不同分子量羧甲基茯苓多糖的制备及其抗氧化活性的研究

目的:研究分子量对羧甲基茯苓多糖抗氧化活性的影响。方法:将茯苓多糖进行羧甲基化得到了一种取代度为0.90±0.007的羧甲基茯苓多糖(CMP-1),凝胶渗透色谱法测得CMP-1的分子量为60.9×10~4u。利用H_2O_2对其进行氧化降解后,得到了分子量分别为10.7×10~4 u、3.22×10~4 u和1.09×10~4 u左右的降解产物CMP-1-1,CMP-1-2和CMP-1-3。应用铁氰化钾还原法、DPPH自由基测定法和Fenton法来测定CMP-1及其低分子量降解产物的抗氧化性。结果:随着分子量的降低,羧甲基茯苓多糖抗氧化活性增强,并且多糖对Fe~(3+)的还原能力和对DPPH自由基、羟自由基的清除能力存在剂量依赖关系,其中CMP-1-3的抗氧化活性最强。结论:羧甲基茯苓多糖作为一种成分单一的多糖,其分子量的降低能有效地增强其生物活性。     

低分子量磺化壳聚糖的制备及其抗氧化活性研究

均相体系中,采用H2O2氧化降解法得到低分子量壳聚糖;以其为原料,氯磺酸-二甲基甲酰胺(DMF)为磺化试剂,在较温和的条件下制备低分子量磺化壳聚糖(S-LCTS),产物分子量较磺化壳聚糖(S-CTS)显著降低.红外光谱分析表明,所得产物在1236cm-1和808cm-1处有特征吸收,分别显示出-SO3H基团中S=O和C-O-S的伸缩振动.本文还检测了所得产物对超氧自由基(O2-·)、过氧化氢(H2O2)以及l,1-二苯代苦味酰基自由基(DPPH·)的清除效果.实验结果显示,S-LCTS对O2-·、H2O2和DPPH·的清除效果明显优于S-CTS,显示了良好的抗氧化活性.     

低分子量的羧甲基壳聚糖的制备

讨论了低分子量羧甲基壳聚糖的制备方法,重点研究了均相反应条件下过氧化氢氧化降解的工艺条件,考察了反应的温度和过氧化氢的浓度对产物的影响.将温度控制在70～80℃、过氧化氢用量比在1.5～2.5左右,得到平均分子量在8000左右的羧甲基壳聚糖.     

羧甲基茯苓多糖的抗氧化活性研究

研究羧甲基茯芩多糖的体内外抗氧化作用.通过测定羧甲基茯苓多糖的总还原能力及对羟基自由基、超氧阴离子和过氧化氢的清除作用,证明羧甲基茯苓多糖的体外抗氧化作用;通过测定小鼠血清和肝脏中的MDA含量和SOD活性的变化,研究了羧甲基茯苓多糖对小鼠体内的抗氧化作用.羧甲基茯苓多糖可以抑制小鼠血清和肝脏中MDA的生成,增强小鼠血清和肝脏中SOD的活性;羧甲基茯苓多糖具有一定的还原能力,可以清除羟基自由基、超氧阴离子和过氧化氢.羧甲基茯苓多糖具有明显的抗氧化作用.     

不同取代度O-羧甲基壳聚糖的抗氧化性能

低聚壳聚糖经醚化得到O-羧甲基壳聚糖OA、OB和OC,取代度(DS)分别为0.54、0.38和0.31,对其结构进行表征,并考察了其对超氧阴离子自由基、过氧化氢的清除活性以及还原能力.结果表明:随着DS的增加,样品清除超氧阴离子的活性增强;而清除过氧化氢的活性以及还原能力的强弱顺序为:OB＞OA＞OC,这可能是由于O-羧甲基壳聚糖的取代度和对自由基的清除机理不同所致.     

