Effect of sodium poly(styrene sulfonate) on thermoreversible gelation of gelatin

The effect of an added polyanion, sodium poly(styrene sulfonate) (NaPSS), on the thermoreversible gelation and remelting of gelatin gels has been investigated by polarimetry and rheology. The presence of NaPSS can either enhance or reduce collagenlike helix formation, depending on the polymer concentration relative to that of gelatin and the gelation temperature. At temperatures < 20°C, the helical content is reduced by increasing the amount of added NaPSS, demonstrating the disruption of helical structure of gelatin by the polyanion. Synchronous measurements of optical rotation and modulus at 25°C, in both gelation and remelting, indicate that the optical rotation at the gel point for the pure gelatin is lowered on addition of NaPSS. At low frequency, the storage modulus of gelatin is increased by the addition of a small amount of NaPSS relative to that of gelatin, but decreased with excess NaPSS. The mechanical properties of gelatin with and without NaPSS will be discussed in light of the competition between network junction formation by strands of triple helices among gelatin chains and temporary ionic crosslinking between gelatin and the polyanion. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 2287–2295, 1999     

Thermal,mechanical, and morphological properties of phenolic resin/silica hybrid ceramers

Phenolic resin/silica hybrid ceramers were prepared through sol–gel technology. Differential scanning calorimetry and thermogravimetric analysis methods were utilized to study the thermal properties of the fabricated hybrid ceramers. The results showed that the heat resistance of the ceramers was slightly higher than that of the phenolic resin. The hydrogen bonding occurring inside the hybrid ceramers was investigated by Fourier transform infrared. The results showed that the intermolecular hydrogen bonding between the phenolic resin and the silica was stronger than the intramolecular hydrogen bonding between the phenolic resin molecules themselves. Furthermore, the hybrid ceramers were utilized to fabricate carbon‐fiber‐reinforced composites. The fabricated ceramer composites possessed better flexural strength and flexural modulus than that fabricated from neat phenolic resin. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 1699–1706, 2000     

Recent progress in the enzymatic glycosylation of phenolic compounds

Phenolic compounds are an important class of chemicals with various beneficial bioactivities. However, they are usually poorly soluble in water and unstable while some of them are toxic. Glycosylation can significantly improve the solubility, stability, and bioactivity of phenolic compounds. The enzymatic method for glycosylation can form a specific glycosidic bond in one step and under environment-friendly conditions. This review covers the progress made in the application of two classes of enzymes, namely, glycosyltransferases and glycosidases, for the glycosylation of phenolic compounds, and illustrates the impact of glycosylation on the properties of these compounds.     

HPLC法同时测定松果菊属中4种酚类化合物

松果菊属(Echinacea Moenck.)是原产于美洲的一类菊科野生花卉,也称“紫锥菊”。该属植物共有8种及数个变种,均为多年生草本,其中已开发为药品者主要为淡紫松果菊(E.palli-a)、狭叶松果菊(E.angustifolia)及紫花松果菊(E.purpurea)[1]。松果菊属植物主要用于促进机体的免疫功能     

偏最小二乘法用于研究酚类物质的竞争吸附

将偏最小二乘法(PLS)用于紫外-可见分光光度分析,同时测定水溶液中苯酚、对甲氧基苯酚和α-萘酚三种组分,并将此方法用于研究苯酚、对甲氧基苯酚和α-萘酚在水溶液中的竞争吸附.结果表明:合成样本的回收率在96%~107.6%之间,结果比较令人满意.采用PLS法计算三种酚类物质吸附后的平衡浓度和吸附量,其结果与采用LCA(Langmuir Competitive Adsorption)模型预测的结果较为接近.     

改进的五氟苄基溴衍生化反应测定水中酚类化合物

建立了气相色谱-质谱法测定水中6种酚类化合物(2,6-二氯酚、2,4-二氯酚、2,4,6-三氯酚、2,4,5-三氯酚、2,3,4,6-四氯酚和五氯酚)的方法.样品经二氯甲烷-乙酸乙酯混合溶剂萃取后,用旋转蒸发浓缩至1 mL,加入五氟苄基溴进行改进版衍生化反应,产物用DB-5 mS毛细管柱分离,采用选择离子监测模式测定....     

