儿茶素类化合物的体外抗氧化作用研究

本实验通过DPPH·法、硫氰酸铁法等方法测定儿茶素清除DPPH·自由基、抗脂质过氧化和还原能力.研究结果表明儿茶素在清除自由基、抗脂质过氧化及还原能力方面均有一定作用,尤其是清除自由基和还原能力较对照品Vc强,差异性较显著;但在抗脂质过氧化方面儿茶素并未表现出剂量-效应关系,然而当加入表面活性剂后,增强了儿茶素的抗脂质过氧化活性.因此,儿茶素在清除自由基和还原能力方面均较优越,但在抗脂质过氧化方面较差,当加入适量的表面活性剂可以改善其活性.     

Aspirin restores normal baroreflex function in hypercholesterolemic rats by its antioxidative action

Besides its well-known effects on platelet aggregation, aspirin has been suggested to be an antioxidant and is also known to improve the lipid profile. In the present study we tested the hypothesis that aspirin by its antioxidant effect, improves haemodynamic profile and baroreflex sensitivity in rat model of hypercholesterolemia. Hypercholesterolemia was induced in Wistar rats by feeding 1% cholesterol rich diet for 10 weeks. Lipid profile, lipid peroxidation and reduced glutathione were estimated in serum. Haemodynamic changes and baroreflex were measured in anaesthetized rats. Hypercholesterolemic rats showed significant increase in total cholesterol, low-density lipoprotein-cholesterol (LDL-C), very low-density lipoprotein-cholesterol (VLDL-C) and atherogenic index and significant decrease in high-density lipoprotein-cholesterol (HDL-C). Significant rise in blood pressure, heart rate and attenuation of baroreflex sensitivity were also found in hypercholesterolemic rat. Aspirin in the dose of 100 mg/kg showed significant decrease in total cholesterol, LDL-C, VLDL-C and atherogenic index and significant increase in HDL-C. Aspirin treatment prevented the rise in blood pressure, heart rate and significantly improved baroreflex sensitivity in hypercholesterolemic rats. Hypercholesterolemic rats showed free radical generation, evident by a significant increase in serum lipid peroxidation and significant reduction in serum reduced glutathione content. Aspirin treatment significantly decreased lipid peroxidation and significantly increased reduced glutathione content. We have demonstrated that aspirin improves baroreflex response and prevents the rise in blood pressure and heart rate possibly by reducing sympathetic activity due to its antioxidant effect in experimentally induced hypercholesterolemic rats.     

Effect of tetracycline on pancreas and liver function of adult male albino rats

The effect of tetracycline, at two doses of 50 and 200 mg kg(-1) daily, was studied on pancreatic and liver tissue function for 14 and 21 days in adult male albino rats. For pancreatic function the parameters studied were content of amylase and lipase in pancreas, serum amylase and lipase, serum glucose and faecal fat excretion. For liver function, liver specific enzymes in serum, namely alanine amino transaminase, aspartate amino transaminase and lactate dehydrogenase were estimated. In addition, total lipid, antiperoxidative enzymes and lipid peroxidation were measured in pancreas and liver. The content of amylase and lipase in pancreas showed a small but significant decrease in the rats given 50 mg kg(-1) for 21 days and the decrease was much more significant in those receiving the 200 mg kg(-1) dose. In pancreas free radical levels show a significant increase and reduced glutathione shows a substantial decrease at the 50 mg kg(-1) level and a significant change in these parameters was observed at the 200 mg kg(-1) dose. Antioxidant enzymes, superoxide dismutase, glutathione peroxidase, glutathione reductase and catalase, showed a small but significant decrease in the pancreas of the rats treated with 50 mg kg(-1) tetracycline. A significant decrease in the antioxidant enzymes level was observed at the 200 mg kg(-1) dose. In the liver, free radical levels and reduced glutathione were within the normal range at the 50 mg kg(-1) level and significant changes were observed at 200 mg kg(-1). The antioxidant status was unaffected in liver after treatment with tetracycline at the 50 mg kg(-1) level and a significant decrease was observed at the higher dose. Our results reveal the safe nature of tetracycline with respect to the liver at the lower dose tested, whereas, both the higher and lower doses seem to have detrimental effect on the pancreas as revealed by the rise in free radical levels and decrease in the antioxidant enzyme levels.     

