Antioxidant and free radical-scavenging activity of Choto-san and its related constituents

The antioxidant properties of Choto-san and its related constituents such as Chotoko and Choto-san without Chotoko, and phenolic compounds contained in Chotoko such as epicatechin, caffeic, acid and quercetin were evaluated. In the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging assay, the scavenging activity of Chotoko (IC(50) 14.3 microg/ml) was found to be higher than that of Choto-san (IC(50) 206.2 microg/ml) and Choto-san without Chotoko (IC(50) 244.3 microg/ml). Epicatechin (IC(50) 10.4 microM), caffeic acid (IC(50) 13.8 microM), and quercetin (IC(50) 7.1 microM) also revealed scavenging activity against DPPH radicals. Choto-san (IC(50) 67.7 microg/ml) exhibited stronger inhibitory activity against superoxide anion formation than Choto-san without Chotoko (IC(50) 92.4 microg/ml) but weaker activity than Chotoko (IC(50) 18.3 microg/ml). The generation of superoxide anion was also inhibited by epicatechin (IC(50) 175.2 microM), caffeic acid (IC(50) 141.7 microM), and quercetin (IC(50) 18.7 microM). In a hydroxyl radical-scavenging experiment, Choto-san (IC(50) 2.4 mg/ml), Chotoko (IC(50) 2.2 mg/ml), Choto-san without Chotoko (IC(50) 2.8 mg/ml), epicatechin (IC(50) 3.9 mM), caffeic acid (IC(50) 3.6 mM), and quercetin (IC(50) 1.9 mM) exhibited activity. In NG108-15 cells, when added simultaneously with H(2)O(2) (500 microM), Choto-san (250 microg/ml), Chotoko (250 microg/ml), Choto-san without Chotoko (500 microg/ml), epicatechin (200 microM), caffeic acid (200 microM), and quercetin (200 microM) effectively protected cells from oxidative damage. In conclusion, the present results provide evidence that Choto-san acts as an antioxidant and cytoprotective agent against oxidative damage, which is due at least partly to the phenolic compounds contained in Chotoko.     

Pharmacological evidence for antidementia effect of Choto-san (Gouteng-san), a traditional Kampo medicine

To clarify the clinical efficacy of one of the traditional medicines in the treatment of patients with vascular dementia, we investigated the pharmacological activities of Choto-san in animal models. Pretreatment with Choto-san (0.75-6.0 g/kg po), a component herb, Chotoko (75-600 mg/kg po), and indole alkaloids and phenolic fractions of Chotoko prevented ischemia-induced impairment of spatial learning behaviour in water maze performance of mice. A single administration of Choto-san (0.5 to 6.0 g/kg po) or Chotoko (Uncaria genus) produced a dose-dependent antihypertensive effect in spontaneously hypertensive rats (SHR) and partly inhibited the induction of the apoplexy in stroke-prone SHR (SHR-SP). Choto-san, Chotoko, and its phenolic constituents, (-)epicatechin and caffeic acid, significantly protected NG108-15 cells from injury induced by H(2)O(2) exposure in vitro and also inhibited lipid peroxidation in the brain homogenate. Indole alkaloids, rhynchophylline and isorhynchophylline (1-100 microM), reversibly reduced N-methyl-D-aspartate (NMDA)-induced current concentration dependently in NMDA receptor-expressed Xenopus oocytes.These results suggest that antidementia effects of Choto-san are due to antihypertensive, free radical scavenging and antiexcitotoxic effects, which are attributed at least partly to phenolic compounds and indole alkaloids contained in Chotoko.     

