黑莓(萨尼)果实体外抗氧化活性研究

采用清除二苯代苦味酰基(DPPH)自由基和[2,2’-连氨-(3-乙基苯并噻唑啉-6-磺酸)二氨盐](ABTS)自由基及铁离子还原/抗氧化能力(FRAP)测定法研究黑莓(萨尼)果实体外抗氧化活性,并于阳性对照丁基羟基茴香醚(BHA)和二丁基羟基甲苯(BHT)比较.萨尼果实正丁醇部位体外抗氧化活性比较好.正丁醇部位清除DPPH和ABTS自由基的能力(IC50 =8.44和4.55 μg/mL)强于阳性对照BHT(IC50=18.71和7.72 μg/mL),弱于阳性对照BHA(IC50=3.2和1.88 μg/mL),乙酸乙酯部位清除DPPH和ABTS自由基的能力(IC50=38.55和17.25 μg/mL)均弱于阳性对照BHA和BHT,乙酸乙酯部位和正丁醇部位对Fe3+的还原能力(Trolox当量=711.57±10.14和628.4±11.30μmol/g)均弱于阳性对照BHA和BHT(Trolox当量=6633.04±114.04和1581.68 ±97.41 μmol/g).     

紫薇花的抗氧化活性研究

采用DPPH法、ABTS法和FRAP三种测定法对银薇和红花紫薇体外抗氧化活性进行综合评价,并与阳性对照二丁基羟基甲苯(BHT)比较。研究结果发现紫薇花具有较好的抗氧化活性。银薇乙酸乙酯部位清除DPPH自由基的能力(IC50=7.4μg/m L)、清除ABTS自由基的能力(IC50=1.8μg/m L)和还原Fe3+的能力(TEAC=2664.7μmol/g)均强于阳性对照BHT(DPPH方法:IC50=23μg/m L;ABTS方法:IC50=2.3μg/m L;FRAP方法:TEAC=1532.7μmol/g),银薇乙酸乙酯部位抗氧化能力最强。     

红背叶提取物的体外抗氧化活性

采用DPPH法、FRAP法、ABTS法和清除羟基自由基法四种抗氧化活性方法,测定了红背叶不同溶剂萃取60%EtOH提取物得到的部位清除自由基的能力.结果表明,乙酸乙酯提取物的抗氧化能力最强,强于阳性对照VC和Trolox;其次是60%乙醇提取物,其抗氧化能力基本与阳性对照BHA相当.     

麻花艽不同部位抗氧化活性研究

本文分别采用DPPH法和铜离子还原能力法(CUPRAC)测定麻花艽花、茎叶和根的抗氧化活性,并比较其不同部位的抗氧化活性。抗氧化活性分析结果表明麻花艽花、茎叶、根的DPPH自由基清除能力均低于没食子酸,其清除DPPH自由基的半数有效量(IC_(50))分别为260、341.3和2920.6μg/m L;麻花艽花、茎叶和根的Cu2+的还原能力Trolox当量(TEAC值)分别为0.127、0.108和0.019μg/m L。结果表明,麻花艽花、茎叶和根均具有抗氧化活性,其抗氧化能力的强弱顺序为花茎叶根。     

河南产景天三七抗氧化活性研究

用清除二苯代苦味酰基(DPPH)自由基、2,2′-连氨-(3-乙基苯并噻唑啉-6-磺酸)二氨盐(ABTS)自由基和铁离子还原/抗氧化能力(FRAP)测定法对洛阳和信阳产景天三七(Sedum aizoon)体外总抗氧化活性进行评价,并与阳性对照丁基羟基茴香醚(BHA)、没食子酸丙酯(PG)和二丁基羟基甲苯(BHT)比较。发现洛阳和信阳景天三七有较好的体外抗氧化活性。洛阳和信阳产乙酸乙酯部位活性最强,正丁醇部位活性次之。在6个提取部位中,信阳产景天三七乙酸乙酯部位活性最强,其清除DPPH、ABTS自由基能力强于阳性对照BHA和BHT,还原Fe3+的能力大于阳性对照BHT,洛阳产景天三七乙酸乙酯部位和正丁醇部位活性次之。     