Relative antioxidant capacities of propofol and its main metabolites

The antioxidant activity of propofol, a widely used anesthetic, has previously been demonstrated, but no study has focused on propofol metabolites although propofol undergoes extensive metabolism. In the present study, the antioxidant properties of propofol and its metabolites were studied by measuring malondialdehyde (MDA) produced from lipid peroxidation by microsomes triggered with several free radical generating systems. True MDA determination was performed using a specific high performance liquid chromatography technique. Gas chromatography–isotope ratio mass spectrometry methodology was also used to assess the antioxidant action in a homogeneous aqueous environment. Propofol, 2,6-di-isopropyl-1,4-quinol (1,4-quinol) metabolite and 3,5-di-tert-butyl-4-hydroxytoluene markedly inhibit lipid peroxidation at concentrations lower than 5 µM. The binding of the glucuroconjugated moiety to either one of two hydroxyl groups of 1,4-quinol lowers the radical scavenging activity. Propofol glucuronide did not exert any radical scavenging activity except when peroxidation was induced with tert-butylhydroperoxide. Our data demonstrate that propofol and its metabolites inhibit lipid peroxidation at concentrations similar to those measured in human plasma during anesthesia. Their antioxidant efficiency is influenced by several factors, including the type of radical initiator involved and the site of radical production.     

Potential in vitro antioxidant and protective effects of Gymnema montanum H. on alloxan-induced oxidative damage in pancreatic β-cells, HIT-T15

The present study describes the antioxidant activities of ethanol extract from Gymnema montanum (GLEt) which is an endemic plant of India. Antioxidant activity of the GLEt was studied in vitro based on scavenging of hydroxyl radicals, superoxide anions, nitric oxide, hydrogen peroxide, peroxynitrite, reducing power and inhibition of lipid peroxidation estimated in terms of thiobarbituric acid reactive substances (TBARS). Further, we examined its protective effect against alloxan-induced oxidative stress in pancreatic β-cells, HIT-T15 by measuring the free radical generation, malonaldehyde formation and antioxidant levels such as CAT, GPx and GSH. Results showed that G. montanum leaves exhibited significant antioxidant activities measured by various in vitro model systems. The HIT-T15 cell line studies showed the tendency of GLEt to increase antioxidant levels meanwhile decrease the free radical formation and inhibit the lipid peroxidation. The antioxidant activity was found to be well correlated with the phenolic phytochemicals present in the extract. GC–MS analyses revealed the presence of few phenolic compounds in the extract. As this plant has already been demonstrated for a variety of medicinal properties from our laboratory, results of this study suggest that G. montanum is an interesting source for antioxidant compounds and useful for various therapeutic applications.     

Effect of diltiazem isomers and thiamine on piglet liver microsomal peroxidation using dichlorofluorescein.

PURPOSE: We investigated a potential hepatoprotective role of d-cis diltiazem, l-cis diltiazem, thiamine and the combination d-cis diltiazem and thiamine against lipid peroxidation in a piglet liver microsomal model. A modified in vitro dichlorofluorescein assay was developed to assess the extent of peroxidative damage induced by reactive oxygen species in the piglet liver microsomal fraction. METHODS: Microsomal membrane fraction, obtained from 3 week old female piglets, was treated with either the biologically vasoactive d-cis diltiazem or the non-vasoactive stereoisomer l-cis diltiazem (5-1000 microM) for 1 hour at 37 degrees C followed by one hour incubation with the free radical generator AAPH (2,2'-azobis-(2-amidinopropane) dihydrochloride; 1 mM) to initiate lipid peroxidation. In a separate study, piglet liver microsomes were pre-treated with d-cis diltiazem (50 or 500 microM) and thiamine (10-100 microM) to assess the antioxidant activity of the combination. RESULTS: A dose dependant inhibition of membrane lipid peroxidation was observed with d-cis diltiazem (p<0.05) but not with l-cis diltiazem, suggesting that diltiazem is stereospecific in protecting against microsomal lipid peroxidation. Combining diltiazem with thiamine further protected microsomes against lipid peroxidation compared to use of individual drugs. CONCLUSION: We conclude that diltiazem and the combination of diltiazem and thiamine offers a hepatoprotective effect against free radicals.     

