Lag-time measurement of antioxidant capacity using myoglobin and 2, 2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid): rationale, application, and limitation.

The application of a simple lag-time assay for antioxidant capacity using myoglobin and 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) or ABTS has been studied for its general application conditions. In the presence of an antioxidant, the ABTS(*+) radical-cation-forming chromogenic reaction, catalyzed by myoglobin and initiated by hydrogen peroxide (H(2)O(2)), has a lag period, and its duration is linearly correlated to the concentration of that antioxidant. The high linearity between the lag time and the antioxidant concentration remained unchanged regardless of the assay conditions. It was also found that the linearity was better for antioxidants at lower concentrations. The change of assay condition could significantly affect the relative antioxidant value of a chemical to the standard (ascorbic acid), although not to a large extent. Most of antioxidants investigated were found suitable to be assayed using this method. Some antioxidants, e.g., genistein, however, were not, probably due to their low reactivity toward ferrylmyoglobin or ABTS(*+). In conclusion, the lag-time assay is a reliable method for measuring the antioxidant capacity, provided caution is taken for antioxidants that mainly act through lowering the rate of the chromogenic reaction.     

ESR study of a biological assay on whole blood: antioxidant efficiency of various vitamins

This study deals with the activity of various vitamins against the radical-mediated oxidative damage in human whole blood. We have used a biological method that allows both the evaluation of plasma and that of red blood cell resistance against the free radicals induced by 2,2′-azobis (2-amidinopropane) hydrochloride (AAPH). Spin trapping measures using mainly 5-(diethoxyphosphoryl)-5-methyl-1-pyrolline N-oxide nitrone (DEPMPO) were carried out under several conditions to identify the free radicals implicated in this test. Only the oxygenated-centred radical generated from AAPH was found highly reactive to initiate red blood cell lysis. With DEPMPO only alkoxyl radicals were observed and no evidence was found for alkylperoxyl radicals. The antioxidant activity of several lipid- and water-soluble vitamins has been assessed by the biological assay and through two chemical methods. We have noticed high antioxidant activities for tocopherols (in the order δ>γ>α) in the biological test but not through chemical methods. At 1 μM, the δ-tocopherol efficiency in inhibiting radical-induced red blood cell hemolysis was three times as high as the α-tocopherol efficiency. For β-carotene no significant activity even in whole blood was shown. Highly surprising antioxidant activities were observed for acid folic and pyridoxine, compared to ascorbic acid. At 10 μM, the effectiveness of folic acid was almost three times as high as vitamin C. The biological test seems clinically more relevant than most other common assays because it can detect several classes of antioxidants.     

High levels of liver antioxidants are associated with life-history strategies characteristic of slow growth and high survival rates in birds

Antioxidants have a large potential to coevolve with life-histories because of their capacity to counteract the negative effects of free radicals on fitness. However, only a few studies have explored the association between antioxidant levels and life-history strategies comparing a large number of species. Here we used an extensive dataset of 125 species of birds to investigate the association between concentrations of antioxidants (carotenoids and vitamin E) in the liver, which is the main storage organ for fat-soluble antioxidants, and life-history and morphology. We found that high liver antioxidant concentrations were associated with life-history strategies characterized by "live slow, die old", in clear contrast to previous studies reporting a relationship between high plasma antioxidants and life-histories characterized by "live fast, die young". Thus, high carotenoid concentrations were present in species with large body, brain and egg sizes, high absolute metabolic rate and a resident lifestyle, while high vitamin E concentrations were present in species with large brain size and long life span and incubation period. Our results indicate that antioxidants and life-histories coevolve, and that this may be mediated by positive fitness consequences of the accumulation of liver antioxidants, as species with higher antioxidant levels live longer.     

