抗氧化型吲哚美辛衍生物的合成及其活性研究

将NSAID吲哚美辛与七种天然酚类抗氧化剂偶连，合成了一系列具有抗氧化活性的吲哚美辛衍生物，试图发挥抗炎和抗氧化的双重功效，以降低吲哚美辛的胃肠毒性，同时提高其抗炎活性。对14个目标产物的抗氧化活性和抗炎活性进行了研究，发现上述化合物均表现出明显的抗氧化能力，但没有表现出明显的抑制巴豆油导致的小鼠耳肿胀作用。     

元宝枫黄酮提取物的抗氧化性能

制备了元宝枫黄酮的乙醇提取物.用电子自旋共振(ESR)法和光敏化合物微生物法检测了元宝枫黄酮提取物对芳香烃自由基、单线态氧自由基及混合氧自由基的抗氧化性能 结果显示,元宝枫黄酮提取物具有良好的综合抗氧化性.     

大豆素和染料木素的光氧化自由基反应动力学

具有共轭电子结构和多酚羟基官能团的类黄酮是天然抗氧化剂,其活性位点及其自由基稳定性是影响抗氧化效能的重要因素. 我们通过时间分辨光谱并结合量化计算对比研究了大豆素和染料木素两种异黄酮的脱质子形式由光氧化引发的自由基反应动力学. 结果表明,光氧化大豆素的酚氧阴离子先产生不稳定的中间态自由基,随后通过分子内电子转移反应生成相对稳定的自由基;异黄酮染料木素的酚氧阴离子光氧化后直接生成自旋密度在整个分子骨架上离域的稳定自由基;染料木素的5位羟基起到增强4’位酚羟基抗氧化活性的作用. 这些结果解释了染料木素远高于大豆素的抗氧化活性.     

连翘不同部位生物活性比较研究

对青翘、老翘、连翘根和连翘茎进行指纹图谱分析,总酚和总黄酮含量测定以及抗氧化和抑菌活性评价,并探讨生物活性的化学物质基础。采用高效液相进行指纹图谱分析;利用Folin-Ciocalteu和NaNO_2-Al(NO_3)_3-NaOH比色法测定总酚和总黄酮含量;分别采用DPPH·法和ORAC法评价抗氧化活性;以最小抑菌浓度(MIC)为评价指标评价抑菌活性。青翘中的总酚和总黄酮含量较高,且其抗氧化和抑菌能力较强;老翘、根、茎均对金黄色葡萄球菌具有抑制作用和具有较好的抗氧化能力,其中,连翘茎表现出对金黄色葡萄球菌较强的抑制能力。除青翘、老翘具有药用价值外,连翘根和连翘茎也具有潜在的利用价值。     

丹皮酚腙类化合物的合成及其抗菌活性

根据拼接原理将活性基团腙引入中药活性成分丹皮酚中对其结构进行修饰,以丹皮酚为原料,与80%水合肼在乙醇中反应得到中间体丹皮酚腙(2),然后与芳香醛反应合成了10个芳甲叉基丹皮酚腙(3a-3j),其结构经IR、~1H NMR、~(13)C NMR和ESI-MS表征。采用二倍稀释法测定目标化合物对金黄色葡萄球菌和大肠杆菌的最低抑菌浓度(MIC),结果表明:大部分化合物金黄色葡萄球菌和大肠杆菌表现出较好的抑菌活性,特别是化合物3i对金黄色葡萄球菌的的MIC为2μg·mL~(-1),优于阳性对照药环丙沙星。     

4种黄酮小分子对DPPH自由基的清除作用及构效关系研究

通过紫外可见光谱测定了4种黄酮小分子芦丁、牡荆素、山奈素、金丝桃苷对DPPH自由基的清除率、稳定性及半抑制浓度(IC50),并以常用的天然抗氧化剂抗坏血酸作为对照,考察了其抗氧化效果,探讨了黄酮类化合物的抗氧化性与结构的关系。结果表明：不同的抗氧化剂清除DPPH自由基达到平衡的时间不同,芦丁所需时间最长。4种黄酮小分子及抗坏血酸均对DPPH自由基有清除效果,并存在一定的量效关系。对DPPH自由基的清除能力从大到小依次为金丝桃苷、抗坏血酸、芦丁、山奈素、牡荆素。结构分析表明,B环邻二酚羟基是黄酮类化合物抗氧化所必需的基团,其羟甲基化及A环羟基糖苷化不利于黄酮类化合物的抗氧化活性。而C环3-OH的糖苷化对抗氧化活性有利,且单糖苷优于双糖苷。     

