天然抗氧化剂茶多酚的提取工艺

茶叶中一般含有20％－30％的多羟基酚类化合物,茶多酚可用作食品抗氧化剂。常用离子沉淀提取法、树脂吸附分离法、有机溶剂萃取法提取。采用酒石酸铁比色法测定茶多酚含量。     

Cultivar Characterization of Tea Seed Oils by Their Active Components and Antioxidant Capacity

Cultivar characterization of tea seed oils based on their active components and antioxidant capacity was carried out, providing fundamental data for authentication. The seeds were collected from 28 cultivars grown under the same conditions in the region of Anxi county of Fujian province and their oils were analyzed. The results showed that total phenols content (TPC), total flavonoids content, α-tocopherol contents, γ-tocopherol content and δ-tocopherol content were 16.7–529.3 mg GAE/kg of oil, 4.4–208.7 mg rutin/kg of oil, 7.7–347.1 mg/kg of oil, 1.8–106.7 mg/kg of oil, 0.003–35.769 mg/kg of oil, respectively. The antioxidant capacity measured by DPPH radical scavenging activity (DPPH), oxygen radical absorbance capacity (ORAC), absorbance of protein carbonyl (APC) and the absorbance of protein hydroperoxides (APH) were 91.0–2,164.5 μmol/100 g of oil, 251.0–1,209.5 μmol/100 g of oil, 0.014–0.135, 0.034–0.458, respectively. The correlation analysis revealed that the presence of phenolic compounds was significantly correlated with the antioxidant capacity of tea seed oil. Principal Component Analysis revealed the first three components accounted for 81.31 % of the total variance within the data and the main contributor parameters were DPPH, ORAC, APC, APH and TPC. Hierarchical cluster analysis classified the cultivars into three groups, which were in line with the genetic relationship among the cultivars. Our results supplied basic data for the antioxidant mechanism research of tea seed oil and provided necessary information to develop a breeding program directed to tea seed cultivar selections with the high nutraceutical value of tea seed oil.     

增效剂对油溶性茶多酚硒的抗氧化增效作用研究

在100℃恒温及黑暗条件下,采用空气自然氧化考察了维生素C、酒石酸、柠檬酸对LTP-Se在蓖麻油中抗氧化性能。结果表明m(增放剂)的添加量为0.01%、0.03%、0.05%时,对油溶性茶多酚硒抗氧化增效效果较好,m(VC)添加量为0.05%,LTP-Se添加浓度为100mg/kg的油样抗氧化生最佳。     

超声辅助低共熔溶剂提取信阳毛尖茶多酚工艺优化及其抗氧化活性和对肠道菌群的影响

目的:探究超声辅助低共熔溶剂法(deep eutectic solvent,DES)提取信阳毛尖茶多酚的工艺流程,及其体内外抗氧化活性和对肠道菌群的调控能力。方法:采用单因素正交法优化超声辅助低共熔溶剂提取信阳毛尖茶多酚的最佳工艺,以对1,1 -二苯基-2-三硝基苯肼(DPPH)、羟基自由基以及2,2-联氮-二(3-乙基-苯并噻唑-6-磺酸)二铵盐(ABTS)的清除能力为体外抗氧化方法。同时利用细胞抗氧化活性(CAA)法测定茶多酚在细胞水平的抗氧化活性。此外将60只健康雄性C57BL/6小鼠随机分为6组,即空白组(NC)、模型组(MC)、阳性对照组(PC)、茶多酚低剂量组(LTP,5.0 mg/kg bw)、茶多酚中剂量组(MTP,10.0 mg/kg bw)和茶多酚高剂量组(HTP,20.0 mg/kg bw),除NC组外腹腔注射50 mg/kg bw的D-半乳糖建立衰老模型。给药结束后测定各组小鼠肝脏和肾脏的脏器指数、血清生化指标、血清免疫指标和血清氧化指标。并采用16S rRNA 基因高通量测序对各组小鼠盲肠内容物进行聚类及多样性分析。结果:信阳毛尖茶多酚提取的最佳工艺为:DES氯化胆碱:乙酸按摩尔比为1:3,含水率30%、超声温度40℃、超声时间25 min、超声功率115 W、料液比1:35 (g:mL)。此外,体外抗氧化活性研究表明当茶多酚浓度为6g/L时,对DPPH自由基、羟基自由基和ABTS自由基的清除率分别高达59.23、60.49%和41.65%。CAA分析表明当茶多酚浓度为5g/L时,CCA值可达到63.2。动物实验结果表明信阳毛尖茶多酚可显著降低血清中低密度脂蛋白胆固醇(LDL-C),谷草转氨酶(AST)和谷丙转氨酶(ALT)水平,并升高高密度脂蛋白胆固醇(HDL-C)的水平,对衰老小鼠脏器具有一定的保护作用。此外茶多酚可升高促炎因子白细胞介素-12(IL-12)、白细胞介素-6(IL-6)和肿瘤坏死因子-α(TNF-α)的水平,降低抗炎因子白细胞介素-10(IL-10)水平,来改善致衰小鼠的炎症反应。茶多酚也可使血清中谷胱甘肽过氧化物酶(GSH-Px)和超氧化物歧化酶(SOD)的酶活升高,而丙二醛(MDA)水平下降,从而增加小鼠抗氧化能力。肠道菌群分析显示茶多酚通过改变肠道菌群的丰度和多样性,特别是增加有益菌乳杆菌属(Lactobacillus)、假丝酵母菌属(Candidatus_Saccharimonas)、棒状杆菌属(Corynebacterium)的丰度,降低有害菌Muribaculaceae和脱硫弧菌属(Desulfovibrio)的丰度,从而改善D-半乳糖致衰小鼠肠道菌群的紊乱,进而有效调控小鼠代谢通路的正常运行。结论:本研究提供了一种绿色高效提取信阳毛尖茶多酚的方法,且该茶多酚具有一定的抗氧化活性和调节肠道菌群的能力,旨在为信阳毛尖茶的深入研究和产业化奠定基础。     