Stress, metabolism, and antioxidants in two wild passerine bird species

Antioxidants protect against free-radical damage, and free radicals, in turn, are thought to underlie aging. Thus, measuring antioxidants may aid field ecologists in understanding the physiological mechanisms that underlie life-history trade-offs. Antioxidant levels are known to vary markedly in response to the stress of capture in many birds. These changes in antioxidants could result from regulation (e.g., by stress-related hormones) or consumption (e.g., by an increase in free radicals due to increased metabolic rate). Here we experimentally test the effect of increased metabolic rate on circulating antioxidant and corticosterone concentrations in two wild passerine bird species, house sparrows (Passer domesticus) and gray catbirds (Dumetella carolinensis). We increased metabolic rate via exposure to low ambient temperatures overnight in captivity and measured circulating antioxidant capacity, uric acid, corticosterone, and oxygen consumption in cold-exposed and control individuals. Both species showed increases rather than decreases in all antioxidant parameters overnight, contradicting a consumption-by-energy-expenditure hypothesis. Both positive and negative correlations between antioxidant response and corticosterone response were occasionally but not consistently present, refuting a generalized regulation-by-corticosterone hypothesis. High baseline uric acid predicted diminished response of corticosterone and all antioxidants. Thus, high uric acid may reflect recent stress, poor condition, or a compensatory response. Relationships among metabolic rate, antioxidants, and corticosterone differed qualitatively between the species.     

Total antioxidant capacity assay of human serum using copper(II)-neocuproine as chromogenic oxidant: the CUPRAC method

BACKGROUND: Tests measuring the combined antioxidant effect of the nonenzymatic defenses in biological fluids may be useful in providing an index of the organism's capability to counteract reactive species known as prooxidants, resist oxidative damage and combat oxidative stress-related diseases. The selected chromogenic redox reagent for the assay of human serum should be easily accessible, stable, selective, respond to all types of biologically important antioxidants such as ascorbic acid, alpha-tocopherol, beta-carotene, reduced glutathione (GSH), uric acid and bilirubin, regardless of chemical type or hydrophilicity. Currently, there is no rapid method for total antioxidant assay of human serum meeting the above criteria.METHODS: Our recently developed cupric reducing antioxidant capacity (CUPRAC) spectrophotometric method for a number of polyphenols and flavonoids using the copper(II)-neocuproine reagent in ammonium acetate buffer was now applied to a complete series of plasma antioxidants for the assay of total antioxidant capacity (TAC) of serum, and the resulting absorbance at 450 nm was recorded either directly (e.g. for ascorbic acid, alpha-tocopherol and glutathione) or after incubation at 50 degrees C for 20 min (e.g. for uric acid, bilirubin and albumin), quantitation being made by means of a calibration curve. The lipophilic antioxidants, alpha-tocopherol and beta-carotene, were assayed in dichloromethane (DCM). Lipophilic antioxidants of serum were extracted with n-hexane from an ethanolic solution of serum subjected to centrifugation. Hydrophilic antioxidants of serum were assayed after perchloric acid precipitation of proteins in the centrifugate.Results: The molar absorptivities, linear ranges and trolox equivalent antioxidant capacity (TEAC) coefficients of the serum antioxidants were established with respect to the CUPRAC spectrophotometric method, and the results (TEAC, or TEAC coefficients) were evaluated in comparison to the findings of the ABTS/TEAC reference method using persulfate as oxidant. As for hydrophilic phase, a linear correlation existed between the CUPRAC and ABTS findings (r=0.58), contrary to current literature reporting that either serum ORAC or serum ferric reducing antioxidant potency (FRAP) does not correlate at all with serum TEAC. The analytical responses of serum antioxidants were shown to be additive, enabling a TAC assay. The intra- and inter-assay CVs were 0.7 and 1.5%, respectively, for serum.Conclusions: The CUPRAC assay proved to be efficient for glutathione and thiol-type antioxidants, for which the FRAP test was nonresponsive. The findings of CUPRAC completely agreed with those of ABTS-persulfate for lipophilic phase. The additivity of absorbances of all the tested antioxidants confirmed that antioxidants in the CUPRAC test did not chemically interact among each other so as to cause an intensification or quenching of the theoretically expected absorbance. As a distinct advantage over other electron-transfer based assays (e.g. Folin, FRAP, ABTS, DPPH), CUPRAC is superior in regard to its realistic pH close to the physiological pH, favourable redox potential, accessibility and stability of reagents and applicability to lipophilic antioxidants as well as hydrophilic ones.     