Brain lipid peroxidation and antioxidant status after acute methacrylonitrile intoxication

The status of brain antioxidant enzymes and glutathione in methacrylonitrile (MeAN)-intoxicated Wistar rats was correlated with the levels of lipid peroxidation products. Optimum changes were observed 30 min and 60 min after oral administration of MeAN at dosages of 50 mg/kg body weight per day (0.25 LD50) and 100 mg/kg body weight per day (0.5 LD50). An increase in lipid peroxidation products, decrease in the activity of antioxidant enzymes such as superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPX), glutathione reductase (GR), glutathione S-transferase (GST), and decrease in reduced glutathione (GSH) were observed. These studies suggest that the membrane lipid peroxidation observed in MeAN intoxication is related, in part, to a compromised antioxidant defense system.     

Antioxidant and hepatoprotective activities of phenolic rich fraction of Seabuckthorn (Hippophae rhamnoides L.) leaves

Present study was aimed to investigate antioxidant and hepatoprotective activities of phenolic rich fraction (PRF) of Seabuckthorn leaves on CCl₄ induced oxidative stress in Sprague Dawley rats. Total phenolic content was found to be 319.33 mg gallic acid equivalent (GAE)/g PRF and some of its phenolic constituents, such as gallic acid, myricetin, quercetin, kaempferol and isorhamnetin were found to be in the range of 1.935-196.89 mg/g of PRF as determined by reverse-phase high-performance liquid chromatography (RP-HPLC).Oral administration of PRF at dose of 25-75 mg/kg body weight significantly protected from CCl₄ induced elevation in aspartate aminotransferase (AST), alanine aminotransferase (ALT), γ-glutamyl transpeptidase (GGT) and bilirubin in serum, elevation in hepatic lipid peroxidation, hydroperoxides, protein carbonyls, depletion of hepatic reduced glutathione (GSH) and decrease in the activities of hepatic antioxidant enzymes; superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPX), glutathione reductase (GR) and glutathione-S-transferase (GST). The PRF also protected against histopathological changes produced by CCl₄ such as hepatocytic necrosis, fatty changes, vacuolation, etc. The data obtained in the present study suggests that PRF has potent antioxidant activity, prevent oxidative damage to major biomolecules and afford significant protection against CCl₄ induced oxidative damage in the liver.     

Brain Lipid Peroxidation and Antioxidant Status After Acute Methacrylonitrile Intoxication

The status of brain antioxidant enzymes and glutathione in methacrylonitrile (MeAN)-intoxicated Wistar rats was correlated with the levels of lipid peroxidation products. Optimum changes were observed 30 min and 60 min after oral administration of MeAN at dosages of 50 mg/kg body weight per day (0.25 LD₅₀) and 100 mg/kg body weight per day (0.5 LD₅₀). An increase in lipid peroxidation products, decrease in the activity of antioxidant enzymes such as superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPX), glutathione reductase (GR), glutathione S-transferase (GST), and decrease in reduced glutathione (GSH) were observed. These studies suggest that the membrane lipid peroxidation observed in MeAN intoxication is related, in part, to a compromised antioxidant defense system.     

Dose- and time-dependent effects of sulfur mustard on antioxidant system in liver and brain of rat

This study investigates the dose- and time-dependent effects of sulfur mustard (SM) on antioxidant system and lipid peroxidation in liver and brain of rats. For this purpose, male Wistar rats were randomly divided into eight groups and treated as follows: group 1 as control and groups 2-8 as experimental groups that received SM (1-80 mg/kg) through intraperitoneal injection. Rats were killed after 2, 7 and 14 days of exposure. SM dose-dependently decreased body weight. Superoxide dismutase (SOD), catalase (CAT) and glutathione S-transferase (GST) activities in liver were significantly increased at SM doses lower than 10 mg/kg after 2 and 7 days of exposure. However, the recovery of these parameters was observed after 14 days. At these concentrations, no significant change in glutathione (GSH) and malondialdehyde (MDA) levels were observed. At doses higher than 10 mg/kg, SM significantly decreased SOD, CAT, glutathione peroxidase (GPX), and GST activities in liver and brain and decreased glutathione reductase (GR) activity in liver, which was associated with a depletion of GSH and increased MDA level. Present data indicate that the effect of SM is dose- and time-dependent and at higher doses (>10 mg/kg) induces an oxidative stress response by depleting the antioxidant defense systems and increasing lipid peroxidation in liver and brain of rats.     

