植物内生真菌抗菌活性物质的研究进展

植物内生真菌的代谢产物中存在一系列具有多样性结构的抗菌活性化合物.对植物内生真菌所产生的抗菌活性物质的结构、对细菌和真菌的抑制效果,以及这些内生真菌的寄主植物等几方面进行了综述.简单讨论了植物内生真菌-寄主植物之间的化学生态学关系、植物内生真菌代谢物的研究价值.希望通过这些活性物质的研究能够开发出更多新型强活性抗生素.     

13位取代苦参碱衍生物抗癌活性的定量构效关系研究

采用密度泛函理论B3LYP方法计算了13个13位取代苦参碱衍生物的电子结构,研究了化合物结构与抑制人肝癌细胞HepG2抗癌活性的定量构效关系(QSAR).结果表明:(1)13位取代的苦参碱类衍生物的最低空轨道能ELUMO越低,最低空轨道与最高占据轨道的能隙ΔE越小,化合物抗癌活性越高;(2)分子的能量Etotal、面积S以及体积V越大,其极化度P越大,活性越大;(3)分子的油水分配系数logP越大,活性越大,即分子的疏水性增大活性增强.综合得到了显著性较好的QSAR方程:-lgIC50=97.008-11.759ΔE+818.602QC2-2.132×10-4Etotal,可用于预测该类衍生物抑制人肝癌细胞HepG2的活性并进行分子设计.     

液相色谱-串联离子阱质谱测定牛奶中的12种β-内酰胺类药物残留的方法研究

β-内酰胺类抗生素是畜牧和牛乳生产中最广泛应用的治疗动物细菌感染的抗生素.而青霉素类和头孢类抗生素作为两类重要的β-内酰胺类抗生素,也是使用最广泛的治疗牛乳腺炎和其它乳牛疾病的抗生素.     

咪唑并吡啶类化合物结构及PDE抑制活性的三维构效关系研究

对咪唑并吡啶类化合物作为环核苷酸磷酸二酯酶(PDE)的抑制剂的抑制活性进行了比较分子力场分析.结果表明,立体效应和静电作用场是描述对PDE抑制活性和进行结构性能关系研究的最重要的结构参数,提出了对该类化合物进行结构修饰的方法,并由新建立的三维定量构效关系模型对该类化合物的PDE抑制活性进行了预报.     

呋虫胺衍生物杀虫活性的理论研究

基于Chem3D Ultra 7.0软件中的MOPAC半经验方法 AM1,计算了13种呋虫胺衍生物的19个量子化学和理化参数(包括ELUMO、EHOMO、△E=ELUMO-EHOMO、QC1、QC2、QN、QN1~QN4、QO、QO、μ、Hf、Ve、E0、Cv、Sm等)。采用最佳变量子集回归方法,建立呋虫胺衍生物对褐飞虱杀虫活性与上述结构参数的定量构效关系模型。结果表明,呋虫胺衍生物对褐飞虱杀虫活性的大小与ELUMO、QN1呈负相关,而与QC2正相关。所建的最优三变量模型具有良好的预报能力(R2=0.928、Rcv2=0.805、Rcv-22=0.797)和较高的稳健性(Radj2、F、VIF、t、AIC和FIT等检验)。设计与预测了4种新颖化合物的杀虫活性,在浓度为500mg/dm3下,它们的杀虫活性预测值均超过115%。所建模型可为化学工作者合成新型高效新烟碱类化合物提供理论参考。     

Theoretical Studies on Quantitative Structure-Activity Relationship and Structural Modification for 3-Substituted Sulfur-5（2-Hydr0xyphenyl）-4H-1,2,4-Triazole Compounds

