快原子轰击离子化质谱研究酚类化合物抗氧化作用

为了建立简便、快速筛选高效、低毒的新型抗氧化药物的方法,本研究采用快原子轰击离子化质谱( FAB-MS)对酚类化合物抗氧化作用强弱进行了研究。考察了基质、轰击时间和样本浓度对FAB-MS 谱中分子离子(M+·)相对强度的影响,研究了黄酮类化合物在FAB-MS谱中的I(M+·)/I([M+H]+)比值与其抗氧化活性的相关性。对12种酚类化合物的抗氧化活性进行了预测与评价,并与硫代巴比妥酸法( TBA)检测的脂质过氧化抑制率进行比较,验证 FAB-MS 方法的可靠性。结果表明,由 FAB-MS 获得的 I ( M+·)/I([ M+H]+)比值能较好地反映酚类化合物抗氧化作用的强弱,可以作为抗氧化剂的体外筛选或预测方法,有助于加速新型抗氧化药物的发现。     

Phytochemical analysis and antidiabetic efficacy of Morus rubra

Morus rubra (red mulberry) is a folk medicine used in management of diabetes. The aim of this article to investigate the antidiabetic activity of hydro alcoholic leaf extracts of Morus rubra in the sprague dawley male rats (SD) model. Authentication of plant material, total Phenolic contents, total flavonoid contents, HPLC analysis, in-vitro antioxidant activity, acute toxicity, in-vivo oral glucose tolerance test, in-vivo STZ induced antidiabetic activity along with biochemical parameters (triglycerides, low-density lipoprotein, high-density lipoprotein, total cholesterol, serum glutamate phosphotransferase, serum glutamate oxaloacetic acid transferase, urea and creatinine). The total phenolic contents 60.32 ​± ​0.80 ​mg/g GAE (gallic acid equivalent) were found higher in ethanolic extract. The total flavonoids 16 ​± ​0.42 ​mg/g QE (quercetin equivalent) were found in petroleum ether extract. M. rubra leaf extracts were tested by HPLC for qualitative and quantitative analysis. 100 ​mg of the dried powder of Morus leaves was dissolve in methanol: water (80:20, v/v) for analysis. Chromatograms of HPLC show the presence of chlorogenic acid 0.55 mg/gm, quercetin 1.90 ​mg/g, isoquercetin 0.68 mg/gm and rutin 0.10 mg/gm. IC₅₀ (Inhibitory concentration) value has been found higher in chloroform extract (92.89 ​μg/ml). Metformin drug is used for positive control, which causes 14.6% improvement in glucose tolerance while M. rubra has been found 11.4. % at the dose of 300 ​mg/kg body wt in normal rats. In STZ treated diabetic rats, it reduces 13.0% blood glucose level while metformin reduces 21.9% up to dosing level of 300 ​mg/kg body wt. It produces reduction in biochemical parameters like, total cholesterol (TC), triglycerides (TG), SGPT, LDL, urea, creatinine and SGOT while HDL has been increased. Results show the hydro-alcoholic leaves extract of Morus rubra exhibited antidiabetic, antioxidant and hypolipidemic properties. This suggests that M. rubra has great potential to develop novel antidiabetic drug to manage this disastrous disease.     

Electroanalytical Approach to Evaluate Antioxidant Capacity in Honeys: Proposal of an Antioxidant Index

A novel electrochemical route to estimate the antioxidant capacity in honey samples is proposed just using flow injection analysis. The analytical strategy involved the selective oxidation of polyphenolic compounds using two different target potentials, +0.8 and +0.5 V, at two different pHs. An oxidation current obtained at the fixed potential was used as an analytical guide of the antioxidant activity of the target honeys. Chemometrics (correlation and principal component analysis, PCA) demonstrated the significance of the electrochemical protocol versus the traditional spectrophotometric ones in the evaluation of antioxidant capacity and revealed the role of detection potential as a screening variable. The proposed protocol is very simple and fast. However, the most relevant merit of the electrochemical procedure is its inherent versatility which allows the evaluation of the antioxidant activity under predesigned controlled oxidation conditions. In addition, since intercept was statistically zero, its corresponding antioxidant content using just a calibration factor is proposed thus simplifying the calibration‐analysis process. As a result, an electrochemical antioxidant index (EAI) is proposed.     