Structure-activity relationship analysis of antioxidant ability and neuroprotective effect of gallic acid derivatives

Gallic acid and its derivatives are a group of naturally occurring polyphenol antioxidants which have recently been shown to have potential healthy effects. In order to understand the relationship between the structures of gallic acid derivatives, their antioxidant activities, and neuroprotective effects, we examined their free radical scavenging effects in liposome and anti-apoptotic activities in human SH-SY5Y cell induced by 6-hydrodopamine autooxidation. It was found that these polyphenol antioxidants exhibited different hydrophobicity and could cross through the liposome membrane to react with 1,1-diphenyl-2-picryl-hydrazyl (DPPH) free radical in a time and dose-dependent manner. At the same time, the structure-antioxidant activity relationship of gallic acid derivatives on scavenging DPPH free radical in the liposome was also analyzed based on theoretical investigations. Analysis of cell apoptosis, intracellular GSH levels, production of ROS and the influx of Ca(2+) indicated that the protective effects of gallic acid derivatives in cell systems under oxidative stress depend on both their antioxidant capacities and hydrophobicity. However, the neuroprotective effects of gallic acid derivatives seem to depend more on their molecular polarities rather than antioxidant activities in the human SH-SY5Y cell line. In conclusion, these results reveal that compounds with high antioxidant activity and appropriate hydrophobicity are generally more effective in preventing the injury of oxidative stress in neurodegenerative diseases.     

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.     

Phytochemical and Biological Activities in Limonium Species Collected in Different Biotopes of Tunisia

A particular interest is nowadays given to natural antioxidants occurring in foods which can reduce the risk of several diseases through their protective effect. The genus Limonium is widely distributed in different salt regions of Tunisia and known in traditional medicine for the presence of highly effective viral and bacterial replication inhibitors. Limonium leaves have possible beneficial effects on human health for their antioxidant activities and free radical scavenging abilities. To exploit the potential of plants from extreme environments as new sources of natural antioxidants, we studied the extracts from leaves of eight Limonium species growing in extreme environments in Tunisia. Antioxidant molecules (polyphenols, flavonoids, flavonols, ascorbate, tocopherols), in vitro (DPPH, ORAC) and ex vivo antioxidant potential on human erythrocytes, antioxidant enzymes activities (superoxide dismutase, peroxidases, glutathione reductase) were evaluated to identify the species with the best antioxidant capacity. The results showed variability among the species considered in function of the environmental conditions of their natural biotopes, as for the antioxidants measured. In particular, L. vulgare from Oued Rane biotope, characterized by dryness and high temperatures, was the species with the highest enzymatic activity and antioxidant capacity, making it interesting as possible edible halophyte plant or as food complement.     

Assessment of antioxidant capacity for scavenging free radicals in vitro: a rational basis and practical application

With increasing evidence showing the involvement of oxidative stress induced by free radicals in the development of various diseases, the role of radical-scavenging antioxidants has received much attention. Although many randomized controlled clinical trials do not support the beneficial effects of indiscriminate supplementation of antioxidants, more recent studies suggest that antioxidants such as vitamin E may be effective for prevention and treatment of some diseases when given to the right subjects at the right time. Many studies on the antioxidant capacity assessed by various available methods showed inconsistent results and the assessment of antioxidant capacity has been the subject of extensive studies and arguments. This study was performed to elucidate the basic chemistry required for the development of a reliable method for the assessment of antioxidant capacity for radical scavenging in vitro. In this study, the capacity of α-tocopherol and its related compounds, ascorbic acid, and uric acid for scavenging radicals was assessed from their effects on the rate of decay of hydrophilic and lipophilic probes with various reactivities toward free radicals induced by hydrophilic and lipophilic radicals in homogeneous solution and heterogeneous micelle systems. Fluorescein, pyranine, and pyrogallol red were used as hydrophilic probes, and BODIPY and N,N-diphenyl-p-phenylenediamine were used as lipophilic probes. We show that the rate and amount of radical scavenging by antioxidants, termed the antioxidant radical absorbance capacity, could be assessed by an appropriate combination of radical initiator and probe. This method was applied to the assessment of radical-scavenging capacity of human plasma, wine, and green tea powder.     

