Michael Hochberg: An Editor’s Guide to Writing and Publishing Science

E. Hywel Evans and Mike. E. Foulkes: Analytical Chemistry. A Practical Approach

Congress, Conferences, and Workshops

Characterization of Lipstatin and the Minor Components from Streptomyces toxytricini Fermentation Broth by HPLC–ESI–Q-TOF–MS Abstract As the major product, lipstatin was originally isolated from the fermentation broth of Streptomyces toxytricini. Moreover, several lipstatin analogs are also produced in the fermentation process. In this study, a high-performance liquid chromatography coupled with electrospray ionization–quadrupole time-of-flight–mass spectrometry (HPLC–ESI–Q-TOF–MS) method was established for rapid separation and identification of multiple constituents in the fermentation broth of Streptomyces toxytricini. Based on the systematic investigation of lipstatin fragmentation pathways, 7 lipstatin analogs were identified as hydroxylipstatin (1), dehydrolipstatin (2, 4), seco-lipstatin (3), desmethyllipstatin (5), methyllipstatin (7), and dihydrolipstatin (8) for the first time. This study enriches the chemical profiling of fermentation broth of Streptomyces toxytricini and could provide valuable information for the biosynthetic study and the separation of lipstatin and further investigation of the preparation of tetrahydrolipstatin.

Field-Flow Fractionation of Cationic Cellulose Derivatives Abstract The asymmetric flow field-flow fractionation (AF4) method was developed for cationic cellulose derivatives. AF4 is the method of choice especially for high-molar mass samples, which are challenging to characterize with conventional chromatographic techniques such as size-exclusion chromatography (SEC). The cationic charge of macromolecules also complicates the size-based separations where no interaction between the analytes and the column stationary phase (SEC) or membrane (AF4) should occur. However, many column matrices and membranes carry negative charge and thus preventing interactions between cationic analytes and negatively charged separation support should be taken into consideration when doing method development. In this study, two eluent compositions, neutral and acidic, were tested for AF4 separation of cationic hydroxyethyl celluloses with varying charge densities. The eluent composition with a pH below the isoelectric point of regenerated cellulose membrane, which was used in this AF4 study, enabled the size-based separation with close to 100% analysis recovery. Macromolecular parameters (molar mass and radius of gyration) and conformation were investigated by coupling a multi-angle light scattering detector and differential refractometer to the AF4 system.

Simultaneous Determination of Fluoride and Chloride in Iron Ore by Steam Distillation Followed by Ion Chromatography Abstract This study illustrates the extraction of fluoride (F−) and chloride (Cl−) from non-combustible inorganic iron ore matrix by employing steam distillation (SD)-based volatilization process followed by ion chromatographic (IC) determination. This cost-effective, simple and green sample preparation setup involved decomposition of sample matrix in H2SO4 for the extraction of volatile halides at 165–180 °C that were subsequently collected in a 100-mL receiving bottle having 0.2 M NaOH as absorption solution. After 15–20 min of absorption, the distillate was injected to the IC system for the isocratic separation and determination of both halides in complex inorganic iron ore sample (IOS). The developed method showed good linearity in the concentration range of 0.02–10 µg/mL with a correlation coefficient (R) greater than ≥ 0.9999. It also showed good accuracy (82.20–87.87%), precision (RSDs ≤ 3.71) and excellent limit of detection (LOD) ranged between 0.0003 and 0.0006 µg/mL with no matrix effect.

Simultaneous Determination of Taurine, N -Acetylcysteine, Glycine and Methionine in Commercial Formulations by High-Performance Liquid Chromatography Abstract A simple, inexpensive, reliable, selective and sensitive liquid chromatographic method was developed and validated for the simultaneous quantification of taurine (Tau), N-acetylcysteine (NAC), glycine (Gly) and methionine (Met) and applied for the first time to the analysis of commercial alimentary supplements. The amino acids (AAs) were analyzed after labeling reaction with 2,4-dinitrofluorobenzene (DNFB) in the presence of cetyltrimethylammonium bromide (CTAB). The derivatization reaction conditions were optimized and the derivatives were separated on a Phenomenex Synergi MAX-RP 4 μm stainless steel column under gradient elution conditions. A mixture of triethylammonium (TEA) phosphate buffer (pH 3) and acetonitrile under gradient elution conditions was used as mobile phase at a flow rate of 0.4 mL/min, UV absorbance detection was set at λ = 360 nm. Linear responses were obtained (determination coefficient ≥ 0.9996). Intra-day precision (RSD) was ≤ 1.71% for corrected peak area ratio (AA to internal standard) and ≤ 0.55% for retention times (tR) without significant differences between intra- and inter-day data. Recovery studies showed good results for all the examined compounds (from 99.26 to 99.90%; RSD ≤ 1.29%)  %) with RSD ≤ 1.29%. The method was found to be specific and sensitive. The method can be useful for the quality control of commercial products.