微波法提取辣椒中抗氧化物质的工艺研究

采用微波法探讨了干辣椒中提取物的抗氧化效果,通过测定吸光度表征提取物对羟自由基(·OH)的清除率并通过正交试验对提取工艺进行优化。结果表明:乙醇体积分数为95%、提取时间为1 min、微波功率为60W时·OH的清除率最高。     

茶多酚及其氧化产物清除不同体系产生的活性氧自由基的分光光度法研究

用分光光度法测定了茶多酚及其氧化产物对不同体系产生的活性氧自由基O2· - 和·OH的清除作用。结果表明 :对由光照核黄素体系产生的O2· - ,在试验质量浓度范围 ( 8 3～ 1 67ug mL)内茶多酚及其氧化产物的最大清除率分别为 96 6%和 92 1 %。对由 2 脱氧 D 核糖体系产生的·OH ,在实验质量浓度范围 ( 5～ 80 0ug mL)内茶多酚及其氧化产物的最大清除率分别为83 4%和 88 5%。茶多酚氧化产物 ,SOD粗酶液 ,茶多酚对邻苯三酚自氧化产生的O2· - 均表现出较强的抑制作用 ,抑制率分别为 66 5% ,47 6% ,45 3%。茶多酚及其氧化产物与SOD有显著的协同增效作用 ,但氧化产物的效果强于茶多酚。     

Facile encapsulation of nanoparticles in nanoorganized bio-polyelectrolyte microshells

We present a facile method for the encapsulation of nanoparticles' (NPs) systems within the interior space of bio-polyelectrolyte microshells. The microshells, constructed by alternate adsorption of alginate sodium (ALG) and chitosan (CHI) onto the surface of colloidal templates and subsequent removal of cores, allow the polystyrene (PS) or SiO₂ nanoparticles (NPs) adsorbed into the internal shells through a simple mix process, as confirmed by confocal laser scanning microscopy (CLSM), and scanning electron microscopy (SEM) analysis. The NPs-filled microshells form the rigid spherical shape in contrast to the flat and folded structure of microshells at the dry state prior to filling. The interior of NPs-encapsulated microshells was directly visualized by transmission electron microscopy (TEM) image of microtomed slices and cross-section SEM image. The loading amount of NPs in a shell composed of (ALG/CHI)₅ was determined in two media i.e. H₂O and 0.1 M NaCl, and the results showed that the loading amount of the former is greater than that of the latter. The possible encapsulation mechanism is also discussed. The hybrid materials with NPs core and bio-polyelectrolyte shells have potential application for controlled-release drug delivery and catalysis.     

Polymer crosslinking controlled by release of catalyst encapsulated in polycarbonate micro-spheres

EVA crosslinking by ester-silane exchange reaction, controlled by catalyst released from polycarbonate micro-particles, was studied from rheological experiments. Firstly, dibutyltin dilaurate in polycarbonate (PC) (DBTDL) catalyst was encapsulated in polycarbonate micro-particles by an emulsion process. These PC micro-particles have a trimodal size distribution with a mean diameter around 25 μm. Furthermore, scanning electronic microscopy analysis revealed that the DBTDL catalyst is homogeneously dispersed in PC micro-particles. This was verified by DSC experiments which showed a T_g equal to 72 °C for the DBTL micro-particles. Secondly, the deformation and break-up studies of PC micro-particles in molten EVA matrix showed that PC micro-particles can only break up in EVA matrix of high molecular weight (EVA28-03) and for temperatures higher than 200 °C. Thirdly, rheological experiments showed that the crosslink reaction is controlled by the diffusion rate of DBTDL from PC micro-particles. However, this diffusion rate was observed to be independent on either the temperature or the PC micro-particles size.     