朱砂根抑制α-葡萄糖苷酶与抗氧化活性研究

对朱砂根抑制α-葡萄糖苷酶与抗氧化活性进行研究.利用96微孔板法筛选α-葡萄糖苷酶抑制活性;采用DPPH、ABTS和FRAP方法分析抗氧化活性.结果表明,乙酸乙酯部位抑制α-葡萄糖苷酶的活性最高(IC50=39.27 μg/mL),石油醚部位次之(IC50 =56.11 μg/mL),正丁醇部位活性最弱(IC50=62.05μg/mL),但均远大于阳性对照Acarbose(IC50=1081.27 μg/mL);乙酸乙酯部位抗氧化能力最强,正丁醇部位次之.乙酸乙酯部位清除DPPH自由基(IC50=38.55 mg/L)的能力比BHT( IC50=18.71 mg/L)低1/2,清除ABTS自由基的能力(IC50=3.60 mg/L)比BHT(IC50=7.44 mg/L)强,但比BHA(IC50=1.74 mg/L)弱,还原Fe3+的能力(FRAP=512.99 ±6.80 μmoTE/g)为BHT(FRAP=1581.68±97.41μmol TE/g)的1/3.结果显示朱砂根乙酸乙酯部位抑制α-葡萄糖苷酶和抗氧化活性最好.     

红花桑寄生叶提取物的抗氧化活性及酚类物质分析

采用DPPH法、TEAC法、FRAP法对红花桑寄生叶不同溶剂提取物的抗氧化活性进行体外评价,并测定其总酚、总黄酮含量。结果表明,溶剂种类对红花桑寄生叶提取物的得率、总酚、总黄酮及抗氧化活性影响显著。在3种评价方法中,不同溶剂提取物的抗氧化活性均表现出不同程度的量效依赖关系。3种溶剂提取物的抗氧化活性强弱依次为丙酮提取物 >甲醇提取物 >水提取物,其中80%丙酮提取物(总酚含量最高,达276.83mg/g)抗氧化活性最强,清除DPPH自由基能力EC₅₀值为0.247,FRAP值(FeSO₄ mmol/100g)为115.81,浓度为1.0mg/ml时,TEAC值为2.04。     

鼠尾草酸的抗氧化活性及抑菌活性研究

通过自由基清除能力、还原力和平板二倍稀释法实验,评价了鼠尾草酸的抗氧化活性、抑菌活性。结果显示:相同浓度的鼠尾草酸抗氧化活性明显高于合成抗氧化剂PG、BHT、BHA、VE,略低于THBQ,其清除DPPH的IC50值为2.53μg/m L,清除ABTS的IC50值为51.58μg/m L。抑菌实验表明:鼠尾草酸具有广谱抗菌性,特别是大肠埃希氏杆菌、绿脓假单胞菌,其最低抑菌浓度分别为4、2μg/m L,表现出了比新洁尔灭、氨苄青霉素钠、红霉素更好的抑菌活性;对于肺炎克雷伯氏菌,则表现出了与红霉素同样的抑菌效果,优于新洁尔灭和氨苄青霉素钠。     

黄连抗氧化活性研究

利用DPPH、FRAP和ABTS三种抗氧化活性分析方法对黄连植物不同部位的有机溶剂提取部分进行抗氧化评价,将所测定结果与Trolox进行比较,发现黄连植物不同部位抗氧化活性不同。其中,黄连须根的抗氧化活性最高;同一部位中,乙酸乙酯和甲醇提取物抗氧化活性一般要高于石油醚提取物。在三种方法中,黄连不同部位的提取物清除自由基的能力均随浓度增大而增大;三种方法之间有很好的相关性,以FRAP法与DPPH法相关性最好(r=0.9261,P<0.01)。     

