Chain-breaking antioxidant activity of natural polyphenols as determined during the chain oxidation of methyl linoleate in Triton X-100 micelles

Natural polyphenols (PP) are known as potent antioxidants, which are believed to prevent many degenerative diseases, including cancer and atherosclerosis. Much attention in the literature has been given to the antioxidant activity of PP-containing products; however, information on the antioxidative properties of individual PP is rather poor and controversial. In this work, the chain-breaking antioxidant activities of several natural PP and their synthetic analogs were determined during the chain oxidation of methyl linoleate in an aqueous buffered, pH 7.40, micellar solution of Triton X-100, induced by 2,2'-azobis(2-amidinopropan) dihydrochloride at 37 degrees C. Use of the mode of the controlled chain reaction allowed separate determination of the rate constant for the reaction of PP with the lipid peroxy radical and the stoichiometric factor of inhibition (f), which shows how many kinetic chains can be terminated by one molecule of PP. All the PP studied display a pronounced antioxidant activity. A significant difference in f value between catechol derivatives and pyrogallol derivatives was found. While with pyrogallol derivatives (gallic acid, epigallocatechin, propyl gallate, myricetin), f was found to be around 2, the theoretically expected value, f, for catechol derivatives (catechol, catechin, epicatechin, quercetin, rutin, caffeic acid) was found to be within the range 3.6-6.3. The elevated antioxidant capacity of catechol derivatives may be explained by the contribution of products of PP oxidative transformation, most likely by dimers, to inhibition. With catechin, epicatechin, and quercetin, the reactivity of products exceeds that of original PP. A real chain-breaking antioxidant activity of PP is likely determined not so much by the reactivity of the original PP as by the probability of the formation of active products and their antioxidant activities. The above findings were applied to explain some features of the antioxidant activity of teas and red wines.     

In Silico Discovery of Novel Potent Antioxidants on the Basis of Pulvinic Acid and Coumarine Derivatives and Their Experimental Evaluation

A pigment from the edible mushroom Xerocomus badius norbadione A, which is a natural derivative of pulvinic acid, was found to possess antioxidant properties. Since the pulvinic acid represents a novel antioxidant scaffold, several other derivatives were recently synthetized and evaluated experimentally, along with some structurally related coumarine derivatives. The obtained data formed the basis for the construction of several quantitative structure-activity and pharmacophore models, which were employed in the virtual screening experiments of compound libraries and for the prediction of their antioxidant activity, with the goal of discovering novel compounds possessing antioxidant properties. A final prioritization list of 21 novel compounds alongside 8 established antioxidant compounds was created for their experimental evaluation, consisting of the DPPH assay, 2-deoxyribose assay, β-carotene bleaching assay and the cellular antioxidant activity assay. Ten novel compounds from the tetronic acid and barbituric acid chemical classes displayed promising antioxidant activity in at least one of the used assays, that is comparable to or even better than some standard antioxidants. Compounds 5, 7 and 9 displayed good activity in all the assays, and were furthermore effective preventers of oxidative stress in human peripheral blood mononuclear cells, which are promising features for the potential therapeutic use of such compounds.     

N-Acetylcysteine as an antioxidant and disulphide breaking agent: the reasons why

The main molecular mechanisms explaining the well-established antioxidant and reducing activity of N-acetylcysteine (NAC), the N-acetyl derivative of the natural amino acid l-cysteine, are summarised and critically reviewed. The antioxidant effect is due to the ability of NAC to act as a reduced glutathione (GSH) precursor; GSH is a well-known direct antioxidant and a substrate of several antioxidant enzymes. Moreover, in some conditions where a significant depletion of endogenous Cys and GSH occurs, NAC can act as a direct antioxidant for some oxidant species such as NO₂ and HOX. The antioxidant activity of NAC could also be due to its effect in breaking thiolated proteins, thus releasing free thiols as well as reduced proteins, which in some cases, such as for mercaptoalbumin, have important direct antioxidant activity. As well as being involved in the antioxidant mechanism, the disulphide breaking activity of NAC also explains its mucolytic activity which is due to its effect in reducing heavily cross-linked mucus glycoproteins. Chemical features explaining the efficient disulphide breaking activity of NAC are also explained.     

Effect of successive acid and enzymatic hydrolysis on the structure and antioxidant activity of pectins

It has been shown that the treatment of pectins under conditions close to those in an artificial gastroenteral medium results in the destruction of their carbohydrate chain. The degree of pectin destruction depends on the structural features of their macromolecules. During successive acid and enzymatic hydrolysis of pectins, an increase in the number of molecules with molecular masses of 300–400 and 100–300 kDa and cleavage of mono- and oligosaccharides occurred. It was found that comaruman, bergenan, potamogetonan, pectins from marsh cinquefoil, Siberian tea, and broad-leaved pondweed possess a high antioxidant activity and contain large amounts of common phenols. Treatment with hydrochloric acid and pectinase led to a significant decrease in their antioxidant activity and simultaneously to a decrease in the amount of common phenols.     

