不同取代度N-邻苯二甲酰壳聚糖抗氧化活性的研究

低聚壳聚糖与邻苯二甲酸酐酰化得到三种取代度不同的N-邻苯二甲酸酐酰低聚壳聚糖NPCOSA、NPCOSB和NPCOSC,取代度分别为0.330、.55和0.65。通过红外光谱对其结构进行表征。并考察了其抗氧化性能。结果表明:COS的抗氧化性能最强;随着取代度的增加,N-邻苯二甲酰低聚壳聚糖对超氧阴离子的清除能力逐渐升高;而对DPPH的清除能力以及还原能力呈逐渐下降趋势;对羟基自由基的清除顺序大小依次为NPCOSB>NPCOSA>NPCOSC,即NPCOSB清除羟基自由基的的能力最佳。     

藜叶中黄酮类化合物体外抗氧化活性研究

为了探讨藜叶中黄酮类化合物的体外抗氧化活性,采用有机溶剂提取法和色谱柱法对藜叶中化学成分进行提取与分离;以Vc作对照,对分离纯化的芦丁、乙酸乙酯浸膏和正丁醇浸膏进行DPPH·、O2^-·和·OH的清除效果试验。结果表明：三者对DPPH·、O2^-·、·OH均具有清除作用,且与浓度呈量效关系,芦丁对·OH清除效果优于Vc,芦丁具有较强的清除DPPH·能力,其IC50为0．05μg／mL。     

Hydroxytyrosol lipophilic analogues: enzymatic synthesis, radical scavenging activity and DNA oxidative damage protection

The olive oil phenol hydroxytyrosol (3), as well its metabolite homovanillic alcohol (4), were subjected to chemoselective lipase-catalysed acylations, affording with good yield 10 derivatives (5-14) bearing C(2), C(3), C(4), C(10) and C(18) acyl chains at C-1. Hydroxytyrosol (3) and its lipophilic derivatives showed very good DPPH. radical scavenging activity. Compounds 3, 4 and their lipophilic analogues 5-14 were subjected to the atypical Comet test on whole blood cells: 3 and its analogues 5 and 6, with little hydrophobic character (logP相似文献   

Synthesis and antioxidant capacities of hydroxyl derivatives of cinnamoylphenethylamine in protecting DNA and scavenging radicals

Cinnamoylphenethylamine (CNPA) derivatives including feruloylphenethylamine (FRPA), caffeoylphenethylamine (CFPA), cinnamoyltyramine (CNTA), feruloyltyramine (FRTA) and caffeoyltyramine (CFTA) were synthesized in order to investigate the influence of the number and position of hydroxyl group on Cu(2+)/glutathione (GSH) and 2,2'-azobis(2-amidinopropane hydrochloride) (AAPH)-induced oxidation of DNA. The radical-scavenging properties of these CNPA derivatives were also evaluated by trapping 2,2'-azinobis(3-ethylbenzothiazoline-6-sulphonate) cationic radical (ABTS(+?)), 2,2'-diphenyl-1-picrylhydrazyl radical (DPPH) and galvinoxyl radical. In addition, these CNPA derivatives were tested by linoleic acid (LH)-β-carotene-bleaching experiment. The chemical kinetic was employed to treat the results from AAPH-induced oxidation of DNA and gave the order of antioxidant ability as CFTA > CFPA > FRTA > FRPA. CFTA and CFPA also possessed high abilities to inhibit Cu2(+)/GSH-mediated degradation of DNA, whereas FRPA and FRTA can protect LH against the auto-oxidation efficiently. Finally, CFPA and FRPA exhibited high activity in trapping ABTS(+?), DPPH and galvinoxyl radicals. Therefore, the cinnamoyl group bearing ortho-dihydroxyl or hydroxyl with ortho-methoxyl benefited for CNPA derivatives to protect DNA, while hydroxyl in tyramine cannot enhance the radical-scavenging abilities of CNPA derivatives.     