Thermoplastic elastomer gels. I. Effects of composition and processing on morphology and gel behavior

Thermoplastic elastomer gels (TPEGs) composed of a poly[styrene-b-(ethylene-co-butylene)-b-styrene] triblock copolymer and a low-volatility, midblock-compatible mineral oil have been investigated at different oil concentrations to ascertain the effect of composition on TPEG morphology and mechanical properties. The impact of thermal processing is also examined by comparing gels thermally quenched to 0°C or slowly cooled to ambient temperature. Transmission electron micrographs reveal that gels with 70 to 90 wt % oil exhibit styrenic micelles measuring ca. 24 nm in diameter. Variation in composition or cooling rate does not have any perceivable effect on micelle size or shape, whereas the rate at which the gels are cooled influences the extent of microstructural order and the time to rupture (t_R) at constant strain. Dynamic rheological testing confirms the presence of a physically crosslinked network at TPEG compositions ranging from 70 to 90 wt % oil, independent of cooling rate. Results presented here suggest that the dynamic elastic shear modulus (G′) scales as t^α_R where α varies from 0.41 to 0.59, depending on cooling rate. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. B Polym. Phys. 36: 2379–2391, 1998     

Evaluation of leishmanicidal and trypanocidal activities of phenolic compounds from Calea uniflora Less.

The phytochemical study of Calea uniflora led to the isolation of nine phenolic compounds identified as noreugenin (1), ethyl caffeate (2), a mixture of butein (3) + orobol (4), α-hydroxy-butein (5), caffeic acid (6), butein 4′-O-glucopyranosyl (7), quercetin 3-O-glucopyranosyl (8) and 3,5-di-O-caffeoylquinic acid (9). The chemical identity of the isolates was established on the basis of NMR and physical data. The chemical shifts of 5 and 7 have been reassigned and all the isolates were tested against Leishmania amazonensis and Trypanosoma cruzi amastigotes. None of the metabolites showed promising leishmanicidal activity. However, 2 and the mixture of 3 and 4 demonstrated interesting trypanocidal effect with IC₅₀ values of 18.27 and 26.53 μM, respectively. Besides, these compounds did not present cytotoxic effect towards THP-1 cells, and compound 2 was 3.5-fold more selective than the mixture of 3+4.     

Effects of hydroxy compounds on gel formation of gelatin

 Network formation of gelatin gel is known to consist of three-dimensionally cross-linked triple helices among polypeptide chains. The effects of added low molecular weight mono-ols, diols and polyols on the higher-order structure formation of gelatin chains were investigated using the following measurements: melting temperature, viscoelasticity and spin-lattice relaxation time (T ₁) of H¹⁷ ₂O of gels, and circular dichroism spectra of diluted gelatin solutions. Furthermore, hydration behaviors of these hydroxy compounds were evaluated from the dynamic hydration numbers (n _DHN) derived from T ₁ of H¹⁷ ₂O in the solutions. It was found that network structures of gelatin gels containing hydoxy compounds were influenced by the number and position of hydroxyl groups as well as the number of carbon atoms of these coexisting compounds. The effect of hydroxyl groups of hydroxy compounds was considered to stabilize the helices among gelatin chains. Especially, the addition of polyols with large number of hydroxyl groups increased the number of cross-linking junctions in the gel networks, which consist of the aggregation among the helices. On the contrary, the effect of carbon atoms of hydroxy compounds is to disturb the formation of the helices and the aggregation among the helices. Received: 18 April 1996/Accepted: 23 July 1996     

超声波提取-气相色谱法测定土壤中21种酚类化合物

建立了超声波提取-气相色谱法同时测定土壤中21种酚类化合物的分析方法。用二氯甲烷和正己烷混合溶剂提取土壤中的酚类化合物,提取液经碱性水溶液分配净化,去除非酸性有机杂质,再酸化萃取酚类化合物,浓缩后采用气相色谱-氢火焰离子化检测器进行检测,外标法定量。以10 g土壤样品计,酚类化合物的检出限为0.01~0.06 mg/kg。实际样品添加回收试验的回收率为62.9%~111.4%,相对标准偏差为4.3%~24.0%(n=6),准确度和精密度均较好。结果表明:该法操作方便,净化效果好,可用于土壤中多种酚类化合物的测定。     

