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BrOnsted-Acid-Catalyzed Substrate-Controlled and Site-Selective Friedel-Crafts Alkylation: A New Strategy for Post-Modification of 1,2-Dihydroquinolines
No full textA variety of C3-, C6-, C8- and C13-functionalized 1,2-dihidroquinolines (1,2-DHQs) have been prepared through post-modification of simple 1,2-DHQs by regioselective Friedel-Crafts alkylations. Several commonly used electrophiles such as 3-indolylmethanol derivatives, nitroolefins, 1,4-benzoquinones, aromatic aldehydes and ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline were rationally used to afford the corresponding 1,2-DHQs with high yield and regioselectivity. The regioselectivity of the reaction appears to be governed by the substituents of the 1,2-DHQ substrates
A tandem annulation with a [1,3]-hydride transfer as the key step leading to isochromans
No full textAn unprecedented method that enables the direct coupling of an alpha-C-H bond in alcohols with 2-arylacetaldehydes through a [1,3]-hydride transfer ([1,3]-HT) of oxocarbenium ions catalyzed by a Lewis acid has been developed. The redox neutral preparation of the isochroman derivatives proceeds via a tandem condensation/[1,3]-HT/Friedel-Crafts sequence with moderate to good yields. Deuterium-labeling studies provide mechanistic insights and reveal that the redox functionalization proceeds via a [1,3]-HT
Semi-IPNs with Moisture-Triggered Shape Memory and Self-Healing Properties
No full textMoisture or water has the advantages of being green, inexpensive, and moderate. However, it is challenging to endow water-induced shape memory property and self-healing capability to one single polymer because of the conflicting structural requirement of the two types of materials. In this study, this problem is solved through introducing two kinds of supramolecular interactions into semi-interpenetrating polymer networks (semi-IPNs). The hydrogen bonds function as water-sensitive switches, making the materials show moisture-induced shape memory effect. The host-guest interactions (-cyclodextrin-adamantane) serve as both permanent phases and self-healing motifs, enabling further increased chain mobility at the cracks and self-healing function. In addition, these polyvinylpyrrolidone/poly(hydroxyethyl methacrylate-co-butyl acrylate) semi-IPNs also show thermosensitive triple-shape memory effect
PEGylation of magnetic multi-walled carbon nanotubes for enhanced selectivity of dispersive solid phase extraction
No full textCarbon nanotubes (CNTs) possess large potential as extraction absorbents in solid phase extraction. They have been widely applied in biomedicine research, while very rare application in natural product chemistry has been reported. In this work, methoxypolyethylene glycol amine (mPEG-NH2) is covalently coupled to CNTsmagnetic nanoparticles (CNTs-MNP) to prepare a novel magnetic nanocomposite (PEG-CNTs-MNP) for use as dispersive solid-phase extraction (DSPE) absorbent. The average particle size was 86 nm, and the saturation magnetization was 52.30 emu/g. This nanocomposite exhibits excellent dispersibility in aqueous systems, high selectivity and fast binding kinetics when used for extraction of Z-ligustilide, the characteristic bioactive compound from two popular Asian herbal plants, R chuanxiong and R. ligusticum. HPLC quantification of Z-ligustilide extracted from the standard sample solution showed a high recovery of 98.9%, and the extraction rate"from the extracts of the above two herbs are both around 70.0%. To our knowledge, this is the first report on using PEG-CNTs-MNP as DSPE nanosorbents for selective extraction of natural products. This nano-material has promising application in isolation and enrichment of targeted components from complex matrices. (C) 2016 Elsevier B.V. All rights reserved