Assessment of the kinetics of the antioxidative capacity of topical antioxidants

While there is at least one standardized test available for evaluating the antioxidant capacity of cosmetic formulations, the authors proposed a new in vivo method to determine kinetics of squalene (SQ) photo-oxidation products (squalene monohydroperoxide, SQmOOH) as a reliable method with which to evaluate antioxidant capacity of a cosmetic formulation. Topical antioxidant formulation was applied on the foreheads of 30 volunteers. Sebum samples were collected before application of topical antioxidant and after one hour, three hours and five hours from the application of topical antioxidant. One half of the sebutape was irradiated and SQmOOH/SQ ratios in the skin lipid were analyzed using HPLC method. These results showed protective action of the topical antioxidant formulation against skin lipid peroxidation with a significant reduction of the quantity of SQmOOH (P<0.0001). Determination of the kinetics of squalene peroxidation is a reliable in vivo method in the evaluation of antioxidant capacity of cosmetic formulations.     

两种茶多酚化学改性制备的脂溶性茶多酚抗氧化性能研究

目的对茶多酚不同改性方法制备的脂溶性茶多酚（LTP）的抗氧化性能研究并与其他抗氧化剂比较。方法以紫外分析、薄层层析、化学发光、氧化还原滴定等方法分别考察了两种改性方法制备的LTP及其他抗氧化剂的紫外表征、脂溶性、抗自由基、抗超氧负离子及抗油脂脂质过氧化性能。结果两种改性方法制备的LTP具有不同的紫外表征及抗氧化特性,且碳酰化LTP性能更优于氧酰化LTP。这两种LTP都具有与TBHQ相近的抗氧化能力,都优于除TBHQ外的其他抗氧化剂。结论两种改性方法制备的LTP都可作为脂相系统抗氧化剂。     

Evaluation of alpha-tocopherol, probucol and ascorbic acid as suppressors of digoxin induced lipid peroxidation

Protective effects of three free radical scavengers, tocopherol (TOC), probucol (PR) and ascorbic acid (AA), on cardiotonic glycoside digoxin (DIG) induced lipid peroxidation in goat liver homogenate, have been studied by measuring malondialdehyde and glutathione contents as indicator parameters. The level of reduced glutathione decreased vis-a-vis malondialdehyde content increased in the drug treated samples in comparison with the controls. This suggests that DIG may have significant lipid peroxidation induction capacity. Considering lipid peroxidation as a toxicity mediating process, this may be related to the toxic potential of the drug. When the liver homogenate samples were incubated with antioxidant (TOC/PR/AA) in conjunction with the drug (DIG), lipid peroxidation was suppressed as indicated by increased level of reduced glutathione and decreased level of malondialdehyde in comparison with those of drug treated samples. This indicates that TOC, PR and AA may have considerable suppressive action on DIG induced lipid peroxidation. Thus, these antioxidants merit further extensive study to explore their potential in reducing DIG induced toxicity that may be mediated by free radical mediated process.     

褪黑素拮抗鼠肝线粒体自由基产生的实验研究

目的观察褪黑素拮抗氧自由基和对膜脂质过氧化损伤的保护作用。方法用电子自旋共振技术，以ＤＭＰＯ和４－ＰＯＢＮ为捕集剂，捕集Ｆｅｎｔｏｎ反应产生的羟自由基和Ｆｅ２＋启动的鼠肝线粒体膜脂质过氧化产生的脂类自由基，以脂肪酸自旋标记物５－Ｄｏｘｙｌ和１６－Ｄｏｘｙｌ标记线粒体膜，研究脂质过氧化损伤后膜流动性的变化。结果褪黑素对羟自由基和脂类自由基有良好的清除作用，５０％清除浓度分别为１８６μｍｏｌ·Ｌ－１和４５０μｍｏｌ·Ｌ－１，而且在５００μｍｏｌ·Ｌ－１浓度范围内能防止脂质过氧化引起的线粒体膜流动性降低。结论褪黑素是一个有效的抗氧化剂，能防止生物膜的脂质过氧化损伤。     

Antioxidative action of aspirin on endothelial function in hypercholesterolaemic rats

