Growth and antioxidant system of the cyanobacterium Synechococcus elongatus in response to microcystin-RR

Microcystins, one type of the cyanobacterial toxins, show a broad range of hazardous effects on other organisms. Most of the researches on the toxic effects of microcystins have involved in animals and higher plants. Little work, however, has been done on evaluating the mechanisms of microcystin toxicity on algae. In this study, the toxicological effects of microcystin-RR (MC-RR) on the cyanobacterium Synechococcus elongatus were investigated. For this purpose, six physio-biochemical parameters (cell optical density, reactive oxygen species (ROS), malondialdehyde (MDA), glutathione (GSH), glutathione peroxidase (GSH-Px) and glutathione S-transferase (GST)) were tested in algal cells when exposed to 100 mug(-1) microcystin-RR. The results showed that the growth of Synechococcus elongatus ( expressed as optical density) was significantly inhibited compared with the control. At the same time, the treated algae exhibited a pronounced increase in production of ROS and MDA after 6 days exposure to microcystin-RR. Signi. cant changes in GSH levels and GSH-Px, GSH activities were also detected in algal cells, with higher values being observed in the toxin treated algae after 6 days exposure. GST activities in the treated algae exhibited a decline after exposure and rapid augmentation on day 3, thereafter, they kept at a high level when compared to the control group. GSH contents and GSH-Px activities were also significantly raised in the toxin-treated algae cells from day 3, but they showed a sharp decrease on day 4, which was the onward of cell proliferation. These results suggested that oxidative stress manifested by elevated ROS levels and MDA contents might be responsible for the toxicity of microcystin to Synechococcus elongatus and the algal cells could improve their antioxidant ability through the enhancement of enzymatic and non-enzymatic preventive substances.

Reactive oxygen species and antioxidant enzymes activity of Anabaena sp PCC 7120 (Cyanobacterium) under simulated microgravity

It was found that reactive oxygen species in Anabaena cells increased under simulated microgravity provided by clinostat. Activities of intracellular antioxidant enzymes, such as superoxide dismutase, catalase were higher than those in the controlled samples during the 7 days' experiment. However, the contents of gluathione, an intracellular antioxidant, decreased in comparison with the controlled samples. The results suggested that microgravity provided by clinostat might break the oxidative/antioxidative balance. It indicated a protective mechanism in algal cells, that the total antioxidant system activity increased, which might play an important role for algal cells to adapt the environmental stress of microgravity. (C) 2004 Elsevier Ltd. All rights reserved.

Responses of antioxidant systems in the hepatocytes of common carp (Cyprinus carpio L.) to the toxicity of microcystin-LR

The freshwater, bloom-forming cyanobacterium (blue-green alga) Microcystis aeruginosa produces a peptide hepatotoxin, which causes the damage of animal liver. Recently, toxic Microcystis blooms frequently occur in the eutrophic Dianchi Lake (300 km(2) and located in the South-Westem of China). Microcystin-LR from Microcystis in Dianchi was isolated and purified by high performance liquid chromatography (HPLC) and its toxicity to mouse and fish liver was studied (Li et al., 2001). In this study, six biochemical parameters (reactive oxygen species, glutathione, superoxide dismutase, catalase, glutathione peroxide and glutathione S-transferase) were determined in common carp hepatocytes when the cells were exposed to 10 mug microcystin-LR per litre. The results showed that reactive oxygen species (ROS) contents increased by more than one-time compared with the control after 6 h exposure to the toxin. In contrast, glutathione (GSH) levels in the hepatocytes exposed to microcystin-LR decreased by 47% compared with the control. The activities of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxide (GSH-Px) increased significantly after 6 h exposure to microcystin-LR, but glutathione S-transferase (GST) activity showed no difference from the control. These results suggested that the toxicity of microcystin-LR caused the increase of ROS contents and the depletion of GSH in hepatocytes exposed to the toxin and these changes led to oxidant shock in hepatocytes. Increases of SOD, CAT and GSH-Px activities revealed that these three kinds of antioxidant enzymes might play important roles in eliminating the excessive ROS. This paper also examined the possible toxicity mechanism of microcystin-LR on the fish hepatocytes and the results were similar to those with mouse hepatocytes. (C) 2003 Elsevier Science Ltd. All rights reserved.

