass spectrometry, as reference substances. Ten phenolic compounds (protocatechuic aldehyde, protocatechuic acid, caffeic acid, danshensu, ferulic acid, isoferulic acid, rosmarinic acid and salvianolic acid A/B/D) were found to be the main absorbed original constituents of DS decoction, which underwent the metabolic reactions of glucuronidation, sulfation, methylation, hydrogenation and glycine conjugation in vivo. In conclusion, the developed method is applicable to the analysis and identification of constituents in biological matrices after administration of DS decoction. Copyright © 2012 John Wiley & Sons, Ltd.     

Identification of bio‐active metabolites of gentiopicroside by UPLC/Q‐TOF MS and NMR

Gentiopicroside (GPS), the main bioactive component in Gentiana scabra Bge., has attracted our attention owing to its high bioactivity, especially the treatment of hepatobiliary disorders. The aglycone form of GPS, a typical secoiridoid glycoside, is considered to be more readily absorbed than its parent drug. This study aimed to identify and characterize the metabolites after GPS incubated with β‐glucosidase in buffer solution at 37°C. Samples of biotransformed solution were collected and analyzed by ultraperformance liquid chromatography (UPLC)/quadrupole–time‐of‐flight mass spectrometry (Q‐TOF MS). A total of four metabolites were detected: two were isolated and elucidated by preparative‐HPLC and NMR techniques, and one of those four is reported for the first time. The mass spectral fragmentation pattern and accurate masses of metabolites were established on the basis of UPLC/Q‐TOF MS analysis. Structure elucidation of metabolites was achieved by comparing their fragmentation pattern with that of the parent drug. A fairly possible metabolic pathway of GPS by β‐glucosidase was proposed. The hepatoprotective activities of metabolites M1 and M2 were investigated and the results showed that their hepatoprotective activities were higher than that of parent drug. Our results provided a meaningful basis for discovering lead compounds from biotransformation related to G. scabra Bge. in traditional Chinese medicine. Copyright © 2013 John Wiley & Sons, Ltd.     

Aliphatic Poly(ether amide)s by Polycondensation of Activated Sebacic Acid Derivatives

Poly(ether amide)s were prepared by polycondensation of 1,13‐diamino‐4,7,11‐trioxatridecane (DTT) with the bisimidazolide or with the bis N‐hydroxysuccinimide ester of sebacic acid. Four different solvents and three different temperatures were compared. The highest molecular weights were obtained with the bisimidazolide in dimethylsulfoxide (DMSO) at 60°C. MALDI‐TOF mass spectra revealed the existence of cyclic oligoamides and polyamides in all samples. The molar fraction of cycles considerably increased with higher molecular weights of the entire sample. The polycondensations were repeated under optimum conditions in the presence of α‐cyclodextrin to prepare polydisperse catenanes consisting of α‐cyclodextrin threaded on cyclic polyamides. Yet, despite broad variation of the reaction conditions, only cylic polyamides free of cyclodextrin were isolated. Furthermore, a pseudorotaxane was prepared from DTT and α‐cyclodetrin and polycondensed with bis‐(4‐chlorophenyl)sebacate. Again, only cyclic polyamides free of cyclodextrin were detectable.     

全二维气相色谱-飞行时间质谱分析焦化柴油中饱和烃的分子组成

建立了全二维气相色谱-飞行时间质谱(GC×GC-TOF MS)分析柴油馏分中饱和烃的分子组成的方法。结合谱库检索、质谱图解析、沸点与分子结构关系和全二维谱图特征,定性(或归类)了焦化柴油饱和烃组分中1057个化合物单体,其中正构烷烃排列规律性最强,一环~三环环烷烃按照极性和沸点的差异呈瓦片状分布在其上方。另外,还准确区分了在一维气相色谱上共流出的正构烷基环己烷和正构烷基环戊烷,以及正构 α 单烯烃。根据质谱采集的总离子流色谱图,采用峰面积归一化法得到了饱和烃组分的碳数分布结果,并将该方法应用于研究不同类型柴油馏分饱和烃的分子组成特点。结果表明,催化裂化和焦化柴油馏分饱和烃组分的化合物类型和分布各不相同。分子组成分析能为油品加工工艺机理的研究提供方法支持。     

Serum pharmacochemistry combined with multiple data processing approach to screen the bioactive components and their metabolites in Mutan Cortex by ultra‐performance liquid chromatography tandem mass spectrometry

Root cortex of Paeonia suffruticosa Andrews (Paeoniaceae), known as Moutan Cortex (MC), is known to have anti‐allergic and anti‐inflammatory properties. However, the constituents absorbed into blood after oral administration of MC remain unknown. A sensitive and rapid method by ultra‐high‐pressure liquid chromatography–electrospray ionization–quadrupole‐time‐of‐flight mass spectrometry (UPLC‐ESI‐Q‐TOF‐MS) technology and the MetaboLynx^TM software combined with multiple data processing approach (Mdpa) was established to investigate the absorbed constituents in rats after oral administration of MC, providing unique high‐throughput capabilities for drug metabolism study. A hyphenated electrospray ionization and quadrupole‐time‐of‐flight analyzer was used for the determination of accurate mass of the fragment ion in negative mode, with excellent MS mass accuracy and enhanced data acquisition. This rapid automated analysis method was successfully applied for screening and identification of the constituents absorbed and metabolized studies of MC after oral administration to rats. A total of 46 peaks were obtained from MC, 41 of which were tentatively characterized. In the VIP‐plot of orthogonal partial least‐squares discriminant analysis, 23 interesting ions in serum samples were extracted, and 16 parent components and seven metabolites were detected in vivo. The integrative serum pharmacochemistry technique, UPLC‐ESI‐Q‐TOF‐MS, and Mdpa method were successfully applied for rapid discovery of multiple components from MC. Copyright © 2013 John Wiley & Sons, Ltd.     