The role of aspirin on vascular endothelial changes during hypercholesterolaemia prior to development of actual atherosclerotic lesions is not known. Therefore, in the present study, we tested the hypothesis that aspirin by its antioxidant action improves endothelial function in a rat model of hypercholesterolaemia. Hypercholesterolaemia was induced in Wistar rats by feeding a 1% cholesterol-rich diet for 10 weeks. Lipid profile, lipid peroxidation and reduced glutathione were estimated in serum. Endothelial function and beta(2)-adrenoceptor activity was tested by studying the dose-response relationship of acetylcholine and isoproterenol, respectively, on isolated aortic tissues in an organ bath setup. Hypercholesterolaemic rats showed a significant increase in total cholesterol, low-density lipoprotein cholesterol (LDL-C) and very low-density lipoprotein cholesterol (VLDL-C), and a significant fall in high-density lipoprotein cholesterol (HDL-C) compared to the control rats. Isolated aortic tissues from hypercholesterolaemic rats showed endothelial dysfunction and decreased sensitivity to beta(2)-adrenoceptor. Treatment with aspirin was associated with a fall in total cholesterol, LDL-C and VLDL-C, and a significant rise in serum HDL-C. Aspirin treatment also restored endothelial function and beta(2)-adrenoceptor activity. Hypercholesterolaemic rats showed free radical generation, evident by increase in serum lipid peroxidation and reduction in serum reduced glutathione content compared to the control rats. Aspirin treatment was associated with reduction in free radical stress evident by decreased lipid peroxidation and significantly prevented reduction in glutathione content compared to hypercholesterolaemic controls. Aspirin improves endothelial function and beta(2)-adrenoceptor activity during experimentally induced hypercholesterolaemia in rats, possibly due to an antioxidant effect.     

Protective effect of black tea against ethanol-induced oxidative modifications of liver proteins and lipids

OBJECTIVE: Black tea has been recently ascertained as a source of water-soluble antioxidants that may enhance cellular antioxidant abilities. The present study was designed to investigate the efficacy of the preventive effect of black tea on oxidative modifications of liver lipids and proteins of 2-month-old rats intoxicated chronically (28 days) with ethanol. METHOD: Lipid peroxidation was estimated by measurement of lipid hydroperoxides, malondialdehyde, and 4-hydroxynonenal by high-performance liquid chromatography (HPLC) and by spectrophotometric determination of conjugated dienes. The markers of protein oxidative modification products-bistyrosine and tryptophan-were quantified by spectrofluorimetry, whereas levels of amino, sulfhydryl, and carbonyl groups were estimated spectrophotometrically. RESULTS: Ethanol intoxication caused changes in liver antioxidant abilities that led to the generation of oxidative stress and, consequently, to the significant increase in products of lipid and protein oxidative modification. Enhanced lipid peroxidation was confirmed by assessment of the concentration of lipid peroxidation products measured at all examined levels. Protein modifications were evidenced by increase in levels of bistyrosine and carbonyl groups and by decrease in concentration of tryptophan and levels of sulfhydryl and amino groups. The metabolic consequences of oxidative modifications of lipids and proteins were reduced by cathepsin B activity and translocation of this lysosomal protease into cytosol as well as markers of liver damage-alanine aminotransferase (ALT) and aspartate aminotransferase (AST)-into the blood serum. Administration of black tea to ethanol-intoxicated rats partially protected antioxidant parameters and, remarkably, prevented the significant increase in concentrations of all measured lipid peroxidation products. Moreover, the levels of markers of the protein-modification process were similar to those of the control group. Protection of biological membranes by black tea prevents changes in the permeability of these membranes and translocation of the examined enzymes. CONCLUSIONS: Our findings indicate that black tea protects proteins and lipids against oxidative modification induced by chronic ethanol intoxication, which preserves changes in redox and proteolytic homeostasis.     

Incorporation in polymeric nanocapsules improves the antioxidant effect of melatonin against lipid peroxidation in mice brain and liver

It has been recently shown that the association of melatonin with polymeric nanoparticles causes a significant increase of the in vitro effect against lipid peroxidation. Hence, the aim of the present study was to compare the in vivo acute antioxidant effect of intraperitoneal administration of melatonin-loaded polysorbate 80-coated nanocapsules with that of melatonin aqueous solution in mice brain (frontal cortex and hippocampus) and liver. The lipid peroxidation through thiobarbituric acid reactive substance levels, the total antioxidant reactivity (luminol-enhanced chemiluminescence) and the free radical levels (formed dichlorofluorescein) has been carried out. Our results show that a single melatonin aqueous solution injection exerted no antioxidant activity in the evaluated range, while the administration of the melatonin-loaded polysorbate 80-coated nanocapsules caused a marked reduction on lipid peroxidation levels in all studied tissues. No differences on free radical content were found in the tissues. The melatonin-loaded nanocapsules also increased the total antioxidant reactivity in the hippocampus. These in vivo results are in accordance with our previous in vitro findings and confirm the hypothesis that polymeric nanocapsules improve the antioxidant effect of melatonin against lipid peroxidation.     

