Iron-induced Lipid Peroxidation Research Articles

Melatonin reduces Fenton reaction-induced lipid peroxidation in porcine thyroid tissue.

Free radicals and reactive oxygen species (ROS) participate in physiological and pathological processes in the thyroid gland. Bivalent iron cation (ferrous, Fe(2+)), which initiates the Fenton reaction (Fe(2+) + H2O2 --> Fe(3+) + *OH + OH(-)) is frequently used to experimentally induce oxidative damage, including that caused by lipid peroxidation. Lipid peroxidation is involved in DNA damage, thus indirectly participating in the early steps of carcinogenesis. In turn, melatonin is a well-known antioxidant and free radical scavenger. The aim of the study was to estimate the effect of melatonin on basal and iron-induced lipid peroxidation in homogenates of the porcine thyroid gland. In order to determine the effect of melatonin on the auto-oxidation of lipids, thyroid homogenates were incubated in the presence of that indoleamine in concentrations of 0.0, 0.00001, 0.0001, 0.001, 0.01, 0.1, 0.25, 0.5, 1.0, 2.5, or 5.0 mM. To study melatonin effects on iron-induced lipid peroxidation, the homogenates were incubated in the presence of FeSO(4) (40 microM) plus H2O2 (0.5 mM), and, additionally, in the presence of melatonin in the same concentrations as above. The degree of lipid peroxidation was expressed as the concentration of malondialdehyde + 4-hydroxyalkenals (MDA + 4-HDA) per mg protein. Melatonin, in a concentration-dependent manner, decreased lipid peroxidation induced by Fenton reaction, without affecting the basal MDA + 4-HDA levels. In conclusion, melatonin protects against iron + H2O2-induced peroxidation of lipids in the porcine thyroid. Thus, the indoleamine would be expected to prevent pathological processes related to oxidative damage in the thyroid, cancer initiation included.

Protective effect of fenugreek (Trigonella foenum graecum) seeds in experimental ethanol toxicity.

The study investigates the effect of aqueous extract of fenugreek seeds (Trigonella foenum graecum) on lipid peroxidation and antioxidant status in experimental ethanol toxicity in rats. The ability of the seed extract to prevent iron-induced lipid peroxidation in vitro was also investigated. Ethanol feeding for 60 days resulted in significant increases in the activities of serum aspartate transaminase, alanine transaminase and alkaline phosphatase. The levels of serum lipid hydroperoxides and thiobarbituric acid reactive substances in liver and brain were also significantly elevated. Significantly lower activities of superoxide dismutase, catalase, glutathione peroxidase, glutathione S-transferase and glutathione reductase were observed in liver and brain accompanied by depletion in glutathione, ascorbic acid and alpha-tocopherol concentrations. Activity of Ca(2+) ATPase in brain was significantly lowered. Simultaneous administration of aqueous extract of fenugreek seeds with ethanol prevented the enzymatic leakage and the rise in lipid peroxidation and enhanced the antioxidant potential. The seeds exhibited appreciable antioxidant property in vitro which was comparable with that of reduced glutathione and alpha-tocopherol. Further, histopathological examination of liver and brain revealed that, aqueous extract of fenugreek seeds could offer a significant protection against ethanol toxicity.

Multiple enzymic activities of human milk lactoferrin.

Lactoferrin (LF) is a Fe3+-binding glycoprotein, first recognized in milk and then in other human epithelial secretions and barrier fluids. Many different functions have been attributed to LF, including protection from iron-induced lipid peroxidation, immunomodulation and cell growth regulation, DNA binding, and transcriptional activation. Its physiological role is still unclear, but it has been suggested to be responsible for primary defense against microbial and viral infection. We present evidence that different subfractions of purified human milk LF possess five different enzyme activities: DNase, RNase, ATPase, phosphatase, and malto-oligosaccharide hydrolysis. LF is the predominant source of these activities in human milk. Some of its catalytically active subfractions are cytotoxic and induce apoptosis. The discovery that LF possesses these activities may help to elucidate its many physiological functions, including its protective role against microbial and viral infection.