Synthesis and antioxidant properties of substituted 3-benzylidene-7-alkoxychroman-4-ones

A series of 3-benzylidene-7-alkoxychroman-4-one derivatives were synthesized and evaluated for their antioxidant activities. The antioxidant activity was assessed using three methods, namely, 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging, ferric reducing antioxidant power (FRAP), and thiobarbituric acid reactive substances (TBARS) assays. 3-Benzylidene-7-alkoxychroman-4-one derivatives bearing catecholic group on benzylidene moiety exhibited excellent antioxidant activity. Compounds having catechol moiety exhibited potent antioxidant activities in all tested methods and they were more active than the reference drug, Trolox.     

Antioxidant potential of natural and synthesised polyprenylated hydroquinones

The metabolites 2-octaprenyl-1,4-hydroquinone (1) and 2-(24-hydroxy)-octaprenyl-1,4-hydroquinone (2), isolated from the sponge Ircinia spinosula, along with a series of synthetic derivatives, were evaluated for their antioxidant capacity, in order to establish a potential relationship between structural characteristics and antioxidant activity. The antioxidant potential of both natural and synthesised compounds was evaluated in vitro by their ability: (1) to interact with the stable free 1,1-diphenyl-2-picrylhydrazyl radical (DPPH) and (2) to inhibit the peroxidation, induced by the Fe(++)/ascorbate system, of heat inactivated hepatic microsomal membrane lipids. Metabolite 1 presented a strong interaction with DPPH and had a moderate effect on lipid peroxidation, while metabolite 2 interacted extensively with DPPH and exhibited a significant effect against lipid peroxidation. All derivatives retaining the free 1,4-hydroquinone system maintained fully or partly the free radical scavenging capacity.     

Antitrypanosomal and antioxidant properties of 4-hydroxycoumarins derivatives

In the present communication we prepared a series of six 4-hydroxycoumarin derivatives, isosters of quercetin, recognized as an antioxidant natural compound, with the aim of evaluating the antitrypanosomal activity against Trypanosoma cruzi, the parasite responsible for Chagas disease, and the antioxidant properties. We have used the 4-hydroxycoumarin moiety (compound 1) as the molecular template for the synthesis of compounds 2-7. These derivates have shown moderate trypanocidal activity. However they have been proved to be good antioxidants. In particular compound 7 is the most active antioxidant and it is, therefore, a potential candidate for a successful employment in conditions characterized by free radicals overproduction.     

Antioxidant aryl-prenylcoumarin, flavan-3-ols and flavonoids from Eysenhardtia subcoriacea

Antioxidant activity (AOA) assay-guided chemical analysis, using a rat pancreas homogenate model, of aerial parts from Eysenhardtia subcoriacea, led to isolation of the new compound subcoriacin (3-(2'-hydroxy-4',5'-methylendioxyphenyl)-6-(3'-hydroxymethyl-4'-hydroxybut-2'-enyl)-7-hydroxycoumarin) together with the known substances: (+)-catechin, (-)-epicatechin, (+)-afzelechin, eriodictyol, (+)-catechin 3-O-beta-D-galactopyranoside and quercetin 3-O-beta-D-galactopyranoside as bioactive constituents. The structure of the compound was determined from 1D and 2D NMR spectroscopic analyses. Additional known constituents were characterized. The bioactive compounds showed also moderate to strong radical scavenging properties against diphenylpicrylhydrazyl radical (DPPH). In addition, subcoriacin, (+)-catechin, (-)-epicatechin and (+)-afzelechin improved the reduced glutathione levels in rat pancreatic homogenate.     