红景天提取物抗氧化性能分析研究

分离提取了红景天抗氧化成分，利用DPPH分光光度法、光敏化合物微生物法和邻二氮菲-Fe^2＋分光光度法对红景天提取物对氮自由基、单线态氧及羟基自由基的抗氧化性能进行了检测。认为红景天具有良好的综合抗氧化性和开发应用前景，对各检测方法的特点进行了讨论。     

蒲公英黄酮抗氧化活性的构效关系分析

蒲公英作为传统的中药材,具有抗氧化、抗肿瘤、抗菌、抗炎等多种药用价值。黄酮是蒲公英发挥抗氧化作用的重要活性成分。蒲公英黄酮抗氧化性能的实验研究备受关注,然而从分子水平对蒲公英黄酮结构与抗氧化活性之间的内在关系缺乏系统的研究。本文借助于密度泛函理论,针对蒲公英中5种重要的黄酮化合物(槲皮素、芦丁、木犀草素、芹菜素、香叶木素),通过优化结构参数、捕获DPPH自由基的热力学能量分析,NBO电荷分布、半醌自由基的自旋密度分析等方面深入探讨了蒲公英黄酮化合物抗氧化活性的构效关系及内在规律。结果表明：5种蒲公英黄酮化合物抗氧化活性为芦丁>槲皮素>木犀草素>>香叶木素>芹菜素,酚羟基的位置是影响蒲公英黄酮抗氧化活性差异的主要因素。蒲公英黄酮不同位点抗氧化活性的高低与其酚羟基上H原子的电荷分布、黄酮自由基的稳定性成正比关系,自由基单电子的离域程度和分子内氢键的稳定化作用共同决定了B环4’-OH是蒲公英黄酮的关键活性位点。     

迷迭香单体的抗氧化活性

采用柱层析方法对迷迭香抗氧化剂(Rao)进行分离,分离出8个含量较高的单体.用光度法、ESR法、滴定法测定了迷迭香的8个单体、单体组合及Rao的抗氧化活性,并分析了抗氧化活性与其结构的关系.结果表明,在单体中,对超氧阴离子自由基及羟基自由基清除率最高的是槲皮素,分别为82.6%和87.1%.对香烟烟气自由基平均清除率最高的是迷迭香二酚,清除率为48.17%.单体活性最强的槲皮素和迷迭香二酚组合后,其抗氧化活性高于单体.活性强的抗氧化剂对油脂过氧化的抑制效果好,但作用时间较短.     

去甲丹皮酚衍生物的合成及其抗炎活性

去甲丹皮酚或丹皮酚分别与非甾体抗炎药(NSAIDs)阿司匹林、布洛芬和双氯芬酸偶联,合成了5个新的去甲丹皮酚衍生物(3a～3c,4b)和丹皮酚衍生物(5b),其结构经1H NMR,IR和HR-MS表征.二甲苯致小鼠耳肿胀试验结果表明,3和5均有较强的抗炎活性,与阴性对照对CMC-Na相比,表现出显著性差异(P＜0.01).     

Melt stabilisation of Phillips type polyethylene, Part II: Correlation between additive consumption and polymer properties

Phillips type polyethylene stabilised with combinations of 700 ppm phenolic antioxidant and different amounts of various phosphorous stabilisers (sterically hindered aryl phosphite [Hostanox PAR 24], phosphonite [Sandostab P-EPQ], and aryl–alkyl phosphine [PEPFINE]) was processed by six consecutive extrusions. The polymer was characterised by FT-IR spectroscopy, rheological (melt flow index, creep compliance), colour and oxidation induction time measurements. Films were prepared by blowing and their mechanical strength was determined by Elmendorf and dart drop tests. The consumption of the antioxidants was compared to the characteristics of the polymer and to the strength of the films. The consumption rate of both the phenolic and the phosphorous antioxidants is reduced in their combinations compared to single antioxidants. The chemical structure of the polymer is modified considerably in the first extrusion even at high antioxidant levels. The mechanism of stabilisation is determined by the type of the antioxidant(s) in further processing steps. The phenolic antioxidant does not prevent the formation of long chain branches. The phosphonite and the phosphine hinder efficiently hydrogen abstraction from the polymer chain and long chain branching. Their efficiency is similar, but the phosphonite is consumed fast, while the phosphine oxidises slowly. The investigated phosphite is less reactive; the contribution of the phenolic antioxidant to the inhibition reactions is significant in phenol/phosphite combinations, therefore long chain branching increases continuously with increasing number of processing steps.     