疏毛绣线菊的抗氧化活性研究北大核心CSCD

采用清除二苯代苦味酰基(DPPH)自由基、清除[2,2-连氨-(3-乙基苯并噻唑啉-6-磺酸)二氨盐](ABTS)自由基和铁离子还原/抗氧化能力(FRAP)测定法对疏毛绣线菊总抗氧化活性行评价,将测定结果与阳性对照药物二丁基羟基甲苯(BHT)进行比较。研究结果发现疏毛绣线菊正丁醇部位具有较强的清除DPPH自由基(IC50=42.2μg/mL)和还原Fe3+的能力(TEAC=1052.46μmol/g),乙酸乙酯部位清除ABTS自由基能力(IC50=6.4μg/mL)较好,但均弱于阳性对照药物BHT(IC50和TEAC值分别为23μg/mL、2.3μg/mL和1532.7μmol/g)。实验证明疏毛绣线菊正丁醇部位体外抗氧化活性较强。     

Antioxidant properties of catechins and proanthocyanidins: Effect of polymerisation, galloylation and glycosylation

A range of catechins and oligomeric procyanidins was purified by high performance liquid chromatography (HPLC) from grape seed, apple skin, lentil and almond flesh. Catechins, galloylated epicatechin, glycosylated catechin, procyanidin dimers, galloylated dimers, trimer, and tetramer species were all identified, purified and quantified by HPLC, LC-MS and NMR. The antioxidant properties of these compounds were assessed using two methods: (a) inhibition of ascorbate/iron-induced peroxidation of phosphatidylcholine liposomes; (b) scavenging of the radical cation of 2,2'-azinobis(3-ethyl-benzothiazoline-6-sulphonate) (ABTS) relative to the water-soluble vitamin E analogue Trolox C (expressed as Trolox C equivalent antioxidant capacity, TEAC). Antioxidant activity in the lipid phase decreased with polymerisation in contrast with antioxidant action in the aqueous phase which increased from monomer to trimer and then decreased from trimer to tetramer. Galloylation of catechin and dimeric procyanidins decreased lipid phase and increased aqueous phase antioxidant activity. Glycosylation of catechin demonstrated decreased activity in both phases.     

Antioxidant properties of catechins and proanthocyanidins: Effect of polymerisation,galloylation and glycosylation

A range of catechins and oligomeric procyanidins was purified by high performance liquid chromatography (HPLC) from grape seed, apple skin, lentil and almond flesh. Catechins, galloylated epicatechin, glycosylated catechin, procyanidin dimers, galloylated dimers, trimer, and tetramer species were all identified, purified and quantified by HPLC, LC-MS and NMR. The antioxidant properties of these compounds were assessed using two methods: (a) inhibition of ascorbate/iron-induced peroxidation of phosphatidylcholine liposomes; (b) scavenging of the radical cation of 2,2′-azinobis(3-ethyl-benzothiazoline-6-sulphonate) (ABTS) relative to the water-soluble vitamin E analogue Trolox C (expressed as Trolox C equivalent antioxidant capacity, TEAC). Antioxidant activity in the lipid phase decreased with polymerisation in contrast with antioxidant action in the aqueous phase which increased from monomer to trimer and then decreased from trimer to tetramer. Galloylation of catechin and dimeric procyanidins decreased lipid phase and increased aqueous phase antioxidant activity. Glycosylation of catechin demonstrated decreased activity in both phases.     

Screening of antioxidant potential of Arctic lichens

Antioxidants are compounds that scavenge the free radicals produced in living organisms. The antioxidant potential of eight Arctic lichen species was evaluated in vitro using free radical scavenging activity (FRS), inhibition of lipid peroxidation (ILP), and Trolox equivalent antioxidant capacity assay (TEAC). FRS activities of lichen species in various organic solvents such as methanol, ethanol, acetone, and dimethyl sulphoxide (DMSO) were in the range 9.6–51.77%, while ILP activities in these solvents ranged from 32.5 to 82.43%. Pseudophebe pubescens showed the highest ILP (82.43%) and FRS (51.77%) activities as compared to other lichen species and the standard antioxidants butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT). The TEAC value was also found to be higher in all species compared to the standard water soluble vitamin E analog Trolox (3.9 mM). The order of antioxidative activities in lichen species was Pseudophebe pubescens > Cladonia amaurocraea > Cladonia mediterranea > Physcia caesia > Flavocetraria nivalis > Cetraria fastigata > Xanthoria elegans > Umbilicaria hyperborea. This is the first report of the measurement of antioxidant potential in Arctic lichens.     

