Biological activity and LC-MS profiling of ethyl acetate extracts from Nitraria sibirica (Pall.) fruits

Nitraria sibirica is a traditional Uighur medicine. This study was undertaken to investigate the bioactivity of N. sibirica fruit extract and to evaluate their chemical compositions. The ethyl acetate extract from N. sibirica fruits exhibited the potential antioxidant activity (SC₅₀ = 30.17 ± 0.06 μg/mL) and protein tyrosine phosphatase 1B inhibitory activity (IC₅₀ = 7.15 ± 0.03 μg/mL) in vitro. In order to investigate the active constituents in this extract, a LC-QTOF-MS/MS method was developed and established. A total of 28 compounds including seven cinnamic acids, nine benzoic acids and 12 flavonoids were identified or partially characterised according to the accurate mass and the characteristic fragment ions at low and high collision energy. Most of them were reported for the first time in this plant. Phytochemical profiles of the active extract will help the development and utilisation of N. sibirica in food and medicine.     

A reversed-phase capillary ultra-performance liquid chromatography-mass spectrometry (UPLC-MS) method for comprehensive top-down/bottom-up lipid profiling

Lipidomics is a critical part of metabolomics and aims to study all the lipids within a living system. We present here the development and evaluation of a sensitive capillary UPLC-MS method for comprehensive top-down/bottom-up lipid profiling. Three different stationary phases were evaluated in terms of peak capacity, linearity, reproducibility, and limit of quantification (LOQ) using a mixture of lipid standards representative of the lipidome. The relative standard deviations of the retention times and peak abundances of the lipid standards were 0.29% and 7.7%, respectively, when using the optimized method. The linearity was acceptable at >0.99 over 3 orders of magnitude, and the LOQs were sub-fmol. To demonstrate the performance of the method in the analysis of complex samples, we analyzed lipids extracted from a human cell line, rat plasma, and a model human skin tissue, identifying 446, 444, and 370 unique lipids, respectively. Overall, the method provided either higher coverage of the lipidome, greater measurement sensitivity, or both, when compared to other approaches of global, untargeted lipid profiling based on chromatography coupled with MS.     

Numerical solution of nonlinear fractional-order Volterra integro-differential equations by SCW

Fractional calculus is an extension of derivatives and integrals to non-integer orders and has been widely used to model scientific and engineering problems. In this paper, we describe the fractional derivative in the Caputo sense and give the second kind Chebyshev wavelet (SCW) operational matrix of fractional integration. Then based on above results we propose the SCW operational matrix method to solve a kind of nonlinear fractional-order Volterra integro-differential equations. The main characteristic of this approach is that it reduces the integro-differential equations into a nonlinear system of algebraic equations. Thus, it can simplify the problem of fractional order equation solving. The obtained numerical results indicate that the proposed method is efficient and accurate for this kind equations.     

Adsorption and Desorption Characteristics of Total Flavonoids from Acanthopanax senticosus on Macroporous Adsorption Resins

We examined the application of six different resins with the aim of selecting a macroporous resin suitable for purifying Acanthopanax senticosus total flavonoids (ASTFs) from Acanthopanax senticosus crude extract (EAS) by comparing their adsorption/desorption capacities, which led to the selection of HPD-600. Research on the adsorption mechanism showed that the adsorption process had pseudo-second-order kinetics and fit the Freundlich adsorption model. Moreover, the analysis of thermodynamic parameters indicated that the adsorption process is spontaneous and endothermic. The optimal conditions for purification of ASTFs were determined as sample pH of 3, 60% ethanol concentration, and 3 BV·h⁻¹ flow rate, for both adsorption and desorption, using volumes of 2.5 and 4 BV, respectively. The application of macroporous resin HPD-600 to enrich ASTFs resulted in an increase in the purity of total flavonoids, from 28.79% to 50.57%. Additionally, the antioxidant capacity of ASTFs was higher than that of EAS, but both were lower than that of L-ascorbic acid. The changes in ASTFs compositions were determined using ultra-performance liquid chromatography–tandem mass spectrometry (UHPLC–MS/MS), with the results illustrating that the levels of seven major flavonoids of ASTFs were increased compared to that in the crude extract.     