壳聚糖／壳寡糖衍生物的制备及其抗氧化性能研究

壳聚糖和壳寡糖经化学改性得到季铵盐衍生物-O-2′-羟丙基三甲基氯化铵壳聚糖/壳寡糖,通过红外光谱对其结构进行表征.考察了两种季铵盐衍生物对DPPH自由基的清除活性以及还原能力.当质量浓度为0.6 mg/mL时,壳聚糖季铵盐和壳寡糖季铵盐对DPPH自由基的清除率分别为9.5 %和29.3 %.在还原体系中,当质量浓度为2.5 mg/mL时,其吸光度分别为0.11和0.43.结果表明:通过化学改性,得到的壳聚糖季铵盐衍生物水溶性优良、具有抗氧化活性;壳寡糖季铵盐清除自由基的活性和还原能力强于壳聚糖季铵盐衍生物.这可能由于壳寡糖分子链短,更多活性氨基和羟基暴露出来参与抗氧化反应所致.     

香蕉皮多酚清除自由基作用的初步研究

采用羟基自由基体系、超氧阴离子自由基体系、还原能力、过氧化氢体系、亚硝酸盐体系对香蕉皮多酚的抗氧化活性进行研究,并与Vc进行了比较。结果表明:在试验浓度范围内(0.1￣4mg/mL),香蕉皮多酚对这几种体系均有不同程度的抗氧化作用。对羟基自由基的清除作用要弱于Vc,对超氧阴离子自由基没有清除作用,还原能力强于Vc,清除过氧化氢和亚硝酸盐能力与Vc接近。     

超声波辅助酶法制备壳寡糖及抗氧化活性研究

壳寡糖是壳聚糖降解后的产物,其与壳聚糖相比分子量更小,水溶性更好,生物利用度更高的特点。本实验拟采用超声波辅助果胶酶处理壳聚糖制备壳寡糖,通过正交试验优化制备工艺。结果表明,最佳工艺条件为:酶浓度1600 U/g,酶解温度50℃,反应时间60 min,超声波功率120 W。在该条件下获得的降解产物中还原糖浓度为1.96 mg/mL,制备效果优于超声波和酶解分别降解的方法。对此法制备的壳寡糖的体外抗氧化活性进行研究,结果表明对DPPH自由基和羟自由基均有较强的清除能力。     

蓝莓冻果多酚粗提物体外抗氧化活性的研究

选用过氧化氢体系、羟基自由基体系、超氧阴离子自由基体系、亚硝酸盐体系、还原能力对蓝莓冻果多酚粗提物进行抗氧化活性的测定,并与VC做对比.在试验浓度范围内(0.5～10 mg/mL),蓝莓冻果的多酚粗提物对几种体系有不同程度的抗氧化作用,清除过氧化氢能力较强,清除羟基自由基和亚硝酸盐的能力明显弱于VC,还原能力及清除超氧阴离子能力与VC较为接近.     

蛋清蛋白肽体外抗氧化作用模式的研究

目的 研究蛋清蛋白肽抗氧化作用模式。方法 利用超滤技术分离蛋清蛋白木瓜蛋白酶酶解产物; 采用Fenton体系、邻苯三酚自氧化体系和亚油酸自氧化体系分别测定超滤各组分清除羟自由基、超氧阴离子及抑制脂质过氧化的能力, 同时测定各组分对二苯代苦味肼基自由基清除能力(DPPH自由基)、还原能力及对猪胎儿成纤维细胞(porcine embryonic fibroblast, PEF)过氧化损伤的保护作用。结果 超滤各组分中分子量小于3 kDa组分(蛋清蛋白酶解产物-Ⅲ, egg white protein hydrolysate, EWPH-Ⅲ)占蛋清蛋白酶解产物(EWPHs)总量的50.06%。EWPH的抗氧化活性随分子量的降低而增强(P<0.05), 其中EWPH-Ⅲ在浓度为5 mg/mL时, 对羟自由基、超氧阴离子、DPPH自由基的清除率分别为52.86%、35.05%和78.74%, 对亚油酸氧化的抑制率为74.57%。在浓度为2.5 mg/mL时, PEF细胞存活率达到70.06%。结论 蛋清蛋白肽具有较强的抗氧化活性且分子量越小, 抗氧化活性越强, 可以作为氢供体、自由基稳定剂和金属离子螯合剂来抑制过氧化作用。     