Melt stabilisation of Phillips type polyethylene, Part I: The role of phenolic and phosphorous antioxidants

The role of a phenolic and three phosphorous (phosphite, phosphonite and phosphine) antioxidants in the melt stabilisation of polyethylene was studied in a Phillips type polyethylene by multiple extrusions. The polyethylene was stabilised with a single antioxidant at 700 ppm and with phenolic/phosphorous antioxidant combinations containing 700 ppm of each component. The functional groups (methyl, vinyl, vinylidene, trans-vinylene and carbonyl) of polyethylene and the residual amount of phosphorous antioxidants were analysed quantitatively by FT-IR methods developed in our laboratory. The rheological characteristics, the colour and the residual thermo-oxidative stability of the polymer were determined and compared. Blown films were prepared and their mechanical strength measured by the Elmendorf and Dart-drop tests. The comparison of the different characteristics revealed that the chemical reactions taking place during the first processing of the nascent polymer powder, as well as the chemical composition of the antioxidants determine the reactions taking place in further processing operations. The changes in the characteristics of stabilised polyethylene during processing are controlled by the phosphorous stabiliser. The effect and final result depend on the chemical structure of the given antioxidant. The phenolic antioxidant itself does not hinder the formation of long chain branches. It reduces the rate of oxidation of the various phosphorous stabilisers, but does not modify the mechanism of stabilisation of the phosphonite and the phosphine. The reactions of the phosphite are significantly modified by the presence of a phenolic antioxidant.     

Phloretamide及其衍生物的合成与抗氧化活性

以3-(4-羟基苯基)丙烯酰胺（Phloretamide）为先导化合物,取代苯丙烯酸为原料,经取代反应和酰胺化反应制得苯丙烯酰胺类化合物(2a~2d); 2经氢化还原反应合成了4个Phloretamide衍生物(3a~3d); 1, 2和3经去甲基化反应分别制得〖WTHZ〗〖STHZ〗1e, 2e~2f和3e~3f〖STBZ〗〖WTBZ〗。其中,3-(3,4,5-三羟基苯基)丙烯酰胺(2f), 3-(2,3,4-三羟基苯基)丙酰胺(3e)和3-(3,4,5-三羟基苯基)丙酰胺(3f)为新化合物,其结构经¹H NMR, ¹³C NMR和ESI-MS表征。初步抗氧化活性测定结果表明：c为10 μmol·L^-1时,2b, 2f和3f具有较好的自由基清除活性,其清除率分别为66.8%, 59.8%和69.4%,均优于阳性对照咖啡酸,咖啡酸苯乙酯和Vc。     

Electrochemical Methods to Evaluate the Antioxidant Activity and Capacity of Foods: A Review

Antioxidants are an important class of food additives playing the fundamental role of retarding oxidation reactions in food. Although their functional role is well-established, less clear is their mechanism of action. Electrochemical methods based on cyclic, differential pulse, square wave voltammetry and coulometry allow direct and rapid screening of antioxidant activity. Their main advantages are sensitivity, rapidity, simplicity and the capacity to directly measure the number of electrons transferred by an antioxidant offer advantage over conventional spectrophotometric assays. This review aims to summarize the most recent efforts towards the use of electrochemical methods to evaluate the antioxidant activity of foods.     

Reactions of antioxidants with molecular oxygen. Part III: Influence of phenolic stabiliser structures on their oxidation in an inert matrix

The oxidation of five different phenolic antioxidants in inert substrates has been investigated varying the temperature and oxygen pressure conditions. The stabiliser consumption in this reaction has been quantified by steric exclusion chromatography. The tendency of the variation of the residual antioxidant concentration with exposure time in the presence of oxygen shows a simple apparent first order process in all cases. The kinetic parameters were determined applying this simple kinetic model. The influence of structural characteristics of stabilisers under study on kinetic parameters of the direct reaction with the oxygen has been analysed. On the other hand, the information obtained about reaction products generated for each antioxidant helped us to explain the results obtained.     

Purification and Identification of Novel Antioxidant Peptides from Enzymatically Hydrolysed Samia ricini Pupae

The emergence of excessive free radicals leads to the destruction of various systems within the body. These free radicals also affect nutritional values, color, taste, and emit an odor akin to rancid food. Most food industries use synthetic antioxidants, such as BHT (butylated hydroxytoluene) or BHA (butylated hydroxy anisole). However, high doses of these can be harmful to our health. Therefore, an antioxidant compounds, such as bioactive peptides from edible animals or plants, have emerged to be a very promising alternative as they reduce potential side effects. This study focused on the purification and identification of antioxidant peptides from protein hydrolysates of wild silkworm pupae (Samia ricini). Antioxidant peptides were purified from the hydrolysate by ultrafiltration and RP-HPLC. The results showed that protein hydrolysate from S. ricini pupae by trypsin with a molecular weight lower than 3 kDa and highly hydrophobic property, exhibited strong DPPH radical scavenging activity and chelating activity. Further identification of peptides from the fraction with the highest antioxidant activity was carried out using LC-MS/MS. Three novel peptides, i.e., Met-Ley-Ile-Ile-Ile-Met-Arg, Leu-Asn-Lys-Asp-Leu-Met-Arg, and Glu-Asn-Ile-Ile-Leu-Phe-Arg, were identified. The results of this study indicated that the protein hydrolysate from S. ricini pupae possessed potent biological activity, and the novel antioxidant peptides could be utilized to develop health-related antioxidants in food industry.     