Identification of Two Novel Antioxidant Peptides from Camel Milk Using Digestive Proteases: Impact on Expression Gene of Superoxide Dismutase (SOD) in Hepatocellular Carcinoma Cell Line

Camel milk has high levels of antioxidant peptides; therefore has a significant role in nutrition and health. There is a wide range of diseases associated with oxidative stress in the body, thereby preventing the production of free radicals followed the occurrence of such reactions have an important role in human health. Some peptides derived from natural sources as natural antioxidants have a significant role in the inhibition of free radicals. The aim of this study was the identification and purification of camel milk proteins and evaluation of their antioxidant properties. For this purpose, camel milk proteins were hydrolyzed and examined the antioxidant properties of resulting peptides. Ultrafiltration and reverse-phase HPLC techniques were used for fractionation of the hydrolysate. Antioxidant activity of peptides were evaluated using different methods such as 2,2′-diphenyl-1-picrylhydrazyl (DPPH^·), 2,2′-azinobis(3-ethylbenzothiazo-line-6-sulfonic acid) diammonium salt (ABTS⁺), superoxide (O2^·?), hydroxyl (OH^·?) and polyunsaturated fatty acid peroxidation assays. The real-time PCR was performed to evaluate changes in expression of superoxide dismutase gene (SOD) as an antioxidant enzyme in HepG2 cells treated with different concentrations of peptide. Active peaks were analyzed using tandem mass spectrometry and thus identified two peptides NEDNHPGALGEPV (NV-13) and KVLPVPQQMVPYPRQ (KQ-15) with 1348.38 and 1780.15 dalton molecular weight, respectively. Both peptides showed antioxidant effects but KQ-15 peptide showed stronger effects than other. Molecular analysis showed that KQ-15 peptide was also able to increase the expression of SOD gene. The results show that the NV-13 and KQ-15 peptides have a high antioxidant capacity and they can be used to deal with diseases associated with oxidative stress.     

牛尾菜HPLC指纹图谱及抗氧化活性谱效关系研究

为筛选牛尾菜抗氧化作用的药效活性物质,提升牛尾菜的药材质量控制标准,该研究测定了13批牛尾菜的高效液相指纹图谱,并进行相似度评价和聚类分析,采用偏最小二乘回归分析法将共有峰与抗氧化的抑制率进行关联性分析,并进行单体化合物抗氧化试验验证。结果表明:(1)该文建立了含有14个主要共有峰的13 批牛尾菜HPLC指纹图谱。(2)13批牛尾菜样品聚为两类。(3)指纹图谱中的1、2、3、5、6、9、14号峰面积与抗氧化效果呈正相关,4、7、8、10、11、12号峰与抗氧化效果呈负相关,其中9、11、3、4、5号峰的VIP值均大于1。(4)9号峰为齐墩果酸,10号峰为熊果酸,9 号峰对ABTS 自由基的清除能力最大。该研究认为牛尾菜抗氧化作用不是单一成分起作用,而是多种成分综合作用的结果,其中9号峰(齐墩果酸)可能是牛尾菜具有抗氧化作用的物质基础。     

Hypoglycemic and hypolipidemic effects and antioxidant activity of fruit extracts from Lycium barbarum