A NEW MODEL FOR ESTIMATION OF DIFFUSION COEFFICIENT OF PHENOL DESORPTION WITHIN POLYMERIC RESIN UNDER ULTRASOUND

1. INTRODUCTION Ultrasound is a kind of mechanical wave whose frequency is more than 20 kilohertz. It can enhance the mass transfer, increase the rate and conversion of chemical reaction, change the reaction pathway [1,2] and accelerate the conversion of…     

Experimental and molecular simulation studies of CO2 adsorption on zeolitic imidazolate frameworks: ZIF-8 and amine-modified ZIF-8

ZIF-8 has been rapidly developed as a potential candidate for CO₂ capture due to its low density, high surface area, and robust structure. Considering the electron-donating effect of amino functional groups, amino-modification is expected to be an efficient way to improve CO₂ adsorption of ZIF-8. In this work, grand canonical Monte Carlo (GCMC) simulation was performed to study the CO₂ adsorption isotherm based on ZIF-8, ZIF-8-NH₂, and ZIF-8-(NH₂)₂. ZIF-8 was synthesized and CO₂ adsorption isotherms based on ZIF-8 was measured. The experimental surface area, pore volume, and CO₂ adsorption isotherm were used to validate the force field. Adsorptive capacity of ZIF-8-NH₂, and ZIF-8-(NH₂)₂ were first estimated. The GCMC simulation results indicated that the order of increasing CO₂ capacity of the ZIF-8 in the lower pressure regime is: ZIF-8 < ZIF-8-NH₂ < ZIF-8-(NH₂)₂, and in the high pressure is: ZIF-8 < ZIF-8-(NH₂)₂ < ZIF-8-NH₂. New adsorption sites can be generated with the existence of-NH₂ groups. In addition, for non-modified and amino-modified ZIF-8, it was the first time to use density functional theory (DFT) calculations to investigate their CO₂ adsorption sites and CO₂ binding energies. The present work indicates that appropriate amine-functionalized can directly enhanced CO₂ capacity of ZIF-8.     

Multimodal Use of New Coumarin‐Based Fluorescent Chemosensors: Towards Highly Selective Optical Sensors for Hg2+ Probing

Despite several types of fluorescent sensing molecules have been proposed and examined to signal Hg²⁺ ion binding, the development of fluorescence‐based devices for in‐field Hg²⁺ detection and screening in environmental and industrial samples is still a challenging task. Herein, we report the synthesis and characterization of three new coumarin‐based fluorescent chemosensors featuring mixed thia/aza macrocyclic framework as receptors units, that is, ligands L1 – L3 . These probes revealed an OFF–ON selective response to the presence of Hg²⁺ ions in MeCN/H₂O 4:1 (v/v), which allowed imaging of this metal ion in Cos‐7 cells in vitro. Once included in silica core–polyethylene glycol (PEG) shell nanoparticles or supported on polyvinyl chloride (PVC)‐based polymeric membranes, ligands L1 – L3 can also selectively sense Hg²⁺ ions in pure water. In particular we have developed an optical sensing array tacking advantage of the fluorescent properties of ligand L3 and based on the computer screen photo assisted technique (CSPT). In the device ligand L3 is dispersed into PVC membranes and it quantitatively responds to Hg²⁺ ions in natural water samples.     

碳化钨对激光熔覆高熵合金的影响

为了获得高性能的涂层材料,采用激光熔覆的方法,在Q235钢基体上制备了FeSiCrCoMo高熵合金涂层,并研究了WC对高熵合金涂层的组织和性能的影响。通过金相、X射线衍射、扫描电镜、硬度计、磨损试验机分别研究了添加WC前后涂层的微观形貌、相结构、硬度及磨损性能。结果表明:高熵合金FeSiCrCoMo涂层组织为粗大枝状晶,主要由BCC相和金属间化合物构成,添加WC后,涂层中形成了致密细小的胞状晶,同时BCC相增多,金属间化合物明显减少;添加WC后涂层的硬度明显增强,平均硬度提升了23%,涂层表面平均硬度达到了687HV0.2;WC的添加使得涂层的摩擦系数减小,磨损率减小,耐磨性能提高。     

Independent generation of the 5-hydroxy-5,6-dihydrothymidin-6-yl radical and its reactivity in dinucleoside monophosphates

Hydroxyl radical is a major reactive oxygen species produced by gamma-radiolysis of water or Fenton reaction. It attacks pyrimidine bases and gives the 5-hydroxy-5,6-dihydropyrimidin-6-yl radical as the major product. Here we report the synthesis of all four stereoisomers of 5-hydroxy-6-phenylthio-5,6-dihydrothymidine (T*), which, upon 254 nm UV irradiation, give rise to the 5-hydroxy-5,6-dihydrothymidin-6-yl radical (I). We also incorporated the photolabile radical precursors into dinucleoside monophosphates d(GT*) and d(TT*) and characterized major products resulting from the 254-nm irradiation of these dinucleoside monophosphates. Our results showed that, under anaerobic conditions, the most abundant product emanating from the 254-nm irradiation of d(GT*) and d(TT*) is an abasic site lesion. Products with the thymine portion being modified to thymine glycol and 5-hydroxy-5,6-dihydrothymine were also observed. In addition, we demonstrated that radical I can attack the C8 carbon atom of its 5' neighboring guanine and give rise to a novel cross-link lesion. Moreover, LC-MS/MS results showed that gamma-radiation of d(GT) under anaerobic condition yielded the same type of cross-link lesions.