Antioxidant and Anticholinesterase Activities of Extracts and Phytochemicals of Syzygium antisepticum Leaves

Bioassay-guided separation of young leaves extracts of Syzygium antisepticum (Blume) Merr. & L.M. Perry led to the isolation of four triterpenoids (betulinic acid, ursolic acid, jacoumaric acid, corosolic acid) and one sterol glucoside (daucosterol) from the ethyl acetate extract, and three polyphenols (gallic acid, myricitrin, and quercitrin) from the methanol (MeOH) extract. The MeOH extract of S. antisepticum and some isolated compounds, ursolic acid and gallic acid potentially exhibited acetylcholinesterase activity evaluated by Ellman’s method. The MeOH extract and its isolated compounds, gallic acid, myricitrin, and quercitrin, also strongly elicited DPPH radical scavenging activity. In HEK-293 cells, the MeOH extract possessed cellular antioxidant effects by attenuating hydrogen peroxide (H₂O₂)-induced ROS production and increasing catalase, glutathione peroxidase-1 (GPx-1), and glutathione reductase (GRe). Furthermore, myricitrin and quercitrin also suppressed ROS production induced by H₂O₂ and induced GPx-1 and catalase production in HEK-293 cells. These results indicated that the young leaves of S. antisepticum are the potential sources of antioxidant and anticholinesterase agents. Consequently, S. antisepticum leaves are one of indigenous vegetables which advantage to promote the health and prevent diseases related to oxidative stress.     

The main and modified CUPRAC methods of antioxidant measurement

The antioxidant activity/capacity levels of biological fluids and foods are measured for the diagnosis and the treatment of oxidative stress-associated diseases in clinical biochemistry, and for meaningful comparison of the antioxidant content of foods. Currently, there is no “total antioxidant” as a nutritional index available for food labeling and biological fluids due to the lack of standardized quantitative methods.The CUPRAC (CUPric Reducing Antioxidant Capacity) method of antioxidant measurement, introduced by our research group, is based on the absorbance measurement of Cu(I)-neocuproine (Nc) chelate formed as a result of the redox reaction of chain-breaking antioxidants with the CUPRAC reagent, Cu(II)-Nc, where absorbance is recorded at the maximal light-absorption wavelength of 450 nm.We introduce the main CUPRAC method and describe modifications to it in the past six years.     

Protective effects of vitamin E against CCl<Subscript>4</Subscript>-induced hepatotoxicity in rabbits

The influence of CCl₄ on the activity of superoxide dismutase (SOD), glutathione peroxidase (GPx), glutathione reductase (GR), the value of the total antioxidant status (TAS), and the concentration of malonic dialdehyde (MDA) and glutathione (GSH) was monitored in plasma or whole blood of rabbits. The administration of CCl₄ caused the increase of the SOD activity to approximately 150 % and the decrease in the activity of GPx and GR by about 50 %. These changes were accompanied with the increase in TAS value and MDA concentration and the decrease of GSH concentration. The effect of CCl₄ was suppressed by the previous 7 days lasting or simultaneous administration of vitamin E. Oxidative stress caused by CCl₄ was accompanied by the development of reactive oxygen forms, especially superoxide radical anion.     

超支化分子桥联受阻酚抗氧化剂的合成与表征

以正十八胺为核的1.0代超支化大分子和β-(3,5-二叔丁基-4-羟基苯基)丙酰氯为原料,通过酰胺化缩合反应,合成了一种具有长链烷基和2个受阻酚基团的新型超支化分子桥联受阻酚类抗氧化剂.通过正交实验确定了超支化分子桥联受阻酚类抗氧化剂的最佳合成体系为:3,5-丙酰氯为酰化剂、K_2CO_3为缚酸剂、苯和水为反应溶剂.通过条件优化实验确定了超支化分子桥联受阻酚类抗氧化剂的最佳合成条件为:3,5-丙酰氯与1.0代超支化大分子的物质的量比为6∶1、反应温度为25 ℃、反应时间为12 h、体系苯与水体积比为6∶1、3,5-丙酰氯与缚酸剂K_2CO_3的物质的量比为1∶1,在此条件下,超支化分子桥联受阻酚类抗氧化剂的收率高达75.5%.FT-IR和1H NMR证实了合成抗氧化剂的化学结构与其理论结构相符.超支化分子桥联受阻酚类抗氧化剂在聚乙烯树脂中的抗氧化性能优于抗氧化剂1076,且随着烷基链长度的增加,抗氧化性能增强.