Lead-Exposed Increase in Movement Behavior and Brain Lipid Peroxidation in Fish#

Lipid peroxides formation and motor activity were studied in fish under lead exposure for a period of 30 days. The in vitro studies of lead exposure were also performed in fish brain homogenates. Spontaneous motor activity of fish was affected by lead exposure (50 µg/L). The behaviors were increased in fish during the first three days with jerky movements and then as spontaneous movements between 16 and 30 days of lead exposure. Lipid peroxidation, which is measured as thiobarbituric acid reactive species, was increased by 52% on 15 days and 156% on 30 days of lead exposure (50 µg/L). The effects of lead exposure (50 µg) were also observed in in vitro fish brain homogenates (1 mL, 5% w/v) alone, in presence of pro-oxidant system (as iron 100 µg) or anti-oxidant system (as α-tocopherol, 100 µg). Steady state increments of lipid peroxidation were apparent up to the concentration of 40 µg of lead treatment in brain homogenates, which subsequently attained a plateau up to the treatment of 100 µg lead. Lead at the concentration of 50 µg promoted lipid peroxidation by 225%. Iron-induced lipid peroxidation was 135% as compared to control. Lead neurotoxicity was further aggravated by iron by 33%, while the combined impact was 476% higher when compared with the control (i.e., untreated brain homogenates). Alpha-tocopherol reduced the levels of lipid peroxidation by 31%. Moreover, treatment of α-tocopherol also suppressed the lead neurotoxicity by 53%. These findings suggest that lead intoxication increases spontaneous motor activity and lipid peroxides in brain of fish in chronic exposure. I, therefore, speculate that presence of iron may accentuate lead neurotoxicity, while on the other hand, treatment with biological anti-oxidant α-tocopherol may provide relief from lead neurotoxicity. #The paper was presented in parts at the Measuring Behavior 2002, 4th International Conference on Methods and Techniques in Behavioral Research, August 27–30, 2002, Amsterdam, The Netherlands, and International Conference on Role of Free Radicals and Antioxidants in Health and Disease and 2nd Annual Conference of Society of Free Radical Research-India, February 10–12, 2003, Lucknow, India

Hypoxic preconditioning prevents cortical infarction by transient focal ischemia-reperfusion.

One of the proposed pathologic actions underlying brain infarction is excess free radicals resulting from reoxygenation. In this paper we report an investigation of the neuroprotective effect of hypoxic preconditioning on transient focal ischemia-reperfusion injuries in rat brain. Female Wistar rats were subjected to 380 mmHg in an altitude chamber for 15 hours/day. Our ex vivo studies showed that auto-oxidation and iron-induced lipid peroxidation of brain homogenates of the four-week hypoxia-preconditioned rats were significantly lower than those of the normoxic rats. A focal infarction in the cerebral cortex of normoxic rats was consistently observed 24 hours after a 60-minute transient ischemic occlusion of the right middle cerebral artery and bilateral common carotid arteries. Hypoxic preconditioning in fact attenuated cortical infarction in a duration-dependent manner. Induction of the neuroprotection required two weeks of hypoxic preconditioning. Four weeks of hypoxic preconditioning significantly reduced the cortical infarcted area, the elevated lipid peroxidation, and resulted in an acute increase in cytosolic cytochrome c in the infarcted cortex of normoxic rats. The protective effect of four weeks of hypoxic preconditioning lasted seven days under a renormoxic condition. Our data suggest that oxidative stress may result in apoptosis in the transient focal ischemia-reperfusion injuries. Furthermore, hypoxic preconditioning attenuated cortical infarction in the rat brain. Although supplementation of antioxidants may encounter difficulty at the blood-brain barrier, hypoxic preconditioning is very likely to protect CNS targets from oxidative injuries without any barrier.

Antioxidative and hepatoprotective effects of Antrodia camphorata extract.

