筛选和评价天然抗氧化剂的方法-DPPH法

从植物中筛选和提取天然抗氧化剂是食品科学研究的热点,用于筛选抗氧化剂、评价抗氧化活性的方法也随之增多。DPPH法是普遍采用的方法之一,此法使用稳定的自由基DPPH筛选抗氧化剂、评价抗氧化效果。本文对DPPH法的原理、操作过程、表示测定结果的方法及该法的特点及应用进行了概括,并对影响测定结果的因素进行了探讨。     

西印度樱桃冻干粉水提液抗氧化性的研究

对西印度樱桃果实冻干粉水提液中还原型维生素C含量及其抗氧化性进行研究。结果表明,与相同含量的维生素C相比,其水提液具有更强的超氧阴离子自由基、羟自由基、DPPH·自由基清除能力,可以作为天然的抗氧化剂应用于食品和化妆品行业。     

In vitro phytotoxicity and antioxidant activity of selected flavonoids

The knowledge of flavonoids involved in plant-plant interactions and their mechanisms of action are poor and, moreover, the structural characteristics required for these biological activities are scarcely known. The objective of this work was to study the possible in vitro phytotoxic effects of 27 flavonoids on the germination and early radical growth of Raphanus sativus L. and Lepidium sativum L., with the aim to evaluate the possible structure/activity relationship. Moreover, the antioxidant activity of the same compounds was also evaluated. Generally, in response to various tested flavonoids, germination was only slightly affected, whereas significant differences were observed in the activity of the various tested flavonoids against radical elongation. DPPH test confirms the antioxidant activity of luteolin, quercetin, catechol, morin, and catechin. The biological activity recorded is discussed in relation to the structure of compounds and their capability to interact with cell structures and physiology. No correlation was found between phytotoxic and antioxidant activities.     

Structure–activity relationship for dihydromyricetin as a new natural antioxidant in polymer

Dihydromyricetin (DMY), a natural product, was used as antioxidant in ethylene vinyl acetate copolymer (EVA) in our laboratory. Oxidation induction temperature (OIT) of EVA with the antioxidant of DMY and effect of pH on OIT was measured by means of differential scanning calorimeter (DSC). The mechanism on that antioxidation of DMY in EVA is produced on basis of determination of UV–Vis absorption, nuclear magnetic resonance (NMR) and the experiment of reacting the pyrogallic (PA) and DMY, respectively, with the DPPH. The result shows that the ortho‐trihydroxyl group (B ring) in DMY has mainly antioxidative activity and hydroxyl group of 7‐position (A ring) not only displayed reversibility to acidic or alkaline medium but also affected in some extent the antioxidative ability in EVA. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

用五种方法评价八种植物的抗氧化活性

运用5种方法对8种植物的抗氧化能力进行了测定,并且对不同方法测定的结果进行了相关性研究,结果表明：3种抗氧化活性指标与总黄酮含量之间都存在一定的相关性.由于植物成份的复杂性,采用多种测定方法对植物抗氧化活性进行综合评价,能够得到比较科学合理的数据。     

白腐菌液体培养产生漆酶的研究

研究了碳源、氮源和综合因素对白腐菌P.conchatus液体培养产漆酶和生长情况的影响。碳源为葡萄糖,氮源为酒石酸铵时,菌株的产漆酶能力较强;麦麸为碳源,酵母膏为氮源,对菌株的生长最为有利。通过正交实验确定了最佳培养基组成为葡萄糖10 g/L,酒石酸铵5 g/L,大量元素为基础培养基的3倍,微量元素为20 mL。葡萄糖是影响菌株生长的主要因素。     

阿魏酸的合成及抗氧化性能的研究

以香草醛和丙二酸为原料、乙酸铵为催化剂、DMF为溶剂、苯为带水剂,合成了阿魏酸。在V（苯）∶V（DMF）=2∶1、乙酸铵用量为6%（以香草醛质量计）、n（香草醛）∶n（丙二酸）=1∶1.4、反应时间为4h的优化条件下,阿魏酸产率达到71.02%。阿魏酸的抗氧化性实验结果表明,阿魏酸对食用油脂有一定的抗氧化能力,其在油脂中的抗氧化能力优于维生素E。     

Antiradical activity of extracts of almond and its by-products

Antioxidant activities of ethanolic extracts of whole almond seed, brown skin, and green shell cover were evaluated using different free radical trapping assays. Trolox equivalent antioxidant capacity assay revealed that the total antioxidant capacities of brown skin and green shell cover extracts were 13 and 10 times greater than that of the whole seed extract at the same extract concentration. The free radical-scavenging activity of extracts of brown skin and green shell cover also exceeded that of the whole seed. The scavenging activity of superoxide radical by different almond extracts ranged from 76 to 97% at 100 ppm and 85 to 99% at 200 ppm. The corresponding reduction of hydrogen peroxide concentration was 59–66% (100 ppm) and 86–91% (200 ppm). The hydroxyl radical-scavenging capacities at 100 and 200 ppm were 16 and 42% for whole seed, 57 and 100% for brown skin, and 40 and 56% for green shell extracts, respectively. A 100% scavenging activity of the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical was observed for brown skin and green shell extracts at 100 and 200 ppm concentrations, respectively, and whole seed extracts scavenged 21 (at 100 ppm) and 73% (at 200 ppm) of the DPPH radical.     