Antioxidant activities and liquid chromatography with electrospray ionization tandem mass spectrometry characterization and quantification of the polyphenolic contents of Rumex nervosus Vahl leaves and stems

In the present study, four compounds, viz. chlorogenic acid, catechin, orientin, and apigenin‐O‐acetylglycoside among 18 polyphenol compounds (17 flavonoids and one hydroxycinnamic acid derivative) were characterized for the first time in Rumex nervosus leaves and stems by using liquid chromatography with electrospray ionization tandem mass spectrometry. Method validation in terms of determination coefficient, limits of detection, and quantification were ≥ 0.9979, 0.68–1.61, and 2.27–5.38 mg/L, respectively. Accuracy, expressed as percent recovery for two spiking levels (10 and 50 mg/L), were in the range 78.9–110.6% with the exception of caffeic acid. The relative standard deviations were 1–17%. The total polyphenol content was higher by approximately two times in the leaf (1073 mg/kg fresh sample) than in the stem (519.86 mg/kg fresh sample). The antioxidant effects increased in a dose‐dependent manner, and the scavenging activities, investigated by measuring 2,2′‐azino‐bis(3‐ethylbenzothiazoline‐6‐sulfonic acid) scavenging activity, ferrous ions chelating activity, superoxide anion radical scavenging activity, and ferric reducing antioxidant power activity, were significant (p < 0.05) using low concentrations of the leaf extract. Overall, the present study suggests that different parts of R. nervosus have great potential for producing a range of extracts with potential applications in medicine.     

Antioxidant behaviour of a nanosilica-immobilized antioxidant in polypropylene

A nanosilica-immobilized antioxidant was prepared and incorporated into polypropylene (PP) by melt compounding. It has been found that the antioxidant efficiency of the nanosilica-immobilized antioxidant was superior to the corresponding low molecular counterpart (AO), based on the measurement of the oxidation induction time (OIT) of PP/nanosilica-immobilized antioxidant and PP/AO compounds containing an equivalent antioxidant component. By paying attention to the changes of carbonyl absorption and tensile strength of PP compounds with thermal oven aging time, it was observed that the thermal oxidative stability of PP/nanosilica-immobilized antioxidant was much higher than that of PP/AO compound during the long-term accelerated thermal aging.     

一种抗氧剂的剖析

利用傅里叶变换红外光谱法、X射线衍射法、电感耦合等离子体原子发射光谱法对一种抗氧剂进行了组成剖析。结果表明:该抗氧剂由吩噻嗪、碳酸钙、硝酸钾组成,其质量分数分别为85.25%,5.72%,9.03%。     

Evaluation of the antioxidant power of honey, propolis and royal jelly by amperometric flow injection analysis

In this paper is described the applicability of a flow injection system, operating with an amperometric detector, for measurement in rapid and simple way the antioxidant power of honey, propolis and royal jelly. The proposed method evaluates the reducing power of selected antioxidant compounds and does not require the use of free radicals or oxidants. Twelve honey, 12 propolis and 4 royal jelly samples of different botanical and geographical origin were evaluated by the electrochemical method and the data were compared with those obtained by the DPPH assay. Since a good correlation was found (R² = 0.92) the proposed electrochemical method can be successfully employed for the direct, rapid and simple monitoring of the antioxidant power of honeybee products. Furthermore, the total phenolic content of samples was determined by the Folin-Ciocalteau procedure and the characteristic antioxidant activities showed a good correlation with phenolics (R² = 0.96 for propolis and 0.90 for honey).     

核桃蛋白酶解物的制备及抗氧化活性

采用碱性蛋白酶对核桃蛋白进行酶解, 检测了所得酶解物的抗氧化能力, 包括对1,1-二苯基-2-三硝基苯肼(DPPH)和羟基自由基(·OH)的清除能力; 利用Sephadex G-25 凝胶层析柱和反相柱对核桃蛋白酶解物进行分离纯化; 采用液相色谱-质谱(LC-ESI-Q-TOF)联用方法测得抗氧化能力最强的多肽的序列为Ala-Gly-Gly-Ala, 其还原力和还原型谷胱甘肽相当.     

