香菇多糖硫酸化衍生物的制备及其结构分析

采用改良的Ｗｏｌｆｒｏｍ方法制备了一系列的硫酸化香菇多糖衍生物。硫酸基含量测定结果表明,硫酸基的取代程序受反应时间和酯化试剂中氯磺酸与吡啶的比例的控制;证明甲基化分析方法不适合硫酸化香菇多糖衍生物的结构分析,＾１３Ｃ－ＮＭＲ数据表明,硫酸基取供在香菇多糖中Ｃ－６上,表明Ｃ－６位羟基的反应活性高于其他位置的羟基。     

硫酸酯化川芎多糖的制备及其抗氧化活性研究

以三种川芎多糖组分和淀粉为原料采用氯磺酸-吡啶法制备硫酸酯化产物,紫外和红外光谱对其进行结构表征,氯化钡-明胶比浊法测定硫酸酯化川芎多糖的取代度,分别考察试样在硫酸酯化前后对邻苯三酚自氧化反应产生的超氧阴离子和1,1-二苯基-2-苦基肼(DPPH)自由基的体外清除率。实验结果表明:川芎粗多糖和硫酸酯化川芎多糖对两种自由基的清除作用远低于阳性对照维生素C,但硫酸酯化修饰有助于提升川芎多糖对DPPH自由基的清除作用,对超氧阴离子自由基无明显影响;硫酸基的引入能够提高淀粉对O2-.的清除作用,但清除作用很弱。     

几种硫酸化试剂和溶剂对菊糖硫酸化改性的影响

为制取硫酸化菊糖,以硫酸钡比浊法测定硫酸基取代度(DS)、红外光谱测定含硫基团的特征吸收峰、核磁共振碳谱(13C NMR)判断硫酸根取代位置等方法,比较了以N,N-二甲基甲酰胺(DMF)、二甲基亚砜(DMSO)和吡啶(Py)三种溶剂,氯磺酸(CA)和三氧化硫(SO3)两种硫酸化试剂对菊糖硫酸酯化的影响.结果表明:以吡啶为溶剂、氯磺酸为硫酸化试剂的方法(CA-Py)与SO3-Py、CA-DMF三种硫酸化方法均获得了硫酸化菊糖,产品均显示不对称S=O键伸缩振动(约1255 cm-1)和对称的C-O-S键伸缩振动(约810 cm-1)特征吸收峰;三种方法的DS分别为:1.24,0.89,1.83;三种产品的13C NMR基本相同,均表明硫酸根连接在C3、C5、C6上.DMSO不适宜用作硫酸化溶剂.三种硫酸化方法是成功的,但以SO3-Py法操作简便,最适于菊糖硫酸化.     

昆布多糖硫酸酯化修饰及抗肿瘤活性的研究

对昆布多糖进行硫酸酯化修饰,考察修饰前后多糖结构及抗肿瘤活性的变化。采用氯磺酸-吡啶法进行多糖硫酸酯化修饰,考察了昆布多糖及其硫酸酯的红外光谱、核磁光谱特征,扫描电镜观察了表面形态,采用MTT比色法进行抗肿瘤活性评价。结果表明,昆布多糖及其硫酸酯都具有典型的多糖红外吸收,昆布多糖硫酸酯具有硫酸基的特征吸收峰;昆布多糖及其硫酸酯均是以β-(1→3)糖苷键为主链的多糖,昆布多糖硫酸酯的硫酸基取代位置在C2-OH与C6-OH。昆布多糖及其硫酸酯表面立体形态差异显著,昆布多糖表面呈云雾状或海绵状,昆布多糖硫酸酯表面呈片状或块状。昆布多糖及其硫酸酯对人肠癌细胞LOVO生长都具有明显的抑制作用,并且昆布多糖硫酸酯的抗肿瘤作用强于昆布多糖。     

