基于美拉德反应的低聚壳聚糖衍生物的生物活性研究

以低聚壳聚糖作为氨基供体分别与提供羰基的葡萄糖和麦芽糖进行美拉德反应(氨基与羰基的物质量比均为1:1),醇沉法提取低聚壳聚糖美拉德反应衍生物CG和CM。对两种衍生物进行红外表征和分子量测定,并研究其抗氧化性能和抑菌性能。结果显示:两种衍生物均保留着低聚壳聚糖的特征吸收峰;其对O2.-、.OH及DPPH的清除能力以及还原能力和对大肠杆菌、铜绿假单胞菌和副溶血性弧菌的抑菌活性均得到显著提高,同时CG的抗氧化性和抑菌活性明显优于CM。即与单糖进行美拉德反应制得的壳聚糖衍生物具有更好的生物活性。     

基于与α-丙氨酸/天冬酰胺美拉德反应的低聚壳聚糖衍生物的抗氧化性能研究

研究低聚壳聚糖(COS)与α-丙氨酸/天冬酰胺(低聚壳聚糖的羰基与氨基的物质量比均为4:1)的美拉德反应。醇沉法提取与α-丙氨酸/天冬酰胺反应8、16h以及24h的低聚壳聚糖衍生物,分别记为:CA-8、CA-16、CA-24、CN-8、CN-16以及CN-24。对衍生物进行红外表征,并研究其对超氧阳离子O2.-、DPPH自由基的清除能力以及还原能力。结果显示:美拉德反应后低聚壳聚糖衍生物抗氧化能力得到显著提高。抗氧化能力强弱次序为CA-8>CN-8、CA-16>CN-16、CA-24>CN-24,即随着反应时间增加,低聚壳聚糖与α-丙氨酸美拉德反应的衍生物抗氧化性始终更强,表明与小分子氨基酸进行美拉德反应制得的壳聚糖衍生物具有更好的抗氧化性。     

基于与葡萄糖美拉德反应的低聚壳聚糖衍生物的抗氧化性能

以低聚壳聚糖作为氨基供体与提供羰基的葡萄糖进行美拉德反应(氨基与羰基的物质的量比分别为1:1、1:3和3:1),醇沉法提取反应4h的低聚壳聚糖衍生物CG11-4、CG13-4、CG31-4以及8h的衍生物CG11-8、CG13-8和CG31-8.对6种衍生物进行红外表征和相对分子质最测定,并研究其对超氧阴离子自由基(O...     

低聚壳聚糖与木糖的美拉德反应及其衍生物抗氧化性能研究

为研究反应时间对低聚壳聚糖衍生物抗氧化性能的影响,通过低聚壳聚糖与木糖的美拉德反应(低聚壳聚糖的氨基与木糖的羰基的物质量比为1∶1),考察了反应过程中吸光度及荧光值的变化,醇沉法提取4 h和8 h的低聚壳聚糖美拉德反应衍生物,分别为CX4和CX8。对两种衍生物进行红外表征和相对分子质量测定,并研究其对超氧阳离子O2-、羟基自由基OH和DPPH的清除能力以及还原能力。结果显示:UV-Vis光谱在278 nm波长处吸收峰于反应前期有明显增强,但4 h后增长非常缓慢;在343 nm的激发波长和435 nm发射波长下的荧光强度于反应前期快速增加,但2 h后呈下降趋势;两种衍生物对O2-、OH及DPPH的清除能力以及还原能力均得到显著提高,且CX8的抗氧化性明显优于CX4,即随着反应的进行壳聚糖衍生物的抗氧化性能不断提升。     

壳聚糖的美拉德反应及其产物的抗氧化性能研究

研究壳聚糖与葡萄糖的美拉德反应,考察了三个不同体系(壳聚糖的氨基与葡萄糖的羰基的物质量之比分别为1∶1、1∶2和2∶1)的反应过程中产物pH、吸光度以及其对超氧阴离子O2-.的清除状况。结果表明:三个体系的pH变化不大;美拉德反应产物(MRPs)的最大吸收波长均在460nm左右;不同体系得到的MRPs对O2-.都具有较好的清除效果,尤其以氨基与羰基物质量之比为1∶2的体系抗氧化性最好,并且MRPs的抗氧化能力不完全依赖于产物的褐变程度。     