虎杖中抗氧化成分的提取分离及其活性研究

提取了虎杖中具有抗氧化活性的总蒽醌(TA),并从总蒽醌中依次分离出强酸成分(SAP)、中酸成分(MAP)和弱酸成分(WAP)。然后采用二苯代苦味酰自由基(DPPH)法对不同质量浓度的TA、SAP、MAP和WAP进行了抗氧化活性测定。TA、SAP、MAP和WAP质量浓度分别为0.2 g/L、0.5 g/L、0.8 g/L、1.2 g/L时,对自由基的最大清除率依次分别为:29.5%、67.1%、85.7%、87.5%;34.0%、74.2%、86.5%、95.4%;9.8%、24.0%、35.2%、47.3%;6.5%、11.1%、19.6%、19.9%。TA、SAP、MAP和WAP对自由基均有程度不同的清除作用,其中SAP的效果最佳,当其质量浓度为1.2 g/L时,最大清除率可高达95.4%。     

灵芝多糖体外抗氧化活性的研究

采用铁氰化钾还原法测定灵芝多糖的还原能力,并对灵芝多糖清除羟自由基、超氧阴离子自由基的能力进行了研究.结果表明,灵芝多糖具有抗氧化的作用和清除自由基的能力,并且其清除能力与多糖的浓度存在一定的正相关量效关系.     

甘蔗花与叶抗氧化活性研究

为了探明农作物甘蔗花和甘蔗叶提取物的抗氧化活性。以甲醇和乙醇为溶剂,采用超声提取法对甘蔗花及甘蔗叶进行提取,考察其对DPPH自由基活性的清除能力,并与多种抗氧化剂的清除能力进行比较。甘蔗花和甘蔗叶的提取物与5种标准品的抗氧化能力对比为:没食子酸咖啡酸芦丁甘蔗花甲醇提取物香草酸甘蔗叶甲醇提取物甘蔗花乙醇提取物甘蔗叶乙醇提取物对香豆酸。结果表明,甘蔗花的甲醇提取物抗氧化能力大于香草酸、对香豆酸两种标准品,因此具有一定的抗氧化能力。     

Photochemical reactions of antioxidant sesamol in aqueous solution

Antioxidant intermediate radicals generated by continuous ultraviolet (UV) and pulsed UV laser irradiation of sesamol in aqueous solutions were investigated. Radical species with the intensity ratio of 1∶4∶6∶4∶1 were observed by using continuous wave electron paramagnetic resonance (EPR) with continuous UV irradiation. The radical was also observed after the irradiation. To observe the intermediate radical right after the excitation, Fourier transform EPR (FT EPR) was used. Trace amounts of the same radical were also detected by FT EPR with pulsed UV laser. Based on the hyperfine coupling constant (2.3 G) and g-value (2.0048), together with FT EPR results, this radical was found to be a benzoquinone anion radical. The radical might have been produced via multistep reactions of the excited sesamol in aqueous solution, and it was stable for at least several minutes. In addition to the benzoquinone radical, the formation and dynamics of the sesamolyl radical were investigated by using FT EPR. FT EPR showed the detailed behavior of the radical. Characterization of the intermediate is important to evaluate the antioxidant sesamol. Part of these results was presented at the 90th American Oil Chemists’ Society Annual Meeting & Expo, Orlando, FL, May 1999.     

多羟基苯甲醛席夫碱的抗氧化性能研究

微波辅助法快速合成26个多羟基苯甲醛席夫碱系列化合物,并从清除羟基自由基和DPPH自由基能力两方面研究了该系列化合物的体外抗氧化活性。结果表明,该系列化合物对上述两种自由基均有较好的清除效果．其中清除羟基自由基的EC50值介于23~187μmol／L,清除率为27．54％～237．2％,清除效果比vc强;而清除DPPH自由基的EC50值介于6．7～7．2mol／L,清除率处于58．0%-69．1％之间．过半测试化合物的清除能力强于Vc。     

异形玉叶金花果实不同提取部位抗氧化活性研究

以乙醇为溶剂提取异形玉叶金花果实,经减压浓缩后,依次用乙酸乙酯和正丁醇进行萃取。用DPPH自由鼙的清除能力来评价两个部位的抗氧化活性。结果表明,己酸乙酯部位浓度为283．20μg/mL时自由基清除率大于50％,IC50=304．85μg／mL,正丁醇部位浓度为17760μg／mL．时自由基清除率大于50％,IC50-224．07μg／mL。正丁醇部位抗氧化能力比乙酸乙酯部位更好。     