Antrodia camphorata (A. camphorata) is well-known in Taiwan as a traditional Chinese medicine. The purpose of this study was to evaluate the ability of A. camphorata extracts to protect against oxidative stress in vitro and against carbon tetrachloride (CCl(4))-induced hepatic injury in vivo. An extract of A. camphorata inhibited nonenzymatic iron-induced lipid peroxidation in rat brain homogenates with an IC(50) value about 3.1 mg/mL. It also scavenged the stable free radical 1,1-diphenyl-2-picrylhydrazyl (DPPH). The dose of the A. camphorata extract resulting in a decrease of 0.20 in the absorbance of DPPH was about 31 +/- 0.7 microg/mL. Furthermore, an A. camphorata extract dose-dependently (250-1250 mg/kg) ameliorated the increase in plasma aspartate aminotransferase (GOT) and alanine aminotransferase (GPT) levels caused by chronic repeated CCl(4) intoxication in mice. Moreover, A. camphorata extract significantly improved the CCl(4)-induced increase in hepatic glutathione peroxidase, reductase, and CCl(4)-induced decrease in superoxide dismutase activities. It also restored the decrement in the glutathione content and catalase activity of hepatic tissues in CCl(4)-intoxicated mice. Furthermore, it also dose-dependently inhibited the formation of lipid peroxidative products during CCl(4) treatment. Histopathological changes of hepatic lesions induced by CCl(4) were significantly ameliorated by treatment with an A. camphorata extract in a dose-dependent manner. These results suggest that A. camphorata extract exerts effective protection against chronic chemical-induced hepatic injury in vivo, by mediating antioxidative and free radical scavenging activities.

Gene expression in the human small intestine in vivo. Effects of iron-induced lipid peroxidation

Imroduction Iron induces lipid peroxidation and the subsequent release of antioxidants in the lumen of the small intestine. This may mediate geue expression in the intestinal waft. The present study aimed to determine which genes are mediated by an iron-induced oxidative challenge in the human small intestine Methods Ten volunteers (22 +/-2 y) were tested on two occasions. Atter an overnight fast, duodenal biopsies, taken in the horizontal part of the duodenum (15 cm distally from the pylorus), were Obtained by duodenoseopy Subsequently, a catheter was inserted into the proximal small intestine ~,ath an injection port positioned in the proximal descending duodenum. After positioning, saline was injected at 10 ml/min and, after reaching steady state, either 80 or 400 mg iron as terrous gluconate was injected for 30 min. Finally, saline was injected for another 60 rain. A second duodenoscopy was pertbrnled to obtain tissue samples after the iron challenges. In the tissue samples, gene expression was measured using Affimetrix U 133A microarray chips (> 20.000 known genes). Resuhs A total number of 9880 genes were expressed in the small intestine. The expression of 91 genes was significantly changed by both the low and the high iron perfusion, whereas 293 genes tended to be regulated by the two iron challenges. Twenty-eight genes were statistically upregulated, whereas 63 genes were significantly dmvnregulated by both iron intervention_s Two of the upregnlated genes serve functions in cell growth and tumor suppression, one gene encodes for sdenoprotein P, which has antioxidant properties, haterestingly, two genes downregnlated by iron are also associated with tumor suppression and negative control of cell proliferation. Conclusion A large number of genes is expressed in the human proximal small intestine. Iron administration, resulting in lipid peroxidation, mediates expression of at least 91 genes in the small bowel.

Quantification of iron-induced lipid peroxidation and antioxidant defense mechanisms in the human small intestine using a newly developed perfusion model

Quantification of iron-induced lipid peroxidation and antioxidant defense mechanisms in the human small intestine using a newly developed perfusion model

Genistein protects primary cortical neurons from iron-induced lipid peroxidation.

Neuroprotective role of isoflavones in particular genistein might be resulted from their antioxidant activities in addition to their estrogenic actions. In the present study, we investigated effect of genistein on iron-induced free radical reaction in cultured cortical neurons. Thiobarbituric-acid-reactive species (TBARS) and superoxide dismutase (SOD) were measured after incubation of the cells with different concentrations of genistein in the absence or presence of iron (12.5 microM) for 24 h. Genistein at 100 microM significantly reduced the iron-induced TBARS, implying that genistein has an inhibitory role on iron-induced lipid peroxidation. Also, genistein (100 microM) led to a relatively higher SOD level than that in iron treatment although no significant difference was found. The findings imply that the antioxidative effect of genistein is partly associated with its neuroprotective function.

Activation of microsomal glutathione s-transferase by peroxynitrite.