L-赖氨酸与葡萄糖美拉德反应及其产物的抗氧化性能研究

研究L-赖氧酸与葡萄糖氨基和羰基不同比例的3个体系的美拉德反应(L-赖氨酸的氨基与葡萄糖的羰基的物质量之比分别为1:1、1:2和2:1),并以对超氧阴离子O_2,清除能力为指标,评价了美拉德反应产物(MRPs)的抗氧化能力。结果表明:美拉德反应是个酸度和褐变不断增强的反应;MRPs的最大吸收波长在460 nm左右;达到相同的褐变程度,即吸光度A为2.0时,3个体系的反应速率:1:2>1:1>2:1;不同体系得到的MRPs对O_2~-,都具有较好的清除效果,并且MRPs的抗氧化能力不完全依赖于产物的褐变程度。     

2种氨基酸与葡萄糖美拉德反应产物的抗氧化活性研究

以对DPPH自由基(DPPH·)的清除能力为抗氧化指标,研究脯氨酸、L-精氨酸分别与葡萄糖在不同反应条件下微波加热美拉德反应产物的抗氧化活性.探究了加热时间、微波功率、pH、氨基与羰基比4个因素对美拉德反应产物抗氧化性的影响,并通过正交实验得到最佳工艺条件.脯氨酸为:加热时间5 min,微波功率800W,pH5,氨基与羰基比1∶2.5,对DPPH·清除率为98.94％.L-精氨酸为:加热时间5min,微波功率800W,pH8,氨基与羰基比为2∶1,对DPPH·清除率为96.81％.4个因素对美拉德反应产物的DPPH·清除率的影响均极显著.     

低聚木糖-脯氨酸美拉德反应衍生物的制备及其抗氧化性能

以低聚木糖作为羰基供体与脯氨酸进行美拉德反应,监测反应过程中p H、紫外-可见吸收值以及荧光值,提取反应5 h、15 h以及30 h的低聚木糖衍生物XP-5h、XP-15h和XP-30h。对3种衍生物进行红外表征和相对分子质量测定,并研究其对DPPH自由基、超氧阴离子自由基(O-2·)的清除能力以及还原能力。结果表明:低聚木糖衍生物对DPPH自由基、O-2·的清除能力以及还原能力均较低聚木糖得到显著提高;XP-30h的抗氧化性最强,XP-15h次之,XP-5h最弱,即随着反应的进行低聚木糖衍生物的抗氧化性能增强。     

葡萄糖与赖氨酸美拉德反应产物的抗氧化性研究

采用赖氨酸与葡萄糖发生美拉德反应,研究了不同反应条件(温度、时间、pH和反应物浓度)对美拉德反应产物(Maillard Reaction Products,MRPs)抗氧化性能的影响,并以对超氧阴离子自由基(02-·)清除率和DPPH·清除率为指标,评价了MRPs的抗氧化能力.确定不同反应体系得到的MRPs,都具有较好的清除效果;其中最佳抗氧化反应模式为:反应时间8h,pH9,温度为100℃,氨基与羰基比1:2时,对02-·和DPPH·清除率分别可达到82.35％和71.12％.     

壳聚糖-单糖美拉德反应产物的制备及其在抗菌和抗氧化中的应用研究进展

蛋白质-单糖在食品加工中发生美拉德反应产生的芳香类物质在食品领域有着广泛的应用。壳聚糖也可与单糖发生美拉德反应,产生的美拉德反应产物(类黑精)与壳聚糖本身相比抑菌和抗氧化能力明显增强。鉴于国内外对壳聚糖-单糖之间的美拉德反应及其产物的深入研究鲜少,本文综述了壳聚糖-单糖美拉德反应产物的制备及其在抑菌和抗氧化方面的最新研究进展,为其在食品加工和保鲜中的广泛应用提供理论依据。     

Antioxidant activity of oligochitosan Maillard reaction products using oligochitosan as the amino or carbonyl groups donors

The purpose of this study was to evaluate the influence of oligochitosan (COS) as amino (–NH₂) or carbonyl group (–C=O) donors on the antioxidant activities of COS Maillard reaction (MR) products. Two kinds of COS MR products (COS MRPs) were prepared by using COS and glucose/α-alanine, respectively. Their structures were characterized by Fourier transform infrared spectroscopy (FT-IR), their molecular weights (Mws) were measured by gel permeation chromatography, and the –NH₂ contents of COS MRPs were determined. The antioxidant activities of COS MRPs were evaluated by measuring the scavenging activity of superoxide anion radical (O₂^?), 1,1-diphenyl-2-picrylhydrazyl radical, and the reducing power. The result showed that C=N absorbance can be observed in CG (MRPs of COS and glucose) and CA (MRPs of COS and α-alanine). The Mw of COS increased after MR. CG and CA showed dramatically enhanced antioxidant activity compared to COS, and the antioxidant activity of CG was better than that of CA. In other words, MR is an efficient way to enhance the antioxidant activity of COS. Moreover, it is a more efficient way to enhance the antioxidant activity of COS by using COS as amino group donor involved in MR. The results may provide some references to the modification and application of COS.     

