Hypohalous acid-mediated halogenation of resveratrol and its role in antioxidant and antimicrobial activities

The reactions of resveratrol with proinflammatory oxidants including hypochlorous and hypobromous acids in phosphate-buffered saline/methanol solution were carried out and eight halogenated resveratrol derivatives differing in the number and position of halogen atoms, and the configuration of double bond were obtained. Halogenation of resveratrol took place only at the aromatic A ring, and interestingly, the halogenation increased antioxidant activity of this parent molecule in the 2,2'-azobis(2-amidinopropane) hydrochloride-induced RBC haemolysis model. Additionally, antimicrobial activity of the derivatives against Gram-positive bacteria, Gram-negative bacteria and fungi were tested, and toward Candida albicans, 2-chloro-resveratrol and 2-bromo-resveratrol were more active than the unmodified form and the reference compound fluconazole.     

金刚藤白藜芦醇的纯化及抗氧化活性研究

采用超声波辅助提取金刚藤白藜芦醇,得到粗提物,再利用硅胶柱层析对粗提物进行纯化,然后通过白藜芦醇对油脂抗氧化及对羟基自由基、超氧阴离子自由基的清除效果,研究金刚藤白藜芦醇的抗氧化活性。结果表明:从金刚藤中提取白藜芦醇的得率为2.36%;金刚藤白藜芦醇具有较强的抗油脂氧化和清除自由基的能力,当金刚藤白藜芦醇质量浓度为8 mg/mL时,对羟基自由基和超氧阴离子自由基的清除率分别为71.91%和75.14%;提取物经过纯化后,抗氧化活性明显增强。     

Antioxidant potential of ethanolic extract of Polygonum cuspidatum and application in peanut oil

Polygonum cuspidatum was extracted with 95% ethanol to obtain a crude antioxidant extract. P. cuspidatum extract (PCE) had a very high content of total phenol, which was 104.83 ± 8.58 mg/g dry weight, expressed as pyrocatechol equivalent. PCE exhibited excellent antioxidant activity, as measured using α,α-diphenyl-β-picryhydrazyl (DPPH) and total antioxidant assays. It also showed a high lipid antioxidant activity and hydroxyl radicals scavenging activity. A positive correlation was found between the reducing power and the antioxidant activity of PCE, which was found to be comparable to resveratrol and butylated hydroxytoluene (BHT). Then the suitability of PCE as an antioxidant was determined in peanut oil, and the decrease of oxidation was monitored using thiobarbituric acid-reactive substances (TBARS) assay. PCE treatment significantly (P <  0.05) reduced lipid oxidation in peanut oil compared to resveratrol and BHT.     

白皮杉醇的合成及抗氧化活性研究

研究了一种白皮杉醇的简便合成方法,以3,4-二甲氧基苄醇为原料,经溴代、Arbuzov重排、Wittig-Horn-er反应和脱甲基4步反应得到白皮杉醇,并对目标产物的结构采用IR,1H NMR及13 C NMR进行了表征。讨论了白皮杉醇的抗氧化活性,包括还原力、清除DPPH自由基和羟基自由基的能力,并与白藜芦醇、TBHQ、BHT和儿茶素作对比。结果表明:白皮杉醇具有较强的抗氧化性能,还原能力和清除羟基自由基的能力均高于白藜芦醇、TBHQ、BHT和儿茶素;其半抑制率IC50分别为DPPH自由基16.57μg/mL、羟基自由基270.00μg/mL。     

基于量子化学分析的类黄酮抗氧化功能区划分

本研究采用量子化学方法对常见类黄酮的最高占有轨道组成、最活泼羟基位置与其抗氧化活性的关系进行研究。结果表明：类黄酮的分子结构可分为3 个功能域：抗氧化能力决定域(B 环)、抗氧化能力加强域(C 环)、溶解性及亲和力调节域(A 环)。 该功能域划分表明,可通过在类黄酮分子的A 环上引入亲油或亲水性的基团来提高其在水相或油相中的溶解性,充分发挥其抗氧化作用。     

大鲵油体外抗氧化活性研究

采用体外抗氧化实验研究大鲵油抗氧化活性,测定大鲵油对DPPH自由基、羟基自由基、超氧自由基清除能力和还原能力、Fe~(2+)螯合能力。以V_C为阳性对照,评价大鲵油的体外抗氧化活性。结果表明:大鲵油抗氧化能力强于鲐鱼油,添加复合抗氧化剂后抗氧化能力更强,对Fe~(2+)的螯合能力表现最好,相同质量浓度条件下强于V_C;对DPPH自由基、羟基自由基清除能力和还原能力与V_C相当。大鲵油对DPPH自由基、羟基自由基和Fe~(2+)螯合能力的半抑制质量浓度(IC_(50))分别为3.523、0.493、0.559 mg/m L,添加了复合抗氧化剂的大鲵油的相应IC_(50)分别为0.572、0.099、0.062 mg/m L。     