用DFT-B3LYP方法,在基组6-31G水平,对24种3-取代硫基-5-（2-羟基苯基）-4H-1,2,4-三唑类化合物分子进行几何优化,并计算了EHOMO,ELUMO,ENHOMO,ENLUMO,QC1～QC8,QN1～QN3,QO,QS和ΔE1,ΔE2,ΣQ等量子化学描述符（qc）.通过最佳变量子集回归建立13种上述化合物对大肠杆菌、白色念珠菌、金黄色葡萄球菌等抑菌活性（AJ：Ae,Am和As）的QSAR模型.对于大肠杆菌的Ae模型的相关系数（R2）和逐一剔除法交叉验证系数Rcv2依次为0.930和0.871,相应白色念珠菌Am模型为0.926和0.869,As模型为0.781和0.572.通过Radj2,F,Rcv2,VIF,AIC,FIT等检验,上述模型具有令人满意的稳健性和预测能力.结果显示ΔE1和ΣQ直接影响这些化合物的生物活性：ΣQ增大,其抑菌活性增强;ΔE1越高,AJ下降.据此提出三唑类化合物分子可能的抑菌机理.由此发现,在三唑类化合物分子的R中合适部位选用吸电子能力较强的取代基团进行结构修饰,有利于提高被修饰后分子的抑菌活性.根据对R进行结构修饰（共提出11种化合物）,得出4种抑菌活性均超出100%的三唑类化合物（质量分数为0.01%）,希望将来得到生物实验的证实.     

1,4,2-二氮磷杂环戊-5-(硫)酮类化合物除草活性的构效关系研究

利用与自由能有关的取代基的物理化学参数,考察了1,4,2－二氮磷杂环戊－5－(硫)酮类化合物对除草活性的相关性.根据Hansch方程及多元回归分析,进行了结构与活性定量关系的研究,建立了较好的结构与活性相关式,预测出化合物的活性并得到实验证实.     

两个典型头孢类β-内酰胺抗生素的化学发光特性比较

研究发现Ce(Ⅳ)氧化含巯基(-SH)的化合物能产生弱发光,且Rh6G能大大增强此弱发光,由此建立了测定头孢类β-内酰胺类抗生素的FIA-CL分析法.在选定的最佳条件下,经测试,几个典型的头孢类抗生素化学发光强度均在1.0×10-8～1.5×10-5 g/mL范围内与其浓度呈良好的线性关系.头孢哌酮钠和头孢拉定的化学发光特性具有突出的差异.     

海洋放线菌S592次级代谢产物及其体外抑菌活性研究

对海洋放线菌S592的次级代谢产物以及体外抑菌活性进行研究.将菌株S592进行大量发酵,采用色谱方法对菌株发酵产物进行分离纯化,通过波谱技术对所获单体化合物进行结构鉴定,并测定化合物的体外抑菌活性.从海洋放线菌S592中分离得到6个化合物,含2个螺环抗生素lobophorin类化合物,1个环肽类化合物,2个苯甲酰胺类化...     

双环β－内酰胺抗生素分子活性构象的理论研究

研究了青霉素、△￣３－头孢菌素和△￣２－头孢菌素等３种典型双β－内酰胺抗生素的构象与活性的关系，指出桥碳原子和与侧酰胺键相连的碳原子的构型是影响它们活性的重要结构因素．     

An Effective and Convenient Esterefication of Cephalospor in Derivatives by Using Quarternary Ammonium Salts as Catalysts

A method for preparing cephalosporin derivatives by reacting cephalosporin alkaline metal salts with organic halide in the presence of quarternary ammonium salts catalyst is disclosed. Δ³ to Δ² isomerization, a side reaction commonly reported in preparation of cephalosporin derivatives, was successfully eliminated. The desired Δ³ was obtained as a sole product in the reaction.     