Di (2-ethylhexyl) phthalate inhibits growth of mouse ovarian antral follicles through an oxidative stress pathway

Di (2-ethylhexyl) phthalate (DEHP) is a plasticizer that has been shown to inhibit growth of mouse antral follicles, however, little is known about the mechanisms by which DEHP does so. Oxidative stress has been linked to follicle growth inhibition as well as phthalate-induced toxicity in non-ovarian tissues. Thus, we hypothesized that DEHP causes oxidative stress and that this leads to inhibition of the growth of antral follicles. To test this hypothesis, antral follicles isolated from CD-1 mice (age 31-35 days) were cultured with vehicle control (dimethylsulfoxide [DMSO]) or DEHP (1-100 μg/ml) ± N-acetyl cysteine (NAC, an antioxidant at 0.25-1 mM). During culture, follicles were measured daily. At the end of culture, follicles were collected and processed for in vitro reactive oxygen species (ROS) assays to measure the presence of free radicals or for measurement of the expression and activity of various key antioxidant enzymes: Cu/Zn superoxide dismutase (SOD1), glutathione peroxidase (GPX) and catalase (CAT). The results indicate that DEHP inhibits the growth of follicles compared to DMSO control and that NAC (0.25-1 mM) blocks the ability of DEHP to inhibit follicle growth. Furthermore, DEHP (10 μg/ml) significantly increases ROS levels and reduces the expression and activity of SOD1 compared to DMSO controls, whereas NAC (0.5 mM) rescues the effects of DEHP on ROS levels and SOD1. However, the expression and activity of GPX and CAT were not affected by DEHP treatment. Collectively, these data suggest that DEHP inhibits follicle growth by inducing production of ROS and by decreasing the expression and activity of SOD1.     

Effect of sub-chronic selenium toxicosis on lipid peroxidation,glutathione redox cycle and antioxidant enzymes in calves

The present investigation reports the effect of sodium selenite-induced sub-chronic toxicity in crossbred cow calves on various antioxidant enzymes. Sodium selenite (0.25 mg/kg for 16 w) resulted in characteristic signs of sub-chronic selenosis, ie alopecia, cracking and enlargement of hooves, interdigital lesions, ring formation on the coronet region, and gangrene at tip of the tail. The sodium selenite resulted in significant rise of blood selenium levels and concurrent increase in erythrocytic glutathione peroxidase (GPx) activity. Blood selenium levels and GPx activity had a high positive correlation (r = 0.97). Blood glutathione levels were lowered from 211.1 +/- 13.4 to 95.56 +/- 11.8 microg/ml. Selenosis caused oxidative stress as evidenced by a 3-fold increase in lipid peroxidation: activities of glutathione-S-transferase, glutathione reductase, superoxide dismutase and catalase were significantly increased. These findings support the hypothesis that the pro-oxidant attributes of selenium play important roles in its toxicity.     

Protective effects of quercetin on nicotine induced oxidative stress in ‘HepG2 cells’

Nicotine is a natural component of tobacco plants and is responsible for the addictive properties of tobacco. Nicotine has been recognized to result in oxidative stress by inducing the generation of reactive oxygen species (ROS). The purpose of this work was to estimate the hepatotoxicity effect of nicotine on viability and on antioxidant defense system in cultures of HepG2 cell line and the other hand, ameliorative effect of quercetin (Q) as an antioxidant was analyzed. Nicotine induced concentration dependent loss in HepG2 cell line viability. The results indicated that nicotine decreased activity of superoxide dismutase (SOD) and glutathione reductase (GR) and increased activities of catalase (CAT) and glutathione peroxidase (GPx) and glutathione (GSH) content in the HepG2 cells. Q significantly increased activity of SOD, GR and GSH content and decreased activity of GPX in nicotine?+?Q groups. Our data demonstrate that Q plays a protective role against the imbalance elicited by nicotine between the production of free radicals and antioxidant defense systems, and suggest that administration of this antioxidant may find clinical application where cellular damage is a consequence of ROS.     