Peroxynitrite (ONOO-) toxicity is associated with protein oxidation and/or tyrosine nitration, usually resulting in inhibition of enzyme activity. We examined the effect of ONOO- on the activity of purified rat liver microsomal glutathione S-transferase (GST) and found that the activity of reduced glutathione (GSH)-free enzyme was increased 4- to 5-fold by 2 mM ONOO-; only 15% of this increased activity was reversed by dithiothreitol. Exposure of the microsomal GST to ONOO- resulted in concentration-dependent oxidation of protein sulfhydryl groups, dimer and trimer formation, protein fragmentation, and tyrosine nitration. With the exception of sulfhydryl oxidation, these modifications of the enzyme correlated well with the increase in enzyme activity. Nitration or acetylation of tyrosine residues of the enzyme using tetranitromethane and N-acetylimidazole, respectively, also resulted in increased enzyme activity, providing additional evidence that modification of tyrosine residues can alter catalytic activity. Addition of ONOO--treated microsomal GST to microsomal membrane preparations caused a marked reduction in iron-induced lipid peroxidation, which raises the possibility that this enzyme may act to lessen the degree of membrane damage that would otherwise occur under pathophysiological conditions of increased ONOO- formation.

Effect of Aluminium on Lipid Peroxidation of Human High Density Lipoproteins

We investigated the effect of aluminium (Al 3+ ) on lipid peroxidation and physico-chemical properties of high density lipoproteins (HDL) isolated from human plasma. Our results demonstrated that Al 3+ enhances lipid peroxidation of human HDL as shown by the significant increase in lipid hydroperoxides in Al-treated HDL with respect to control HDL. The oxidative effect was higher at acid pH (pH 5.5) with respect to pH 7.4. Moreover, a stimulating effect of Al 3+ on iron-induced lipid peroxidation of HDL was demonstrated. The study of the effect of Al 3+ on the physico-chemical properties of HDL, using the fluorescence polarization (Pf) of the probes TMA-DPH (1-(4-trimethylammoniumphenyl)-6-phenyl-1,3,5-hexatriene iodide) and DPH (1,6-diphenyl-1,3,5-hexatriene), showed a significant decrease of Pf in Al-treated HDL with respect to control. These results suggest that Al 3+ induces a decrease of molecular order at the lipoprotein surface. Moreover, the study of tryptophan (Trp) fluorescence demonstrated that aluminium induces structural modifications of HDL apoproteins and on HDL physico-chemical properties. The effect of Al 3+ on lipid peroxidation of HDL was observed at aluminium concentrations similar to those observed in the brain of patients affected by neurological diseases. Aluminium-induced oxidative damage of HDL could be involved in the development of neurological diseases.

6-Hydroxymelatonin converts Fe (III) to Fe (II) and reduces iron-induced lipid peroxidation

Disorders of iron accumulation are known to produce hepatotoxicity. Agents, which can reduce Fe 3+ to a more usable form Fe 2+ could potentially limit such damage. Since it has been previously demonstrated that the pineal secretory product, melatonin, is able to bind iron, we decided to investigate the potential protective properties of the principal melatonin metabolite and degradant, 6-hydroxymelatonin (6-OHM). Using adsorptive cathode stripping voltammetry (AdCSV) we showed that Fe 3+ in the presence of 6-OHM is converted to Fe 2+. We further demonstrated that 6-OHM reduces the Fe 2+-induced rise in lipid peroxidation in rat liver homogenates. The results imply that 6-OHM facilitates the conversion of Fe 3+ to Fe 2+ which is a more biologically usable form of iron. While such a conversion could also potentially make more Fe 2+ available for driving the Fenton reaction and the consequent generation of the dangerous hydroxyl radical, 6-OHM is able to quench these radicals, thereby providing tissue protection.

Metabolic syndrome in the rat: females are protected against the pro-oxidant effect of a high sucrose diet.