硫酸酯化银耳多糖的制备及抗氧化性活性研究

采用氯磺酸-吡啶法化学合成硫酸酯化银耳多糖,对硫酸酯化反应的吡啶与氯磺酸的体积比进行优化,氯化钡-明胶比浊法测定硫酸酯化银耳多糖的取代度,并对不同取代度的硫酸酯化银耳多糖进行体外抗氧化实验。结果表明:硫酸酯化银耳多糖取代度随吡啶与氯磺酸体积比的提高而增加;当吡啶与氯磺酸体积比为4∶1,反应温度60℃,反应时间3 h时,产物的取代度为1.32,在0.8～2.0 mg/mL浓度范围内对Fenton反应产生的羟基自由基体外清除率相对于银耳多糖具有明显优势。     

薤白多糖的硫酸化修饰及体外抗氧化活性

为探讨薤白多糖硫酸化修饰的最佳条件,以及硫酸化修饰提高薤白多糖活性的可能性,采用氯磺酸-吡啶法对醇沉法得到的薤白多糖和柱层析纯化的3种分级薤白多糖进行硫酸化修饰,以氯磺酸-吡啶配比、反应温度和反应时间为自变量,修饰产物的硫酸基取代度(DS)为响应值,应用响应面设计法确定硫酸化修饰的最佳条件,用H2O2/Fe2+体系法和邻苯三酚自氧化法测定修饰产物的抗氧化活性。结果表明:薤白多糖氯磺酸-吡啶法修饰的最佳条件为氯磺酸∶吡啶=1∶3,反应温度65℃,反应时间2 h,此条件下硫酸根取代度为0.470,硫酸化修饰能提高薤白多糖的体外抗氧化活性。     

不同硫取代度昆布多糖硫酸酯的合成及理化性质初步研究

目的:对昆布多糖进行不同硫取代度的硫酸酯化修饰,并对其产物的硫酸基含量、糖含量与分子量进行检测,为研究不同硫取代度昆布多糖硫酸酯的生物活性奠定物质基础。方法:采用氯磺酸-吡啶法对昆布多糖进行硫酸化修饰,通过改变硫酸化修饰条件,来制取不同硫酸基取代度的昆布多糖硫酸酯;利用盐酸水解-硫酸钡比浊法测定昆布多糖硫酸酯的硫酸基含量,并通过公式求得其硫取代度;用苯酚-硫酸法测定昆布多糖硫酸酯的多糖含量,并使用HPGPC法测定其分子量。结果:两种不同硫取代度昆布多糖硫酸酯的硫酸基含量分别为37.8%、45.92%,取代度分别为1.07、1.51,糖含量分别为44.52%、37.19%,分子量分别为13000、16000。结论:利用氯磺酸-吡啶法对昆布多糖进行硫酸酯化修饰,该方法可以获取不同取代度产物,酯化率高。     

响应面法优化猴头菌硫酸化多糖

[目的]为了获得猴头菌多糖的最佳硫酸化修饰条件,提高猴头菌硫酸化多糖硫酸基团的取代度。[方法]采用单因素比较氯磺酸-吡啶摩尔比、反应温度和反应时间对猴头菌硫酸化多糖取代度的影响,利用响应面法对各因素的最佳水平以及各因素之间的交互作用进一步研究。[结果]猴头菌多糖的最佳硫酸化修饰条件为:氯磺酸-吡啶摩尔比为1:4、反应温度为59℃、反应时间为2. 6 h,取代度为0. 457,与模型的预测值基本相符。[结论]响应面法优化得到猴头菌多糖的硫酸化修饰条件参数准确,该模型可以用于猴头菌多糖硫酸化修饰条件的优化。     