Protective effects of L-arginine on pulmonary oxidative stress and antioxidant defenses during exhaustive exercise in rats

AIM: To assess the effects of L-arginine (L-Arg) supplementation on pulmonary oxidative stress and antioxidant defenses in rats after exhaustive exercise. METHODS: Rats were randomly divided into four groups: sedentary control (SC), sedentary control with L-Arg treatment (SC+Arg), exhaustive exercise with control diet (E) and exhaustive exercise with L-Arg treatment (E+Arg). Rats in groups SC+Arg and E+Arg received a 2% L-Arg diet. Rats in groups E and E+Arg underwent an exhaustive running test on a motorized treadmill. Pulmonary oxidative stress indices [xanthine oxidase (XO), myeloperoxidase (MPO), and malondialdehyde (MDA)] and antioxidant defense systems [superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPX), glutathione reductase (GR), and glutathione (GSH)] were investigated in this study. RESULTS: L-Arg supplementation significantly reduced exercise-induced elevations of XO and MPO activities in lung. L-Arg reversed the exercise-induced increase in SOD and GR activities, but increased CAT and GPX activities. L-Arg administration also significantly increased the GSH levels in plasma. CONCLUSION: L-Arg supplementation can prevent elevations of XO and MPO activities in the lung and favorably influence pulmonary antioxidant defense systems after exhaustive exercise.     

Hormonal regulation of superoxide dismutase, catalase, and glutathione peroxidase activities in rat macrophages

This study examined the effects of glycocorticoids, insulin, thyroxine, and epinephrine upon the activities of CuZn- and Mn-superoxide dismutases (SOD), catalase, and glutathione peroxidase (GPX) and upon hydrogen peroxide production in rat macrophages obtained from the intraperitoneal cavity. The experiments were performed in vivo under conditions causing hormonal dysfunctions: adrenal demedullation, dexamethasone treatment, thyroidectomy, administration of -tri-iodothyronine (T₃) and -thyroxine (T₄), and diabetes. Macrophages were also cultured for 24 hr in the presence of dexamethasone, thyroid hormones, and insulin as to evaluate possible interferences caused in vivo by changes in other hormones. The results indicated that these hormones do control the activities of the antioxidant enzymes and hydrogen peroxide production both in vivo and in vitro. Insulin increased the activities of CuZn-SOD, catalase, and GPX and reduced that of Mn-SOD. Thyroid hormones raised the activities of CuZn- and Mn-SOD and decreased that of GPX, whereas glucocorticoids reduced both Mn-SOD and GPX. The removal of the adrenal medulla caused a decrease of Mn-SOD and GPX activities in the macrophages. Hydrogen peroxide production was increased by insulin and reduced by thyroid hormones and glucocorticoids. The changes in antioxidant enzyme activities caused by these hormones in macrophages may indicate important mechanisms for the establishment of impaired immune function in endocrine pathologies.     

Effect of diquat on the antioxidant system and cell growth in human neuroblastoma cells