Biologically important hydrazide-containing fused azaisocytosines as antioxidant agents

Objectives: Two important classes of hydrazide-containing fused azaisocytosines were evaluated as possible antioxidants and characterised by UV spectroscopy.

Methods: 2,2-Diphenyl-1-picrylhydazyl (DPPH), nitric oxide (NO), hydrogen peroxide (H₂O₂) scavenging potencies and reducing power of molecules were evaluated.

Results: The strongest DPPH scavengers were found to be 9, showing the potency superior to that of butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), propyl gallate (PG) and 6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid (Trolox) and comparable to that of ascorbic acid (AA), and 6, revealing the antioxidant potency superior to that of BHA, BHT, PG and Trolox. In turn, 3 and 9 were the most promising NO scavengers, exhibiting the potency superior to that of BHA, BHT (3 and 9) and AA (3). The most potent H₂O₂ scavengers proved to be 10 and 9 showing similar or even better neutralising potency than that of Trolox, BHT and BHA. Simultaneously, the majority of hydrazides revealed higher ferric reducing abilities than that of AA and BHT. Some structure-activity relationships were explored. A possible mechanism for the DPPH radical scavenging ability of hydrazide-containing molecules was proposed.

Discussion: Hydrazides 3, 6 and 9 with an antioxidant potential better or comparable to that of the well-known antioxidants are proposed as new antioxidant candidates.     

Measurement of relative antioxidant activity of compounds: a methodological note

The relative activities of some hydrogen-donating antioxidants were assessed by comparing their activities with that of Trolox (Trolox equivalent antioxidant capacity, TEAC) for scavenging the ABTS radical cation (ABTS.+) generated in the aqueous phase. We have verified, however, that TEAC values may change with the concentration of compounds and with the measuring times used. Not withstanding, TEAC values do not differ significantly if the compounds have kinetic curves of ABTS.+ formation similar to that of Trolox. This is the case with ascorbic acid, whose TEAC values, determined by using five concentrations at three different measuring times, are very close. For the flavonoids studied (catechin, rutin, naringenin and silibinin) which have kinetic curves of ABTS.+ formation different from that of Trolox, the TEAC values decrease with increasing concentrations of the compounds for each measuring time, and increase with increasing measuring times for each concentration. In the present study, we conclude that, in order to evaluate relative antioxidant activities of compounds by the ABTS assay, it is essential to perform kinetic studies to assess scavenging of ABTS.+ by these compounds. Therefore, when the TEAC values of compounds are determined for more than one measuring time, we may be sure that all the antioxidant potential of compounds is being considered and whether or not it is possible to establish a hierarchy for their antioxidant activities.     

Measurement of relative antioxidant activityof compounds: a methodological note

Abstract

The relativeThe relative activities of some hydrogen-donating antioxidants were assessed by comparing their activities with that of Trolox (Trolox equivalent antioxidant capacity, TEAC) for scavenging the ABTS radical cation (ABTS^?+) generated in the aqueous phase. We have verified, however, that TEAC values may change with the concentration of compounds and with the measuring times used. Not withstanding, TEAC values do not differ significantly if the compounds have kinetic curves of ABTS^?+ formation similar to that of Trolox. This is the case with ascorbic acid, whose TEAC values, determined by using five concentrations at three different measuring times, are very close. For the flavonoids studied (catechin, rutin, naringenin and silibinin) which have kinetic curves of ABTS^?+ formation different from that of Trolox, the TEAC values decrease with increasing concentrations of the compounds for each measuring time, and increase with increasing measuring times for each concentration. In the present study, we conclude that, in order to evaluate relative antioxidant activities of compounds by the ABTS assay, it is essential to perform kinetic studies to assess scavenging of ABTS^?+ by these compounds. Therefore, when the TEAC values of compounds are determined for more than one measuring time, we may be sure that all the antioxidant potential of compounds is being considered and whether or not it is possible to establish a hierarchy for their antioxidant activities.     