取代度相同的N-酰化低聚壳聚糖清除自由基作用的研究

低聚壳聚糖经N-酰化得到取代度相同的N-马来酰低聚壳聚糖和N-邻苯二甲酰低聚壳聚糖,其取代度均为0.25。用红外光谱对其结构进行表征,凝胶色谱测定其相对分子质量大小。并考察了其对羟基自由基(.OH)和1,1-二苯基苦基苯肼自由基(DPPH)的清除能力。结果表明:取代度相同,N-邻苯二甲酰低聚壳聚糖对.OH、DPPH的清除能力优于N-马来酰低聚壳聚糖。这说明取代度相同时,取代基的结构会影响N-酰化低聚壳聚糖对自由基的清除活性。     

壳寡糖修饰多聚半乳糖醛酸酶优化条件研究

以水溶性低分子量壳寡糖作为修饰剂对已纯化的多聚半乳糖醛酸酶进行化学修饰,通过单因素试验和正交试验探讨pH值、温度、修饰时间、壳寡糖的用量等因素对修饰效果的影响和最佳修饰条件的优化筛选.结果表明,通过正交试验筛选出最佳修饰反应条件为:80 mg活化的多聚半乳糖醛酸酶,反应体系中pH为4.0,反应温度为3℃,反应时间为12h,壳寡糖用量为150 mg,修饰效果最佳.利用此条件对多聚半乳糖醛酸酶进行化学修饰具有显著的激活作用,修饰后酶的比活力是340.10 U/mg protein,比修饰前提高了153.42％.     

Synthesis,characterization and functional properties of galactosylated derivatives of chitosan through amide formation

Low molecular weight chitosan (LMWC) and chitooligosaccharide (COS) derivatives were obtained by the introduction of lactobionic acid (LA) through amide formation, obtaining different complexes COS-LA and LMWC-LA (1–5), with a degree of substitution (DS) between 3 and 16%. The synthesis of these derivatives was monitored by Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FT-IR), High-Performance Liquid Chromatography-Size Exclusion Chromatography (HPLC-SEC) and proton Nuclear Magnetic Resonance (¹H NMR) analyses. Different functional properties, solubility, water binding capacity (WBC) and fat binding capacity (FBC), as well as the antioxidant activity (DPPH radical scavenging activity) of these derivatives were evaluated. Solubility, WBC and FBC increased in all of the chitosan derivatives respect to those of the native LMWC or COS. The most substituted derivative (LMWC-LA1, DS 15%) presented the highest value of solubility (14.4 mg/mL) while the highest levels of WBC and FBC were obtained for the derivative with a DS of 3% (LMWC-LA5; 4730% and 7100%, respectively). COS and COS-LA presented the best DPPH scavenging abilities, as shown by their low values of EC₅₀ (1.29 and 3.45 mg/mL, respectively). An inverse relationship between the DS of chitosan derivatives and antioxidant activity was observed. LMWC-LA5 (3% DS) was the derivative with the highest DPPH activity, being higher than LMWC in all the concentrations assayed (10.2–14.3% and 6.9–13.7%, respectively). Due to their enhanced functional properties, these chitosan derivatives could be considered as very promising for their future use as additives in the food industry (i.e. to bind fat and cholesterol or avoid hardening of foods).     

2,4-二氯苯氧乙酸壳寡糖酯的制备及抗菌活性研究

以壳寡糖、2,4-二氯苯氧乙酸为原料,经壳寡糖氨基保护、2,4-二氯苯氧乙酸的羧基酰氯化、酰氯化后的2,4-二氯苯氧乙酸与壳寡糖羟基反应、脱除壳寡糖氨基保护最终得到2,4-二氯苯氧乙酸壳寡糖酯(Dcpo-O-COS)。通过傅里叶红外、紫外可见吸收、1 H核磁共振对2,4-二氯苯氧乙酸壳寡糖酯进行了结构表征,证明成功合成终产物。经X射线衍射仪、热分析仪、抗菌性研究测定,终产物的热稳定性、对大肠杆菌及金黄色葡萄球菌的抗菌性较原料壳寡糖有所提高。     

