The in‐capillary DPPH‐capillary electrophoresis‐the diode array detector combined with reversed‐electrode polarity stacking mode for screening and quantifying major antioxidants in Cuscuta chinensis Lam

An in‐capillary 2, 2‐diphenyl‐1‐picrylhydrazyl (DPPH)‐CE‐the DAD (in‐capillary DPPH‐CE‐DAD) combined with reversed‐electrode polarity stacking mode has been developed to screen and quantify the active antioxidant components of Cuscuta chinensis Lam. The operation parameters were optimized with regard to the pH and concentration of buffer solution, SDS, β‐CDs, organic modifier, as well as separation voltage and temperature. Six antioxidants including chlorogenic acid, p‐coumaric acid, rutin, hyperin, isoquercitrin, and astragalin were screened and the total antioxidant activity of the complex matrix was successfully evaluated based on the decreased peak area of DPPH by the established DPPH‐CE‐DAD method. Sensitivity was enhanced under reversed‐electrode polarity stacking mode and 10‐ to 31‐fold of magnitude improvement in detection sensitivity for each analyte was attained. The results demonstrated that the newly established in‐capillary DPPH‐CE‐DAD method combined with reversed‐electrode polarity stacking mode could integrate sample concentration, the oxidizing reaction, separation, and detection into one capillary to fully automate the system. It was considered a suitable technique for the separation, screening, and determination of trace antioxidants in natural products.     

Determination of the modes of action and synergies of xylanases by analysis of xylooligosaccharide profiles over time using fluorescence‐assisted carbohydrate electrophoresis

The structure of xylan, which has a 1,4‐linked β‐xylose backbone with various substituents, is much more heterogeneous and complex than that of cellulose. Because of this, complete degradation of xylan needs a large number of enzymes that includes GH10, GH11, and GH3 family xylanases together with auxiliary enzymes. Fluorescence‐assisted carbohydrate electrophoresis (FACE) is able to accurately differentiate unsubstituted and substituted xylooligosaccharides (XOS) in the heterogeneous products generated by different xylanases and allows changes in concentrations of specific XOS to be analyzed quantitatively. Based on a quantitative analysis of XOS profiles over time using FACE, we have demonstrated that GH10 and GH11 family xylanases immediately degrade xylan into sizeable XOS, which are converted into smaller XOS in a much lower speed. The shortest substituted XOS produced by hydrolysis of the substituted xylan backbone by GH10 and GH11 family xylanases were MeGlcA²Xyl₃ and MeGlcA²Xyl₄, respectively. The unsubstituted xylan backbone was degraded into xylose, xylobiose, and xylotriose by both GH10 and GH11 family xylanases; the product profiles are not family‐specific but, instead, depend on different subsite binding affinities in the active sites of individual enzymes. Synergystic action between xylanases and β‐xylosidase degraded MeGlcA²Xyl₄ into xylose and MeGlcA²Xyl₃ but further degradation of MeGlcA²Xyl₃ required additional enzymes. Synergy between xylanases and β‐xylosidase was also found to significantly accelerate the conversion of XOS into xylose.     

Paeonenoides D and E: Two New Nortriterpenoids from Paeonia lactiflora and Their Inhibitory Activities on NO Production

Two new nortriterpenoids, paeonenoides D and E ( 1 and 2 , resp.), together with seven known compounds, were isolated from the roots of Paeonia lactiflora. Their structures were elucidated on the basis of spectroscopic evidence. Compounds 1 – 7 were screened for inhibitory effects against NO production in LPS‐induced RAW246.7 macrophages and for cytotoxic activities against HL‐60, Hep‐G2, and SK‐OV‐3 cell lines. Compounds 1 – 3 and 5 – 7 exhibited inhibitory activities with IC₅₀ values in the range of 9.6–32.2 μM . Triterpenoids with an epoxide ring and a free COOH function, 1 – 3 , showed effectively increased activities compared with other pentacyclic triterpenoids. Compounds 1 – 6 showed significant cytotoxic activities against the Hep‐G2 cell line and modest cytotoxic activities against HL‐60 and SK‐OV‐3 cell lines.     

High Temperature Affects Photosynthetic and Molecular Processes in Field‐Cultivated Vitis vinifera L. × Vitis labrusca L.