Effects of chloroquine on lysosomal enzymes, NADPH-induced lipid peroxidation, and antioxidant enzymes of rat retina

Chloroquine (1, 5 and 10 mg/kg), given in acute and in chronic (7 and 15 days) treatment schedules, caused characteristic alterations in the lysosomal enzyme system, antioxidant enzymes, NADPH-induced lipid peroxidation, and glutathione content in the retina of the rat. One-half hour and four hours after chloroquine administration, increased free activities of lysosomal enzymes and NADPH-induced lipid peroxidation were observed, associated with a decrease in tissue glutathione content. In contrast to the acute effect, chloroquine, given in 7- and 15-day treatment schedules, had no significant effect on the lysosomal enzyme system, while at the same time a normalization or a decrease in NADPH-induced lipid peroxidation, associated with a significant increase in tissue glutathione content, was noted. Catalase and peroxidase activities were decreased after both the acute and the daily treatment schedules. Superoxide dismutase activity, although increased in the high dose acute study, appeared otherwise little affected by chloroquine treatment.     

Free radical scavenger and lipid peroxidation inhibiting effects of medicinal plants used in phytotherapy

Epidemiological and clinical studies have proved the beneficial effect of bioactive compounds of vegetables and medicinal plants used in phytotherapy on prevention of several diseases. Beyond the well-known natural antioxidants, such as vitamins, other natural substances can function as antioxidants. In 1992 the Saas Fee Declaration was published by leader nutritionist and biochemists underlining the importance of prevention in health maintenance based on scientific studies with natural compounds. According to the declaration the antioxidants are the main active and beneficial components. Authors joining with the spirit of Saas Fee Declaration have worked out a complex examination system to study the antioxidant, free radical scavenging and inhibitory effects on lipid peroxidation of isolated components, natural plant extracts and herbal preparations. The members of the system are the followings: hydrogendonating ability, reducing power, chelating activity, free radical scavenging activities measured by chemiluminescence techniques, electron paramagnetic resonance / spin trapping studies, inhibition of lipid peroxidation induced in rat brain / liver microsomes, consequencies and treatment of experimental hyperlipidemia, morphological and histological studies. Only one measurement cannot give enough information about the antioxidant properties of the products. Complex in vitro examination of a novel antioxidant can draw pictures of correlation between the chemical structure and antioxidant effect, the mechanism of its favourable effect and its presumable role in prevention of lipid peroxidation. With the use of these results planning and execution of in vivo examinations should be more precise, practical and essential.     

Spirulina fusiformis provides protection against mercuric chloride induced oxidative stress in Swiss albino mice

Oxidative stress induced by mercuric chloride (5 mg/kg body weight i.p.) in mice substantially increases the lipid peroxidation level along with corresponding decrease in the reduced glutathione and various antioxidant enzymes in liver and increase in serum transaminases activity. Supplementation of Spirulina (800 mg/kg body weight orally, in olive oil, along with mercuric chloride) for 40 days resulted in decreased LPO level, serum glutamate oxaloacetate and serum glutamate pyruvate transaminase activity along with increase in liver GSH level. The activities of antioxidants enzymes superoxide dismutase, catalase and glutathione-S-transferase were also concomitantly restored to near normal level by Spirulina supplementation to mercuric chloride intoxicated mice. The results clearly demonstrate that Spirulina treatment augments the antioxidants defense mechanism in mercuric chloride induced toxicity and provides evidence that it may have a therapeutic role in free radical mediated diseases.     

The effects of carbamazepine and valproic acid on the erythrocyte glutathione, glutathione peroxidase, superoxide dismutase and serum lipid peroxidation in epileptic children.