Metabolic syndrome is more prevalent in men than in women. In an experimental dietary model of metabolic syndrome, the high-fructose-fed rat, oxidative stress has been observed in males. Given that estradiol has been documented to exert an antioxidant effect, we investigated whether female rats were better protected than males against the adverse effects of a high-sucrose diet, and we studied the influence of hormonal status in female rats. Males and females were first fed a sucrose-based or starch-based diet for 2 weeks. In the males, the plasma triglyceride (TG)-raising effect of sucrose was accompanied by significantly lowered plasma alpha-tocopherol and a significantly lowered alpha-tocopherol/TG ratio (30%), suggesting that vitamin E depletion may predispose lipoproteins to subsequent oxidative stress. In males, after exposure of heart tissue homogenate to iron-induced lipid peroxidation, thiobarbituric reactive substances were significantly higher in the sucrose-fed than in the starch-fed rats. In contrast, in sucrose-fed females, neither a decrease in vitamin E/TG ratio nor an increased susceptibility of heart tissue to peroxidation was observed, despite both a significantly decreased heart superoxide dismutase activity (14%) and a significant 3-fold increase in plasma nitric oxide concentration compared with starch-fed females. The influence of hormonal status in female rats was then assessed using intact, ovariectomized, or estradiol-supplemented ovariectomized female rats fed the sucrose or starch diet for 2 weeks. After exposure of heart tissue to iron-induced lipid peroxidation, higher susceptibility to peroxidation was found only in ovariectomized females fed the sucrose diet compared with the starch group and not in intact females or ovariectomized females supplemented with estradiol. Thus, estrogens, by their effects on antioxidant capacity, might explain the sexual difference in the pro-oxidant effect of sucrose diet resulting in metabolic syndrome in rats.

Rationale for clinical trials of selenium as an antioxidant for the treatment of the cardiomyopathy of Friedreich's ataxia

A pure selenium deficiency is harmful to the heart and causes a fatal dilated congestive cardiomyopathy in animals (white muscle disease) and in man (Keshan disease). Both of these syndromes are selenium-responsive. A deficiency of the micronutrient has also been reported in patients with Friedreich's ataxia and there are histological similarities between Friedreich's cardiomyopathy and Keshan disease. A low selenium status results in reduced selenium-dependent glutathione peroxidase activity. This essential antioxidant enzyme protects membrances from oxidative deterioration, a function it shares in common with vitamin E. As iron-induced mitochondrial lipid peroxidation is central to the pathology of Friedreich's ataxia, the administration of selenium supplements should normalize the antioxidant activity of myocardial glutathione peroxidase and slow the progression of the life-shortening cardiomyopathy associated with this illness.

The effects of glutathione and vitamin E on iron toxicity in isolated rat hepatocytes

This study examined the acute toxicity of ferrous sulfate on rat hepatocyte suspensions, the correlation between lipid peroxidation and cell death, and the roles of glutathione and vitamin E in protecting against iron toxicity. Incubation with ferrous sulfate for 2 h produced lipid peroxidation, but did not decrease cell viability in the hepatocytes. When diethyl maleate (DEM) was added to deplete cellular glutathione concentrations, ferrous sulfate treatment (2.0–5.0 mM) did cause cell death and lipid peroxidation developed more extensively, suggesting that iron-mediated hepatotoxicity is influenced by glutathione content. Reduced glutathione (GSH), N-acetylcysteine (NAC) and α-tocopherol (vitamin E), alone and in combination, were added to hepatocyte suspensions in an attempt to protect cells against iron-induced damage. In iron–DEM-treated cells, GSH and NAC treatment increased viability by 43 and 36%, respectively, but only the combination of the two agents reduced lipid peroxidation (53% decrease). Vitamin E treatment reduced lipid peroxidation by 39% and also increased cell viability by 12%. The greatest protection against iron-induced lipid peroxidation occurred with the combination of GSH, NAC and vitamin E, which reduced lipid peroxidation by 94% in iron-treated cells, and by 98% in iron–DEM-treated cells. However, this combination did not prevent iron-induced cell death, although it did increase viability by 18%. These results suggest that iron-induced cell death may not be dependent upon lipid peroxidation, at least in short-term exposures. The results also suggest an interaction between GSH and vitamin E in protecting against lipid peroxidation.

Effects of citrinin on iron-redox cycle.