Oxidative stress elicits an adaptive antioxidant response, which varies with tissue type. Diquat, a potent redox cycler that generates reactive oxygen species, has been used to study oxidative stress; however, its effect on the antioxidant system has not been characterized in neuronal cells. Accordingly, we measured antioxidant parameters and cell growth in human neuroblastoma SH-SY5Y cells cultured for 48 h in medium containing 5, 10, or 25 microM diquat dibromide or phosphate-buffered saline. Viable cells were assayed for glutathione (GSH) and activities of catalase (CAT), superoxide dismutase (SOD), glutathione reductase (GR), glutathione peroxidase (GPX), and glucose-6-phosphate dehydrogenase (GPDH). Mitochondrial function was evaluated by glutamate dehydrogenase (GDH) activity and MTT reduction. Diquat caused a marked concentration-related decrease in viable cell count ( by 26, 51, and 87% at 5, 10, and 25 microM diquat). Cell viability was only affected at 10 and 25 microM diquat and did not fully account for the decreased viable cell count. Concentration-related increases also occurred with GSH levels and a majority of antioxidant enzymes activities; however, the mode and magnitude varied with parameter. Increases in GSH, CAT, SOD, and GR were maximal at 25 microM diquat (to 3-, 6-, 2-, and 1.5-fold control values, respectively). GPDH activity was maximal at 10 microM diquat and then decreased to 86% of control activity at 25 microM diquat. GPX activity showed a concentration-related decrease (to 35% of control). Activity of the mitochondrial enzyme GDH increased 3-fold at 25 microM diquat, along with a lesser increase in MTT reduction. We conclude that diquat reduces cell growth in neuroblastoma cells and induces an adaptive antioxidant response, which are concentration dependent and occur at sublethal concentrations. At higher concentrations, diquat alters mitochondrial function and becomes increasingly toxic.     

Modulation of phase-II enzyme activities in benzene treated ovariectomized rats

The aim of the study was to determine the influence of ovariectomy on phase II enzymes viz. glutathione-S-transferase (GST), glutathione peroxidase (GPX) and catalase (CAT) in liver and kidney of female rats treated with benzene. The results showed the significant decrease of the GST and GPX activity in benzene treated rats after ovariectomy. However progesterone supplementation stimulated the activity of GST and GPX in liver and kidney of benzene treated non ovariectomized and ovariectomized rats. Progesterone supplementation to benzene treated ovariectomized rats helps to gain in CAT activity. Our results on DNA damage using single cell gel electrophoresis also confirmed our findings on antioxidant enzymes. The results showed that lack of protective progesterone against benzene toxicity is reflected in alterations in antioxidant enzyme activities. However progesterone therapy to benzene treated ovariectomized rats results in activating the antioxidant defence system. Since female workers are engaged in industrial sector, these results are important from occupational health point of view. Benzene exposure affects their reproductive health. Nevertheless, it could be modulated by suitable hormonal therapy.     

Phenolics-rich extracts from Silybum marianum and Prunella vulgaris reduce a high-sucrose diet induced oxidative stress in hereditary hypertriglyceridemic rats.

The study tested the effects of phenolics-rich extracts from the plants Silybum marianum (silymarin) and Prunella vulgaris (PVE) on blood and liver antioxidant status and lipoprotein metabolism. Hereditary hypertriglyceridemic rats fed on standard diet (STD) or high-sucrose diet (HSD, 70cal% of sucrose) for two weeks were used. HSD doubled plasma and liver triacylglycerol (TAG) and increased plasma VLDL-TAG and VLDL-cholesterol compared to STD. Administration of silymarin or PVE as 1% dietary supplements in HSD did not influence lipid levels in plasma or liver, but both extracts caused decrease in plasma VLDL-cholesterol levels. HSD-induced oxidative stress was manifested in increased TBARS and conjugated dienes (CD) content, decreased GSH levels and glutathione peroxidase (GPX) activity in blood and liver. In blood the activity of superoxide dismutase (SOD) decreased, whereas in liver the activity of catalase increased after HSD. Feeding on HSD containing phenolics-rich extracts resulted in reduction of TBARS and CD content and in increase of blood GPX activity and elevated GSH content in liver. Besides, silymarin increased the activity of SOD and level of GSH in blood. Catalase activity in blood or liver was not influenced by the presence of plant extracts in the diet. These results indicate that silymarin and PVE improve antioxidant status in blood and liver and positively affect plasma lipoprotein profile in an experimental model of dietary induced hypertriglyceridemia.     