Antioxidant N-acetylcysteine attenuates the acute liver injury caused by X-ray in mice

The aim of this study was to evaluate the protective effects of different doses and administration modes of N-acetylcysteine (NAC) against X-ray-induced liver damage in mice. Kun-Ming mice were divided into four groups, each composed of six animals: two control groups and two NAC-treated groups. An acute study was carried out to determine alterations in lipid peroxidation (determined by measuring malondiadehyde (MDA) level), glutathione (GSH) content and superoxide dismutase (SOD) activity (assayed by colorimetric method), and DNA damage (characterized by DNA-single strand break using with comet assay) as well as cell apoptosis (measured by flow cytometry) at 12 h after irradiation. The results showed that there were dose-related decreases in MDA level, DNA damage and cell apoptosis, and dose-dependent increases in GSH content and SOD activity in all NAC-treated groups compared to control groups, indicating that pre-treatment or post-treatment with NAC significantly attenuates the acute liver damage caused by X-ray. In addition, significant positive correlations were observed between MDA level and DNA damage or cell apoptosis, implying that lipid peroxidation plays a major role in X-ray-induced liver injury. The data suggest that NAC exerts its radioprotective effect by counteracting accumulated reactive oxygen species in the liver through its properties as a direct antioxidant and a GSH precursor, when administered before or after X-ray irradiation.

Antioxidant Sensors Based on Iron Diethylenetriaminepentaacetic Acid, Hematin, and Hemoglobin Modified TiO2 Nanoparticle Printed Electrodes

Antioxidant amperometric sensors based on iron-containing complexes and protein modified electrodes were developed. Indium tin oxide glass was printed with TiO2 nanoparticles, onto which iron-containing compounds and protein were adsorbed. When applied with negative potentials, the dissolved oxygen is reduced to H2O2 at the electrode surface, and the H2O2 generated in situ oxidizes Fe-II to Fe-III, and then electrochemical reduction of Fe-III therefore gives rise to a catalytic current. In the presence of antioxidants, H2O2 was scavenged, the catalytic current was reduced, and the decreased current signal was proportional to the quantity of existing antioxidants. A kinetic model was proposed to quantify the H2O2 scavenging capacities of the antioxidants. With the use of the sensor developed here, antioxidant measurements can be done quite simply: put the sensor into the sample solutions (in aerobic atmosphere), perform a cathodic polarization scan, and then read the antioxidant activity values. The present work can be complementary to the previous studies of antioxidant sensor techniques based on OH radicals and superoxide ions scavenging methods, but the sensor developed here is much easier to fabricate and use.

Effects of ultrahigh pressure extraction conditions on yields and antioxidant activity of ginsenoside from ginseng

Ultrahigh pressure technique was employed to extract ginsenosides from roots of ginseng (Panax ginseng C.A. Meyer). The optimal conditions for ultrahigh pressure extraction (UPE) of total ginsenosides were quantified by UV-vis spectrophotometry with the ginsenoside Re as standard, the signal ginsenosides were quantified by HPLC and ELSD with ginsenosides Re, Rg(1), Rb-1, Rc and Rb-2 as standards. Orthogonal design was applied to evaluate the effects of four independent factors (extraction pressure, extraction temperature, extraction time and ethanol concentration) on the yield and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity of ginsenoside, which are based on microwave extraction (ME), ultrasound extraction (UE), soxhlet extraction (SE) and heat reflux extraction (HRE) method. The results showed that UPE method can produce ginsenoside with the highest yield and the best radical scavenging activity compared to other used ones. Scanning electron microscopic (SEM) images of the plant cells after ultrahigh pressure treatment was obtained to provide visual evidence of the disruption effect.

Studies on principal components and antioxidant activity of different Radix Astragali samples using high-performance liquid chromatography/electrospray ionization multiple-stage tandem mass spectrometry

The principal components, isoflavonoids and astragalosides, in the extract of Radix Astragali were detected by a high-performance liquid chromatography Couple to electrospray ionization ion trap multiple-stage tandem mass spectrometry (HPLC-ESI-IT-MSn) method. By comparing the retention time (t(R)) of HPLC, the ESI-MSn data and the structures of analyzed Compounds with the data of reference compounds and in the literature, 17 isoflavonoids and 12 astragalosides have been identified or tentatively deduced. By Virtue of the extracted ion chromatogram (EIC) mode, simultaneous determination of isoflavonoids and astragalosides could be achieved when the different components formed overlapped peaks. And this method has been utilized to analyze the constituents in extracts of Radix Astragali from Helong City and of different growth years. Then the antioxidant activity of different samples has been Successfully investigated by HPLC-ESI-MS method in multiple selected ion monitoring(MIM) mode, applying the spin trapping technology, and the Ferric Reducing Antioxidant Power (FRAP) assay was applied to support the result.

Influence of intraperitoneal injection of rare earth compounds on the activities of antioxidant enzymes and the level of lipid peroxidation in mice livers

Following intraperitoneal injection of lanthanum and terbium chloride and their complexes of diethyltriaminopentagacetic acid (DTPA) to adult mice with a dose of 0.28 mmol/kg body weight/day for three days. The activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) and the content of lipid end product, malonaldehyde (MDA) in the mice livers have been assayed respectively. The results show that the activity of SOD was increased and the content of MDA was reduced for LaCl3 treated mice and the two targets were not changed for TbCl3, but the activity of GSH-Px was reduced markedly for both LaCl3 and TbCl3 while the above three targets were not changed for La-DTPA and Tb-DTPA complexes.