白藜芦醇丹阳黄酒抗氧化活性和稳定性研究

将白藜芦醇添加至丹阳黄酒中,形成含有质量浓度为0.1 mg/mL白藜芦醇的新型丹阳黄酒,以此为研究对象,对其清除DPPH、 羟基、ABTS自由基和总还原能力进行测定,来评价白藜芦醇丹阳黄酒产品的抗氧化活性及稳定性。 结果表明,0.1 mg/mL的白藜芦醇 丹阳黄酒对DPPH、羟基、ABTS自由基的半抑制浓度（IC50值）依次为0.40 mL/mL、0.80 mL/mL、0.51 mL/mL,普通丹阳黄酒IC50值依次 0.70 mL/mL、0.81 mL/mL、0.80 mL/mL,新型丹阳黄酒的总还原力明显高于普通丹阳黄酒。 综合比较,含白藜芦醇丹阳黄酒抗氧化能 力高于普通丹阳黄酒。 同时,新型丹阳黄酒在常温下存放前3 d的白藜芦醇含量快速下降,之后趋于稳定。     

Antioxidant properties of major metabolites of quercetin

Dietary flavonoids have been related to health promotion, which has been attributed in part to their antioxidant properties as demonstrated in many in vitro studies. However, in the human organism most flavonoids are little bioavailable and largely transformed to different metabolites that are crucial to explain the health effects associated with their dietary intake, although little is known about their biological activities. Quercetin is a majority flavonoid in the human diet that has been commonly used in studies on the flavonoid and health relationships. In this study, the antioxidant activity of different conjugated metabolites of quercetin (quercetin 3′-O-sulphate, quercetin 4′-O-sulphate, quercetin 3-O-glucuronide and isorhamnetin 3-O-sulphate) prepared in the laboratory, and of some phenolic acids that may result from its colonic degradation, was investigated by two in vitro assays (ABTS and FRAP assays). As expected, substitution of the hydroxyl groups of quercetin by the conjugating substituents resulted in a decrease in the antioxidant activity with regard to the parent compound. Despite this, the conjugated metabolites still retained significant antioxidant activity and behave as significantly better radical scavengers and reducing compounds than usually recognized antioxidants like α-tocopherol. Greater antioxidant activity of the metabolites was found in the ABTS assay, conducted at pH 7.4, suggesting that quercetin derivatives could act as potential radical scavengers in physiological conditions. Similarly, antioxidant activity significantly higher than α-tocopherol was also found in the ABTS assay for 3,4-dihydroxyphenylacetic, 3-methoxy-4-hydroxyphenylacetic and 3-(3,4-dihydroxyphenyl)propionic acids, described as products of the colonic degradation of quercetin. Phenylacetic acids were more active than benzoic and phenylpropionic acids, and the activity increased with the number of phenolic hydroxyls in the molecule; methoxylated derivatives showed, in general, lower activity than the equivalent O-dihydroxylated forms but greater than that of the monohydroxylated precursor. The results obtained are expected to contribute to the understanding of the mechanisms involved in the biological effects associated with the intake of flavonoid-rich diets.     

Comparative Study of the Antioxidant Capacity of Four Stilbenes Using ORAC,ABTS<Superscript>+</Superscript>, and FRAP Techniques

Researchers use several different analytical techniques, such as ORAC, ABTS^·+, or FRAP, for measuring the antioxidant capacity of bioactive compounds. However, many authors do not take into account that these three techniques have different objectives. This contribution reports on the use of two types of tests to evaluate the antioxidant activity of four stilbene tests based first on the hydrogen atom transfer reaction (ORAC method) and the second on the single electron transfer reaction (ABTS^·+ and FRAP assays). For the ORAC assay, the greatest antioxidant activity was shown by resveratrol, followed by oxyresveratrol, pterostilbene, and pinosylvin, while in the ABTS^.+ assay, the highest antioxidant capacity was presented by oxyresveratrol, followed by resveratrol, pinosylvin, and finally pterostilbene. In the FRAP assay, the reducing activity shown by all the stilbenes was below that obtained for trolox. The role of phenolic hydroxyl groups was studied. The technique used should be selected taking into account the objectives and the conditions of the medium.