降解壳聚糖对肉品保鲜效果的试验研究

目的:制备降解(低分子质量)壳聚糖并考察对肉品的保鲜效果。方法:采用H2O2均相氧化降解壳聚糖,以乌氏黏度法测其黏均分子质量;用牛津杯法测定降解壳聚糖对大肠杆菌、金葡菌、霉菌的抑菌圈直径;喷洒降解壳聚糖溶液于肉品表面,用表面涂抹法测定肉品在25℃放置过程中菌落总数的变化。结果:影响降解壳聚糖分子质量大小的因素顺序为:时间>温度>H2O2浓度>HAc浓度;在反应时间6h、温度75℃、H2O2体积分数6%和HAc体积分数4%时,可得黏均相对分子质量为2300的可溶性壳聚糖;降解壳聚糖对大肠杆菌、金葡菌的抑菌率高于未降解壳聚糖,而对霉菌的抑菌性变化不大;经质量分数6%、黏均分子质量2300壳聚糖溶液喷洒肉品表面后,鲜猪肉4d、熟猪肉6d可保持良好色泽、弹性、气味,且菌落总数符合GB2726-2005要求。结论:低分子质量壳聚糖可作为肉品防腐保鲜剂。     

Preparation of chitosan oligomers and their antioxidant activity

Chitosan oligomers with different molecular weights were prepared by oxidative degradation method involving hydrogen peroxide (H₂O₂) and the combined degradation method using hydrogen peroxide and microwave radiation. Viscosity determination and end group analysis were applied to measure molecular weights of chitosan oligomers. Effects of concentration of H₂O₂ and degradation time on molecular weights of chitosan oligomers were studied. Both methods were effective to prepare chitosan oligomers from the initial chitosan (8.5×10⁵ Da). The degradation process of chitosan will be accelerated with the aid of microwave and degradation time may be reduced. The antioxidant activity of chitosan oligomers was evaluated as radical scavengers against superoxide anion and hydroxyl radical by application of flow injection chemiluminescence technology. Chitosan oligomers A, B, C and D (2300, 3270, 6120, and 15,250 Da) had different antioxidant activity. Among the four chitosan oligomers, oligomer D (15,250 Da) had the lowest scavenging ability against superoxide anion and hydroxyl radicals. For superoxide anion scavenging, the 50% inhibition concentrations (IC₅₀s) of other three oligomers A, B, and C were 5.54, 8.11, and 12.15 mg/mL, respectively. And for hydroxyl radical scavenging the values were 0.4, 0.76, and 1.54 mg/mL, respectively. At the concentration range examined, the maximal inhibiting efficacy of A, B, C, and D were 89, 75, 74, and 41% for superoxide anion, and 71, 65, 51, and 7% for hydroxyl radical. These results indicated that chitosan oligomers with lower molecular weight had better antioxidant activity.     

不同黏均分子量壳聚糖制备及在染整中的应用

研究了壳聚糖在中性条件下用H2O2进行氧化降解的情况，讨论了反应温度和H2O2浓度对氧化降解反应的影响。结果表明，用H2O2使壳聚糖在中性条件下氧化降解是制备低分子量壳聚糖的一种简便易行的方法，以分子量为4.5万左右的壳聚糖预处理的棉织物，对活性染料染色增深效果最明显。     

糖化酶/H2O2二步法降解壳聚糖的研究

研究糖化酶/H2O2二步法降解壳聚糖的工艺条件。以降解产物壳寡糖的相对分子质量和收率为指标,采用单因素和正交试验确定壳聚糖降解的优化工艺条件为酶底质量比0.008,酶解温度62℃,酶解时间33h,H2O2的添加量12.6%,该条件下可以将相对分子质量为2.5×105的壳聚糖降解为分子量为470～1 102的壳聚糖,收率为83.3%。二步法可以更好地降解高分子量的壳聚糖,为壳聚糖的综合利用提供了新途径。     

H_2O_2/HAc氧化降解壳聚糖的探讨

采用过氧化氢-醋酸氧化降解法,探讨冰醋酸用量、反应温度、过氧化氢用量和反应时间对降解壳聚糖分子量的影响。     

Antibacterial Activity of Ozone‐Depolymerized Crawfish Chitosan

ABSTRACT: Antimicrobial activities of chitosan samples with different molecular weights (1333, 432, 201, 131, and 104 kDa) prepared by ozone treatment were examined against 2 Gram‐positive bacteria (Listeria monocytogenes and Staphylococcus aureus) and 2 Gram‐negative bacteria (Escherichia coli and Pseudomonas fluorescen) to investigate the effect of chitosan's molecular weight and concentration on the inhibition of bacterial growth. Antimicrobial activity of chitosan varied depending on the molecular weight, concentration of chitosan, and type of microorganism. Generally, the effectiveness of the chitosans significantly increased with increasing chitosan concentration, regardless of molecular size and types of bacteria. Chitosan with molecular weights ranging from 104 to 201 kDa showed relatively greater antimicrobial activity against L. monocytogenes, S. aureus, and P. fluorescen; whereas for E. coli, intermediate molecular weight chitosan was more effective in growth inhibition than lower or higher molecular weight chitosan particularly at 0.1% concentration.     