Preparation of the different derivatives of the low-molecular-weight porphyran from Porphyra haitanensis and their antioxidant activities in vitro

Porphyran extracted from Porphyra haitanensis is a sulfated polysaccharide, which possesses excellent antioxidant activities. In this study, we prepared one low-molecular-weight porphyran and its sulfated, acetylated, phosphorylated and benzoylated derivatives. Their antioxidant activities were investigated including scavenging effect of superoxide, hydroxyl and 1,1-diphenyl-2-picrylhydrazyl radicals. The results of chemical analysis and FT-IR spectrums showed the modification was successful. And in addition, we found that certain derivative exhibited stronger antioxidant activity than low-molecular-weight porphyran. The benzoylated derivative showed the most excellent antioxidant activity in three assays, so this derivative needs to be attended to.     

Study of the neuroprotective action of hybrid structures based on fullerene C60

The neuroprotective action of hybrid structures based on fullerene C₆₀ with attached proline amino acid has been studied. Hybrid structures contained natural antioxidant carnosine or addends with one or two nitrate groups. It has been shown that all studied compounds had antioxidant activity and decreased the concentration of malondialdehyde in homogenates of the rat brain. Compound I, which contained the antioxidant carnosine, has been found to be the most effective antioxidant. All compounds except IV and V inhibited the activity of monoamine oxidase B, while compounds I–IV increased the activity of monoamine oxidase A. All investigated compounds inhibited glutamate-induced Ca²⁺ uptake into synaptosomes of the rat brain cortex. Compound III, containing two nitrate groups, has been found to be the most effective inhibitor. This compound caused a significant increase of the currents of AMPA receptors (AMPA, alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid).     

Characterization of a novel Dunaliella salina (Chlorophyta) strain and the assessment of its cultivation parameters

Physiological characteristics of a novel strain of the halophilic alga Dunaliella salina IPPAS D-232 isolated from the hypersaline lake Razval (Sol-Iletsk, Orenburg region) were studied. It was shown that the extract from the cells of this strain manifested antioxidant properties and also antibacterial activity relative to opportunistic bacteria. The influence of medium stirring and salinity on the level of D. salina antioxidant activity was assessed: it was established that medium salinization (93 g/L) and continuous stirring favored the highest accumulation of D. salina IPPAS D-232 biomass. It was found that the extremely halophilic archaea Halorubrum tebenquichense and moderately halophilic bacterium Marinococcus halophilus stimulated D. salina development and increased its antioxidant activity. The results obtained expand our knowledge of specific ecological features of the studied microalgal species; they could form the basis for the development of new approaches to the mass cultivation of D. salina.     

Prediction of antioxidant proteins using hybrid feature representation method and random forest

Natural antioxidant proteins are mainly found in plants and animals, which interact to eliminate excessive free radicals and protect cells and DNA from damage, prevent and treat some diseases. Therefore, accurate identification of antioxidant proteins is important for the development of new drugs and research of related diseases. This article proposes novel method based on the combination of random forest and hybrid features that can accurately predict antioxidant proteins. Four single feature extraction methods (188D, profile-based Auto-cross covariance (ACC-PSSM), N-gram, and g-gap) and hybrid feature representation methods were used to feature extraction. Three feature selection methods (MRMD, t-SNE, and the optimal feature set selection) were adopted to determine the optimal features. The new hybrid feature vectors derived by combining 188D with the other three features all have indicators ranging from 0.9550 to 0.9990. The novel method showed better performance compared with the other methods.     

Antioxidant properties of fungal metabolite nigerloxin in vitro

We have recently reported the beneficial influence of the fungal metabolite nigerloxin, a new aldose reductase inhibitor and a lipoxygenase inhibitor on oxidative stress in streptozotocin induced diabetic rats. In the present study we have investigated the antioxidant potential of nigerloxin in vitro as compared to one of the well known natural antioxidant, curcumin. The fungal metabolite nigerloxin was found to be an effective antioxidant in different in vitro assays including the phosphomolybdenum, 2,2-diphenyl-1-picrylhydrazyl (DPPH^·), 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS^·+) and ferric reducing antioxidant power (FRAP) methods. The antioxidant potency of nigerloxin may be attributed to its electron donating nature. The ferric reducing potency of nigerloxin as demonstrated by FRAP assay method was even found to be superior to that of the natural antioxidant curcumin.     