Identification of the metabolites of gigantol in rat urine by ultra‐performance liquid chromatography combined with electrospray ionization quadrupole time‐of‐flight tandem mass spectrometry

Gigantol is a typical bibenzyl compound isolated from Dendrobii Caulis that has been widely used as a medicinal herb in China for the treatment of diabetic cataract, cancer and arteriosclerosis obliterans and as a tonic for stomach nourishment, saliva secretion promotion and fever reduction. However, few studies have been carried out on its in vivo metabolism. In the present study, a rapid and sensitive method based on ultra‐performance liquid chromatography/electrospray ionization quadrupole time‐of‐flight tandem mass spectrometry (UPLC‐Q/TOF‐MS) in positive ion mode was developed and applied to identify the metabolites of gigantol in rat urine after a single oral dose (100 mg/kg). Chromatographic separation was performed on an Acquity UPLC HSS T3 column (100 × 2.1 mm i. d., 1.8 µm) using acetonitrile and 0.1% aqueous formic acid as mobile phases. A total of 11 metabolites were detected and identified as all phase II metabolites. The structures of the metabolites were identified based on the characteristics of their MS, MS² data and chromatographic retention times. The results showed that glucuronidation is the principal metabolic pathway of gigantol in rats. The newly identified metabolites are useful to understand the mechanism of elimination of gigantol and, in turn, its effectiveness and toxicity. As far as we know, this is the first attempt to investigate the metabolic fate of gigantol in vivo. Copyright © 2014 John Wiley & Sons, Ltd.     

A sample preparation method for recovering suppressed analyte ions in MALDI TOF MS

In matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI TOF MS), analyte signals can be substantially suppressed by other compounds in the sample. In this technical note, we describe a modified thin‐layer sample preparation method that significantly reduces the analyte suppression effect (ASE). In our method, analytes are deposited on top of the surface of matrix preloaded on the MALDI plate. To prevent embedding of analyte into the matrix crystals, the sample solution were prepared without matrix and efforts were taken not to re‐dissolve the preloaded matrix. The results with model mixtures of peptides, synthetic polymers and lipids show that detection of analyte ions, which were completely suppressed using the conventional dried‐droplet method, could be effectively recovered by using our method. Our findings suggest that the incorporation of analytes in the matrix crystals has an important contributory effect on ASE. By reducing ASE, our method should be useful for the direct MALDI MS analysis of multicomponent mixtures. Copyright © 2015 John Wiley & Sons, Ltd.     

Investigation of Mizoroki‐Heck coupling polymerization as a catalyst‐transfer condensation polymerization for synthesis of poly(p‐phenylenevinylene)

Mizoroki‐Heck coupling polymerization of 1,4‐bis[(2‐ethylhexyl)oxy]‐2‐iodo‐5‐vinylbenzene ( 1 ) and its bromo counterpart 2 with a Pd initiator for the synthesis of poly(phenylenevinylene) (PPV) was investigated to see whether the polymerization proceeds in a chain‐growth polymerization manner. The polymerization of 1 with ^tBu₃PPd(Tolyl)Br ( 10 ) proceeded even at room temperature when 5.5 equiv of Cy₂NMe (Cy = cyclohexyl) was used as a base, but the molecular weight distribution of PPV was broad. The polymerization of 2 hardly proceeded at room temperature under the same conditions. In the polymerization of 1 , PPV with H at one end and I at the other was formed until the middle stage, and the polymer end groups were converted into tolyl and H in the final stage. The number‐average molecular weight (M_n) did not increase until about 90% monomer conversion and then sharply increased after that, indicating conventional step‐growth polymerization. The occurrence of step‐growth polymerization, not catalyst‐transfer chain‐growth polymerization, may be interpreted in terms of low coordination ability of H‐Pd(II)‐X(^tBu₃P) (X = Br or I), formed in the catalytic cycle of the Mizoroki‐Heck coupling reaction, to π‐electrons of the PPV backbone; reductive elimination of H‐X from this Pd species with base would take place after diffusion into the reaction mixture. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 543–551     

Short monolithic columns for purification and fractionation of peptide samples for matrix-assisted laser desorption/ionization time-of-flight/time-of-flight mass spectrometry analysis in proteomics

This study records a novel application of methacrylate-based monolithic columns for MALDI-TOF/TOF MS analyses in proteomics for pre-concentration and separation of peptides derived from protein digestion. Reversed-phase monolithic capillary columns (30 mm × 0.32 mm i.d.) were created inside the fused silica capillary via thermal-initiated free-radical polymerization of ethylene glycol dimethacrylate and lauryl methacrylate monomers in the presence of 1-propanol and 1,4-butandiol as a porogen system. The elution of peptides was achieved using a linear gradient of acetonitrile from 0 to 60% in water with 0.1% trifluoroacetic acid formed in a microsyringe. Individual fractions of separated peptides were collected on the MALDI target spots covered with alpha-cyano-4-hydroxycinnamic acid used as a matrix and then they were analyzed using MALDI-TOF/TOF mass spectrometry. The developed method was tested with a mixture of tryptic peptides from bovine serum albumin and its applicability was also tested for tryptic in-gel digests from barley grain extracts of water soluble proteins separated using SDS gel electrophoresis. The number of detected peptides was approximately three to four times higher compared to the analysis without previous separation. These results show an improved quality of sample information with the higher amount of identified peptides which increased protein sequence coverage and improved sensitivity of mass spectrometry measurements.