The hypoglycemic and hypolipidemic effects of Lycium barbarum fruit water decoction, crude polysaccharide extracts (crude LBP), and purified polysaccharide fractions (LBP-X) in alloxan-induced diabetic or hyperlipidemic rabbits were investigated through designed sequential trials and by measuring blood glucose and serum lipid parameters. Total antioxidant capacity was also assessed using trolox equivalent antioxidant capacity (TEAC) and oxygen radical absorbance capacity (ORAC) assay. It was found that the three Lycium barbarum fruit extracts/fractions could significantly reduce blood glucose levels and serum total cholesterol (TC) and triglyceride (TG) concentrations and at same time markedly increase high density lipoprotein cholesterol (HDL-c) levels after 10 days treatment in tested rabbits, indicating that there were substantial hypoglycemic and hypolipidemic effects. Hypoglycemic effect of LBP-X was more significant than those of water decoction and crude LBP, but its hypolipidemic effect seemed to be weaker. Total antioxidant capacity assay showed that all three Lycium barbarum extracts/fractions possessed antioxidant activity. However, water and methanolc fruit extracts and crude polysaccharide extracts exhibited stronger antioxidant activity than purified polysaccharide fractions because crude extracts were identified to be rich in antioxidants (e.g., carotenoids, riboflavin, ascorbic acid, thiamine, nicotinic acid). Lycium barbarum polysaccharides (glycocojugates), containing several monosaccharides and 17 amino acids, were major bioactive constituents of hypoglycemic effect. Both polysaccharides and vitamin antioxidants from Lycium barbarum fruits were possible active principles of hypolipidemic effect.     

Target-guided isolation and purification of antioxidants from Selaginella sinensis by offline coupling of DPPH-HPLC and HSCCC experiments

Selaginella sinensis (Selaginellaceae) is used extensively in traditional Chinese medicine (TCM) for the treatment of many kinds of chronic diseases. In this study, fractionation of the methanol extract of S. sinensis by different polarity solvents indicated the ethyl acetate fraction exhibited an potent 1,1-diphenyl-2-picryhydrazyl (DPPH) radical scavenging activity with the IC(50) value of 44.9 μM. In order to evaluate the scientific basis, antioxidant peaks were firstly screened using DPPH spiking test through high performance liquid chromatography (DPPH-HPLC). Under the target-guidance of DPPH-HPLC experiment, two flavonoids and six biflavonoids, quercetin (1), apigenin (2), amentoflavone (3), robustaflavone (4), 2,3-dihydroamentaflavone (5), hinokiflavone (6), 4'-O-methyl-robustaflavone (7) and ginkgetin (8) were separated by high-speed counter-current chromatography (HSCCC) method using n-hexane-ethyl acetate-methanol-water (8:8:9:7) as the solvent system with purities 98.2%, 97.6%, 99.4%, 92.3%, 98.5%, 98.9% and 99.6%, respectively. The structures were identified by electrospray ionization mass spectrometry (ESI-MS) and nuclear magnetic resonance (NMR) analysis. Antioxidant activity of eight isolated compounds was assessed by the radical scavenging effect on DPPH radical, compound 1 showed strongest antioxidant activities with IC(50) values of 3.2 μM, while compounds 2-8 showed weak antioxidant activities. This is the first report on simultaneous separation of eight antioxidant compounds from S. sinensis by HSCCC, moreover, apigenin and 4'-O-methyl-robustaflavone were first identified from this plant. Results of the present study indicated that the combinative method using DPPH-HPLC and HSCCC could be widely applied for rapid screening and isolating of antioxidants from complex TCM extract.     