Some epileptic drugs may change antioxidant enzyme activities in humans and experimental animals. Recent studies suggest that membrane lipid peroxidation may be causally involved in some forms of epilepsy, and the differences are reported in free radical scavenging enzyme levels. GSHpX, SOD, GSH are important parameters of antioxidant defence mechanisms. This study was undertaken to evaluate the effects of valproic acid and carbamazepine (CBZ) therapy on erythrocyte glutathione (GSH), glutathione peroxidase (GSHpX), superoxide dismutase (SOD) and lipid peroxidation. During the treatment with VPA or CBZ, the erythrocyte GSHpX and GSH levels of epileptic children were significantly changed as compared to those of health control subjects. The mean levels of serum lipid peroxidation and erythrocyte superoxide dismutase were not statistically different from controls. The methods used for investigation of glutathione peroxidase, superoxide dismutase, glutathione and serum lipid peroxidation were all based on spectrophotometric measurement.     

Biochemical studies on a novel antioxidant from lemon oil and its biotechnological application in cosmetic dermatology

It is generally accepted that lipid peroxides play an important role in the pathogenesis of free radical-induced cellular injury and that antioxidants such as glutathione, ascorbic acid and alpha-tocopherol are vital in cellular defense against endogenous and exogenous oxidants. The purpose of this study was to investigate the effectiveness of a natural compound, derived from lemon oil extract, in controlling free radical-induced lipid peroxidation and tissue damage in the skin. We provide evidence that a compound isolated from lemon oil, which we have called Lem1, is endowed with a strong antioxidant activity and that it is capable of inhibiting free radical-mediated reactions, evaluated by both in vitro and in vivo biochemical systems. The present study aims to give a preclinical perspective on the biochemical properties of Lem1, a natural compound, as well as to provide a better understanding of the endogenous antioxidant potential of skin and the real validity of a natural antioxidant biotechnology in the antiaging management of the skin.     

Determination of the antioxidant capacity of samples of different types of tea,or of beverages based on tea or other herbal products,using a superoxide dismutase biosensor

Research was performed to experimentally evaluate the antioxidant capacity of different plant products sold by herbalists (ginger, dog rose, ginseng and camomile) and of several types of tea (ordinary tea, green tea, detheinated tea, lemon and peach flavoured tea) using a superoxide dismutase (SOD) biosensor recently developed by the present authors. Measurements were carried out by comparing biosensor response to the superoxide radical produced in solution using the xanthine-xanthine oxidase system, both in the presence and absence of the antioxidant sample considered. Precision of antioxidant capacity measures for herbal products and for non diluted samples was good, generally with a R.S.D.%< or =10% and a LOD value about 0.1 for relative antioxidant capacity. Also a "pool" of polyphenols from different tea samples was measured using a tyrosinase biosensor (LOD approximately 2 microM).     

Influence of naringenin on oxytetracycline mediated oxidative damage in rat liver

Naringenin is a naturally occurring citrus flavanone, which has been reported to have a wide range of pharmacological properties. The present work was carried out to evaluate the effect of naringenin on antioxidant and lipid peroxidation status in liver of oxytetracycline-intoxicated rats. Intraperitonial administration of oxytetracycline 200 mg/kg for 15 days resulted a significant elevation in serum hepatospecific markers such as aspartate transaminase, alanine transaminase, alkaline phosphatase, lactate dehydrogenase, and bilirubin and the levels of lipid peroxidation markers (thiobarbituric acid reactive substances (TBARS) and lipid hydroperoxides) in liver. Oxytetracycline also caused a significant reduction in the activities of superoxide dismutase, catalase, glutathione peroxidase, reduced glutathione (GSH), vitamin C and vitamin E in liver. Oral administration of naringenin (50 mg/kg b.w.t.) with oxytetracycline significantly decreased the activities of serum aspartate transaminase, alanine transaminase, alkaline phosphatase, lactate dehydrogenase and the levels of bilirubin along with significant decrease in the levels of lipid peroxidation markers in the liver. In addition, naringenin significantly increased the activities of superoxide dismutase, catalase and GSH peroxidase as well as the level of GSH, vitamin C and vitamin E in liver of the oxytetracycline-treated rats. Our results demonstrate that naringenin exhibited antioxidant property and decrease the lipid peroxidation against oxytetracycline-induced oxidative stress in liver.