Factors influencing encapsulation behavior in composite droplet-type polymer blends

In this study the influence of the molecular weight of the dispersed phase components on encapsulation effects in the composite droplet phase was examined for high density polyethylene (HDPE)/PS/PMMA ternary blends. Three different blends composed of various PS and PMMA materials dispersed in an HDPE matrix were prepared using an internal mixer. The morphology was studied by light and electron microscopy. Current models used for predicting encapsulation effects and composite droplet formation in ternary systems (based on static interfacial tension) predict in all cases that PS will encapsulate the PMMA. However, in one case, an unexpected encapsulation of PS by PMMA was observed. It was found that arguments based on the effect of viscosity ratio or the absolute viscosity of the different dispersed phases do not explain that discrepancy. In addition, the reversal of that latter composite droplet morphology from PMMA encapsulating PS to PS encapsulating PMMA was observed upon annealing treatment. Considering all the above, a conceptual model was developed to predict encapsulation effects in composite droplet type systems based on the use of a dynamic interfacial tension (i.e. taking into account the elasticity of the polymer components). Calculations based on the dynamic interfacial tension model, using elasticities based on constant shear stress, were able to account for all of the observed encapsulation effects in this study.     

Green one-step synthesis of boron and nitrogen co-doped carbon dots based on inner filter effect as fluorescent nanosensors for determination of Fe3+

Significant efforts need to be devoted to enhancing the photoluminescence quantum yields (PLQY) of carbon dots (CDs) due to the typically low PLQY (< 10%) of currently synthesized CDs. Moreover, certain special industries such as textiles, paper, and food all have high requirements for water since Fe³⁺ can affect its color, odor, and taste. The traditional detection methods require expensive equipment, so a facile method to detect Fe³⁺ is urgently needed. In this work, the self-doping of nitrogen (N-CDs) has been achieved through tea residues as the carbon source to inhibit the oxygen-deficient state, and the doping of boric acid (BN-CDs) can activate the electron transition at the carbon site, which effectively enhanced the PLQY of CDs from 11.4% to 25.79% compared to N-CDs. Furthermore, as hydroxylated polyphenols in tea residues can adsorb metal ions, stable non-fluorescent matrix state complexes have been established between BN-CDs and Fe³⁺ to quench the FL owing to the inner filter effect. The linear relationship was formed in the concentration range of 0–60 μM, and the detection limit reached 0.07 μM. It demonstrates that along with the effective treatment of waste tea residues, the synthesized high fluorescence property BN-CDs are suitable to detect Fe³⁺ in water for textiles, paper, food, and other special industries.     

Formation and characterization of thiourea encapsulated polyethylene oxide

The structure and dynamics of PEO chains encapsulated in thiourea (TU) channels formed in the PEO-TU-inclusion compound (PEO-TU-IC) were studied by XRD, FTIR and solid state NMR spectroscopy. XRD and FTIR observations clearly show PEO-TU-IC adopts a crystal structure different from neat thiourea, and the usual rhombohedral crystal structure of thiourea small molecule ICs. PEO chains in the channel adopt a conformation similar to bulk PEO, as confirmed by solid state NMR spectroscopy. Contact-time array (VCT) NMR profiles shows that PEO chains in the TU channels are considerably more mobile than in bulk PEO. Infrared bands for the PEO shift in the IC, and these were attributed to changes in the secondary forces.     

塑封模浇注系统设计及充模CAE分析

某塑封模具在生产中易出现个别型腔充不满以及浇口处有瑕疵等问题。本文利用充模ＣＡＥ分析确定,上述问题是因为模具浇注系统设计不当所致。针对塑封模在浇注系统开设上易出现的问题,提出了新的解决方法和思路。     

Thermosensitive dendritic stars of tert-butyl-glycidylether and glycidol - Synthesis and encapsulation properties