Photoswitchable Norbornadiene–Quadricyclane Interconversion Mediated by Covalently Linked C60

The synthesis and properties of various norbornadiene/quadricyclane (NBD/QC) fullerene hybrids are reported. By cyclopropanation of C₆₀ with malonates carrying the NBD scaffold a small library of NBD–fullerene monoadducts and NBD–fullerene hexakisadducts was established. The substitution pattern of the NBD scaffold, as well as the electron affinity of the fullerene core within these hybrid systems, has a pronounced impact on the properties of the corresponding energy rich QC derivatives. Based on this, the first direct photoisomerization of NBD–fullerene hybrids to their QC derivatives was achieved. Furthermore, it was possible to use the redox-active fullerene core of a QC–fullerene monoadduct to enable the back reaction to form the corresponding NBD–fullerene monoadduct. Combining these two processes enables switching between NBD and QC simply by changing the irradiation wavelength between 310 and 400 nm. Therefore, turning this usually photo/thermal switch into a pure photoswitch. This not only simplifies the investigation of the underlying processes of the NBD–QC interconversion within the system, but also renders such hybrids interesting for applications as molecular switches.     

Studies on orally active cephalosporin esters. V. A prodrug approach for oral delivery of 3-thiazoliomethyl cephalosporin

Oral delivery of 3-thiazoliomethyl cephalosporin 1 was attempted through a prodrug approach by applying thiamine chemistry. The 3-thiazoliomethyl group was modified to a ring-opened structure with no ionic charge, and the 4-carboxyl group was converted to pivaloyloxymethyl ester. Lipophilicity of the resulting derivatives (8-10) was suitable for passive absorption from the intestinal tract, and chemical stability in phosphate buffer solution (pH 6.86) was moderate. When administered orally to mice, these derivatives were mainly transformed to a novel 3-spiro cephalosporin 11, and desired reconversion to the 3-thiazoliomethyl cephalosporin was minor. Isomerization to delta 2-cephalosporin 14 was also observed. These results showed that the derivatives (8-10) tested in this study did not serve as orally active prodrugs of 3-thiazoliomethyl cephalosporin 1.     

Repurposing FDA-Approved Compounds for the Discovery of Glutaminyl Cyclase Inhibitors as Drugs Against Alzheimer's Disease

Alzheimer's disease (AD) is one of the most common neurodegenerative causes of dementia, the pathology of which is still not much clear. It′s challenging to discover the disease modifying agents for the prevention and treatment of AD over the years. Emerging evidence has been accumulated to reveal the crucial role of up-regulated glutaminyl cyclase (QC) in the initiation of AD. In the current study, the QC inhibitory potency of a library consisting of 1621 FDA-approved compounds was assessed. A total of 54 hits, 3.33 % of the pool, exhibited QC inhibitory activities. The Ki of the top 5 compounds with the highest QC inhibitory activities were measured. Among these selected hits, compounds affecting neuronal signaling pathways and other mechanisms were recognized. Moreover, several polyphenol derivatives with QC inhibitory activities were also identified. Frameworks and subsets contained in these hits were analyzed. Taken together, our results may contribute to the discovery and development of novel QC inhibitors as potential anti-AD agents.     

Tunable Photoswitching in Norbornadiene (NBD)/Quadricyclane (QC) – Fullerene Hybrids

With respect to molecular switches, initializing the quadricyclane (QC) to norbornadiene (NBD) back-reaction by light is highly desirable. Our previous publication provided a unique solution for this purpose by utilizing covalently bound C₆₀. In this work, the fundamental processes within these hybrids has been investigated. Variation of the linker unit connecting the NBD/QC moiety with the fullerene core is used as a tool to tune the properties of the resulting hybrids. Utilizing the Prato reaction, two unprecedented NBD/QC – fullerene hybrids having a long-rigid and a short-rigid linker were synthesized. Molecular dynamics simulations revealed that this results in an average QC–C₆₀ distance of up to 14.2 Å. By comparing the NBD–QC switching of these derivatives with the already established one having a flexible linker, valuable mechanistic insights were gained. Most importantly, spatial convergence of the QC moiety and the fullerene core is inevitable for an efficient back-reaction.     

Synthesis of 3-Alkylidenecepham-4-carboxylic Acid derivatives by Samarium(II) Iodide Reduction

Samarium(II) iodide promoted reductive deacetoxylation of 7-aminocephalosporanic acid derivatives to synthesize 3-alkylidenecepham-4-carboxylates, which could be valuable intermediates for the synthesis of new cephalosporin antibiotics, was investigated.     