Antioxidant capacity and lipophilic content of seaweeds collected from the Qingdao coastline

Lipophilic extracts from 16 species of seaweeds collected along the Qingdao coastline were screened and evaluated for their antioxidant activities (AA) using the beta-carotene-linoleate assay system. The diethyl ether soluble extracts of all selected seaweeds exhibited various degrees of antioxidative efficacy in each screen. The highest antioxidant capacities among the tested samples were observed for Rhodomela confervoides and Symphyocladia latiuscula and were comparable with that of the well-known antioxidant butylated hydroxytoluene and greater than that of propyl gallate. The lipophilic content of all 16 samples and the chemical composition of 4 selected seaweeds, R. confervoides and S. latiuscula, which had higher AA, Laminaria japonica, which had intermediate AA, and Plocamium telfairiae, which had lower AA, were analyzed by gas chromatography and gas chromatography-mass spectrometry, respectively. Fatty acids and alkanes were found. The present data indicated an increase in antioxidative property with increasing content of unsaturated fatty acid. The result of this study suggests that seaweeds can be considered as a potential source for the extraction of lipophilic antioxidants, which might be used as dietary supplements or in production in the food industry. This is the first report on the antioxidant activities of lipophilic extracts from seaweeds.

The influence of the cation of quaternized chitosans on antioxidant activity

Various quaternized chitosans (QCSs) were synthesized according to previous method. Their reducing power and antioxidant potency against hydroxyl radicals ((OH)-O-center dot) and hydrogen peroxide (H2O2) were explored by the established systems in vitro. The QCSs exhibited markedly antioxidant activity, especially TCEDMCS, whose IC50 on hydroxyl radicals was 0.235 mg/mL. They showed 65-80% scavenging effect on hydrogen peroxide at a dose of 0.5 mg/mL. Generally, the antioxidant activity decreased in the order TCEDMCS > TBEDMCS > EDMCS > PDMCS > IBDMCS > Chitosan. Furthermore, the order of their (OH)-O-center dot and H2O2 scavenging activity was consistent with the electronegativity of different substituted groups in the QCSs. The QCSs showed much stronger antioxidant activity than that of chitosan may be due to the positive charge density of the nitrogen atoms in QCSs strengthened by the substituted groups. (C) 2009 Elsevier Ltd. All rights reserved.

A thioredoxin with antioxidant activity identified from Eriocheir sinensis

Thioredoxin, with a redox-active disulfide/dithiol in the active site, is the major ubiquitous disulfide reductase responsible for maintaining proteins in their reduced state. In the present study, the cDNA encoding thioredoxin-1 (designated EsTrx1) was cloned from Chinese mitten crab Eriocheir sinensis by using rapid amplification of cDNA ends (RACE) approaches. The full-length cDNA of EsTrx1 was of 641 bp, containing a 51 untranslated region (UTR) of 17 bp, a 3' UTR of 306 bp with a poly (A) tail, and an open reading frame (ORF) of 318 bp encoding a polypeptide of 105 amino acids. The high similarity of EsTrx1 with Trx1s from other animals indicated that EsTrx1 should be a new member of the Trx1 sub-family. Quantitative real-time PCR analysis revealed the presence of EsTrx1 transcripts in gill, gonad, hepato-pancreas, muscle, heart and haemocytes. The expression of EsTrx1 mRNA in haemocytes was up-regulated after Listonella anguillarum challenge, reached the maximum level at 6 h post-stimulation, and then dropped back to the original level gradually. In order to elucidate its biological functions, EsTrx1 was recombined and expressed in E. coli BL21 (DE3). The rEsTrx1 was demonstrated to possess the expected redox activity in enzymatic analysis, and to be more potent than GSH in antioxidant capacity. These results together indicated that EsTrx1 could function as an important antioxidant in a physiological context, and perhaps is involved in the responses to bacterial challenge. (C) 2009 Elsevier Ltd. All rights reserved.

Factors that effect antioxidant activity of C-phycocyanins from Spirulina platensis

Currently, antioxidants are added in the human diet to prevent free radical-induced cell damage, and there has been an explosive interest in the use of antioxidant nutritional supplements. The effects of different factors on the antioxidant activity of phycocyanins (PCs) were studied. The results showed that PCs generated hydroxyl radicals in the light, while scavenging them in the dark. When PCs were denatured by sodium dodecyl sulfate, urea and in alkaline condition, their ability to generate hydroxyl radicals disappeared and that of scavenging them greatly increased. This showed that the phycobilin moiety is the main part of PC involved in scavenging hydroxyl radicals. Trypsin hydrolysis of PCs showed that the apoprotein portion of the molecule also made a significant contribution to the antioxidant activity.