Selected lactic acid bacteria synthesize antioxidant peptides during sourdough fermentation of cereal flours

A pool of selected lactic acid bacteria was used for the sourdough fermentation of various cereal flours with the aim of synthesizing antioxidant peptides. The radical-scavenging activity of water/salt-soluble extracts (WSE) from sourdoughs was significantly (P < 0.05) higher than that of chemically acidified doughs. The highest activity was found for whole wheat, spelt, rye, and kamut sourdoughs. Almost the same results were found for the inhibition of linoleic acid autoxidation. WSE were subjected to reverse-phase fast protein liquid chromatography. Thirty-seven fractions were collected and assayed in vitro. The most active fractions were resistant to further hydrolysis by digestive enzymes. Twenty-five peptides of 8 to 57 amino acid residues were identified by nano-liquid chromatography-electrospray ionization-tandem mass spectrometry. Almost all of the sequences shared compositional features which are typical of antioxidant peptides. All of the purified fractions showed ex vivo antioxidant activity on mouse fibroblasts artificially subjected to oxidative stress. This study demonstrates the capacity of sourdough lactic acid bacteria to release peptides with antioxidant activity through the proteolysis of native cereal proteins.     

On the use of acridinium indicators for the chemiluminescent determination of the total antioxidant capacity of dietary supplements

Acridinium salts, due to their chemiluminogenic properties, have found several applications in biomedical analysis as labels and indicators, where the assessment of emission intensity is used for the end‐point detection. This work presents the use of chemiluminescent indicators in the form of selected acridinium esters in order to determine the antioxidant properties of exemplary formulations, namely quercetin, vitamin C and the dietary supplement, Apiextract. The principle of measurements is based on a change in the kinetics of emission decay derived from the acridinium cations in alkaline solutions of hydrogen peroxide in the presence of an antioxidant (the analyte). The proposed system makes a beneficial alternative to related methods, which mostly rely on the assessment of emission efficiency and use the luminometric standard luminol – due to superior parameters of acridinium chemiluminescence, among others ‐ high temporary emission efficiency. The features of the proposed method are manifested by a shorter time period of analysis and lower background signals associated with the environmental influences, as compared to typical approaches. The chromatographic (RP‐HPLC) analyses of the substrates and products generated during chemiluminogenic oxidation of acridinium cations under assay conditions are also presented.     

Study of antioxidant and membrane activity of rosmarinic acid using different model systems

Rosmarinic acid is found in many species of different families of higher plants and its chemical structure is phenol propanoid with various biological activity. In this paper, we conducted a comparative study of antioxidant (radical-scavenging) properties of rosmarinic acid in systems of 2,2tāzo-bis(2-methylpropionamidin)dihydrochloride-luminol and hemoglobin-hydrogen peroxide-luminol, determined its protective potential in preventing peroxidation of linoleic acid, and evaluated the effect on the permeability of planar bilayer lipid membranes. Linoleic acid peroxidation was assessed by iron-thiocyanate method. In these studies, trolox was used as a reference antioxidant, and ascorbic acid, and dihydroquercetin were taken as standards. Rosmarinic acid is significantly superior to trolox, ascorbic acid and dihydroquercetin in the tests for antioxidant activity in the systems studied, as well as in inhibition of linoleic acid peroxidation. According to their activity the investigated substances can be arranged in the following order: rosmarinic acid > dihydroquercetin trolox > ascorbic acid. Rosmarinic acid does not cause significant changes in the permeability of planar bilayer membranes in a dose range of 0.5 to 10 μg/mL. Antioxidant activity of rosmarinic acid is due to the neutralization of reactive oxygen species and/or luminol radicals generated in model systems. The observed features of the antioxidant and membrane activity of rosmarinic acid, which may underlie the previously mentioned pharmacological effects are discussed.     

Functional enrichment of mannanase-treated spent brewer yeast

In this study, the effect of Bacillus amyloliquefaciens-produced β-mannanase on the nutrient diffusion (release) and antioxidant activity of spent brewer yeast (SBY) was investigated. Three pretreatments were performed: (1) autolysis at 50°C for 24?h; (2) autolysis at 50°C for 24?h, with the addition of β-mannanase during the autolysis; (3) autolysis at 50°C for 24?h, and the β-mannanase was added for another 12?h treatment. The pretreatments with the addition of β-mannanase caused significant cell wall degradation, markedly increased the yield of SBY extracts. More importantly, this study found that polysaccharides were degraded to be oligosaccharides with a considerable reduction in molecular weights. Meanwhile, pretreatment with the enzyme also exhibited a higher antioxidant activity in SBY extract compared to autolysis itself. The current study indicated that pretreatment (3) had a better effect than pretreatment (2) in terms of improving in antioxidant activity in SBY extract. These improved characteristics of SBY extracts isolated through enzymatic treatment appear to show promising features for their prospective use as natural functional agents.     

A novel 19F-NMR method for the investigation of the antioxidant capacity of biomolecules and biofluids.

