Separation of flavonoids from Aleurites moluccana leaves using chitosan modified with heptaldehyde

Heptaldehyde-modified chitosan (heptyl-chitosan, CH-Hp) was investigated as adsorbent for chromatograhic separation of the flavonoids from A. moluccana. The amount of 2"-O-rhamnosylswertisin isolated (30.0 mg) was approx. twice as high as swertisin (17.5 mg). The improved surface hydrophobicity effected by the heptyl groups promoted the separation of flavonoids. From the results obtained, CH-Hp seems to be more suitable for separation of glycosylated flavonoids than other flavonoids. Thus, modified chitosan described here can be used for hydrophobic interaction chromatography as sucessfully illustrated with flavonoids.     

Separation of magnetic affinity biopolymer adsorbents in a Davis tube magnetic separator

A Davis tube (a matrix-free, flow-through magnetic separator used mainly in mineral processing) has been tested for separation of magnetic affinity biopolymer adsorbents from larger volumes of suspensions. Both magnetic chitosan and magnetic cross-linked erythrocytes could be efficiently separated from litre volumes of suspensions. Up to 90% adsorbent recovery was achieved under optimised separation conditions.     

Biflavonoids isolated from Selaginella tamariscina regulate the expression of matrix metalloproteinase in human skin fibroblasts

The methanol extract from Selaginella tamariscina significantly inhibited UV irradiation induced activity of matrix metalloproteinase-1 (MMP-1) in primary fibroblasts from human skin. Using the technique of bioassay-directed chromatographic separation, five biflavonoids were isolated from the ethyl acetate soluble fraction of S. tamariscina. Here, we investigated the effect of these five biflavonoids on the regulation of MMP-1 and -2 in UV irradiated cultured dermal fibroblasts from human neonatal foreskins. Among these biflavonoids, sumaflavone and amentoflavone showed significant MMP-1 inhibitory activity in primary human dermal fibroblasts after UV irradiation. The IC(50) values of sumaflavone, amentoflavone and retinoic acid, which was used as a positive control, were 0.78, 1.8, and 10microM, respectively.     

Adsorption of phenol, p-chlorophenol and p-nitrophenol onto functional chitosan

Functional chitosan, chemically modified by salicylaldehyde (CS-SA), beta-cyclodextrin (CS-CD), and a cross-linked beta-cyclodextrin polymer (EPI-CD) were prepared as adsorbents to remove phenol, p-nitrophenol and p-chlorophenol from aqueous solution. Langmuir and Freundlich models were applied to describe the adsorption isotherm of phenols, and adsorption parameters were evaluated. Functional chitosan displayed outstanding adsorption ability for phenols. To our surprise, CS-CD exhibited specific adsorption ability for p-chlorophenol. The possible adsorption interaction was discussed. Effects of pH and KCl on the adsorption suggested that the adsorption of phenols was predominated by hydrogen bonding, hydrophobic interaction and pi-pi interaction not electrostatic interaction. Effect of temperature indicated that the low temperature was favorable for the adsorption of phenols. Separation of phenols and adsorbent regeneration were carried out by simple washing with ethanol and filtrating.     

Structurally unique biflavonoids from Selaginella chrysocaulos and Selaginella bryopteris

Chemical investigation of Selaginella chrysocaulos from Northeast India yielded three new (i.e., 1-3) and two known biflavonoids. From Selaginella bryopteris, collected in the southern part of India, one new (11) and eleven known biflavonoids of the amentoflavone- and hinokiflavone-type were isolated and identified. The structures of the compounds were elucidated by 1D- and 2D-NMR spectroscopy, and by mass spectrometry. The absolute configurations of chiral biflavonoids with flavanone subunits (from S. bryopteris) were determined with the aid of circular-dichroism (CD) spectroscopy. Several very rare or even unprecedented substructures in biflavonoids were found.     

Separation and purification of enzymes by continuous pH-parametric pumping

Trypsin and chymotrypsin were separated from porcine pancreas extract by continuous pH-parametric pumping. CHOM (chicken ovomucoid) was convalently bound to laboratory-prepared crab chitin with glutaraldehyde to form an affinity adsorbent of trypsin. The pH levels of top and bottom feeds were 8.0 and 2.5, respectively. Similar inhibitor, DKOM (duck ovomucoid), and pH levels 8.0 and 2.0 for top and bottom feeds, respectively, were used for separation and purification of chymotrypsin. epsilon-Amino caproyl-D-tryptophan methyl ester was coupled to chitosan to form an affinity adsorbent for stem bromelain. The pH levels were 8.7 and 3.0. Separation continued fairly well with high yield, e.g., 95% recovery of trypsin after continuous pumping of 10 cycles. Optimum operational conditions for concentration and purification of these enzymes were investigated. The results showed that the continuous pH-parametric pumping coupled with affinity chromatography is effective for concentration and purification of enzymes.     