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Graphical Abstract ?

     

Physical and antioxidant properties of chitosan and methylcellulose based films containing resveratrol

New trends in edible films focus on the improvement of their functionality through the incorporation of active compounds, such as antimicrobial or antioxidant agents. Resveratrol is a natural antioxidant found in a variety of plant species, such as grapes, and could be used for minimizing or preventing lipid oxidation in food products, retarding the formation of oxidation products, maintaining nutritional quality and prolonging the food shelf life. The aim of this work was to develop and characterize two different polymeric composite films (made with chitosan (CH) and methylcellulose (MC)) containing different amounts of resveratrol. This compound could be incorporated efficiently into both films, but provoke structural changes in the matrices, which became less stretchable (65–70% reduction of deformation at break at the greatest resveratrol content) and resistant to fracture (26 and 54% reduction of tensile at break for MC and CH, respectively, at the greatest resveratrol content) more opaque (significant reduction of the internal transmittance) and less glossy (about 60–65% reduction of gloss at the greatest resveratrol content). Film barrier properties were hardly improved by the presence of resveratrol; water vapour and oxygen permeability tend to slightly decrease when resveratrol was incorporated into both polymers. Composite films showed antioxidant activity, which was proportional to the resveratrol concentration in the film. None of the films showed antimicrobial activity against Penicillium italicum and Botrytis cinerea. Thus, these films could be applied to food products which are sensitive to oxidative processes to prolong their shelf life.     

Identification of hydroxylated polybrominated diphenyl ether metabolites in blood plasma from polybrominated diphenyl ether exposed rats

Polybrominated diphenyl ethers (PBDEs) are ubiquitous environmental contaminants due to their use as flame retardants. Similarly to PCBs, the PBDEs are metabolized to hydroxylated metabolites (OH-PBDEs) in mammals. In the present study equimolar doses of seven environmentally relevant PBDE congeners were given intraperitoneally as a mixture to rats, and their blood plasma was analyzed for parent compounds and hydroxylated metabolites 1 and 5 days after dosing. Sixteen OH-PBDEs and two diOH-PBDEs were detected as PBDE metabolites in the rat plasma, a novel finding. Four OH-tetraBDEs were structurally identified by comparison (gas chromatography/mass spectrometry) with authentic reference standards. The position of the hydroxyl groups was suggested according to the mass spectrometric fragmentation patterns of the corresponding PBDE methyl ether derivatives. The OH-PBDE metabolites were dominated by hydroxyl groups in the meta- and parapositions. The results show that OH-PBDE congeners have an ability to be retained in rat blood, most likely by a mechanism similar to that of OH-PCBs. The results will be useful for determination of the origin of OH-PBDEs present in wildlife and in humans, since OH-PBDEs are also common natural products in marine environments.     

黄酮类化合物抗氧化活性的构效关系

分别应用DPPH分光光度法和连苯三酚自氧化法比较了4种黄酮类化合物及5种具有羟基的化合物的抗氧化活性。结果表明,这些化合物由于分子结构上的相似性而都具有一定的抗氧化活性,其清除DPPH作用大小顺序依次为:槲皮素>连苯三酚>芦丁>儿茶素>邻苯二酚>抗坏血酸>桑色素>间苯二酚>苯酚,并且这种作用随其浓度的增加而增大;而对连苯三酚自氧化反应的抑制作用强弱顺序依次为:抗坏血酸>邻苯二酚>间苯二酚>苯酚>芦丁>儿茶素>槲皮素>桑色素。结合试验数据从而推断除抗坏血酸以外的8种化合物的构效关系为:①邻位羟基清除自由基的活性强于间位羟基;②同样在B环上具有邻位羟基的条件下,C环的2,3位为双键结构时,清除自由基的作用增强;③C环3位上羟基被糖基化时可能减弱其他酚羟基活性。     

牛蒡根总黄酮抗氧化活性研究

以牛蒡根为材料,采用常规方法测定牛蒡根总黄酮的DPPH自由基清除能力、羟基自由基清除能力、总抗氧化能力、还原力、金属螯合能力、抗脂质过氧化能力和对DNA氧化损失的保护作用,同时测定了牛蒡根总黄酮的含量。结果表明,牛蒡根总黄酮的自由基清除能力、总抗氧化能力、金属螯合能力和还原力随浓度的增加而增强,且呈剂量依赖性相关,DPPH自由基清除能力的半数抑制浓度（IC50）为15.7mg/mL;对大鼠肝脂质过氧化产生的丙二醛（MDA）有较好的清除效果,IC50为34μg/mL;对K562细胞DNA氧化损伤具有保护作用。由此说明,牛蒡根为一种很好的天然抗氧化剂。     