超声波提取的当归多糖化学修饰及其抗氧化活性研究

采用超声波辅助法从当归中提取水溶性当归粗多糖(ASP),经过4种化学修饰分别得到硫酸化当归多糖(S-ASP)、磷酸化当归多糖(P-ASP)、乙酰化当归多糖(Ac-ASP)、羧甲基化当归多糖(C-ASP)。通过红外光谱对化学修饰前后ASP的结构进行表征,并进行抗氧化活性和清除自由基能力的测定,以获得一种抗氧化活性较强的当归多糖。结果显示:经化学修饰后的ASP分别具有相应的特征吸收峰,表明当归多糖的4种化学修饰均已成功;经化学修饰的4种当归多糖总还原能力均弱于未修饰多糖,且清除羟基自由基(·OH)的能力无明显变化,但清除1,1-二苯基-2-苦苯肼(DPPH·)自由基和抑制Fe2+诱发的脂质过氧化反应的能力有所增强,其中P-ASP清除超氧阴离子(O2·-)自由基的能力最强;Ac-ASP抑制Fe2+诱发的脂质过氧化反应的能力最强,且均呈现出一定的量效关系。本实验结果为当归多糖的进一步研究与开发利用提供了一定的科学依据。     

硫酸酯化剂和溶剂对海参岩藻聚糖硫酸酯化修饰的影响

比较了以N,N-二甲基甲酰胺(DMF)和吡啶(Py)两种溶剂,氯磺酸-吡啶(CA-Py)和三氧化硫-吡啶(SO3-Py)两种硫酸酯化剂对海参岩藻聚糖硫酸酯化的影响。结果表明:以CA-Py为酯化剂可使硫酸基的含量高达50%以上,以SO3-Py为酯化剂,硫酸基的含量仅达到20%左右;DMF为溶剂时可低温反应,Py为溶剂时反应温度必须90℃以上,但产品得率较高。红外光谱分析显示:硫酸酯化后,四种产品硫酸酯的特征吸收峰均显著增强。抗氧化活性实验结果表明:四种硫酸酯化产品对1,1-二苯基-苦肼基自由基的清除效果最好,对羟基自由基的清除效果次之,对超氧阴离子自由基的清除效果最小;以SO3-Py为酯化剂所得产品的抗氧化活性优于CA-Py为酯化剂的产品,DMF为溶剂的产品优于Py为溶剂的产品。因此,操作简便的SO3-Py法更适于海参岩藻聚糖的硫酸酯化。     

Location of sulfate groups on sulfoacetate derivatives of cellulose

A water-soluble cellulose acetate sulfate (CAS) with a degree of acetylation (DS(Ac)) 2.4 and a degree of sulfation (DS(Sulf)) of 0.3 was obtained by direct acetylation of cellulose using sulfuric acid as catalyst. Using methylation analysis, IR and NMR spectroscopy, sulfate groups have been located on primary alcohol function of glucose residues. The distribution of the sulfate groups along the cellulose chain has been investigated using enzymatic hydrolysis. CAS was first de-acetylated under mild hydrolysis conditions (NaOH 0.25 mol/L at room temperature), and then cellulose sulfate was hydrolyzed by a cellulolytic complex (Celluclast 1.5L). Reaction products were separated by ion exchange chromatography on a DEAE Sepharose CL6B column into five fractions F(1), F(2), F(3), F(4) and F(5), which were analyzed for their chemical composition. F(1) was glucose and represented the main product of reaction (approximately 50% of the initial glucose), F(2) was a dimer (approximately 30%) with a ratio Sulfates-Glucose of 0.41 (about one sulfate group for two glucose units), F(3) a trimer (approximately 10%) with a ratio Sulfates-Glucose of 0.62 (about two sulfate groups for three glucose units), and F(4) a tetramer (approximately 5%) with a ratio Sulfates-Glucose of 0.69. The structure of the oligomers was established using 1H and 13C NMR. The observed proportion of the different blocks of sulfate groups was in good agreement with computed random distribution.     