Synthesis of dimeric phenol derivatives and determination of in vitro antioxidant and radical scavenging activities

In this study, di(2,6-dimethylphenol) (Di-DMP), di(2,6-diisopropylphenol) (Di-DIP, dipropofol) and di(2,6-di-t-butylphenol) (Di-DTP) were synthesized by the reaction of monomeric phenol derivatives with catalytic CuCl(OH). TMEDA and Na2S2O4. Their antioxidant capacity and radical scavenging activity were examined using different in vitro methodologies such as 1,1-diphenyl-2-picryl-hydrazyl (DPPH*) free radical scavenging, 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) radical scavenging activity, total antioxidant activity by ferric thiocyanate, total reducing power by potassium ferricyanide reduction method, superoxide anion radical scavenging, hydrogen peroxide scavenging and ferrous ions chelating activities.     

日本虫草子实体多糖抗氧化及免疫调节作用

为明确日本虫草子实体多糖（CJPs）的抗氧化活性及免疫调节作用,本研究以子实体为原料,采用热水浸提法得多糖,通过对ABTS自由基、DPPH自由基、·OH自由基清除能力评价CJPs的体外抗氧化活性;探讨CJPs对氢化可的松诱导的免疫抑制小鼠的免疫调节作用。结果表明,CJPs对ABTS、DPPH、·OH自由基均有明显的清除效果,且存在量效关系,IC₅₀分别为0.165、0.098、0.253mg/mL;灌胃CJPs的小鼠与模型组相比,免疫器官指数、巨噬细胞吞噬指数、血清中细胞因子水平、免疫球蛋白含量均有所提高,脾脏中乳酸脱氢酶（LDH）和酸性磷酸酶（ACP）的活力显著增强（P<0.05或P<0.01）。该研究表明CJPs是一种潜在的抗氧化剂,并能显著提高免疫低下小鼠的免疫功能,为其进一步研究和应用提供了科学依据。     

树莓粗多糖对UVB诱导HaCaT细胞光损伤的防护作用

多糖是树莓功能性成分之一,具有抗炎、抗氧化、抗疲劳、降血糖、免疫调节等多种药理作用。但树莓多糖对紫外线造成的皮肤细胞光损伤是否具有防护作用尚未见报道。本研究旨在探究树莓粗多糖(raspberry crude polysaccharide, RCP)对中波紫外线(ultraviolet B,UVB)诱导的人永生化角质形成细胞(human immortalized keratinocytes, HaCaT)光损伤的防护作用。通过建立HaCaT细胞的UVB光损伤模型,利用CCK-8法测定细胞活力,酶联免疫吸附法(enzyme linked-immuno-sorbent assay, ELISA)和微板法测定HaCaT细胞中炎症因子、基质金属蛋白酶和抗氧化因子的含量,评估RCP的抗UVB活性。采用体外自由基清除实验检测RCP对DPPH自由基(DPPH·)和ABTS自由基(ABTS·⁺)的清除能力。结果表明,RCP能明显提高被UVB损伤的HaCaT细胞活力,且随浓度升高作用增强(P<0.01或P<0.05)。与未加入RCP处理的HaCaT细胞比较,人基质金属蛋白...     

Antioxidant activity of galloyl quinic derivatives isolated from P. lentiscus leaves

The antioxidant properties of galloyl quinic derivatives isolated from Pistacia lentiscus L. leaves have been investigated by means of Electron Paramagnetic Resonance spectroscopy (EPR) and UV-Vis spectrophotometry. Antioxidant properties have been also estimated using the biologically relevant LDL test. The scavenger activities of gallic acid, 5- O -galloyl, 3,5- O -digalloyl, 3,4,5- O -trigalloyl quinic acid derivatives, have been estimated against 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical, superoxide ( O 2 - ) radical, and hydroxyl (OH) radical. On the whole, the scavenger activity raised as the number of galloyl groups on the quinic acid skeleton increased. The half-inhibition concentrations (IC 50 ) of di- and tri-galloyl derivatives did not exceed 30 μM for all the tested free radicals. All the tested metabolites strongly reduced the oxidation of low-density lipoproteins (LDL), following a trend similar to that observed for the scavenger ability against OH radical.     

