Synthesis of Condensed Tannin Derivatives and their Protein-Precipitating Capacity

Four regiospecifically methylated condensed tannin derivatives were synthesized by the condensation of regiospecifically methylated flavan-3, 4-diols protected by benzyl groups, and subsequent debenzylation. The monomeric flavan-3,4-diols were obtained via four reaction steps starting from phloroacetophenone derivatives and protocatechualdehyde derivatives. Protein—precipitating capacity of these synthetic condensed tannin derivatives was tested and a comparision of these capacity suggests the following results: 1) Phenolic hydroxyl groups in tannins are essential sites for protein precipitation. 2) Although the A-ring has been considered not to be important for tannin—protein interactions, it was proved that the A-ring also plays an important role together with the B-ring. 3) Both hydroxyl groups of A- and B-rings may synergistically interact with proteins.     

Effects of the Hydroxylation Patterns and Degrees of Polymerization of Condensed Tannins on their Metal-Chelating Capacity

Abstract

We studied the effects of the hydroxylation patterns and the degrees of polymerization of condensed tannins on their metal-chelating capacity. These effects were evaluated by the relative stability of aluminium complexes with proanthocyanidin. The relative stability of aluminium complexes was determined qualitatively in methanol solution by the competition with the metallochromic reagent (chrome azurol S). A comparison of these capacities indicates the following results: 1) phenolic hydroxy groups in tannins are essential sites for the chelation with metal. 2) the sites of tannins interacting with metal ions are mainly o-dihydroxyphenyl groups in B-ring. 3) increasing degrees of polymerization of tannins tends to increase the relative stability of condensed tannin-aluminium chelate.     

Thermal Degradation of Condensed Tannins from Radiata Pine Bark

Abstract

In order to understand the influence of the inherent chemistry on the relative thermal stability of condensed tannins, the thermal degradation behaviors of various radiata pine bark extracts have been investigated using thermogravimetric analysis (TGA). Generally, results suggest pine bark extract fractions may be readily processed at temperatures below 200°C if co-extracted polysaccharides contents are minimized. Those extracts possessing greater carbohydrate content and lower tannin purity tend to have decreased thermal stability. The initial onset temperature for degradation of relatively crude extracts with high proportions of carbohydrate contents were relatively low (ca. 150°C), whereas extract purification to < 5% carbohydrate content gave increases in thermal stability of at least 50°C. The complicity of the carbohydrate content in the degradation of the tannin samples was also supported by calculated Ozawa activation energies and modulated TGA experiments. While no increase in the thermal stability was gained by acetylating the pendant hydroxyl groups of the pine bark tannin extract, chemical variations such as sulfonation have a large effect on thermal degradation, promoting lower degradation temperatures.     

Fluctuational Variation in the Relationship Between Water Capacity and Soil-Water Suction

The relationship between the water content of a soil and the suction component of the water-moving potential, expressible either as the water-retention curve or the water-capacity function, is often tacitly expected to decrease smoothly and monotonically with increasing suction, once the maximum water capacity has been reached. For two nonswelling artificial soils, a calcined clay and a sand-kaolinite, the general position of the water retention curve was found to be essentially the same regardless of the size of the suction increment applied in obtaining the curve. The water-capacity function, computed as the incremental reduction in water content per unit increase in suction head, was also found to be essentially smooth and monotonically decreasing with increasing suction when the applied suction increments were relatively large (≥ 100 mb), but consistent and marked fluctuations were found when the decrements of water content and increments of suction were small (suction steps of 50 and 25 mb). Concerning possible causes of this fluctuating behavior, it is suggested that the microbehavior of pore-water removal might be failing to average out statistically to a monotonically smooth macrobehavior, or that if water properties were modified by particle-water interaction such as to induce threshold gradients for water flow, effects of this nature might somehow be involved.     

Extraction of Condensed Tannins from Cervid Feed and feces and Quantification using a Radial Diffusion Assay

A radial diffusion assay was employed to quantify condensed tannins (CT) in feed and feces of mule deer (Odocoileus hemionus) and white-tailed deer (O. virginianus). This biological assay measures the precipitation of bovine serum albumin (BSA), with the area of the precipitation ring being proportional to the amount of extracted CT applied to the well. CT extracted from the bark of white spruce (Picea glauca) was used as the standard. CT were extracted with 70% (v/v) aqueous acetone and precipitated with 50% (v/v) aqueous methanol or 70% (v/v) aqueous acetone. Functional range of CT weights for suitable ring measurement was 0.5–4.0 mg, and equilibrium was achieved within an incubation period of 24 hr. Methanol (50%) was a more effective precipitation solvent than acetone (70%) having 13 ± 4% greater specific activity (P < 0.05) and superior capabilities for predicting CT content. Precipitation rings were evaluated on images magnified on a photocopier. Ring diameters measured on a 200% enlarged photocopy provided the most precise estimate of ring area (R² = 0.98). This convenient method reduced analysis times and enhanced accuracy and precision of tannin quantification. Analytical consequences and future research requirements are considered.     