Spectrophotometric assay of long-chain unsaturated and hydroxy fatty acids in concentrated sulfuric acid

A spectrophotometric method has been developed for the determination of long-chain unsaturated and hydroxy fatty acids in concentrated sulfuric acid. The assay is based on the absorbance produced in the 290 to 300-nm range from their reaction with sulfuric acid at 100°C. α,β-Unsaturated aliphatic acids give absorption bands at 235–240 nm and thus can be easily differentiated from unsaturated fatty acids having the double bond(s) at positions not conjugated with the carboxyl group. A certain minimum chain length is required for full development of the absorption band at 300 nm. Position and intensity of the so-formed absorption band is independent on the position and number of the double bonds or hydroxyl groups. Carboxyl groups are not essential, as unsaturated hydrocarbons and higher alcohols likewise react with sulfuric acid to produce the absorbing species at 300 nm, providing a minimum chain length of 5 carbon atoms is present. The nature of the absorbing species at 300 nm is discussed.     

Chemical modification of a variant of human MIP-1alpha; implications for dimer structure

A sequence variant of human MIP-1alpha, in which Asp26 has been replaced by Al alpha, has been chemically modified by the addition of 13C-labeled methyl groups at each of the lysine residues and the N-terminus. The sites of methylation have been verified by a combination of MALDI-TOF mass spectrometric experiments and tryptic digestion followed by N-terminal mapping. The effect of the modification on the structure and activity of the protein have been determined by analytical ultra-centrifugation, 13C NMR spectroscopy and receptor binding studies. The results of these experiments suggest that huMIP-alpha D26A (BB10010), when present as a dimer, adopts a globular structure, like MCP-3, rather than the elongated or cylindrical structure determined for dimers of huMIP-1beta and RANTES.     

A new process for the esterification of wood by reaction with vinyl esters

A novel route to wood modification by transesterification of vinyl esters is developed in the current study. The reaction between varied saturated and unsaturated vinyl esters and the hydroxyl groups of maritime pine sapwood (Pinus pinaster Soland) was examined using potassium carbonate as a catalyst. The esterification of wood was investigated by weight percent gain calculations (WPG), Fourier-transform infrared spectroscopy (FTIR) and ¹³C cross-polarization with magic-angle spinning nuclear magnetic resonance spectroscopy (¹³C CP–MAS NMR). Differences in the rates of modification were noted, depending on the vinyl ester used, but relatively high yields were obtained in all cases. The infrared and NMR spectra of the different esterified samples were analysed in detail and the assignment of the signals corresponding to the grafted acyl groups confirmed that esterification occurred.     

Combined effects of an oxidative enzyme and dissolved humic substances on 13C-labelled 2,4-D herbicide as revealed by high-resolution 13C NMR spectroscopy

Phenoxyalkanoic acids are a widely used class of herbicides. This work employed high-resolution ¹³C NMR to study the structural changes induced by humic substances and horseradish perodixase on 2,4-dichorophenoxyacetic acid (2,4-D) ¹³C-labelled in the side chain. NMR spectra showed that humic substances chemically catalyze abiotic splitting of [¹³C]2,4-D into 2,4-dichlorophenol and [¹³C]acetic acid at pH 7 but not at pH 4.7. Peroxidase did not catalyze the oxidative degradation of [¹³C]2,4-D at any pH tested and inhibited the effect of humic substances. Catalytic degradation by humic substances was attributed to free-radical reactions enhanced by the stereochemical contribution of large conformational structures formed by heterogeneous humic molecules at neutral pHs. Inhibition of 2,4-D degradation when humic substances were combined with peroxidase was explained by modification of both chemical and conformational humic structure due to peroxidase-promoted oxidative cross-coupling among humic molecules. Our findings show for the first time that the abiotic degradation of 2,4-D is catalyzed by dissolved humic substances at neutral pH. Journal of Industrial Microbiology & Biotechnology (2001) 26, 70–76. Received 09 February 2000/ Accepted in revised form 22 May 2000     

Spectroscopic, mass spectrometry, and semiempirical investigation of a new ester of Monensin A with ethylene glycol and its complexes with monovalent metal cations