Comparison of antioxidant capacity and phenolic compounds of berries, chokecherry and seabuckthorn

Antioxidant capacity and phenolic compounds (phenolic acids and anthocyanins) of four berry fruits (strawberry, Saskatoon berry, raspberry and wild blueberry), chokecherry and seabuckthorn were compared in the present study. Total phenolic content and total anthocyanin content ranged from 22.83 to 131.88 g/kg and 3.51 to 13.13 g/kg, respectively. 2,2-Diphenyl-1-picryhydrazyl free radical scavenging activity ranged from 29.97 to 78.86%. Chokecherry had the highest antioxidant capacity when compared with berry fruits and seabuckthorn. The highest caffeic acid, gallic acid and trans-cinnamic acid levels were found in chokecherry (6455 mg/kg), raspberry (1129 mg/kg) and strawberry (566 mg/kg), respectively. Caffeic acid was also the major phenolic acid in Saskatoon berry (2088 mg/kg) and wild blueberry (1473 mg/kg). The findings that chokecherry has very high antioxidant capacity and caffeic acid levels, are useful for developing novel value-added antioxidant products and also provide evidence essential for breeding novel cultivars of fruit plants with strong natural antioxidants.     

Methylated polyphenols are poor "chemical" antioxidants but can still effectively protect cells from hydrogen peroxide-induced cytotoxicity

Several polyphenolic compounds, including flavonoids and phenolic acids, were compared with their per-methylated forms in both chemical and cell-based assays for antioxidant capacity. Methylation largely eliminated "chemical" antioxidant capacity, according to ferric reducing antioxidant power and oxygen radical absorbance capacity assays. Methylation, however, only moderately reduced protection of human Jurkat cells in culture, from hydrogen peroxide-mediated cytotoxicity, at physiologically relevant concentrations. Neither methylated nor un-methylated compounds were detectably metabolized by the cells. It appears that the protective mechanism of polyphenolic antioxidants against high concentrations of hydrogen peroxide in human cells may be largely unrelated to chemical antioxidant capacity.     

Sequence Determination of an Antioxidant Peptide Obtained by Enzymatic Hydrolysis of Oyster <Emphasis Type="Italic">Crassostrea madrasensis</Emphasis> (Preston)

Soft tissue from cultured farm fresh oysters (Crassostrea madrasensis) was subjected to two standard enzymatic peptide extraction procedures using pepsin and papain. The crude extracts obtained were partially purified by column chromatography and were freeze-dried. The hydrolysates obtained were compared with respect to their degree of hydrolysis (DH), antioxidant potential (AP) and total phenolic content (TPC). The hydrolysate showing better antioxidant property was further subjected to purification by high performance liquid chromatography and characterized by LC-MS/MS. Papain-digested oyster protein (OPHpap) hydrolysate showed higher DH, AP and TPC. OPHpap was further subjected to ultrafiltration and fractionated into 3 sizes namely, above 10, 3–10 and 1–3 kDa according to the molecular size. Antioxidant capacity of <3 kDa fraction OPHpap-3 evaluated by DPPH free radical scavenging assay, metal chelating activity, linoleic acid autoxidation assay showed maximum effectiveness. Of the seven fractions collected by purification of OPH-pap-3 on semi-preparative RP-HPLC, fraction 7 that showed the highest antioxidant activity was further characterized by LC-ESI-MS/MS and its sequence determined. An antioxidant peptide molecule with thirteen amino acids was identified in oyster protein hydrolysate obtained by papain digestion that may find application as a nutraceutical or may be utilized in food industry for prevention of rancidity in foods.     

The antioxidant activity of aqueous spinach extract: chemical identification of active fractions

In previous studies we have elucidated the presence of powerful, natural antioxidants (NAO) in water extracts of spinach leaves and demonstrated their biological activity in both in vitro and in vivo systems. In the present study, the chemical identity of several of these antioxidant components is presented. Spinach leaves were extracted with water and the 20,000 g supernatant which contained the antioxidant activity was extracted with a water:acetone (1:9) solution. The 20,000 g supernatant obtained was further purified on reverse phase HPLC using C-8 semi-preparative column. Elution with 0.1% TFA resulted in five hydrophilic peaks. Elution with acetonitrile in TFA resulted in seven additional hydrophobic peaks. All the peaks were detected at 250 nm. All the fractions obtained showed antioxidant activity when tested using three different assays. Based on 1H and 13C NMR spectroscopy four of the hydrophobic fractions were identified as glucuronic acid derivatives of flavonoids and three additional fractions as trans and cis isomers of p-coumaric acid and others as meso-tartarate derivatives of p-coumaric acid. The present study demonstrates for the first time the presence of both flavonoids and p-coumaric acid derivatives as antioxidant components of the aqueous extract of spinach leaves.     