甲苯吸附与活性炭孔隙结构关系的研究

选用4种活性炭为吸附剂,7.537 g/m3甲苯为吸附质,在298.15 K下进行吸附试验,探讨了4种活性炭的甲苯吸附量与其比表面积和孔容的关系。对活性炭不同孔径区间的孔容和甲苯吸附量进行线性回归分析,并对分析结果进行显著性检验。结果表明:4种活性炭均具有微孔吸附特征;活性炭比表面积、孔容大则其甲苯吸附量大,活性炭孔径结构对甲苯吸附效果产生直接影响;孔径在0.8～2.4 nm之间的孔容和甲苯吸附量之间存在较好的线性关系,其线性相关度R最大。     

Comparison of Chemical Compositions and Antioxidant Activities of Condensed Tannins From Different Parts of Calliandra haematocephala

In this study, the condensed tannins in 70% acetone extracts of leaf, twig, and stem bark of Calliandra haematocephala were purified by a Sephadex LH-20 column, and their structures were identified using MALDI-TOF-MS and thiolysis-HPLC-ESI-MS analyses. The results showed that the condensed tannin structures varied significantly among C. haematocephala organs. The condensed tannins from leaf were essentially of prodelphinidins, consisting mainly of (epi)gallocatechin and (epi)gallocatechin-3-O-gallate units; the condensed tannins from twig and stem bark were predominately of procyanidins, with catechin, epicatechin, and (epi)catechin-3-O-gallate as the main constitutive units for the former and epicatechin as the main constitutive unit for the latter, respectively. Furthermore, in vitro antioxidant activities of these condensed tannins were evaluated using the ABTS^·+ and FRAP methods. All of the condensed tannins exhibited stronger antioxidant activities compared to those of synthetic antioxidant BHA. For all organs, the two tested activities were found to be the highest in leaf condensed tannins, followed by that in twig condensed tannins and stem-bark condensed tannins. The results suggested that the number of hydroxyl groups on the B-ring and the level of 3-O-galloylation in condensed tannins were closely related with their antioxidant activities, and that the condensed tannins from different parts of C. haematocephala could be used as a natural additive in the food and cosmetic industries.     

Condensed Tannins: The Formation of a Diarylpropanol-Catechinic Acid Dimer from Base-Catalyzed Reactions of (+)-Catechin

Reaction of (+)-catechin at pH 12 and 40 °c results in the stereoselective (if not stereospecific) formation of an enolic form of 1-[6-(3′,4′-dihydroxyphenyl)-7-hydroxybicyclo[3.3.1]nonane-2,4,9-trione-3-yl] -1-(3,4-dihyroxyphenyl)-3-(2,-4,6-trihydroxyphenyl)-propan-2-ol. The n.m.r. chemical shift assignments determined by a variety of two-dimensional experiments permit a conclusion that the compound is one of four diastereoisomers possible from reaction of the two quinone methide intermediates. Stereoselectivity in the formation of this compound can be accounted for by preference for Re-face attack on both 2-C's of the quinone methides involved in the formation of the molecule.     

Ellagitannins have Greater Oxidative Activities than Condensed Tannins and Galloyl Glucoses at High pH: Potential Impact on Caterpillars

Plants synthesize a diversity of tannin structures but little is known about whether these different types have different oxidative activities in herbivores. Oxidative activities of hydrolyzable and condensed tannins were compared at pH 10 with two methods: EPR spectrometry was used to quantify semiquinone radicals in anoxic conditions and a spectrophotometric assay was used to measure the rate of browning of phenolics oxidized in ambient oxygen conditions. A little-studied group of hydrolyzable tannins (ellagitannins) contained the most active tannins examined, forming high concentrations of semiquinone radicals and browning at the highest rates. On average, galloyl glucoses and high-molecular-weight gallotannins had intermediate to low oxidative activities. Condensed tannins generally formed low levels of semiquinone radicals and browned most slowly. The results suggest that ellagitannin-rich plants have active oxidative defenses against herbivores, such as caterpillars, whereas the opposite may hold true for plants that contain predominantly condensed tannins or high-molecular-weight gallotannins.     