The ability of the mycotoxin citrinin to act as an inhibitor of iron-induced lipoperoxidation of biological membranes prompted us to determine whether it could act as an iron chelating agent, interfering with iron redox reactions or acting as a free radical scavenger. The addition of Fe3+ to citrinin rapidly produced a chromogen, indicating the formation of citrinin-Fe3+ complexes. An EPR study confirms that citrinin acts as a ligand of Fe3+, the complexation depending on the [Fe3+]:[citrinin] ratios. Effects of citrinin on the iron redox cycle were evaluated by oxygen consumption or the o-phenanthroline test. No effect on EDTA-Fe2+-->EDTA-Fe3+ oxidation was observed in the presence of citrinin, but the mycotoxin inhibited, in a dose-dependent manner, the oxidation of Fe2+ to Fe3+ by hydrogen peroxide. Reducing agents such as ascorbic acid and DTT reduced the Fe3+-citrinin complex, but DTT did not cause reduction of Fe3+-EDTA, indicating that the redox potentials of Fe3+-citrinin and Fe3+-EDTA are not the same. The Fe2+ formed from the reduction of Fe3+-citrinin by reducing agents was not rapidly reoxidized to Fe3+ by atmospheric oxygen. Citrinin has no radical scavenger ability as demonstrated by the absence of DPPH reduction. However, a reaction between citrinin and hydrogen peroxide was observed by UV spectrum changes of citrinin after incubation with hydrogen peroxide. It was also observed that citrinin did not induce direct or reductive mobilization of iron from ferritin. These results indicate that the protective effect on iron-induced lipid peroxidation by citrinin occurs due to the formation of a redox inactive Fe3+-citrinin complex, as well as from the reaction of citrinin and hydrogen peroxide.

Individual and synergistic antioxidative actions of melatonin: studies with vitamin E, vitamin C, glutathione and desferrioxamine (desferoxamine) in rat liver homogenates.

The pharmacological effects of melatonin, vitamin E, vitamin C, glutathione and desferrioxamine (desferoxamine) alone and in combination on iron-induced membrane lipid damage in rat liver homogenates were examined by estimating levels of malondialdehyde and 4-hydroxyalkenals (MDA+4-HDA). Individually, melatonin (2.5-1600 microM), vitamin E (0.5-50 microM), glutathione (100-7000 microM) and desferrioxamine (1-8 microM) inhibited lipid peroxidation in a concentration-dependent manner. Vitamin C had both a pro-oxidative (25-2000 microM) and an antioxidative (2600-5000 microM) effect. The IC50 (concentration that reduces damage by 50%) values were 4, 10, 426, 2290 and 4325 microM for vitamin E, desferrioxamine, melatonin, glutathione and vitamin C, respectively. The synergistic actions of melatonin with vitamin C, vitamin E, and glutathione were systematically investigated. When melatonin was combined with vitamin E, glutathione, or vitamin C, the protective effects against iron-induced lipid peroxidation were dramatically enhanced. Even though melatonin was added at very low concentrations, it still showed synergistic effects with other antioxidants at certain concentrations. Furthermore, melatonin not only reversed the pro-oxidative effects of vitamin C, but its efficacy in reducing lipid peroxidation was improved when it was combined with pro-oxidative concentrations of vitamin C. The results provide new information in terms of the possible pharmacological use of the combination of melatonin and classical antioxidants to treat free radical-related conditions.

A unique antioxidant activity of phosphatidylserine on iron-induced lipid peroxidation of phospholipid bilayers.

The relationship between the antioxidant effect of acidic phospholipids, phosphatidic acid (PA), phosphatidylglycerol (PG) and phosphatidylserine (PS), on iron-induced lipid peroxidation of phospholipid bilayers and their abilities to bind iron ion was examined in egg yolk phosphatidylcholine large unilamellar vesicles (EYPC LUV). The effect of each acidic phospholipid added to the vesicles at 10 mol% was assessed by measuring phosphatidylcholine hydroperoxides (PC-OOH) and thiobarbituric acid-reactive substances. The addition of dipalmitoyl PS (DPPS) showed a significant inhibitory effect, although the other two acidic phospholipids, dipalmitoyl PA (DPPA) and dipalmitoyl PG (DPPG), did not exert the inhibition. Neither dipalmitoyl PC (DPPC) nor dipalmitoyl phophatidylethanolamine (DPPE) showed any remarkable inhibition on this system. None of the tested phospholipids affected the lipid peroxidation rate remarkably when the vesicles were exposed to a water-soluble radical generator. The iron-binding ability of each phospholipid was estimated on the basis of the amounts of iron recovered in the chloroform/methanol phase after separation of the vesicle solution to water/methanol and chloroform/methanol phases. EYPC LUV containing DPPS, DPPA, and DPPG had higher amounts of bound iron than those containing DPPC and DPPE, indicating that these three acidic phospholipids possess an iron-binding ability at a similar level. Nevertheless, only DPPS suppressed iron-dependent decomposition of PC-OOH significantly. Therefore, it is likely that these three acidic phospholipids possess a significant iron-binding ability, although this ability per se does not warrant them antioxidative activities. The ability to suppress the iron-dependent decomposition of PC-OOH may explain the unique antioxidant activity of PS.