Interaction of Taspine Derivative TPD7 with Vascular Endothelial Growth Factor Receptor 2 by Cell Membrane Chromatography Abstract Affinity chromatography, as one of the important tools for studying the binding affinity between ligands and receptors, plays a key role in the process of screening and analyzing active compounds. Cell membrane chromatography (CMC) utilizes cell membrane receptors as stationary phases to perform screening and binding affinity of compounds with specific receptors whose three-dimensional configurations and biological activities were largely retained. In this study, a highly vascular endothelial growth factor receptor 2 (VEGFR2) expressing CMC method was established to investigate the binding affinity between TPD7 and VEGFR2. Competitive binding study taking sunitinib malate as the marker was used to inspect the binding site of TPD7 on VEGFR2. Results showed that TPD7 shared the same binding site with sunitinib on VEGFR2, which was consistent with the results of molecular docking. The equilibrium dissociation constants (KD) of TPD7 was (0.29 ± 0.02) × 10−6 M. Furthermore, TPD7 could alter the VEGFR2 kinase and significantly decrease phosphorylation of VEGFR2 in a dose-dependent manner. The studies showed that TPD7 could bind to VEGFR2 and then down-regulate the phosphorylation of VEGFR2. Graphic Abstract

Qualitative and Quantitative Analysis of 24 Components in Jinlianhua Decoction by UPLC–MS/MS Abstract Jinlianhua Decoction (JD), composed of Flos Trollii, Herba Taraxaci, Folium Isatidis, Radix Puerariae Lobatae, and Folium Perillae in a ratio of 6:15:10:10:6, is a prescription for Fengwen which is a group of febrile diseases due to wind in Chinese medicine. It was originally used for the prevention and treatment of severe acute respiratory syndrome (SARS), and could also be used to treat influenza due to their common pathomechanism. To elucidate the unclear pharmacodynamic basis of JD, the LC-QExactive-MS system was used to qualitatively analyze its main components in this study. As a result, 89 compounds were identified and 24 important ones were selected thereby to further perform the simultaneous quantification in 8 batches of JD samples using LC-QTrap-MS with multiple reaction monitoring (MRM). Based on the qualitative and quantitative results in combination with the bioactivities reported, 16 compounds including orientin, 2″-O-β-l-galactopyranosylorientin, puerarin, trollisin I, rosmarinic acid, 2″-O-(2′″-methylbutanoyl) isoswertisin, daidzin, scutellarin, 3′-methoxy puerarin, vitexin, 3′-hydroxy puerarin, 2″-O-(2′″-methylbutanoyl) vitexin, kaempferol, caffeic acid, 3,4-dimethoxybenzoic acid, and cynaroside were determined as the major components of JD. This study provides a useful combinational method for analyzing the major pharmacodynamic substances of JD and lays a foundation for the quality control research of the decoction.

Ultrasound-Assisted Ionic Liquid Solid–Liquid Extraction Coupled with Aqueous Two-Phase Extraction of Naphthoquinone Pigments in Arnebia euchroma (Royle) Johnst. Abstract A simple, rapid and green ultrasound-assisted ionic liquid solid–liquid extraction coupled with aqueous two-phase extraction method was developed and applied to the extraction of shikonin, acetylshikonin and β,β′-dimethylacrylshikonin in Arnebia euchroma (Royle) Johnst. The separation and determination of the analytes was performed by high-performance liquid chromatography coupled with diode array detection. In the study, 1-butyl-3-methylimidazolium tetrafluoroborate ([C4MIM][BF4]) was used as extraction solvent. Ionic liquid-based solid–liquid extraction and aqueous two-phase extraction were performed simultaneously in one tube under the assistance of ultrasound. The liquid–liquid–solid three-phase system, namely surfactant-rich phase, water-rich phase and sample-rich phase, was formed. The target analytes were enriched in the surfactant-rich phase. Under the optimal experimental conditions, the calibration curves of target analytes showed good linear relationship (r > 0.9997). The inter-day and intra-day precision were in the range of 3.42–8.53 and 1.98–3.14%, respectively. The LOD and LOQ for the target analytes were in the range of 5.0–19.2 and 16.7–64.2 ng mL−1, respectively. The recoveries of naphthoquinone pigments ranged from 90.00 to 97.73% and relative standard deviations were less than 4.50%. Compared with heat reflux extraction and ultrasonic-assisted extraction, the proposed method is simpler, faster and more effective, because the mass transfer process for the analytes was always performed in one centrifugal tube and the steps such as filtration, concentration and redissolution were avoided. The present method was demonstrated to be efficient and satisfactory for the extraction of naphthoquinone pigments in medicinal plants. Graphic Abstract