Automatic thermal desorption in GC analysis of dairy product volatiles

Summary Automatic thermal desorption (ATD) has been evaluated for the analysis of volatile components from dairy products. It has resulted in a fast and reproducible method which needs only a low amount of sample. Volatile components from milk are collected by off-line purging and trapped on cartridges packed which a suitable adsorbent. Cheese samples are submitted to the same process or directly introduced into the cartridges. The desorption step that follows is carried out automatically and on-line with the chromatographic analysis. Repeatability and sensitivity were satisfactory for both types of products.     

Antioxidant activity of a polysaccharide from Dictyophora indusiata volva and MECC analysis of its monosaccharide composition

In this paper, a crude polysaccharide (PDI) was extracted from D. indusiata volva. The antioxidant activities of PDI were examined by 1,1-diphenyl-2-picryl-hydrazyl (DPPH) radical, hydroxyl radical and ABTS radicals scavenge assay. The results showed that PDI had antioxidant activities in all these assays, indicating that it could be used as an antioxidant. Then a rapid and highly efficient micellar electrokinetic capillary chromatography (MECC) method coupled with diode array detector was developed to determine the monosaccharides composition of the polysaccharide sample. The optimum conditions were as follows: 20 ​mM borate (pH ​= ​9.3) and 15 ​mM SDS as the electrophoresis medium, the separation temperature was 20 ​°C. Under these conditions, monosaccharides could be separated within 8 ​min. The polysaccharide of the volva was mainly composed of glucose, mannose, galactose and arabinose.     

树状桥联半受阻酚类抗氧剂的合成与抗氧化性能

从端基为胺基树状大分子出发, 合成了一种具有多个半受阻酚抗氧化基团、 结构对称的树状桥联半受阻酚类抗氧剂. 元素分析、 傅里叶变换红外光谱(FTIR)、 氢核磁共振波谱(¹H NMR)、 质谱(MS)和冰点降低法证实合成的树状桥联半受阻酚类抗氧剂的化学结构与理论结构一致, 纯度较高. 采用1,1-二苯基-2-苦基肼(DPPH)法和差热扫描量热(DSC)法研究了树状桥联半受阻酚类抗氧剂的抗氧化性能, 并与相应的树状桥联全受阻酚类抗氧剂进行了对比. 研究结果表明, 树状桥联半受阻酚类抗氧剂清除DPPH自由基的活性不仅与清除体系中抗氧剂的浓度有关, 而且与清除时间有关; 清除时间为30 min时的抗氧化能力是清除时间为400 min时抗氧化能力的近2倍. 树状桥联半受阻酚类抗氧剂的半受阻效应使其在DPPH体系和HDPE树脂中的抗氧化能力均优于其相应的树状桥联全受阻酚类抗氧剂.     

Trends in product analysis for research in the pharmaceutical industry

Characterization of substances and formulations with respect to purity and stability is a major analytical chemical task during product development in the pharmaceutical industry. The importance of separation methods, especially liquid chromatography, is shown with some examples from work with omeprazole. The role of mass spectrometry (MS) for structure elucidation is emphasized. Dissolution testing comprises a large number of samples and adaptation to standardized procedures is important. Work is exemplified with dissolution testing of felodipine. Automation and robots with multivariate calibration are necessary approaches. Macromolecular characterization is exemplified from the fields of biomolecules and macromolecular excipients. Separation methods and MS are important tools. New challenges in the area of process analytical chemistry are discussed and chemometrics will play an important role. In all fields method validation is stressed, but should not require more power than necessary in a specification.     

Antioxidant activity of polyaniline nanofibers

Well-confined uniform polyaniline (PANI) nanofibers were synthesized by using photo-assisted chemical oxidative polymer- ization of aniline in the presence of different dopant acids,and the radical scavenging ability of the produced PANI nanofibers was determined by the DPPH assay.It was found that the antioxidant activity of PANI nanofibers was higher than conventional PANI, and increased with decreasing of averaged diameter of the nanofibers.The enhanced antioxidant activity was concerned with increased surface area of PANI nanofibers.     