Modifications on Antioxidant Capacity and Lipid Peroxidation in Mice under Fraxetin Treatment

Fraxetin belongs to an extensive group of natural phenolic antioxidants. We have investigated the modifications in endogenous antioxidant capacity; superoxide dismutase (SOD), catalase (CAT), total and selenium-dependent glutathione peroxidases (GPx) and glutathione reductase (GR) and stress index; glutathione disulphide (GSSG)/reduced glutathione (GSH) ratio and thiobarbituric acid-reactive substances (TBARs) in liver and brain supernatants of C57BL/6J male 12-month-old mice under fraxetin treatment for 30 days. Liver SOD and GPx (total and Se-dependent) activities were not significantly affected by fraxetin, whereas they were increased in the brain compared with control animals. GR activity increased significantly only in the liver of treated mice. Fraxetin treatment-related decreases were shown for GSSG/GSH ratio and rate of accumulation of TBARs (not significant in TBARs) in both tissues. We concluded that the net effect of fraxetin treatment on endogenous antioxidant capacity suggests that this compound might provide an important resistance to, or protection against, free-radical-mediated events which contribute to degenerative diseases of ageing.     

Methoxychlor inhibits growth and induces atresia of antral follicles through an oxidative stress pathway.

The mammalian ovary contains antral follicles, which are responsible for the synthesis and secretion of hormones that regulate estrous cyclicity and fertility. The organochlorine pesticide methoxychlor (MXC) causes atresia (follicle death via apoptosis) of antral follicles, but little is known about the mechanisms by which MXC does so. Oxidative stress is known to cause apoptosis in nonreproductive and reproductive tissues. Thus, we tested the hypothesis that MXC inhibits growth and induces atresia of antral follicles through an oxidative stress pathway. To test this hypothesis, antral follicles isolated from 39-day-old CD-1 mice were cultured with vehicle control (dimethylsulfoxide [DMSO]), MXC (1-100 microg/ml), or MXC + the antioxidant N-acetyl cysteine (NAC) (0.1-10 mM). During culture, growth was monitored daily. At the end of culture, follicles were processed for quantitative real-time polymerase chain reaction of Cu/Zn superoxide dismutase (SOD1), glutathione peroxidase (GPX), and catalase (CAT) mRNA expression or for histological evaluation of atresia. The results indicate that exposure to MXC (1-100 microg/ml) inhibited growth of follicles compared to DMSO controls and that NAC (1-10 mM) blocked the ability of MXC to inhibit growth. MXC induced follicular atresia, whereas NAC (1-10 mM) blocked the ability of MXC to induce atresia. In addition, MXC reduced the expression of SOD1, GPX, and CAT, whereas NAC reduced the effects of MXC on their expression. Collectively, these data indicate MXC causes slow growth and increased atresia by inducing oxidative stress.     

Prolonged cardiac dysfunction after withdrawal of chronic cocaine exposure in rats

Cocaine abuse causes myocardial dysfunction and induces oxidative stress. However, the reversibility of these effects is unknown. We evaluated myocardial function and oxidative stress after cocaine withdrawal, in a rat model of chronic cocaine exposure. Standard echocardiography and Doppler tissue imaging were performed after 4 weeks (W4) of cocaine administration (2 x 7.5 mg/kg/d, i.p.) and 4 weeks after interruption (W8). At these time points, redox state (reduced glutathione GSH, oxidized glutathione GSH, and GSH/GSSG) as well as activities of GSH peroxidase (GPX), superoxide dismutase (SOD), and catalase were determined in the left ventricle (LV). At W4, LV fractional shortening, posterior wall thickening, systolic myocardial ventricular gradient (SMVG), dP/dt(max), and dp/dt(min) were decreased, compared with control values while LV myocardial thickness was increased. At W8, even though dP/dtmax and dp/dt(min) were restored, myocardial function was still impaired as demonstrated by the decrease in posterior wall thickening, and systolic myocardial velocity gradient. At W4, CAT and GPX activities as well as GSH/GSSG ratio were reduced while SOD activity was increased. Antioxidant markers and redox ratio remained altered 4 weeks after the last injection. Thus, these data demonstrate the persistence of LV dysfunction after cocaine withdrawal, which occurs in a context of a deficit in antioxidant defenses.     