Studies on the Performance of Ethylamine-Modified Chitosan Carbonized Rice Husk Composite Beads for Adsorption of Metal Ion

Heavy metals in the soil and ground water have endangered our environment and human bodies by direct or indirect pathways. Currently, bioremediation is a developing process that offers the possibility to destroy various contaminants using natural biological activity. Biopolymers are industrially attractive because of their capability of lowering transition metal ion concentrations to parts per billion, they are widely available, and they are environmentally safe. This paper deals with the preparation of an ethylamine-modified biopolymer (chitosan) and carbon from biowaste (rice husk) composite beads (EAM-CCRCB) for metal ion removal. The prepared adsorbent was used for the adsorption of hexavalent chromium ions from aqueous solutions. The activation and surface properties of the adsorbent were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and Brunauer-Emmett-Teller (BET) analyses. The effect of process variables such as initial metal ion concentration, adsorbent dosage, and pH of the solution on the performance of percentage removal and adsorption capacity were studied. Various isotherm and kinetic models were fitted with experimental data to describe the solute interaction and nature of adsorption with the adsorbent through batch studies. Mass thermodynamic parameters were determined. Regeneration studies were attempted to check the stability and activity of the adsorbent.     

Enzymatic grafting of carboxyl groups on to chitosan--to confer on chitosan the property of a cationic dye adsorbent

Chitosan (CTS) is a good adsorbent for dyes but lacks the ability to adsorb cationic dyes. In this study, chitosan was modified to possess the ability to adsorb cationic dyes from water. Four kinds of phenol derivatives: 4-hydroxybenzoic acid (BA), 3,4-dihydroxybenzoic acid (DBA), 3,4-dihydroxyphenyl-acetic acid (PA), hydrocaffeic acid (CA) were used individually as substrates of tyrosinase to graft onto chitosan. FTIR analysis provided supporting evidence of phenol derivatives being grafted. The grafting amounts of these phenol derivatives onto chitosan were examined by the adsorption of an anionic dye (amaranth) and reached a plateau value. The final contents of carboxyl groups in chitosan (mmol carboxyl groups per kg chitosan) were measured as 46.36 for BA, 70.32 for DBA, 106.44 for PA, and 113.15 for CA. These modified chitosans were used in experiments on uptake of the cationic dyes crystal violet (CV) and bismarck brown Y (BB) by a batch adsorption technique at pH 7 for CV and at pH 9 for BB and 30 degrees C. Langmuir type adsorption was found, and the maximum adsorption capacities for both dyes were increased with the following order CTS-CA>CTS-PA>CTS-DBA>CTS-BA.     

Dehydration from alcohols by polyion complex cross-linked chitosan composite membranes during evapomeation

This study describes the dehydration of an ethanol/water azeotrope during evapomeation using polyion complex cross-linked chitosan composite (q-Chito-PEO acid polyion complex/PES composite) membranes, constructed from quaternized chitosan (q-Chito) and poly(ethylene oxydiglycolic acid) (PEO acid) on a porous poly(ether sulfone) (PES) support. Both the q-Chito/PES composite and the q-Chito-PEO acid polyion complex/PES composite membranes showed high water permselectivity for an ethanol/water azeotrope. Both the permeation rate and the water permselectivity of the q-Chito/PES composite membranes were enhanced by increasing the degree of quaternization of the chitosan molecule because the affinity of the q-Chito/PES composite membranes for water was increased by introducing a quaternized ammonium group into the chitosan molecule. q-Chito-PEO acid polyion complex/PES composite membranes prepared from an equimolar ratio of carboxylate groups in the PEO acid versus quaternized ammonium groups in the q-Chito showed the maximum separation factor for water permselectivity without lowering the permeation rate. With an increasing molecular weight of PEO acid, the separation factor for water permselectivity increased, but the permeation rate almost did not change. The mechanism responsible for the separation of an ethanol/water azeotrope through the q-Chito-PEO acid polyion complex/PES composite membranes was analyzed by the solution-diffusion model. The permeation rate, separation factor for water permselectivity, and evapomeation index of q-Chito-PEO acid 400 polyion complex/PES composite membrane with an equimolar ratio of carboxylate groups in PEO acid 400 and ammonium groups in q-Chito were 3.5 x 10(-1) kg/(m(2) hr), 6300, and 2205, respectively, and very high membrane performance. The separation factor for water permselectivity for aqueous solutions of n-propyl and isopropyl alcohol was also maximized at an equimolar ratio of carboxylate groups and ammonium groups and was greater than that for an ethanol/water azeotrope. The above results were discussed from the viewpoint of the physical and chemical structure of the q-Chito-PEO acid polyion complex/PES composite membranes and the permeants.     