Synthesis, antioxidant and toxicological study of novel pyrimido quinoline derivatives from 4-hydroxy-3-acyl quinolin-2-one

A series of novel pyrimido and other fused quinoline derivatives like 4-methyl pyrimido [5,4-c]quinoline-2,5(1H,6H)-dione (4a), 4-methyl-2-thioxo-1,2-dihydropyrimido [5,4-c]quinoline-5(6H)-one (4b), 2-amino-4-methyl-1,2-dihydropyrimido [5,4-c]quinolin-5(6H)-one (4c), 3-methylisoxazolo [4,5-c]quinolin-4(5H)-one (4d), 3-methyl-1H-pyrazolo [4,3-c]quinoline-4(5H)-one (5e), 5-methyl-1H-[1,2,4] triazepino [6,5-c]quinoline-2,6(3H,7H)-dione (5f), 5-methyl-2-thioxo-2,3-dihydro-1H-[1,2,4]triazepino [6,5-c]quinolin-6(7H)-one (5 g) were synthesized regioselectively from 4-hydroxy-3-acyl quinolin-2-one 3. They were screened for their in vitro antioxidant activities against radical scavenging capacity using DPPH(), Trolox equivalent antioxidant capacity (TEAC), total antioxidant activity by FRAP, superoxide radical (O(2)(°-)) scavenging activity, metal chelating activity and nitric oxide scavenging activity. Among the compounds screened, 4c and 5 g exhibited significant antioxidant activities.     

Antioxidative polyphenols from berries of Pimenta dioica

The ethyl acetate-soluble part of allspice, berries of Pimenta dicica, showed strong antioxidant activity and radical-scavenging activity against 1,1diphenyl-2-picrylhydrazl (DPPH) radical. From the ethyl acetate-soluble part, two new compounds, 5-galloyloxy-3-4-dihydroxypentanoic acid and 5-(5-carboxmethyl-2-oxocyclopenty)3Z-penteny 6-O-galloy-beta-D-glucoside were isolated together with 11 known polyphenols by repeated column chromatography. Their structures were elucidated on the basis of MS and various NMR spectroscopic data. All isolated compounds were evaluated for antioxidative effects on oxidation of methyl linoleate under aeration and heating, anf on peroxidation of liposome induced by 2-2'-azobis-(2-amidinopropane)dihydrocloride (AAPH) as water-soluble initiator along with their radical-scavenging activity against DPPH. Quercetin and its glycoside showed remarkable activity for scavenging DPPH radical and inhibiting peroxidation of liposome. Two new compounds also exhibited strong DPPH radical-scavenging activity and inhibitory effect on the peroxidation od liposome as myricetin.     

Phenylpropanoid glucosides from leaves of Coussarea hydrangeifolia (Rubiaceae)

Phenylpropanoid glycosides, 1'-O-benzyl-alpha-L-rhamnopyranosyl-(1'-->6')-beta-D-glucopyranoside (1) and alpha-L-xylopyranosyl-(4'-->2')-(3-O-beta-D-glucopyranosyl)-1'-O-E-caffeoyl-beta-D-glucopyranoside (2), together with the known derivatives, 1,6-di-O-caffeoyl-beta-D-glucopyranoside (3), 1-O-(E)-caffeoyl-beta-D-glucopyranoside (4) and 1-O-(E)-feruloyl-beta-D-glucopyranoside (5), were isolated from leaves of Coussarea hydrangeifolia. Their structures were determined by IR, HRESIMS, and 1D and 2D NMR experiments, and their antioxidant activities, evaluated by assaying the free radical scavenging capacity using the DPPH (1,1-diphenyl-2-picrylhydrazyl) radical as substrate. The antioxidant activities of 3 and 4 (IC50 values of 15.0 and 19.2 microM, respectively) were comparable to that of the standard positive control caffeic acid, whilst 2 and 5 were only weakly active and 1 was inactive.     