A new assay for the measurement of the antioxidant capacity of biomolecules by high resolution 19F-NMR spectroscopy is presented here. This method is based on the use of trifluoroacetanilidic detectors, namely trifluoroacetanilide, N-(4-hydroxyphenyl)-trifluoroacetamide and 2-hydroxy-4-trifluoroacetamidobenzoic acid. Upon hydroxyl radical attack, such fluorinated detectors yield trifluoroacetamide and trifluoroacetic acid that can be quantitatively determined by 19F-NMR spectroscopy. Trifluoroacetamide was found to be a reliable reporter of hydroxyl radical attack on the fluorinated detectors, whereas N-(4-hydroxyphenyl)-trifluoroacetamide was found to be the most sensitive detector amongst the ones considered. Therefore, N-(4-hydroxyphenyl)-trifluoroacetamide has been used in competition experiments to assess the antioxidant capacity of a number of low and high molecular weight antioxidants. The antioxidant capacity of a given compound has been scaled in terms of an adimensional parameter, kF, that represents the ratio between the scavenger abilities of the fluorinated detector and the competitor. kF values obtained for low-molecular-mass compounds fall in the range 0.17 < kF < 1.5 and are in good agreement with second order rate constants (k2OH) for the reaction of the antioxidant with hydroxyl radicals. The kF value for serum albumin is much larger (46.9) than that predicted from the reported k2OH value. This finding supports the view that the protein can very effectively scavenge hydroxyl radicals as well as secondary radicals. Human blood serum showed that its antioxidant capacity is even higher than that shown by aqueous solutions of albumin at physiologic concentration suggesting a further contribution from other macromolecular serum components.     

Formation of antioxidant defence system of geese in embryogenesis and early postnatal ontogenesis

The features of antioxidant protection of tissues of a liver and blood of the gooses in embriogenesis and early postnatal ontogenesis are found out. Maximal contents TBA active products both in a liver, and in a blood are observed in 28 diurnal embriones. Is shown, that in a liver the activity of basic antioxidant enzymes (superoxide dismutases, catalase and glutathione peroxidase) in a liver is developed already at early stages embriogenesis and is considerably enlarged in the end embriogenesis. The becoming of enzymatic system of a blood descends much more slower.     

The oxidant/antioxidant network: role of melatonin

Melatonin is now known to be a multifaceted free radical scavenger and antioxidant. It detoxifies a variety of free radicals and reactive oxygen intermediates including the hydroxyl radical, peroxynitrite anion, singlet oxygen and nitric oxide. Additionally, it reportedly stimulates several antioxidative enzymes including glutathione peroxidase, glutathione reductase, glucose-6-phosphate dehydrogenase and superoxide dismutase; conversely, it inhibits a prooxidative enzyme, nitric oxide synthase. Melatonin also crosses all morphophysiological barriers, e.g., the blood-brain barrier, placenta, and distributes throughout the cell; these features increase the efficacy of melatonin as an antioxidant. Melatonin has been shown to markedly protect both membrane lipids and nuclear DNA from oxidative damage. In every experimental model in which melatonin has been tested, it has been found to resist macromolecular damage and the associated dysfunction associated with free radicals.     

Modification of Antioxidant Status of Host Cell in Response to Bougainvillea Antiviral Proteins

Bougainvillea xbuttiana antiviral proteins (AVPs) exhibited high antioxidant activity as measured by ferric reducing / antioxidant (FRAP) power assay. These AVPs were also found to modify activities of antioxidant enzymes like superoxide dismutase, peroxidase and catalase. The activities of superoxide dismutase and peroxidase increased, while the activity of catalase decreased in Tobacco mosaic virus (TMV) infected tobacco leaves. The trend was reversed when the leaves were treated with AVP alone. However, in TMV + AVP treated leaves, the activities of all the three enzymes were found to be midway between the activities obtained with other two treatments. It is therefore, suggested that Bougainvillea AVPs might be controlling viral diseases by scavenging reactive oxygen species as well as by altering host plant cell metabolism to maintain its antioxidant status.     

香露兜叶的抗氧化活性(英文)

本文评价了香露兜叶的乙醇提取物以及石油醚、乙酸乙酯、正丁醇和水相组分的抗氧化活性。在体外测定了提取物和组分的总抗氧化活性,二苯代苦味肼基(DPPH)自由基清除活性,超氧阴离子自由基清除活性和铁离子还原能力,并利用分光光度法测定了其总酚和总黄酮的含量。结果表明,所有的提取物和组分均表现出抗氧化和自由基清除活性。抗氧化活性的大小如下:正丁醇部分>乙酸乙酯部分>乙醇提取物>水部分>石油醚部分。总酚含量的顺序和其相似,说明提取物和组分中的酚类化合物使其具有抗氧化活性。香露兜叶提取物可能会成为有价值的天然抗氧化资源,并将在保健品和食品中得到应用。