A new ester of Monensin A with ethylene glycol (MON2) has been synthesized by a new method and its ability to form complexes with Li+, Na+, and K+ cations has been studied by ESI MS, 1H and 13C NMR, FT-IR, and PM5 semiempirical methods. It is demonstrated that MON2 forms stable complexes of 1:1 stoichiometry with monovalent metal cations. The structures of the complexes are stabilized by intramolecular hydrogen bonds in which the OH groups are always involved. In the structure of MON2 the oxygen atom of the C=O ester group is involved in very weak bifurcated intramolecular hydrogen bonds with two hydroxyl groups, whereas in the complexes of MON2 with monovalent metal cations the C=O ester group is not engaged in any intramolecular hydrogen bonds. The structures of the MON2 and its complexes with Li+, Na+, and K+ cations are visualized and discussed in detail.     

Characterisation of thermally modified hard- and softwoods by C CPMAS NMR

The changes induced by thermal modification in the chemical structure of spruce [Picea abies (L.) Karst.], birch (Betula pendula), aspen (Populus tremula) and oak (Quercus robur) were studied by ¹³C CPMAS NMR spectroscopy. Spruce, birch and aspen were thermally modified at 195 °C and oak at 160 °C, under steam, according to an industrial-scale heat treatment process. In both hard- and softwood samples, ¹³C CPMAS NMR measurements revealed a degradation of less ordered carbohydrates (i.e. hemicelluloses and amorphous cellulose) in the thermally modified wood, which resulted in an increase in the cellulose crystallinity. Furthermore, thermal modification induced changes in the lignin structure by a cleavage of the β-O-4 linkages. In the softwood lignin, a decrease also occurred in the methoxyl group content leading to a more condensed lignin structure.     

Antineoplastic activity of new lanthanide (cerium, lanthanum and neodymium) complex compounds

Cerium (III), lanthanum (III) and neodymium (III) complexes with 3,3'-benzylidenebis[4-hydroxycoumarin] were synthesized in view of their application as cytotoxic agents. The complexes were characterized by different physicochemical methods: elemental analysis, mass spectrometry, 1H NMR, 13C NMR and IR spectroscopy. The spectra of the complexes were interpreted on the basis of comparison with the spectrum of the free ligand. The vibrational analysis showed that in the complexes the ligand coordinated to the metal ion through both deprotonated hydroxyl groups; however, participation of the carbonyl groups in the coordination to the metal ion was also suggested. The evaluation of the cytotoxic activity of the novel lanthanide complexes on HL-60 myeloid cells revealed that they are potent cytotoxic agents. The cerium complex was found to exhibit superior activity in comparison to the lanthanum and neodymium coordination compounds, the latter being the least active. Our data give us reason to conclude that the newly synthesized lanthanide complexes should be submitted to further more detailed pharmacological and toxicological evaluation.     

Spectroscopic aspects of the coordination modes of 2,4-dithiohydantoins: Experimental and theoretical study on copper and nickel complexes of cyclohexanespiro-5-(2,4-dithiohydantoin)

The complexation of cyclohexanespiro-5-(2,4-dithiohydantoin), L, with copper and nickel was studied by means of experimental and theoretical methods. The Cu(I) and Ni(II) complexes were synthesized and characterized using ¹³C CPMAS NMR, IR and FAB-MS. Reduction of Cu(II) ions and the formation of Cu(I) complexes with dithiohydantoin was proved. Various coordination modes were investigated on the basis of calculated (DFT-GIAO) shielding constants of the free ligand and model structures of the complexes. General trends in the changes of spectroscopic parameters (NMR chemical shifts, vibrational modes) upon different types of coordination were outlined. Dimeric structures for the Cu(I) and Ni(II) complexes were proposed in which the ligands were coordinated in N3^S4- and N3^S2-bridging ways, respectively, acting as monoanions. The results demonstrate that the combined experimental (¹³C CPMAS NMR, IR) and theoretical (DFT) approach can be used to characterize the molecular structure of solid complexes for which crystallographic data are not available.