Dendritic block copolymers of hydrophobic core and hydrophilic shell were prepared by a multi-step process based on anionic ring-opening polymerization. In the first step, amphiphilic stars with four or six poly(tert-butyl-glycidylether)-block-polyglycidol arms were synthesized. The hydroxyl groups of polyglycidol after ionization served as initiation centers for sequential anionic polymerization of tert-butyl-glycidylether and 1-ethoxyethyl-glycidylether. Selective removal of protective groups of glycidol hydroxyls yielded amphiphilic, dendritic copolymers with a hydrophobic core and hydrophilic shell. The hydrophobicity of the dendritic core depended on the composition of the star macroinitiator. The number of reactive hydroxyl groups in the shell was controlled by the number and length of the outer polyglycidol blocks. The structure and molar mass of the copolymers obtained were characterized by GPC-MALLS and NMR spectroscopy.The aqueous solution properties of the copolymers were studied. Some of dendritic copolymers aggregated at elevated temperature. The dependence of phase transition temperature and dimension of aggregates on the copolymer composition were followed by light scattering techniques. The spherical aggregates were visualized by AFM. The encapsulation efficiency of a hydrophobic compound (pyrene) was followed by UV-VIS spectroscopy.     

Polyaniline/polyacrylate core–shell composites: Preparation,morphology and anticorrosive properties

Polyaniline/partially phosphorylated poly(vinyl alcohol)/polyacrylate nanoparticles ((PAn/P-PVA)_x/PAc_y) were synthesized by encapsulation of varying amounts of PAn/P-PVA nanoparticles (x = 0.3, 0.5 or 0.7 g) with PAc (y = 4, 6 or 8 g acrylate monomers) via emulsifier-free emulsion polymerization. A monomer conversion level of 93.9% was achieved for the synthesis of the (PAn/P-PVA)_0.5/PAc₄ nanoparticles. X-ray diffraction analysis revealed that PAc was intercalated between the PAn/P-PVA layers, whilst transmission electron microscopy analysis of the different nanoparticles revealed they were spherical PAn/P-PVA agglomerates coated with PAc. Thermogravimetric analysis revealed that the thermal stability of the (PAn/P-PVA)/PAc nanoparticles decreased with increasing amounts of PAc. Cyclic voltammetry based analysis of the different (PAn/P-PVA)/PAc nanoparticles coated onto carbon fiber electrodes revealed that the PAn/P-PVA nanoparticles were encapsulated sufficiently by the non-conductive PAc and that the peak current decreased with increasing amounts of acrylate. With respect to the corrosion resistance in 1.0 M sulfuric acid, steel coated with the (PAn/P-PVA)_0.7/PAc₈ nanocomposite showed the best corrosion resistance (11.4%), but for the nanocomposites at each PAn/P-PVA loading level, the anticorrosive properties increased with increasing PAc levels, presumably due to the increasing tortuosity of the diffusion pathway through the coating for any corrosion agents.     

Preparation of acrylate polymer/silica nanocomposite particles with high silica encapsulation efficiency via miniemulsion polymerization

Acrylate polymer/silica nanocomposite particles were prepared through miniemulsion polymerization by using methyl methacrylate/butyl acrylate mixture containing the well-dispersed nano-sized silica particles coupling treated with 3-(trimethoxysilyl)propyl methacrylate (MPS). The encapsulation efficiency of silica particles was determined through the elution and hydrofluoride acid etching experiments, and the size distribution and the morphology of the composite latex particles were characterized by dynamic light scattering and transmission electron microscopy. The coupling treatment of silica with MPS can improve the encapsulation efficiency of silica and the degree of grafting of polymer onto silica. When 0.10 g MPS/g silica was used to modify silica, the encapsulation efficiency of silica was greater than 95%, and the degree of grafting of acrylate polymer onto silica was about 60%. Although the average size and the size distribution index of the composite latex particles increased as the weight fraction of silica increased, the stable latex containing the ‘guava-like’ composite particles was obtained. The grafting of polymer onto silica particles improved the dispersion of silica particles in the solvents for acrylate polymer and in the polymer matrix.     

Multivariate Analysis of the Stability of Spray-Dried Eupenicillium javanicum Peptidases

Peptidases occupy a central position in the enzyme market because of their importance in many areas, such as for physiological processes, foods, and detergents, as well as in the pharmaceutical, leather, and biotechnology industries. Microbial production is among the major sources of peptidases because it presents many advantages when compared with other methods. In this study, the metallopeptidases produced by the fungus Eupenicillium javanicum under a solid-state fermentation bioprocess were spray-dried. The enzymatic extract was dried using drying adjuvants, and optimal conditions for preserving enzymatic activity were studied following a Box-Behnken experimental design. The spray process factors studied were the air-drying temperature, enzyme feed flow rate, and the proportion of enzyme/additive. The responses analyzed were the dry extract yield and enzymatic activity after spray drying. Additionally, the stability of the dry extracts was assessed during 180 days at 4°C and 25°C. The results revealed extract yields of up to 66.12% and good enzymatic activity for intermediate values of temperature and adjuvant proportions. Furthermore, the dried enzymatic extracts showed potential for future commercial applications because of their stability at 25°C for 180 days.