Characterization of Condensed Tannins Purified From Legume Forages: Chromophore Production,Protein Precipitation,and Inhibitory Effects on Cellulose Digestion

To identify simple screening tools for selecting condensed tannin (CT)-containing forages as candidate sources for further study, CT were isolated from nine legumes, and their molecular weights (MW), chromophore production, capacity to precipitate bovine serum albumin (BSA) and Fraction 1 protein (Rubisco) isolated from alfalfa, and inhibition of filter paper digestion were compared. Sources were as follows: leaves of sericea lespedeza (Lespedeza cuneata Dum.-Cours.), crown vetch (Coronilla varia L.), and sainfoin (Onobrychis viciifolia Scop.); stems of hedysarum (Hedysarum alpinum L.); seeds of alfalfa (Medicago sativa L.); and whole plants of birdsfoot trefoil (Lotus corniculatus var. corniculatus L.) and three varieties of big trefoil (Lotus pedunculatus Cav.), viz., Lotus uliginosus Schkuhr, L. uliginosus var. glabriusculus, and L. uliginosus var. villosus. Molecular weights and sizes (degrees of polymerization) of the CT varied considerably within and among plant species. Average MW ranged from 3036 Da (crown vetch) to 7143 Da (lespedeza). All CT exhibited greater capacity (w/w basis) to bind alfalfa Rubisco than BSA. Relative astringencies (μg CT required to precipitate 1 mg protein) against BSA ranged from 262.5 for CT from lespedeza to 435.5 for CT from L. corniculatus, and against Rubisco, from 49.6 (sainfoin) to 108.2 (alfalfa seed). Including CT at 300 μg/ml in cultures of Fibrobacter succinogenes reduced digestion of cellulose filter paper by 19.8% (sainfoin) to 92.4% (crown vetch) and increased the specific activity of cell-associated endoglucanase. There were no correlations between inhibitory effects of CT on filter paper digestion and (1) chromophore formation during CT assay by butanol–HCl, vanillin–HCl, or H₂SO₄; (2) precipitation of BSA or alfalfa Rubisco; and (3) MW of CT. The most inhibitory CT for cellulose digestion included those with broad and with narrow MW distributions. Sainfoin was the most desirable source of CT, as it had the highest capacity to bind alfalfa protein and was least inhibitory to cellulose digestion by F. succinogenes. This study suggests that these properties are not easily defined via chemical means, and that biological assays using rumen bacteria may help identify those CT with properties of nutritional interest.     

Relationship Between Chemical Functional Groups on Eucalyptus Secondary Metabolites and their Effectiveness as Marsupial Antifeedants

Eucalyptus displays strong intraspecific variation in resistance to browsing by marsupial folivores that can be attributed to variation in the concentration and type of diformylphloroglucinol compounds (DFPCs) in the foliage. In this study, we ask which functional groups of diformylphloroglucinol compounds determine their effectiveness in deterring feeding. We used a simple and highly deterrent compound, jensenone, as a model DFPC and compared its activity to structural variants that differ in the types of functional groups on the phloroglucinol molecule. Torquatone, a naturally occurring compound in the steam volatile fraction of Eucalyptus torquata foliage, has neither the aldehyde nor phenol groups that are believed to contribute to the antifeedant actions of jensenone. From the naturally occurring compounds we have synthesized two intermediates, a capped phenol/free aldehyde compound (acetyl-jensenone) and a free phenol/no aldehyde compound (demethyl-torquatone). Addition of jensenone and acetyl-jensenone to diets of common ringtail possums (Pseudocheirus peregrinus) substantially reduced their food intakes. Torquatone showed less activity, and there was little reduction in food intake when demethyl-torquatone was added to the diet. We conclude that at least the aldehyde groups attached to the aromatic nucleus are important in determining whether these compounds deter feeding by common ringtail possums, whereas the phenol groups may play only a minor role.     

EPA-乙酯和DHA-乙酯在超临界二氧化碳中色谱容量因子与溶解度的关系

以二氧化碳为流动相,ODS柱为固定相,测定了二十碳五烯酸乙酯（EPA－EE）和二十二碳六烯酸乙酯（DHA－EE）的超临界流体色谱容量因子。从宏观热力学出发,研究了溶质的超临界流体色谱容量因子及其在超临界二氧化碳中溶解度的关系,并用实验数据对该热力学关系作了验证。     

电缆分布电容与继电器误动作

通过工程项目建设实例说明交流电对信号电缆所产生的分布电容会引起信号继电器误动作.分析分布电容计算的公式,阐述分布电容与电缆材料、长度等的关系,通过实例计算信号继电器的技术规格,给出抗分布电容的方案.最后介绍实际使用情况与思考意见.     