Oxidative stress,circulating antioxidants,and dietary preferences in songbirds

Oxidative stress is an unavoidable consequence of metabolism and increases during intensive exercise. This is especially problematic for migratory birds that metabolize fat to fuel long-distance flight. Birds can mitigate damage by increasing endogenous antioxidants (e.g. uric acid) or by consuming dietary antioxidants (e.g. tocopherol). During flight, birds may increase protein catabolism of lean tissue which may increase circulating uric acid and many birds also consume an antioxidant-rich frugivorous diet during autumn migration. We evaluated three related hypotheses in a migratory passerine: (1) protein consumption is positively related to circulating antioxidants, (2) a dietary oxidative stressor [i.e. polyunsaturated fatty acid (PUFA)] influences antioxidant capacity and oxidative damage, and (3) oxidative stress influences dietary antioxidant preferences. White-throated Sparrows (Zonotrichia albicollis) consuming a high protein diet increased circulating uric acid; however, uric acid, antioxidant capacity, and oxidative stress did not differ between birds consuming a high PUFA versus a low PUFA diet, despite increased oxidative damage in high PUFA birds. Birds did not prefer antioxidant-rich diets even when fed high PUFA, low protein. We conclude that White-throated Sparrows successfully mitigated oxidative damage associated with a high PUFA diet and mounted an endogenous antioxidant response independent of uric acid, other circulating antioxidants, and dietary antioxidants.     

樟子松乙醇提取物体外抗氧化活性研究

测定了樟子松球果、树皮、树叶、木质部4个部位提取物的总抗氧化能力、总还原力、二苯代苦味酰基（DPPH·）清除能力、羟基自由基（·OH）清除能力、超氧阴离子（O^·₂）清除能力5个指标,并以抗坏血酸（Vc）为阳性对照评价从樟子松4个部位提取的松多酚体外抗氧化活性。结果表明：（1）从樟子松树皮中提取的樟子松多酚表现出较强的抗氧化能力,在较高浓度下与抗氧化剂（Vc）相差较小;从樟子松球果中提取的樟子松多酚也表现出较强的还原力,甚至超过阳性对照抗氧化剂Vc;（2）从樟子松树皮中提取的樟子松多酚在二苯代苦味酰基（DPPH·）清除能力、羟基自由基（·OH）清除能力上均为三者之中最高的,但都不超过抗氧化剂（Vc）的抗氧化能;（3）超氧阴离子（O^·₂）清除能力。三者的清除率均为负值,说明该方法测定超氧阴离子（O^·₂）清除率存在干扰因素,无法比较三者在这一指标上的能力大小。上述结果表明樟子松乙醇提取物具有较强的抗氧化能力,可作为天然的抗氧化剂。     

Antioxidant lipoate and tissue antioxidants in aged rats

Oxidative metabolism produces free radicals that must be removed from the cellular environment for the cell to survive. The levels of nonenzymic antioxidants involved in the elimination of free radicals were investigated in an attempt to correlate any changes in the levels of enzymic antioxidants during aging with changes in free radical mediated cellular damage. Antioxidants were measured in liver and kidney of young and aged rats with respect to DL-alpha-lipoic acid supplemented rats. In both organs lipid peroxidation damage (a marker of free radical mediated damage) increased with age, and a significant decrease in antioxidant systems was observed. Moreover, DL-alpha-lipoic acid treated aged rats showed a decrease in the level of lipid peroxides and an increase in the antioxidant status. The results of this study provide evidence that DL-alpha-lipoic acid treatment can improve antioxidants during aging and minimize the age-associated disorders in which free radicals are the major cause.