Antioxidant activities of hot water extracts from various spices

Recently, the natural spices and herbs such as rosemary, oregano, and caraway have been used for the processing of meat products. This study investigates the antioxidant activity of 13 spices commonly used in meat processing plants. The hot water extracts were then used for evaluation of total phenolic content, total flavonoids content and antioxidant activities. Our results show that the hot water extract of oregano gave the highest extraction yield (41.33%) whereas mace (7.64%) gave the lowest. The DPPH radical scavenging ability of the spice extracts can be ranked against ascorbic acid in the order ascorbic acid > clove > thyme > rosemary > savory > oregano. The values for superoxide anion radical scavenging activities were in the order of marjoram > rosemary > oregano > cumin > savory > basil > thyme > fennel > coriander > ascorbic acid. When compared to ascorbic acid (48.72%), the hydroxyl radical scavenging activities of turmeric and mace were found to be higher (p < 0.001). Clove had the highest total phenolic content (108.28 μg catechin equivalent (CE)/g). The total flavonoid content of the spices varied from 324.08 μg quercetin equivalent (QE)/g for thyme to 3.38 μg QE/g for coriander. Our results indicate that hot water extract of several spices had a high antioxidant activity which is partly due to the phenolic and flavonoid compounds. This provides basic data, having implications for further development of processed food products.     

马齿苋中总黄酮提取工艺优化及其抗氧化活性研究

采用直接回流法提取马齿苋中总黄酮,通过单因素实验与正交实验对提取工艺进行了优化;并以芦丁为对照品,采用分光光度法对马齿苋中的总黄酮含量进行了检测;同时研究了马齿苋总黄酮提取液对羟基自由基(·OH)和超氧阴离子自由基(·O-2)的清除效果,并与Vc的抗氧化活性进行了比较。确定马齿苋中总黄酮最优提取工艺为:提取时间50min、水浴温度90℃、提取溶剂为30%乙酸乙酯、固液比1∶50(g∶mL),在此条件下,马齿苋总黄酮提取率可达7.15mg·g-1。当马齿苋总黄酮浓度为0.18 mg·mL-1时,对·OH的清除率高达73.12%,对·O-2的清除率可达49.02%,相同浓度时,其抗氧化活性低于Vc。     

Oxovanadium(IV) complexes based on S-alkyl-thiosemicarbazidato ligands. Synthesis,characterization, electrochemical,and antioxidant studies

Reaction of VOSO₄ with 2-hydroxy-napthaldeyde-S-R-thiosemicarbazones (R: methyl, ethyl, propyl or allyl) and salicyl aldehyde yielded five-coordinate oxovanadium(IV) complexes having a N¹,N⁴-diarylidene-S-R-thiosemicarbazidato structures. The compounds were characterized by elemental analysis, magnetic measurements, electronic, infrared, ¹H-NMR, and electron paramagnetic resonance (EPR) spectra. The X-band EPR signals were recorded from powder forms and also in solution. All the complexes have a single asymmetric line shape and theoretical fit studies prove the presence of axial symmetry around the paramagnetic vanadium ions. A computer simulation of the EPR spectrum of each complex was carried out to derive the related EPR parameters. Cyclic voltammograms of the complexes exhibited two metal-based reversible redox peaks around 500 and ?800?mV corresponding to one electron oxidation/reduction of V^IVO/V^VO and V^IVO/V^IIIO, respectively. The reductive response in the 50–350?mV region was assigned to ligand reduction. Antioxidant activities of the compounds were determined with CUPric Reducing Antioxidant Capacity, 2,2-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid, and 1,1-diphenyl-2-picrylhydrazyl assays. The test results indicated that the antioxidant capacity of the compounds increases with the carbon number of saturated hydrocarbon chain on sulfur atom.     

希夫碱配体结构的改变对Cu（Ⅱ）SOD模拟物的抗氧

在希夫碱Cu(II)配合物1 (Cu(II)双香草醛缩乙二胺)、4 (Cu(II)双香草醛缩邻苯二胺)的基础上,对配体结构进行了设计,将重原子效应、共轭效应、空间位阻效应等结构影响因素引入到SOD(超氧化物歧化酶)模拟物的结构设计中,合成了4种希夫碱类铜金属配合物,并用X 射线单晶衍射法测定了配合物2的晶体结构。运用改进的NBT还原法测定了这6种SOD模拟物的抗氧化活性,结果表明：结构改变后的SOD模拟物较原结构配合物的抗氧化活性均有明显的提高且各因素影响幅度有所不同。     

雪莲果中绿原酸的提取及其抗氧化性测定

以雪莲果为原料,采用醇提法提取绿原酸,通过对不同乙醇质量分数、提取时间、提取温度、料液的提取效果进行比较分析,确定了最佳提取条件为：乙醇质量分数40%,提取时间2.5 h,提取温度80℃,料液比1∶20（g∶mL）,绿原酸提取量为1.63mg/g。邻二氮菲-Fe2＋法测定雪莲果提取物清除.OH（羟自由基）的能力,结果表明雪莲果中的绿原酸具有一定的抗氧化性。