银杏叶单组分双黄酮分离制备及抗氧化活性研究

从银杏叶中分离制备高纯度双黄酮对照品,探讨其抗氧化活性强弱。以60%乙醇-水提取的银杏叶浸膏为原料,反溶剂沉淀得到含量80.40%的双黄酮粗品,再以甲醇-水为流动相,半制备色谱梯度洗脱。结果得到了4种符合中药化学对照品要求的高纯度双黄酮,在最佳制备条件下,4种双黄酮纯度:阿曼托黄素(98.45%)、白果素(98.66%)、银杏黄素异构体(98.87%)、金松双黄酮(99.29%),其产率(mg/kg)分别为:22.5、23.8、192.5、71.8,考察了它们的抗氧化活性,并采用60%乙腈和有机酸水溶液对银杏黄素异构体进行了完全分离。建立的制备方法快速简便,所得单组分双黄酮纯度、产量高。本工作为单组分银杏双黄酮新药的研究与开发提供重要的技术支持。     

壳聚糖与细菌细胞膜相互作用的分子动力学研究

目的 壳聚糖（chitosan,CS）是一种天然的广谱抗菌活性物质。现有研究表明，壳聚糖与细菌细胞膜的相互作用是其发挥抗菌功能的关键。受限于传统实验技术的表征能力，壳聚糖与细菌细胞膜相互作用的具体机制仍有待研究。本文旨在研究壳聚糖与细菌细胞膜相互作用的分子机制。方法 本研究利用全原子分子动力学模拟技术主要探究了完全脱乙酰化的不同聚合度壳聚糖（八聚糖、十二聚糖和十六聚糖）与革兰氏阴性菌外膜（outer membrane,OM）和革兰氏阳性菌质膜（cytoplasmic membrane,CM）相互作用的动态过程。结果 壳聚糖主要依靠其氨基、碳6位羟基和碳3位羟基与OM和CM的头部极性区发生快速结合。随后壳聚糖末端糖基单元倾向于插入OM内部，深度约1 nm，并与脂质分子脂肪酸链上的羰基形成稳定的氢键相互作用。与之相比，壳聚糖分子难以稳定地插入CM内部。壳聚糖结合对膜结构性质产生影响，主要表现在降低OM和CM的单分子脂质面积，显著减少OM和CM极性区的Ca2+和Na+数目，破坏阳离子介导的脂质间相互作用。结论 本研究证明，壳聚糖带正电的氨基基团是介导其与膜相互作用的关键，并破环脂质间的相互作...     

Osteoblast differentiation stimulating activity of biflavonoids from Cephalotaxus koreana

Six amentoflavone-type biflavonoids, bilobetin (1), ginkgetin (2), 4',7'-di-O-methyl-amentoflavone (3), 7-O-methyl-isoginkgetin (4), sciadopitysin (5), and 7,4',7',4'-O-methyl-amentoflavone (6), were isolated from the EtOAc fraction of Cephalotaxus koreana Nakai (Cephalotaxaceae) by bioactivity-guided fractionation technique using primary cultures of mouse osteoblasts as an in vitro assay system. Among the six biflavonoids isolated, bilobetin (1), sciadopitysin (5), and 7,4',7',4'-O-methyl-amentoflavone (6) significantly increased osteoblast differentiation as assessed by alkaline phosphatase activity, collagen synthesis, and mineralization. Considering structure-activity relationship, methoxyl groups at 4' and 4' in the B rings in amentoflavone-type biflavonoid might be important in osteoblast differentiation. Taken together, our present study suggests therapeutic potential of biflavonoids against bone diseases such as osteoporosis.     