The association of aqueous phenolic resin with polyethylene oxide and poly(acrylamide-co-ethylene glycol)

Comb copolymers formed from acrylamide and poly(ethylene-glycol) methacrylate macro-monomer (PAM-co-PEG) were compared to poly(ethylene oxide) (PEO) with respect to hydrogen bond complex formation with water-borne phenolic resins. The behaviors of the two types of high molecular weight polyethers were similar. Complex formation gave a transient increase in viscosity followed by precipitation. Copolymers with pendant PEG chain lengths ≥ 9 formed complexes with phenolic resin whereas PEG homopolymer with a molecular weight of 2000 did not form a complex. For both copolymer and high molecular weight PEO, the tendency of the complex to precipitate increased when the pH was decreased from 7 to 4. Acridine orange, a cationic dye, bound to the phenolic resin and, after the addition of PEO, yielded visible complex gels with diameters about 20 μm. © 1995 John Wiley & Sons, Inc.     

酚类化合物在树脂XAD-4上吸附性能的QSPR研究

应用密度泛函方法(DFT)在B3 LYP/6-311G**水平上全优化计算酚类化合物的量子化学参数,结合疏水性参数logP、温度T与酚类化合物在树脂XAD-4上的Frendlich等温吸附方程常数进行定量构效关系研究(QSPR).经逐步回归筛选变量后,所建多元线性回归方程的复相关系数R2及去一法(LOO)交互检验复相关...     

Strength of hydrogen bonding in the novolak-type phenolic resin blends

The specific interaction strength of novolak-type phenolic resin blended with three similar polymers [i.e., poly(ethylene oxide) (PEO), poly(ethylene glycol) (PEG), and poly(vinyl alcohol) (PVA)] were characterized by means of glass transition temperature behavior and Fourier transform infrared (FTIR) spectroscopy. The interassociation formed within phenolic blends with the addition of a modifier not only overcomes the effect of self-association of the phenolic upon blending, but also increases the strength of phenolic blend. The strength of interassociation within the phenolic blend is the function of the hydrogen bonding group of a modifier, in increasing order, is phenolic/PVA, phenolic/PEG, and phenolic/PEO blend, corresponding to the result of “q” value in the Kwei equation. The FTIR result is in agreement with the inference of T_g behavior. In addition, the fact that the specific strength of hydrogen bonding of hydroxyl–hydroxyl is stronger than that of hydroxyl–ether can also be concluded. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1721–1729, 1998     

Liquid chromatography on unmodified and modified Spheron gels III. Phenolic compounds

Summary Chromatographic behaviour of phenolic compounds is studied on the ethyleneglycol methacrylate gel Spheron and on ion-exchangers produced by the chemical modification of this gels (cation exchanger Spheron S and anion exchanger Spheron DEAE) as compared to octadecyl silica. The hydrophobic effects obviously predominate in the retention mechanism on Spherons in aqueous methanolic mobile phases, but a selectivity differring from the behaviour on octadecyl silica was found for a number of phenolic compounds This is due to interactions with the functional groups in the unmodified and modified Spheron materials and may be utilized for the separation of phenols by liquid chromatography.     

Retention effects of oxidized polyphenols during analytical extraction of phenolic compounds of virgin olive oil

The hydrophilic extract of virgin olive oil contains several phenolic compounds such as simple phenols, lignans, and secoiridoids that have been widely studied in recent years. Interest in the hydrophilic extract has also been extended to the fraction of oxidized phenols that form during storage as a consequence of oxidative stress. The present investigation compares the two most commonly used extraction methods, namely liquid-liquid extraction and SPE, on fresh virgin olive oil and that kept at different temperatures in the presence of oxygen to promote the formation of oxidative products. The selective retention of these natural and oxidized phenolic compounds in relation to the extraction method was assessed. Quantification of eight identified phenolic molecules and 11 unknown peaks was performed by HPLC-DAD/MSD.     