Anticoagulant activity of heterochitosans and their oligosaccharide sulfates

Three kinds of partially deacetylated heterochitosans, 90% deacetylated chitosan, 75% deacetylated chitosan and 50% deacetylated chitosan, were prepared from crab chitin by N-deacetylation with 40% sodium hydroxide solution for different durations. Nine kinds of heterochitooligosaccharides (hetero-COSs) with relatively high molecular weights (5,000–10,000 Da; 90-HMWCOSs, 75-HMWCOSs, and 50-HMWCOSs), medium molecular weights (1,000–5,000 Da; 90-MMWCOSs, 75-MMWCOSs, and 50-MMWCOSs), and low molecular weights (below 1,000 Da; 90-LMWCOSs, 75-LMWCOSs, and 50-LMWCOSs) were prepared using an ultrafiltration membrane reactor system, respectively. In addition, their sulfated derivatives were prepared by a method using a trimethylamine-sulfur trioxide, and the anticoagulant properties of the heterochitosans and their COS sulfates with different chain lengths and degrees of deacetylation were investigated. Clotting times in thrombin-time assay were prolonged in the presence of various concentrations of the heterochitosans and their COS sulfates using normal human plasma. The 90% deacetylated chitosan sulfate exhibited the highest anticoagulant activity among all the heterochitosans and their COS sulfates.     

Synthesis of chitosan-caffeic acid derivatives and evaluation of their antioxidant activities

In this study, the antioxidant activities of different molecular weights (M_w) and grafting ratios of chitosan–caffeic acid derivatives were investigated. The grafting process was achieved using 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDAC) as covalent connector under different conditions such as molecular-weight of chitosan, molar ratio of chitosan and caffeic acid, reaction temperature, pH, and reaction time. The half-inhibition concentrations (IC₅₀) of products were calculated by reduction of the 1,1-diphenyl picryl hydrazyl in the radical-scavenging assay and reduction of the Fe³⁺/ferricyanide complex to the ferrous form in reducing power assay. The EDAC showed maximum activity at 3-h, pH 5.0 and room temperature conditions, except high-molecular-weight chitosan in pH 2.0. The products were water-soluble in all pH and showed lower viscosity than native chitosan. The highest grafting ratio of caffeic acid was observed at 15% in low-molecular-weight chitosan. After 5% grafting of caffeic acid into chitosan, the grafting efficiency was increased by decreasing molecular-weight of chitosan at the same conditions. Caffeic acid has main role in the antioxidant activity of products. The maximum IC₅₀ of radical-scavenging activity (0.064 mg/ml) was observed at the highest caffeic acid containing derivative. Water-soluble chitosan and caffeic acid derivatives were obtained by this study without activity loss.     

Preparation of antibacterial chito‐oligosaccharide by altering the degree of deacetylation of β‐chitosan in a Trichoderma harzianum chitinase‐hydrolysing process

BACKGROUND: Chito‐oligosaccharide (COS) is generally known to possess many specific biological functions, especially antibacterial activity, depending on its size. To prepare a specific size range of COS, however, has proved difficult. The aim of this study was to establish a method for preparing a specific size range of antibacterially active COS by adjusting the degree of deacetylation (DD) of β‐chitosan in a Trichoderma harzianum chitinase‐hydrolysing process. RESULTS: The molecular weight spectrum, elucidated by viscosity‐average molecular weight, high‐performance liquid chromatography and thin layer chromatography, of COS in chitosan hydrolysate was significantly related to the DD of its original chitosan. Compared with the original form, COS produced at 90% DD showed superior activity against most Gram‐negative bacteria tested, with a minimum inhibition concentration (MIC) ranging from 55 ± 27 to 200 ± 122 µ g mL^?1. Conversely, most Gram‐positive strains tested were less sensitive to COS (MIC > 880 ± 438 µ g mL^?1) than to its original form. Among the Gram‐positive strains, Staphylococcus xylosus was the only exception in that it showed a high susceptibility to COS and had an MIC as low as 45 ± 11 µ g mL^?1. CONCLUSION: The results indicate that the production of a specific size range of COS product is possible by altering the DD of chitosan in the chitinase‐catalysed process. To produce various sizes of COS for versatile biological functions, as seen in this study to inhibit various types of bacteria, is made possible in this established process. Copyright © 2008 Society of Chemical Industry