Assessment of antioxidant activity by using different in vitro methods

In this study, six common tests for measuring antioxidant activity were evaluated by comparing four antioxidants and applying them to beverages (tea and juices): Trolox equivalent antioxidant capacity assay (TEAC I-III assay), Total radical-trapping antioxidant parameter assay (TRAP assay), 2,2-diphenyl- l -picrylhydrazyl assay (DPPH assay), N , N -dimethyl- p -phenylendiamine assay (DMPD assay), Photochemiluminescence assay (PCL assay) and Ferric reducing ability of plasma assay (FRAP assay). The antioxidants included gallic acid representing the group of polyphenols, uric acid as the main antioxidant in human plasma, ascorbic acid as a vitamin widely spread in fruits and Trolox ® as water soluble vitamin E analogue. The six methods presented can be divided into two groups depending on the oxidising reagent. Five methods use organic radical producers (TEAC I-III, TRAP, DPPH, DMPD, PCL) and one method works with metal ions for oxidation (FRAP). Another difference between these tests is the reaction procedure. Three assays use the delay in oxidation and determine the lag phase as parameter for the antioxidant activity (TEAC I, TRAP, PCL). They determine the delay of radical generation as well as the ability to scavenge the radical. In contrast, the assays TEAC II and III, DPPH, DMPD and FRAP analyse the ability to reduce the radical cation (TEAC II and III, DPPH, DMPD) or the ferric ion (FRAP). The three tests acting by radical reduction use preformed radicals and determine the decrease in absorbance while the FRAP assay measures the formed ferrous ions by increased absorbance. Gallic acid was the strongest antioxidant in all tests with exception of the DMPD assay. In contrast, uric acid and ascorbic acid showed low activity in some assays. Most of the assays determine the antioxidant activity in the micromolar range needing minutes to hours. Only one assay (PCL) is able to analyse the antioxidant activity in the nanomolar range. Black currant juice showed highest antioxidant activity in all tests compared to tea, apple juice and tomato juice. Despite these differences, results of these in vitro assays give an idea of the protective efficacy of secondary plant products. It is strongly recommended to use at least two methods due to the differences between the test systems investigated.     

Phenolics as potential antioxidant therapeutic agents: mechanism and actions

Accumulating chemical, biochemical, clinical and epidemiological evidence supports the chemoprotective effects of phenolic antioxidants against oxidative stress-mediated disorders. The pharmacological actions of phenolic antioxidants stem mainly from their free radical scavenging and metal chelating properties as well as their effects on cell signaling pathways and on gene expression. The antioxidant capacities of phenolic compounds that are widely distributed in plant-based diets were assessed by the Trolox equivalent antioxidant capacity (TEAC), the ferric reducing antioxidant power (FRAP), the hypochlorite scavenging capacity, the deoxyribose method and the copper-phenanthroline-dependent DNA oxidation assays. Based on the TEAC, FRAP and hypochlorite scavenging data, the observed activity order was: procyanidin dimer > flavanol > flavonol > hydroxycinnamic acids > simple phenolic acids. Among the flavonol aglycones, the antioxidant propensities decrease in the order quercetin, myricetin and kaempferol. Gallic acid and rosmarinic acid were the most potent antioxidants among the simple phenolic and hydroxycinnamic acids, respectively. Ferulic acid displayed the highest inhibitory activity against deoxyribose degradation but no structure–activity relationship could be established for the activities of the phenolic compounds in the deoxyribose assay. The efficacies of the phenolic compounds differ depending on the mechanism of antioxidant action in the respective assay used, with procyanidin dimers and flavan-3-ols showing very potent activities in most of the systems tested. Compared to the physiologically active (glutathione, -tocopherol, ergothioneine) and synthetic (Trolox, BHA, BHT) antioxidants, these compounds exhibited much higher efficacy. Plant-derived phenolics represents good sources of natural antioxidants, however, further investigation on the molecular mechanism of action of these phytochemicals is crucial to the evaluation of their potential as prophylactic agents.