Screening of novel RGD peptides to modify nanoparticles for targeted cancer therapy
No full textNew targeted RGD peptides obtained by solid phase peptide synthesis (SPPS) were successfully screened by Molecular Operating Environment (MOE) and used for the building of the 6-O-carboxymethyl chitosan based carrier with an active target on the surface. CRGDYC-6-O-carboxymethyl chitosan based nanoparticles (NPs) loaded with doxorubicin hydrochloride (DOX) were successfully prepared by an ionic gelation method with the carrier synthesized before. Synthesis conditions and formulation parameters were optimized by determining the characteristics of nanoparticles including the particle size and drug encapsulation efficiency. 6-O-Carboxymethyl chitosan concentration, calcium chloride concentration and calcium chloride/6-O-carboxymethyl chitosan ratio all had effects on the particle size and drug encapsulation efficiency. Nanoparticles with an average diameter of 193.4 nm, an average drug loading efficiency of up to 69.5% and an average drug loading of up to 0.395% were prepared successfully with the optimal formulation. Flow cytometry and confocal microscopy analyses showed that the cellular uptake of DOX in human breast cancer cell lines (MCF-7) was higher in the CRGDYC-modified nanoparticles compared with the unmodified nanoparticles. In vivo imaging showed that the distribution of CRGDYC-modified nanoparticles in the tumor site was higher compared with the unmodified nanoparticles. These results suggest that CRGDYC-6-O-carboxymethyl chitosan may be a promising cancer targeting carrier which can enhance the intracellular uptake and cytotoxicity of the drug-loaded nanoparticles
溴代乙酰葡萄糖和溴代乙酰鼠李糖的便捷合成
No full text以高氯酸为催化剂,D-葡萄糖和L-鼠李糖分别与乙酸酐反应,制得相应的全乙酰化糖,不经分离直接加入乙酰溴和甲醇,利用反应生成的溴化氢原位发生溴代反应,一锅法制备了溴代乙酰葡萄糖和溴代乙酰鼠李糖,收率分别达到92.5%和85.6%。从产品结晶后的母液中,以干燥的二氯甲烷作溶剂,采用重结晶法分离得到溴代乙酰鼠李糖合成的副产物2,3,4-三-O-乙酰基鼠李糖。产品和副产物的结构均经过核磁共振氢谱、碳谱和高分辨质谱确认
桂枝茯苓丸抗大鼠慢性心衰的实验研究
No full text目的:研究桂枝茯苓丸对异丙肾上腺素诱导大鼠慢性心衰模型的影响,并初步探讨药物对AngⅡ、TGF-β相关因子的影响.方法:健康SD大鼠60只,体重180~220 g,按体质量随机分为6组,即空白对照组、模型对照组、桂枝茯苓丸1.125 g/kg剂量组、桂枝茯苓丸2.25 g/kg剂量组、桂枝茯苓丸4.5 g/kg剂量组和阳性药物对照组(普萘洛尔).建立异丙肾上腺素致大鼠慢性心衰模型,并给予相应药物治疗15 d.末次给药后12 h,麻醉后取血,分别检测血清AST、ALT、CK和LDH水平.取心脏,固定,采用免疫组化方法分别检测心肌TGF-β和AngⅡ的表达水平.结果:与模型对照组相比,桂枝茯苓丸能明显或部分降低ALT的水平(P<0.05~0.01);抑制TGF-β、AngⅡ的表达(P<0.01~0.05).结论:桂枝茯苓丸具有一定的减轻慢性心衰大鼠心肌损伤的作用,其心肌保护机制可能与TGF-β、AngⅡ的降低有关
一测多评法同时测定降脂减肥保健品中儿茶素类活性成分的含量
No full text目的:建立同时测定减肥降脂保健品中儿茶素类活性成分含量的方法。方法:采用高效液相色谱法,以表没食子基儿茶素没食子酸酯(EGCG)为内标,计算其与没食子儿茶素(EGC)、儿茶素(C)、表儿茶素(EC)、没食子基儿茶素没食子酸酯(GCG)和没食子酰表儿茶素(ECG)的相对校正因子(RCF),通过RCF计算样品中EGC、C、EC、GCG、ECG的含量,以外标法测定的EGC、C、EC、GCG和ECG含量作实测值;采用向量夹角余弦法评估实测值与计算值之间的相似性。结果:EGC、C、EC、EGCG、GCG、ECG检测质量浓度线性范围分别为0.006 5~0.130 5 mg/m L(r=0.999 8)、0.000 5~0.010 7 mg/m L(r=0.999 7)、0.002 0~0.040 0mg/m L(r=0.999 9)、0.015 3~0.305 3 mg/m L(r=0.999 8)、0.000 8~0.015 5 mg/m L(r=0.999 8)、0.004 0~0.079 2 mg/m L(r=0.999 9);精密度、稳定性、重复性试验的RSD0.05)。结论:该方法操作简便,精密度、稳定性、重复性好,可用于减肥降脂保健品中儿茶素类活性成分的含量测定
Crystal structure and iterative saturation mutagenesis of ChKRED20 for expanded catalytic scope