山杏果肉可溶性膳食纤维的抗氧化活性与红外光谱分析

对2种不同制备方法制得的山杏果肉可溶性膳食纤维(SDF)的抗氧化活性进行了比较。文中通过对DPPH自由基清除能力,总还原能力,在邻二氮菲-Fe2+体系中清除羟基自由基能力,邻苯三酚自氧化法中清除超氧阴离子能力等的测定,评价了二者的抗氧化活性,并对其进行了红外光谱对比分析。结果表明:2种不同方法制备的山杏果肉可溶性膳食纤维(SDF)均具有一定的抗氧化活性,且复合酶酶解法制备的SDF较微生物法发酵液酶解法制备的抗氧化效果更好,由于水解程度不同导致二者在红外光谱吸收方面略有差别,吸收强度差别明显。     

Isolation and identification of new compound, 2,7″-phloroglucinol-6,6′-bieckol from brown algae,Ecklonia cava and its antioxidant effect

Brown algae, Ecklonia cava has been regarded as a useful material in the prevention or treatment of several human diseases in Jeju Island, Korea. In this study, we investigated its antioxidant activity, and isolated a new antioxidative compound, which was identified as 2,7″-phloroglucinol-6,6′-bieckol (PHB) on the basis of LC/MS, as well as ¹H and ¹³C NMR spectroscopy results. The antioxidant activity of PHB was evaluated via several in vitro assays, such as radical scavenging activities using electron spin resonance spectrometry, intracellular reactive oxygen species scavenging activity, and DNA damage assays. PHB evidenced profound scavenging activities on DPPH, alkyl, hydroxyl, and superoxide radicals (IC₅₀: 0.51, 2.07, 75.64 and 57.19 μM for DPPH, alkyl, hydroxyl and superoxide radicals, respectively). The antioxidant activity of PHB was higher than that of ascorbic acid. Furthermore, PHB effectively inhibited H₂O₂-induced DNA damage. The results of this study indicate that PHB may prove useful as a novel natural marine antioxidant.     

A thermal treatment to increase the antioxidant capacity of natural phenols: catechin, resveratrol and grape extract cases

In this work, the critical role of temperature (the values assayed were 22, 37 and 60 °C), the chemical characteristics of the medium (ethanol, methanol and water) and the reaction time on the antiradical capacity of phenolic systems was studied. An initial increase and a following decrease in antiradical activity were observed for catechin and resveratrol solutions in all solvents assayed. The maximum antioxidant activity was higher and occurred in a shorter time as the storage temperature was increased or the solvent polarity was decreased. The maximum values of the latter variable in the catechin and resveratrol cases (reaching an antiradical activity value higher than 50% in comparison with the initial one) were detected when oxidation was carried out in ethanol at 60 °C after 6 and 24 h of storage, respectively. Such variations were due to different reaction pathways. In fact, oxidative polymerization and oxidative formation of hydroxyl groups were found to be responsible for the enhancements of antiradical activity in catechin and resveratrol, respectively. A similar trend with variations of temperature in the different media was also observed in the grape extract case. The evolution of antiradical activity was followed by high-performance liquid chromatography analysis, which pointed to the phenol polymerization of the monophenols detected (catechin, gallic acid, epicatechin and quercetin) as mainly responsible for such variations.     

Free-radical scavenging capacity and antioxidant activity of selected plant species from the Canadian prairies

Ethanolic extracts from the roots of wild licorice (Glycyrrhiza lepidota), narrow-leaved echinacea (Echinacea angustifolia), senega (Polygala senega), leaves of bearberry (Arctostaphylos uva-ursi) and aerial parts of two varieties of horsetail (Equisetum spp.) were prepared and evaluated for their free-radical scavenging capacity and their antioxidant activity, by a number of chemical assays. Assays employed included a β-carotene-linoleic acid (linoleate) model system, reducing power, scavenging effect on the DPPH free radical and capacity to scavenge hydroxyl free radicals (HO), by use of electron paramagnetic resonance (EPR) spectroscopy. The bearberry-leaf extract consistently exhibited the highest antioxidant activity based on the tests performed, and seems to be a promising source of natural antioxidants. The polyphenolic constituents appear to be responsible, at least in part, for the extract's radical-scavenging capacity. Research is progressing to characterize the antioxidant compounds in the bearberry-leaf extract and their mode of action in imparting antioxidant activity to various food systems.     