微波强化壳聚糖固相酸降解研究

本文研究了微波强化下的壳聚糖固相酸降解反应,分析了降解过程中微波辐射功率和盐酸用量等参数对降解产物分子量变化的影响,并利用红外光谱和核磁共振氢谱对降解产物的结构进行了表征。研究表明,微波辐射功率和盐酸用量的增加均有利于壳聚糖分子量的降低。采用微波辐射壳聚糖固相酸化物料15 min,即可获得重均分子量低于50000的低分子量壳聚糖,且糖单元的结构在反应过程中保持稳定。采用微波强化固相酸降解和酶降解复合工艺制备壳寡糖,壳寡糖单位时间内的产能可提高4倍以上。综上所述,本研究建立了一种基于微波强化的壳聚糖固相酸降解的高效制备低分子量壳聚糖和壳寡糖的方法,有助于低分子量壳聚糖和壳寡糖的广泛应用。     

乙酸均相体系中脉冲电场对壳聚糖降解的影响

以脉冲电场为处理手段,研究电场强度、处理时间、壳聚糖质量浓度和电导率等因素对壳聚糖大分子降解的影响。结果表明：壳聚糖降解产物的相对分子质量随着电场强度的增大而降低,且在高场强下降解显著,电场强度为33.3kV/cm时,降解率达54.2%;降解速率随处理时间的延长逐渐变缓,前20min和后70min的降解率分别为18.5%和8.5%;而壳聚糖质量浓度和电导率的升高则不利于壳聚糖的降解。傅里叶变换红外光谱分析(FT-IR)分析表明,降解前后壳聚糖的侧链结构未发生改变;原料及经相同方法处理过的降解产物在2θ为10.4°和20.2°处均存在X射线衍射峰,表明产物的晶体结构没有发生明显变化。     

Effect of the molecular weight and concentration of chitosan in pork model burgers

Chitosan of high and low molecular weights was added at 0%, 0.25%, 0.5% and 1% concentrations to a burger model system. Burgers were evaluated by physicochemical analysis, cooking characteristic and storage stability. The antioxidant activity of chitosan was studied in vitro. The addition of chitosan influenced pH and color properties, in molecular weight and concentration dependent ways. Cooking properties were significantly affected by the chitosan. High molecular weight chitosan improved all cooking characteristics compared with control samples. Low molecular weight chitosan increased the shelf life of burgers, enhanced the red color and reduced total viable counts, compared with control and high molecular weight chitosan samples. The antioxidant activity of chitosan was dependent on molecular weight and concentration. The results indicate that high molecular weight chitosan (HMWC) improves all cooking characteristics and antioxidant activity while low molecular weight chitosan extends the red color and reduces total viable counts.     

Radical scavenging activity of hetero-chitooligosaccharides

Nine hetero-chitooligosaccharides (hetero-COSs) consisting of relatively high molecular weights (90-, 75-, and 50-HMWCOS), medium molecular weights (90-,75-, and 50-MMWCOS), and low molecular weights (90-, 75-, and 50-LMWCOS) were prepared from partially deacetylated hetero-chitosans (90%, 75%, and 50% deacetylated chitosan), and their antioxidant activity based on their scavenging potency on the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical was investigated. The results showed that the 90-MMWCOS, prepared from 90% deacetylated chitosan, showed the highest scavenging activity on the DPPH radical. Their scavenging pattern was dose- and time-dependent. Electron spin resonance (ESR) spectrum of DPPH treated with 90-MMWCOS decreased in a time-dependent manner and the reducing power of hetero-COSs increased in a dose-dependent manner. These results indicated that hetero-COSs have an antioxidant activity which is dependent on their degree of deacetylation and molecular weight.