No full textChKRED20 is an efficient and robust anti-Prelog ketoreductase that can catalyze the reduction of ketones to chiral alcohols as pharmaceutical intermediates with great industrial potential. To overcome its limitation on the bioreduction of ortho-substituted acetophenone derivatives, the X-ray crystal structure of the apo-enzyme of ChKRED20 was determined at a resolution of 1.85 and applied to the molecular modeling and reshaping of the catalytic cavity via three rounds of iterative saturation mutagenesis together with alanine scanning and recombination. The mutant Mut3B was achieved with expanded catalytic scope that covered all the nine substrates tested as compared with two substrates for the wild type. It exhibited 13-20-fold elevated k (cat)/K (m) values relative to the wild type or to the first gain-of-activity mutant, while retaining excellent stereoselectivity toward seven of the substrates (98-> 99% ee). Another mutant 29G10 displayed complementary selectivity for eight of the ortho-substituted acetophenone derivatives, with six of them delivering excellent stereoselectivity (90-99% ee). Its k (cat)/K (m) value toward 1-(2-fluorophenyl)ethanone was 5.6-fold of the wild type. The application of Mut3B in elevated substrate concentrations of 50-100 g/l was demonstrated in 50-ml reactions, achieving 75-> 99% conversion and > 99% ee
The process-related dynamics of microbial community during a simulated fermentation of Chinese strong-flavored liquor
No full textBackground: Famous Chinese strong-flavored liquor (CSFL) is brewed by microbial consortia in a special fermentation pit (FT). However, the fermentation process was not fully understood owing to the complicate community structure and metabolism. In this study, the process-related dynamics of microbial communities and main flavor compounds during the 70-day fermentation process were investigated in a simulated fermentation system. Results: A three-phase model was proposed to characterize the process of the CSFL fermentation. (i) In the early fermentation period (1-23 days), glucose was produced from macromolecular carbohydrates (e.g., starch). The prokaryotic diversity decreased significantly. The Lactobacillaceae gradually predominated in the prokaryotic community. In contrast, the eukaryotic diversity rose remarkably in this stage. Thermoascus, Aspergillus, Rhizopus and unidentified Saccharomycetales were dominant eukaryotic members. (ii) In the middle fermentation period (23-48 days), glucose concentration decreased while lactate acid and ethanol increased significantly. Prokaryotic community was almost dominated by the Lactobacillus, while eukaryotic community was mainly comprised of Thermoascus, Emericella and Aspergillus. (iii) In the later fermentation period (48-70 days), the concentrations of ethyl esters, especially ethyl caproate, increased remarkably. Conclusions: The CSFL fermentation could undergo three stages: saccharification, glycolysis and esterification. Saccharomycetales, Monascus, and Rhizopus were positively correlated to glucose concentration (P < 0.05), highlighting their important roles in the starch saccharification. The Lactobacillaceae, Bacilli, Botryotinia, Aspergillus, unidentified Pleosporales and Capnodiales contributed to the glycolysis and esterification, because they were positively correlated to most organic acids and ethyl esters (P < 0.05). Additionally, four genera, including Emericella, Suillus, Mortierella and Botryotinia, that likely played key roles in fermentation, were observed firstly. This study observed comprehensive dynamics of microbial communities during the CSFL fermentation, and it further revealed the correlations between some crucial microorganisms and flavoring chemicals (FCs). The results from this study help to design effective strategies to manipulate microbial consortia for fermentation process optimization in the CSFL brew practice