煤的荧光特性与其工艺性能的关系研究

简述了煤中镜质组荧光产生的机理及荧光参数的测量方法,通过测定一系列煤的粘结性和10kg小焦炉结焦性试验,探讨了煤的荧光特性与其工艺性能的关系。煤的荧光参数与其反射率呈正的线性相关关系,与其挥发分含量呈负的线性相关关系;煤的粘结性、结焦性均与其荧光参数有关;当煤化程度相同、煤岩组成基本相同时,煤的荧光强度愈强,其结焦性能愈好。     

浅析可持续发展与环境保护的关系

社会的进步离不开经济的发展,而经济的发展避免不了要影响它所处的环境。可持续发展作为科学发展观的基本要求之一,解答了在增进国民经济的同时,怎样处理好与环境的关系。浅析了可持续发展战略、环境保护的重要性以及它们之间的平衡关系。     

水性聚氨酯结构与性能关系研究

以聚酯二元醇（PHA）、聚醚二元醇（N-210、N-220）、蓖麻油（C．O．）、甲苯二异氰酸酯（TDI）、二羟甲基丙酸（DMPA）为主要原料合成了系列水性聚氨酯（WPU）,并对聚醚N-220型WPU分别使用有机硅、有机氟、端羟基聚丁二烯（HTPB）橡胶改性。通过红外、吸水率测试、电子拉力试验机、接触角测试研究了软段类型（N-210,N-220,PHA）、交联、改性对WPU耐水性、力学性能、涂膜手感的影响。研究发现,由PHA制备的聚氨酯耐水性、拉伸强度优于聚醚（N-210、N-220）制备的聚氨酯,适度交联可提高胶膜拉伸强度及耐水性。有机硅、有机氟改性可改进WPU的耐水性及表而性能,HTPB橡胶改性可提高胶膜的柔顺性及力学性能。     

脂联素与肥胖的相关性的meta分析

目的本研究拟探讨脂联素与肥胖的相关性及其在肥胖相关的2型糖尿病中的可能作用。方法对上溯至2000年的脂联素与糖尿病及肥胖的前瞻性及横断面研究进行检索。数据分析采用Cochrane协作网提供的RevMan4.2软件进行meta分析。危险度分析采用比值比作为效应量表示结果,连续性变量采用加权均数差值分析。两者均以95%可信区间(CI)表示。应用固定效应模型和随机效应模型分析结果。结果(1)脂联素四分位最低组与最高组相比,男性(P<0.00001)和女性(P=0.0001)BMI都有明显差异。女性差异比男性更大些;(2)在男性肥胖者中,脂联素的水平与非肥胖组差异不明显(P=0.64);在女性肥胖者中,两者差异也不明显(P=0.20)。结论脂联素与肥胖具有明显关联,但其机制较复杂,且可能在肥胖在2型糖尿病的早期作用机制中起到作用。     

不同SEBS结构与性能关系探究

高聚物的性能取决于结构。本文以两种苯乙烯-乙烯-丁烯-苯乙烯嵌段共聚物(SEBS)为研究对象,通过红外、核磁、差示扫描量热法和动态力学分析对其结构进行了剖析,并对其制备的大输液膜制品的形貌和性能进行了表征。结果表明,SEBS中硬段含量、软段成分及不饱和度都会对其制品性能产生影响。     

浅谈油灰渣与硫酸铵产量的关系

为了解决大量油灰渣的处理问题,将其与原煤和矸石混合作为锅炉燃料。脱硫系统采用一炉一塔的布置,3台440t/h锅炉烟气直接进入对应吸收塔,脱硫后净湿烟气脱硫塔直接排放。通过煤的热解反应也就是加氢裂化等多种试验后产生的残渣,其中油灰渣的含量比较多,而油灰渣又属于高热值、高挥发分、低灰分的燃料。油灰渣是一种很好的燃料,如果能有效并且合理地掺烧在现有的燃料中,将大量节约原煤量,因其易结焦但含硫量较多,为了达到系统稳定运行必须把握好其掺烧比例。     

试油与稳产关系探讨

通过对新立新北油田试油数据及产量数据的分析和整理,建立起二者之间的联系,在油田进行有无试油井分类的基础上,认为不同年份的数据及不同工作方式下,对稳定产能预测的影响程度不同,并提出影响该区稳产的主要因素有:单井含油性差异、沉积环境、压裂改造效果、重复压裂、早期注水等。通过研究这些因素与产能关系,为产能预测提供依据。