Group-type separation and determination of phenolic compounds in coal-derived products by HPLC

Summary A rapid method was developed for the direct extraction of phenolic compounds from coal-derived products and subsequent isocratic HPLC analysis in a reversed-phase system by using the backflush technique.     

醇-盐双水相技术去除废水中的酚类物质

A novel method for treatment of phenolic compounds in cokery wastewater by propyl-alcohol ammonium sulfate aqueous two-phase system was investigted.The effects of the amount of ammonium sulfate used,the amount of propyl-alcohol used,pH value on extractield was studied.Extraction was optimized using a L9(34)orthogonal test.The results indicated optimum extraction conditions were the amount of ammonium sulfate used of 18.0 g,the amount of propyl-alcohol used of 16 mL,and pH value of 3.0.A extraction yield of 99.37% was achived under optimum extraction conditions and via secondary extraction.     

Evaluation of antioxidant activities of the edible and medicinal Acacia albida organs related to phenolic compounds

This study compared phenolic contents and antioxidant activity in different organs of Acacia albida (leaves and bark) and focuses on identification of phenolic compounds of leaves by HPLC-DAD. The analysed organs exhibited differences in total polyphenol contents (100 and 59.5 mg GAE g^? 1 DW). Phenolic contents of leaves were two times higher than those in bark. Ethanolic extracts exhibited good antioxidant activities with IC₅₀ = 26 μg mL^? 1 for DPPH and EC₅₀ = 50 μg mL^? 1 for FRAP. Identification by HPLC-DAD revealed the presence of nine phenolic compounds known for their high antioxidant activity. The results suggested that this species can be used as source of natural antioxidants.     

Effects of microcrystallites on swelling behavior in chemically crosslinked poly(vinyl alcohol) gels

We report the swelling ratio and network structure of a poly(vinyl alcohol) (PVA) gel chemically crosslinked by glutaraldehyde with different degrees of crosslinks. Microcrystallites were formed in a chemical PVA gel during a drying process and were confirmed by X‐Ray diffraction (XRD) measurements and Fourier transform infrared (FTIR) spectroscopy. The formation of microcrystallites in the dried gels was suppressed by increasing the degrees of chemical crosslinks. When the dried samples were immersed in pure water at 25 °C, the swelling ratio depended on the degree of chemical crosslinks resulting from the destruction of physical crosslinks by microcrystallites. On the other hand, when the dried samples were immersed in a poor solvent of a mixture of dimethyl sulfoxide and water at 8 °C, the gels did not swell and stayed in the collapsed state. Starting from the collapsed state, the equilibrium swelling ratios were measured while the temperature was increased to 90 °C and then decreased to 8 °C. As a result, irreversible swelling behaviors were observed for all gels with different degrees of crosslinks, which were attributed to the destruction of microcrystallites. The swelling behavior is discussed in terms of the formation and destruction of additional physical crosslinks in the chemical PVA gels. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011     

Swelling behavior of chemically crosslinked PVA gels in mixed solvents

We report the swelling behavior of chemically crosslinked polyvinyl alcohol (PVA) gels with different degrees of hydrolysis in water, several organic solvents, and their mixed solvents. The gels were dried after gelation and were put into their respective solvents. The gel volume in pure water decreased with increasing temperatures, and the total changes increased with decreasing degrees of hydrolysis. The swelling ratio depends on the solvent and its concentration. In the cases of mixed solvents of methanol–water, ethanol–water, and acetone–water, the gels shrank continuously with increasing concentrations of solvents and reached the collapsed state in the pure organic solvent. In the case of dimethyl sulfoxide (DMSO), on the other hand, the gels shrunk, swelled, and finally reached the swollen state in pure DMSO. Results of measurements using Fourier Transform infrared spectroscopy (FTIR) and X‐ray diffraction (XRD) suggested that crosslinks and microcrystallites were formed due to hydrogen bonds during the drying process after gelation. The hydrogen bonds were partly destroyed in a rich solvent, but the residual hydrogen bonds had an essential role in determining the swelling behavior in a poor solvent. The swelling behavior and the possible phase transition of the present system are discussed in terms of the solubility of polymers with different degrees of hydrolysis in given mixed solvents and in terms of the formation and destruction of physical crosslinks in the chemical PVA gels. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1978–1986, 2010