Removal of perfluorooctane sulfonate from aqueous solution by crosslinked chitosan beads: sorption kinetics and uptake mechanism

The crosslinked chitosan beads were used as an efficient biosorbent to remove perfluorooctane sulfonate (PFOS) from aqueous solution. The chitosan biosorbent had a sorption capacity up to 5.5 mmol/g for PFOS at the equilibrium concentration of 0.33 mmol/L, much higher than some conventional adsorbents. The sorption kinetics indicated that the sorption equilibrium was reached quickly at high pH and low PFOS concentrations, and the adsorbent size also affected the sorption rate to some extent. The double-exponential model described the kinetic data well, and the sorption of PFOS on the chitosan beads was a diffusion-controlled process. Based on the sorption kinetics and adsorbent characterization, the uptake mechanisms including electrostatic and hydrophobic interactions were identified to be responsible for PFOS sorption, and the hemi-micelles and micelles may form in the porous structure due to high PFOS concentrations within the adsorbent, which had the main contribution to the high sorption capacity.     

Effect of oppositely charged polymer and dissolution medium on swelling, erosion, and drug release from chitosan matrices

The purpose of this research was to investigate the potential use of anionick-carrageenan and nonionic hydroxypropyl-methylcellulose (HPMC, K4) to improve the matrix integrity of directly compressed chitosan tablets containing naproxen sodium, an anionic drug. The influence of buffer pH and drug:polymer ratio on the water uptake, matrix erosion, and drug release were studied. The rapid release of naproxen sodium was seen from matrices containing 100% chitosan due to loss in the matrix cohesiveness; whereas, it was relatively slow for matrices containing optimum concentration ofk-carrageenan. In-situ interaction between oppositely charged moieties resulted in the formation of polyelectrolyte complexes with stoichiometric charge ratios of unity. Fourier transform in frared (FTIR) spectroscopy and powder x-ray diffraction (PXRD) data confirmed the importance of ionic bonds in polyelectrolyte complexation. The ionic interactions between polymers were absent in matrices containing HPMC and the integrity of tablets was improved owing to the presence of viscous gel barrier. The reasons for retarded release of naproxen sodium from the chitosan matrices at different pH include poor aqueous solubility of drug, the formation of a rate-limiting polymer gel barrier along the periphery of matrices, the interaction of naproxen sodium with protonated amino, groups of chitosan, and the interaction of ionized amino groups of chitosan with ionized sulfate groups ofk-carrageenan. Published: June 15, 2007     

Modeling of protein monomer/aggregate purification and separation using hydrophobic interaction chromatography

Hydrophobic interaction chromatography (HIC) is commonly used to separate protein monomer and aggregate species in the purification of protein therapeutics. Despite being used frequently, the HIC separation mechanism is quite complex and not well understood. In this paper, we examined the separation of a monomer and aggregate protein mixture using Phenyl Sepharose FF. The mechanisms of protein adsorption, desorption, and diffusion of the two species were evaluated using several experimental approaches to determine which processes controlled the separation. A chromatography model, which used homogeneous diffusion (to describe mass transfer) and a competitive Langmuir binary isotherm (to describe protein adsorption and desorption), was formulated and used to predict the separation of the monomer and aggregate species. The experimental studies showed a fraction of the aggregate species bound irreversibly to the adsorbent, which was a major factor governing the separation of the species. The model predictions showed inclusion of irreversible binding in the adsorption mechanism greatly improved the model predictions over a range of operating conditions. The model successfully predicted the separation performance of the adsorbent with the examined feed.     

Removal of phthalate esters by alpha-cyclodextrin-linked chitosan bead

Removal of phthalate esters (PAEs) by alpha-cyclodextrin (CD)-linked chitosan bead in aqueous solution was studied. Results of kinetic experiments indicated that diheptyl phthalate (DHpP) was adsorbed most efficiently (3.21 mg/g) among the six PAEs. DHpP recovery was 94.6% from alpha-CD-linked chitosan bead by shaking both with a mixture of methanol and water (v/v = 8/2). The recovered alpha-CD chitosan bead was reusable as an adsorbent 20 times in the batch tests. The adsorbed PAE by alpha-CD-linked chitosan bead decreased as temperature increased. However, coexisting pH, NaCl, and Ca2+ did not affect adsorption efficiency. It was concluded that the application of low cost alpha-CD-linked chitosan bead could have the potential to effectively remove PAEs from different aquatic environments.     