Antioxidant potential of Cymbopogon citratus extract: alleviation of carbon tetrachloride-induced hepatic oxidative stress and toxicity

This study was aimed to evaluate the effect of Cymbopogon citratus against carbon tetrachloride (CCl(4))-mediated hepatic oxidative damage in rats. Rats were administrated with C. citratus extract (100, 200 and 300 mg/kg b.w.) for 14 days before the challenge of CCl(4) (1.2 ml/kg b.w. p.o) on 13th and 14th days. Hepatic damage was evaluated by employing serum biochemical parameters (alanine aminotransferase-ALT, aspartate aminotransferase-AST and lactate dehydrogenase-LDH), malondialdehye (MDA) level, reduced GSH and antioxidant enzymes (catalase: CAT, glutathione peroxidase: GPX, quinone reductase: QR, glutathione S-transferase: GST, glutathione reductase: GR, glucose-6-phosphate dehyrogenase: G6PD). In addition, CCl(4)-mediated hepatic damage was further evaluated by histopathological examination. However, most of these changes were alleviated by prophylactic treatment of animals with C. citratus dose dependently (p < 0.05). The protection was further evident through decreased histopathological alterations in liver. The results of the present study indicated that the hepatoprotective effect of C. citratus might be ascribable to its antioxidant and free radical scavenging property.     

Microcystin-RR-induced accumulation of reactive oxygen species and alteration of antioxidant systems in tobacco BY-2 cells.

Microcystins are cyclic heptapeptide hepatoxins produced by cyanobacteria. It has been shown that microcystins have adverse effects on animals and on plants as well. Previous researches also indicated that microcystins were capable of inducing oxidative damage in animals both in vivo and in vitro. In this study, tobacco BY-2 suspension cell line was applied to examine the effects of microcystin-RR on plant cells. Cell viability and five biochemical parameters including reactive oxygen species (ROS), superoxide dismutase (SOD), catalase (CAT), glutathione peroxide (GPX) and peroxide dismutase (POD) were investigated when cells were exposed to 50mg/L microcystin-RR. Results showed that microcystin-RR evoked decline of the cell viability to approximately 80% after treating for 144 h. ROS levels, POD and GPX activities of the treated cells were gradually increased with a time dependent manner. Changes of SOD and CAT activities were also detected in BY-2 cells. After 168 h recovery, ROS contents, POD, GPX and CAT activities returned to normal levels. These results suggest that the microcystin-RR can cause the increase of ROS contents in plant cells and these changes led to oxidant stress, at the same time, the plant cells would improve their antioxidant abilities to combat mirocystin-RR induced oxidative injury.     

Effects of phenolic compounds on bromobenzenemediated hepatotoxicity in mice

1. The hepatic protective effects of the phenolic compounds 7,8-dihydroxyflavone, morin, silymarin, caffeic acid and chlorogenic acid on bromobenzene-induced toxicity in mice were studied.

2. Morin, caffeic acid and chlorogenic acid at an oral dose of 200mg/kg failed to influence hepatotoxicity in vivo, while 7,8-dihydroxyflavone exhibited efficacy and potency higher than those of the reference compound silymarin.

3. 7,8-Dihydroxyflavone, an antioxidant and hepatoprotective agent in vitro, decreased serum glutamate-pyruvate transaminase levels (SGPT) in a dose-related manner, and at 200mg/kg inhibited bromobenzene-induced glutathione depletion in liver.