Antioxidant effects of photodegradation product of nifedipine

Recently, increasing evidence suggests that the antihypertensive drug nifedipine acts as a protective agent for endothelial cells, and that the activity is unrelated to its calcium channel blocking. Nifedipine is unstable under light and reportedly decomposes to a stable nitrosonifedipine (NO-NIF). NO-NIF has no antihypertensive effect, and it has been recognized as a contaminant of nifedipine. The present study for the first time demonstrated that NO-NIF changed to a NO-NIF radical in a time-dependent manner when it interacted with human umbilical vein endothelial cells (HUVECs). The electron paramagnetic resonance (EPR) signal of NO-NIF radicals in HUVECs showed an asymmetric pattern suggesting that the radicals were located in the membrane. The NO-NIF radicals had radical scavenging activity for 1,1-diphenyl-2-picrylhydrazyl, whereas neither NO-NIF nor nifedipine did. In addition, the NO-NIF radical more effectively quenched lipid peroxides than NO-NIF or nifedipine. Furthermore, NO-NIF attenuated the superoxide-derived free radicals in HUVECs stimulated with LY83583, and suppressed iron-nitrilotriacetic acid (Fe-NTA)-induced cytotoxicity in rat pheochromocytoma (PC12) cells. Our findings suggest that NO-NIF is a candidate for a new class of antioxidative drugs that protect cells against oxidative stress.     

Valorization of Zea mays hairs waste extracts for antioxidant and anticorrosive activity of mild steel in 1 M HCl environment

The extraction of Zea mays hairs (Z. mays) was carried out by soxhlet and ultrasound techniques and through three solvents. Phytochemical tests and quantitative analysis of total phenols content (TPC) and flavonoids content (FC) for all extracts were also determined. The antioxidant activity, for different fractions, was determined by using three methods; DPPH, FRAP and TAC. All extracts were rich in polyphenols and the analysis of TPC and FC showed that the hydro-ethanolic extract obtained by ultrasound was characterized by a significant amount of TPC and FC. The n-butanolic fraction was rich in FC and also had a very high antioxidant capacity. On the other hand, the inhibiting effect of hydro-ethanolic extract, n-butanolic fraction and standard (flavone) on mild steel corrosion in 1 M HCl solution was investigated by electrochemical measurements. The polarization curves along with EIS diagrams indicated that flavone was the major molecule responsible for inhibition and acted as mixed-type inhibitor with predominant control of cathodic reaction. The antioxidant activity of BF was well correlated to corrosion inhibition efficiency.     

Antioxidant activity assay based on laccase-generated radicals

A novel antioxidant activity assay was developed using laccase-oxidized phenolics. In a three-step approach, phenolic compounds were first oxidized by laccase. Laccase was then inhibited using 80% (v/v) methanol which also stabilized the oxidized phenolics which were then used to measure antioxidant activities of ascorbic acid and Trolox. From a number of laccase-oxidized phenolics screened for potential use in the measurement of antioxidant activities, syringaldazine emerged the best, giving results comparable to the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical, which is currently used in conventional methods. Like DPPH radicals, two moles of stoichiometric oxidized syringaldazine were reduced by one mole of either ascorbic acid or Trolox. For the first time we show that antioxidant activity can be correlated to oxygen consumption by laccase. Reduction of one molecule of oxygen corresponded to oxidation of four molecules of syringaldazine which in turn is reduced by two molecules of Trolox or ascorbic acid. This study therefore demonstrates the great potential of using laccase-oxidized syringaldazine for the measurement of antioxidant activity.     