Identification and antioxidant activity of novel chlorogenic acid derivatives from bamboo (Phyllostachys edulis).

One known and two novel antioxidant compounds have been isolated from bamboo (Phyllostachys edulis). The butanol-soluble extract of the bamboo leaves was found to have a significant antioxidant activity, as measured by scavenging the stable 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical and the superoxide anion radical (O(2)(-)) in the xanthine/xanthine oxidase assay system. Antioxidant activity-directed fractionation of the extract led to the isolation and characterization of three structural isomeric chlorogenic acid derivatives: 3-O-(3'-methylcaffeoyl)quinic acid (1), 5-O-caffeoyl-4-methylquinic acid (2), and 3-O-caffeoyl-1-methylquinic acid (3). Compounds 2 and 3 were isolated and characterized for the first time from the natural products. In the DPPH scavenging assay as well as in the iron-induced rat microsomal lipid peroxidation system, compounds 2 (IC(50) = 8.8 and 19.2 microM) and 3 (IC(50) = 6.9 and 14.6 microM) showed approximately 2-4 times higher antioxidant activity than did chlorogenic acid (IC(50) = 12.3 and 28.3 microM) and other related hydroxycinnamates such as caffeic acid (IC(50) =13.7 and 25.5 microM) and ferulic acid (IC(50) = 36.5 and 56.9 microM). Among the three compounds, compound 1 yielded the weakest antioxidant activity, and the DPPH scavenging and lipid peroxidation inhibitory activity (IC(50) = 16.0 and 29.8 microM) was lower than those of chlorogenic and caffeic acids. All three compounds exhibited both superoxide scavenging activities and inhibitory effects on xanthine oxidase. Their superoxide anion (O(2)(-)) scavenging activities (IC(50) = 1, 4.3 microM; 2, 2.8 microM; and 3, 1.2 microM) were markedly stronger than those of ascorbic acid (IC(50) = 56.0 microM), alpha-tocopherol (IC(50) > 100 microM), and other test compounds, although their inhibition effects on xanthine oxidase may contribute to the potent scavenging activity. alpha-Tocopherol exerted a significant inhibitory effect (65.5% of the control) on superoxide generation in 12-O-tetradecanoylphorbol-13-acetate-induced human promyelocytic leukemia HL-60 cells, and compound 3 showed moderate activity (36.0%). On the other hand, other compounds including 1, 2, chlorogenic acid, and other antioxidants were weakly active (24.8-10.1%) in the suppression of superoxide generation.

Lack of protective effect by intermittent hypoxia on MPTP-induced neurotoxicity in mice.

In the study we report here, several lines of evidence support the preventive action of intermittent hypoxia against oxidative injuries in CNS. Our in vitro data showed that autooxidation and iron-induced lipid peroxidation were attenuated in cortical homogenates of intermittent hypoxia-treated animals. Furthermore, our preliminary study found that iron induced oxidative injuries were abolished in rat brain after intermittent hypoxic treatment (paper submitted). Several antioxidative defensive systems improve in response to intermittent hypoxia. Since attenuation of autooxidation and iron-induced lipid peroxidation were observed in cortical homogenates of intermittent hypoxia-treated mice, the lack of prevention by intermittent hypoxia of MPTP-induced neurotoxicity may be due to the MPTP action that is not oxidative related. Together with our previous studies, in which several antioxidants were shown to successfully prevent oxidative injuries, our data here suggest that intermittent hypoxia may offer a potential treatment for preventing CNS degenerative diseases.