基于分子模拟的离子交换层析中静电相互作用研究

将分子模拟方法引入到蛋白质离子交换层析中的静电相互作用研究。选用蛋清溶菌酶和牛胰凝乳蛋白酶为模型蛋白质,阳离子交换吸附剂SP Sepharose FF等为模型层析介质。从蛋白质数据库(PDB)中获得蛋白质三维结构数据,分析了介质孔径和配基分布,以点电荷模拟离子交换层析介质的功能配基,构筑了蛋白质-介质配基模拟表面体系。采用MCCE、Delphi和GRASP等程序包进行了分子模拟计算,考察了作用方向、作用距离、盐浓度、pH等对蛋白质和模拟配基平面间静电相互作用的影响。结果表明,宏观的层析平衡常数与微观分子模拟计算的相互作用能量参数间存在良好的线性关系。     

Preparation and properties of chitosan/carbon nanotube nanocomposites using poly(styrene sulfonic acid)-modified CNTs

Poly(styrene sulfonic acid)-functionalized carbon nanotubes (CNT-PSSA), which was obtained with atom transfer radical polymerization (ATRP), was utilized in preparation of chitosan/CNT nanocomposites (CH/CNT-PSSA). Chemical linkages between chitosan and CNTs form in the nanocomposites through the reaction between the sulfuric acid groups of CNT-PSSA and the amino groups of chitosan, to warrant the homogenous dispersion of CNTs. The CH/CNT-PSSA nanocomposites were superior to the neat chitosan polymer in thermal and mechanical properties, water and solvent uptakes, bond water ratios, and electrical conductivity. The attractive property of the CH/CNT-PSSA nanocomposites also implied their application potentials for separation membranes and sensor electrodes.     

Separation, characterization and hydrogel-formation of hemicellulose from aspen wood

Hemicellulose from aspen (Populus tremula) was isolated by an alkali extraction method, which was followed by hydrogen peroxide treatment, ultrafiltration and recovery by spray drying. The sugar composition and lignin content were monitored with HPLC at each step of the separation procedure. Size-exclusion chromatography showed a polymeric hemicellulose of relatively high molar mass. The product was characterized by ¹H and ¹³C NMR spectroscopy and was found to be composed of a linear (1→4)-β-linked -xylose main chain with a 4-O-methyl-- -glucuronic acid substituting the 2-position of approximately every eighth xylose unit. Lignin and O-acetyl groups had largely been removed in the separation process. The xylan was soluble in hot water, and the film forming properties were examined at various mixtures of the hemicellulose and chitosan. These films formed hydrogels with a high swelling capacity at certain compositions. The morphologies of the films were examined with wide angle X-ray spectroscopy, and a pure xylan film was found to be crystalline, which was suggested to be a consequence of the lack of O-acetyl groups. The crystallinity of the films was found to decrease with an increasing amount of chitosan, and the film of chitosan alone showed no crystallinity. The cohesive forces of the hydrogels are suggested to be the result of the crystalline arrangement of the polymers and of electrostatic interactions between acidic groups in the hemicellulose and amine groups in the chitosan.     

The influence of the degree of cross-linking on the adsorption properties of chitosan beads

The influence of the degree of cross-linking (DCL) on chitosan beads was studied. Chitosan was prepared from the exoskeleton of Cape rock-lobsters, collected from the surroundings of Cape Town, South Africa. The chitosan beads were characterized; the beads water contents and pKa varied in the range of 90-96% and 4.3-6.0, respectively, and were found to decrease with increasing DCL (0.0-34.0%). A pH-model, which described the reversibility of the metal adsorbed onto the beads, was used to predict the equilibrium properties of copper adsorption onto the cross-linked beads. The model accounts for the effect of pH and the important model parameters, the equilibrium adsorption constant (Kads) and to a lesser extent the adsorbent adsorption capacity (qmax) showed to decrease with the DCL. The adsorbent capacity and the adsorption constant were determined as 3.8-5.0mmol/g chitosan and (9-90)x10(-4), respectively. The adsorption kinetics could be described using a shrinking core model and the effective diffusion coefficient (Deff) was determined as (8.0-25.8)x10(-11)m2/s. It was found that Deff decreases with the DCL mainly due to the decreased in water content of the beads at high DCL.