光电化学技术应用于抗氧化分析的研究进展

在新陈代谢过程中,机体会产生大量以自由基为主要形式的氧化活性物质,而抗氧化剂可以通过电子转移的方式捕获并中和自由基,从而有效抵御自由基引起的细胞损害,以保障和维护人体健康.食品作为人体外源性抗氧化剂的重要来源可以有效补充因体内代谢及体液排出而损失的抗氧化物质,因此对食品中抗氧化物质消除自由基的能力即抗氧化能力的测定和评价具有重要意义.光电化学技术作为一种简单快捷、低成本、低背景且高灵敏度的测定方法,能够有效克服光学法、色谱法和电化学法等传统测试手段在抗氧化容量分析中的不足.本文综述了基于半导体及其复合材料的光电化学传感平台的构建及食品体系抗氧化容量分析的研究进展,评论了多种检测体系的特点并对其研究前景进行了展望.     

Total phenolic and flavonoid contents,antioxidant, antidiabetic and antiplasmodial activities of Garcinia forbesii King: A correlation study

Garcinia forbesii King belongs to Clusiaceae is a source of secondary metabolites especially xanthones with various biological activities. G. forbesii King is also known for its empirical use for malaria and diabetes. This study investigated the total phenolic and flavonoid contents, in vitro antioxidant, antidiabetic and antiplasmodial activities of four extracts attained from the stem bark of G. forbesii King. The total phenolic and flavonoid contents were determined by spectrophotometric methods and antioxidant activity was evaluated by DPPH, ABTS, FRAP assays. In vitro antidiabetic activity was assessed by α-glucosidase and α-amylase assays and antiplasmodial activity was studied against chloroquine sensitive Plasmodium falciparum strain 3D7. The highest value of total phenolic (187.37 ± 0.06 mg GAE/g) and flavonoid (35.97 ± 0.02 mg QE/g) contents were recorded in n-hexane and methanolic extracts. n-Hexane extract showed the highest DPPH activity with IC₅₀ of 8.12 ± 0.02 μg/mL. Ethyl acetate extract exhibited better scavenging ability for ABTS with IC₅₀ of 3.88 ± 0.04 μg/mL. The FRAP assay showed better activity in methanol extract with an inhibition value of 73.68 ± 3.66 µM Fe²⁺/g. The strong inhibition against α-glucosidase and α-amylase were displayed by dichloromethane extract with IC₅₀ of 35.13 ± 2.01 μg/mL and 4.83 ± 0.20 μg/mL. n-Hexane and methanol extracts showed significant antiplasmodial activity with IC₅₀ of 0.23 ± 0.01 μg/mL and 0.73 ± 0.01 μg/mL, respectively. The correlation analysis indicated a positive relationship of total phenolic and flavonoid contents with antiplasmodial activity. The results revealed that n-hexane and methanol extracts could be used as a potential natural antiplasmodial, while dichloromethane extract is a promising natural antidiabetic.     

Antioxidant behavior of a novel sulfur-bearing hindered phenolic antioxidant with a high molecular weight in polypropylene

A novel sulfur-bearing hindered phenolic antioxidant with a molecular weight of 1305.9 (SAO) was successfully synthesized via thiol-acrylate Michael addition reaction and its structure was clarified by nuclear magnetic resonance (NMR) and fourier transform infrared spectra (FTIR). The short-term oxidation induction time (OIT) of polypropylene (PP) compounds obtained at 210 °C showed that the OIT value of SAO-containing PP was higher than that of PP using Chinox 1035 with a molecular weight of 642.9 as a stabilizer. Long-term accelerated thermal aging test of PP compounds in an air oven at 150 °C, however, exhibited that the aging resistance of SAO-stabilizing PP was inferior to that of 1035-containing PP, quite contrary to their respective short-term effect on PP stabilization. The possible reasons of this contradiction were discussed from the viewpoint of the antioxidants' molecular structure and the limitations of the OIT approach in lifetime prediction.     

Antioxidant capacity of the algae using a biosensor method

Three different methods, i.e. a biosensor method, a voltammetric method and a spectrophotometric method, have been used to evaluate the total antioxidant capacity of certain types of algae. In the final evaluation of the data also the variation in time of the antioxidant capacity of cultivated algae was considered and some experimental factors, such as the use of different solvent mixtures to extract the antioxidant substances contained in the algae, were discussed.