Evaluation of antioxidant and antimicrobial activities and characterization of bioactive components of two Brazilian propolis samples using a pKa-guided fractionation

The ethanolic extracts of two Brazilian propolis samples were submitted to a fractionation procedure based on the pKa values of their components. The fractions obtained were evaluated for their antimicrobial activity against Staphylococcus aureus as well as for their antioxidant properties (reduction of DPPH radical). Their phenolic and flavonoid contents were measured spectrophotometrically, in order to establish the correlations between these contents and the measured activities. Further, the most active fractions of both extracts were analyzed by HRGC-MS and about twenty compounds could be characterized. Among them were 3-prenyl-4-hydroxycinnamic acid (drupanin) and 3,5-diprenyl-4-hydroxycinnamic acid (artepillin C), which seem to be the major antioxidant components of the bioactive fractions.     

Synthesized phosphorylated and aminated derivatives of fucoidan and their potential antioxidant activity in vitro

Three sulfated polysaccharide derivatives (phosphorylated and aminated fucoidan) were synthesized, and their potential antioxidant activities were investigated employing various established in vitro systems. Two methods were used in phosphorylation fucoidan: polyphosphoric acid and POCl₃ method. Aminated fucoidan was prepared using the epichlorohydrin and ammonia water. All fucoidan derivatives possessed considerable antioxidant activity, and exhibited stronger antioxidant ability than fucoidan in certain tests. The phosphorylated fucoidan showed stronger hydroxyl radical and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity and reducing power. The mechanism on influence the antioxidant activity of samples of phosphate and amino group was indicated.     

A study on the antioxidant activities of some new benzazole derivatives

The in vitro antioxidant properties of some new benzazole derivatives (1-10) such as benzoxazoles, benzimidazoles, and benzothiazoles were determined by their effects on the rat liver microsomal NADPH-dependent lipid peroxidation (LP) level, the scavenging of superoxide anion and the stable radical 2,2-diphenyl-1-picrylhydrazyl (DPPH). Compounds 1, 2, 4 and 6, showed potent scavenging effect on superoxide radical at 10(-3) M. Compound 8, 5-nitro-2-(phenoxymethyl)benzimidazole, strongly inhibited lipid peroxidation at 10(-3) M concentration.     

Synthesis, antioxidant and radical scavenging activities of novel benzimidazoles

The synthesis and antioxidant evaluation of some novel benzimidazole derivatives (10-24) are described. Antioxidant properties of the compounds were investigated employing various in vitro systems viz., microsomal NADPH-dependent inhibition of lipid peroxidation (LP), interaction of 2,2-diphenyl-1-picrylhydrazyl (DPPH) and scavenging of superoxide anion radical. Compounds 12 and 13 showed very good antioxidant capacity and were 17-18-fold more potent than BHT (IC50 2.3 x 10(-4) M) with 1.3 x 10(-5) M and 1.2 x 10(-5) M IC50 values, respectively, by interaction of the stable DPPH free radical.     

Anti-plasmodial and antioxidant activities of constituents of the seed shells of Symphonia globulifera Linn f

A xanthone derivative, named gaboxanthone (1), has been isolated from the seed shells of Symphonia globulifera, together with known compounds, symphonin (2), globuliferin (3), guttiferone A (4), sistosterol, oleanolic acid and methyl citrate. The structure of the compound was assigned as 5,10-dihydroxy-8,9-dimethoxy-2,2-dimethyl-12-(3-methylbut-2-enyl) pyrano [3,2-b]xanthen-6(2H)-one, by means of spectroscopic analysis. The anti-plasmodial and antioxidant activities of the phenolic compounds were evaluated, respectively, in culture against W2 strain of Plasmodium falciparum and using the free radical scavenging activity of the DPPH radical, respectively. Compounds 1-4 were found to be active against the Plasmodium parasites (IC(50) of 3.53, 1.29, 3.86 and 3.17 microM, respectively). Guttiferone A (4) showed a potent free radical scavenging activity compared to the well-known antioxidant caffeic acid.