Quality Index, Consumer Acceptability, Bioactive Compounds, and Antioxidant Activity of Fresh-Cut "Ataulfo" Mangoes (Mangifera Indica L.) as Affected by Low-Temperature Storage

ABSTRACT:  To measure bioactive compound losses due to minimal processing, mature green fresh-cut mangoes ( Mangifera indica L.) cv. "Ataulfo" were subjected to an antioxidant treatment and stored at 5 °C during 15 d. Quality index, total phenols, flavonoids, β-carotene, ascorbic acid, vitamin E, and antioxidant activity were measured during the storage period of fruits. Antioxidant capacity was estimated using ORAC_FL, TEAC, and DPPH assays. The dipping treatments with ascorbic acid (AA) + citric acid (CA) + CaCl₂ affected positively quality delaying deterioration of fresh-cut mango as compared with whole fruit. However, dipping treatment affected the consumer preferences of fresh-cut mangoes. The highest vitamin C, β-carotene, and vitamin E losses were observed after 10 d, being similar in whole and fresh-cut mangoes. The antioxidant activity was not significantly affected by storage time. We conclude that fresh-cut mangoes retained their bioactive compound content during storage and their antioxidant and nutritional properties make them a good source of these compounds.     

姜黄醇提物化学成分及其抗氧化活性分析

目的：研究姜黄（Curcuma longa L.）的化学成分及其抗氧化活性。方法：应用硅胶柱色谱、Sephadex LH-20凝胶柱色谱以及高效液相制备色谱等方法进行分离纯化,根据高分辨质谱、核磁共振谱鉴定化合物的结构;同时采用1,1-二苯基-2-三硝基苯肼（1,1-diphenyl-2-picrylhydrazyl,DPPH）法、2,2’-联氮双(3-乙基苯并噻唑啉-6-磺酸)（2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid),ABTS）法和铁氰化钾还原法对分离得到的化合物进行抗氧化活性筛选。结果：从姜黄中分离鉴定了7 个合物,分别为Zingerol（1）、Dihydroferulic acid ethyl ester（2）;乙基-3-(4-羟基-苯基)-丙酸乙酯（3）、Zingerone dimer [4,4’-(6,6’-dihydroxy-5,5’-dimethoxy-[1,1’-biphenyl]-3,3’-diyl) bis(butan-2-one)]（4）、姜酮（5）、4-(3,4-二甲氧基苯基)丁烷-2-酮（6）、香草醛（7）。其中,化合物1～5均具有一定的抗氧化活性,ABTS阳离子自由基清除实验中,化合物1和化合物2的IC50值分别为（3±0.2）μmol/L和（12±1.0）μmol/L,化合物1优于阳性对照VC（VC的IC50值（13±1.1）μmol/L）,化合物2与VC效果相当,还原力实验中,化合物1活性优于VC,浓度低于0.125 μmol/mL时化合物2活性强于VC。结论：化合物4为新的天然产物,化合物1、2、3和6为姜黄属中首次发现,化合物1抗氧化活性较强可能与其脂肪链2位上羟基取代有关,姜黄醇提物中的酚类成分是姜黄抗氧化活性的物质基础之一。     

基于亚铁螯合能力的灰树花蛋白酶解工艺优化及其抗氧化活性

以灰树花为原料,探究灰树花蛋白亚铁螯合肽的最佳制备条件,并对其抗氧化活性进行评价。从6?种蛋白酶中筛选出酶解最佳用酶,在此基础上,以亚铁螯合能力为响应值,进行单因素和正交试验,同时研究了灰树花蛋白亚铁螯合肽对1,1-二苯基-2-三硝基苯肼（1,1-diphenyl-2-picrylhydrazyl,DPPH）自由基、羟自由基的清除效果。结果表明,碱性蛋白酶酶解物的亚铁螯合能力最强,在pH?9、加酶量1?800?U/g、酶解温度55?℃、底物质量浓度0.5?g/100?mL、酶解时间2.5?h的条件下,灰树花蛋白亚铁螯合肽的亚铁螯合能力最强,可达1.854?mg/g,此时水解度为6.14%。灰树花蛋白亚铁螯合肽对DPPH自由基和羟自由基有较强的清除效果,且与多肽质量浓度呈正相关。结果显示,灰树花蛋白亚铁螯合肽具有良好的亚铁螯合能力,并具有较好的抗氧化活性,有望发展为新型的膳食补充剂。