Quaternized celluloses as new dynamic coatings in capillary electrophoresis for basic protein separation

In this work, a series of quaternized celluloses (QCs), homogeneously synthesized in the NaOH/urea aqueous solutions, were studied as dynamic coatings for capillary electrophoresis. Capillaries coated with these cationic cellulose derivatives at the concentration as low as 3 μg/mL were able to generate a stable, reversed electroosmotic flow. The effects of QC molecular parameters, such as the degree of cationic substitution and molecular weight, and the effect of buffer pH on the EOF mobility as well as the separation of basic proteins were investigated in detail. It was shown that the use of QC coatings in CE could drastically reduce the analysis time and improve the separation performance within a broad pH range. Five basic proteins, that is, lysozyme, ribonuclease A, cytochrome C, bovine pancreatic trypsin inhibitor, and chymotrypsinogen were baselinely separated even at pH 8.0. The separation efficiency and analysis reproducibility demonstrated that the QC coatings were efficient in minimizing the adsorption of basic proteins on the fused silica capillary. The successful performance was further demonstrated for biosample analysis.     

Synthesis of rigid polymer containing pendant norbornadiene moieties and its photochemical valence isomerization

Polymers having pendant norbornadiene (NBD) moieties and rigid main chain were prepared from the reaction of partially brominated poly(2,6-dimethyl-p-phenylene oxide) with a potassium carboxylate derivative of the corresponding NBD using a phase transfer catalyst in chlorobenzene. The photochemical valence isomerization of pendant NBD to quadricyclane (QC) moieties proceeded smoothly in the film state as well as polymer solution upon the irradiation by sunlight, xenon lamp, or high-pressure mercury lamp. The rate of isomerization was affected by the structure of main chain in the polymer and the substituent groups of NBD derivatives. The catalytic reversion of the resulting QC moiety to the original NBD proceeded smoothly in the solution with (5,10,15,20-tetraphenyl-21H,23H-por-phine)cobalt(II) as the catalyst at room temperature; however, the reaction of NBD polymer containing poly(2,6-dimethyl-p-phenylene oxide) (PPO) showed lower reactivity than that of the corresponding low molecular weight QC compound. When the cycle between the photochemical valence isomerization of NBD moiety to quadricyclane (QC) moiety and thermal reversion of QC moiety to NBD moiety at 160°C was repeated, the NBD polymer synthesized from PPO degraded gradually, whereas NBD polymer prepared from poly(4-chloromethylstyrene) decomposed easily. Therefore, the rigid PPO structure showed high resistance for the degradation of NBD moiety. © 1994 John Wiley & Sons, Inc.     

Antifungal activity and humidity sensitivity of quaternized cellulose synthesized in NaOH/urea aqueous solution

In this work we report the fabrication of cellulose-based humidity responsive material with antifungal activity. The quaternized cellulose (QC) derivatives with low degree of substitution (DS) values of 0.08–0.37 were synthesized in NaOH/urea aqueous solution. Water insoluble QC membranes (c-QCM) were prepared by casting from QC aqueous solutions, followed by crosslinking with glutaraldehyde. The c-QCMs were disintegrated in acid solutions, but were able to keep membrane shape in neutral and mild basic solutions with pH value of 7.2 and 9.7. The equilibrium water adsorption ratios of c-QCMs were in the range of 66–98%, depending on the DS values of quaternary ammonium groups and the pH value of the aqueous solutions. The antifungal activity of QC was evaluated and found that QC could effectively inhibit the reproduction of Rhizopus stolonifer, Aspergillus flavus and Penicillium digitatum, with minimum inhibitory concentration of 5, 10, and 7.5 mg/mL, respectively. The resistivity of the c-QCM changed for about 65–134 times corresponding to the change of environmental relative humidity from 20 to 99%; and the performance of c-QCM as a resistive-type humidity responsive material was consistent in the cycling of relative humidity.