High‐temperature stress markedly influences grape growth and development. However, how high‐temperature stress response differs between controlled and field‐cultivated grape is poorly understood. In this study, the effects of heat treatment on grapevines were studied for changes in photosystem II (PSII) activity and expression levels of heat‐responsive genes and heat shock protein HSP21. July 31st, 2015 was considered as the post high‐temperature treatment (“42°C”; temperatures above 40°C for a period of time each day ranging from 1–7 h) under field cultivation in our experiment. The recovery of chlorophyll fluorescence indicators and the increasing expression of heat‐responsive genes and the heat shock protein HSP21 suggested the development of heat tolerance in the form of acclimation in grape. Changes in various parameters of photosynthetic pigment fluorescence and of the electron transport chain (Fv/Fm, PI_ABS, W_k, RC_QA, Φ_Po, and Φ_Eo) between “42°C” and the 45°C treatment demonstrated that the donor side, reaction center, and acceptor side of PSII were influenced by a critical high temperature. Furthermore, the difference between the two cultivation conditions studied was attributed to other environmental factors and inherent tree vigor.     

Bioassay‐guided isolation of an active compound with protein tyrosine phosphatase 1B inhibitory activity from Sargassum fusiforme by high‐speed counter‐current chromatography

A rapid and efficient method using high‐speed counter‐current chromatography was established for the bioassay‐guided separation of an active compound with protein tyrosine phosphatase 1B inhibitory activity from Sargassum fusiforme. Under the bioassay guidance, the ethyl acetate extract with the best IC₅₀ value of 0.37 ± 0.07 μg/mL exhibited a potential protein tyrosine phosphatase 1B inhibitory activity, which was further separated by high‐speed counter‐current chromatography. The separation was performed with a two‐phase solvent system composed of n‐hexane/methanol/water (5:4:1, v/v). As a result, dibutyl phthalate (19.7 mg) with the purity of 95.3% was obtained from 200 mg of the ethyl acetate extract. Its IC₅₀ was 14.05 ± 0.06 μM, which was further explained by molecular docking. The result of molecular docking showed that dibutyl phthalate enfolded in the catalytic site of protein tyrosine phosphatase 1B. The main force between dibutyl phthalate and protein tyrosine phosphatase 1B was the hydrogen bond interaction with Gln266. In addition, hydrogen bond, van der Waals force and hydrophobic interaction with the amino acids (Ala217, Ile219, and Gly220) were also responsible for the stable protein‐ligand complex.     

生色冠醚研究.Ⅱ.2、6-二溴靛酚冠醚在甲醇溶液中与碱金属和碱土金属盐的变色作用

冠醚化酚(1a,1b)和酚型开链冠醚(2a,2b)在甲醇中氢氧化锂的作用下,与2、6—二溴醌氯亚胺反应,生成兰色的2、6—二溴靛酚冠醚(1c,1d,2c,2d)锂盐。在其甲醇溶液中加入其它碱金属和碱土金属盐时,产生颜色变化,其中以2c和2d表现出对Sr~(2+)和Ba~(2+)有较明显的选择性变色作用,其△λ_(max)(nm)分别为:2c:38(SrCl_2),37(BaCl_2);2d:64(SrCl_2),56(BaCl_2)。还考查了介质中含水量对变色作用的影响和锶盐的阴离子效应,探讨了选择性变色作用的机理。     

用超临界气体抽提方法研究抚顺烟煤的组成和结构——Ⅰ.抽出物的分离及GC、GC/MS分析

将抚顺烟煤用甲苯作溶剂,在半连续抽提装置上,于350℃、20MPa条件下,进行超临界气体抽提。抽出物先分离成油、沥青烯及前沥青烯三个族组份,再用离子交换树脂、硅胶柱色谱作进一步分离。GC和GC/MS的分析结果表明,油段分中存在正构烷烃(C_(13)—C_(31))、类异戊二烯化合物及长链烷基苯系列,这些化合物可提供抚顺烟煤的地球化学信息。     

新型无泵阀毛细管等速电泳仪的研制——Ⅰ.积木式分离管路结构及电位梯度检测器

本文介绍本实验室研制的新型无泵阀毛细管等速电泳仪的积木式分离管路结构及电位梯度检测器,该管路结构及检测器构造均较现有的仪器简单、合理,拆卸和组接方便,造价低廉,用其构成的无泵阀毛细管等速电泳仪分离分析阴、阳离子样品,结果表明该仪器的检测灵敏度及重现性等均良好。