Peroxide-induced Oxidative Damage Research Articles

Dihydromyricetin protects endothelial cells from hydrogen peroxide-induced oxidative stress damage by regulating mitochondrial pathways.

Dihydromyricetin (DMY) is the most abundant ingredient in vine tea. Here, we investigated the cytoprotective effects and possible mechanisms of DMY on hydrogen peroxide (H2O2)-induced oxidative stress damage in human umbilical vein endothelial cells (HUVECs). The percentage of cell viability was evaluated using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. We determined the antioxidant properties of DMY by measuring the activity of superoxide dismutase (SOD) and malondialdehyde (MDA). Flow cytometry was used to measure apoptosis in HUVECs that were double stained with Hoechst 33342 and propidium iodide (PI). The generation of intracellular reactive oxygen species (ROS) was measured in 2',7'-dichlorofluorescin diacetate (DCFH-DA)-loaded HUVECs using a fluorescent microscope. Moreover, the expression of apoptosis-related proteins was determined by Western blotting. In addition, the release of nitric oxide (NO) was analyzed using a commercial kit. HUVECs treated with H2O2 had a notable decrease in cell viability that was attenuated when cells were pretreated with DMY (37.5-300μM). DMY pretreatment significantly attenuated H2O2-induced apoptosis in HUVECs and inhibited intracellular ROS overproduction. Finally, pretreatment of cells with DMY prior to H2O2 exposure resulted in the inhibition of p53 activation, followed by the regulation of the expression of Bcl-2 and Bax, the release of cytochrome c, the cleavage (activation) of caspase-9 and caspase-3, and then the suppression of PARP cleavage in H2O2-induced HUVECs. Our study is the first to report that DMY can protect HUVECs from oxidative stress damage, an effect that is mediated by the mitochondrial apoptotic pathways.

Protective Effect of Total Phenolic Compounds from Inula helenium on Hydrogen Peroxide-induced Oxidative Stress in SH-SY5Y Cells.

Inula helenium has been reported to contain a large amount of phenolic compounds, which have shown promise in scavenging free radicals and prevention of neurodegenerative diseases. This study is to investigate the neuroprotective effects of total phenolic compounds from I. helenium on hydrogen peroxide-induced oxidative damage in human SH-SY5Y cells. Antioxidant capacity of total phenolic compounds was determined by radical scavenging activity, the level of intracellular reactive oxygen species and superoxide dismutase activity. The cytotoxicity of total phenolic compounds was determined using a cell counting kit-8 assay. The effect of total phenolic compounds on cell apoptosis due to hydrogen peroxide-induced oxidative damage was detected by Hoechst 33258 and Annexin-V/PI staining using fluorescence microscope and flow cytometry, respectively. Mitochondrial function was evaluated using the mitochondrial membrane potential and mitochondrial ATP synthesis by JC-1 dye and high performance liquid chromatography, respectively. It was shown that hydrogen peroxide significantly induced the loss of cell viability, increment of apoptosis, formation of reactive oxygen species, reduction of superoxide dismutase activity, decrease in mitochondrial membrane potential and a decrease in adenosine triphosphate production. On the other hand, total phenolic compounds dose-dependently reversed these effects. This study suggests that total phenolic compounds exert neuroprotective effects against hydrogen peroxide-induced oxidative damage via blocking reactive oxygen species production and improving mitochondrial function. The potential of total phenolic compounds and its neuroprotective mechanisms in attenuating hydrogen peroxide-induced oxidative stress-related cytotoxicity is worth further exploration.

Singlet-oxygen-derived products from linoleate activate Nrf2 signaling in skin cells

Linoleates are required for normal mammalian health and development, but they are also prone to oxidation, resulting in biologically active metabolites such as hydroxyoctadecadienoic acids (HODEs). To investigate the biological activity of 9-EZ-HODE, 10-EZ-HODE, 12-ZE-HODE, and 13-ZE-HODE, the metabolites of singlet-oxygen-derived products from linoleates, we assessed adaptive cytoprotection in HaCaT skin cells. Treating HaCaT cells with sublethal concentrations of 10-EZ-HODE and 12-ZE-HODE, which are singlet-oxygen-mediated specific oxidation metabolites of linoleates, but not 9-EZ-HODE and 13-ZE-HODE, caused resistance to hydrogen peroxide-induced oxidative damage. Microarray analysis of HaCaT cells revealed that 10-EZ-HODE and 12-ZE-HODE induced cellular antioxidant genes that are responsive to nuclear factor-erythroid 2 p45-related factor 2 (Nrf2), such as heme oxygenase-1 and glutathione synthesis enzymes. Although 10-EZ-HODE and 12-ZE-HODE did not induce Nrf2 mRNA, treatment with these metabolites increased the intranuclear expression of Nrf2. These results suggest that 10-EZ-HODE and 12-ZE-HODE initiate adaptive responses that reduce the damage caused by oxidative stress.

Hydrogen Peroxide-Induced Oxidative Damage in Human Chondrocytes: The Prophylactic Effects of Hypericum Perforatum Linn Extract on Deoxyribonucleic acid Damage, Apoptosis and Matrix Remodeling by a Disintegrin-Like and Metalloproteinase With Thrombospondin Motifs Proteinases

1Department of Medical Biology, Medical Faculty of Turgut Ozal University, Ankara, Turkey 2Department of Medical Biology, Medical Faculty of Ankara University, Ankara, Turkey 3Department of Biology Education, Gazi University, Faculty of Education, Ankara, Turkey 4Department of Medical Biochemistry, Medical Faculty of Dumlupinar University, Kutahya, Turkey 5Department of Chemistry, Ankara Regional Office of Council of Forensic Medicine, Ankara, Turkey 6Department of Medical Biochemistry, Medical Faculty of Hacettepe University, Ankara, Turkey

Evaluating the effects of galbanic acid on hydrogen peroxide-induced oxidative DNA damage in human lymphocytes.

Ferula szowitsiana has been widely used for medicinal purposes around the world. The anti-oxidant effect of F. szowitsiana had been proved. The current study aims to determine the protective effects of galbanic acid, a sesquiterpene coumarin from F. szowitsiana, against hydrogen peroxide (H2O2) - induced oxidative DNA damage in human lymphocytes. Human lymphocytes were incubated with H2O2 (0, 25, 50, 100, and 200 µM), galbanic acid (200 and 400 µM) and a combination of galbanic acid (200 and 400 µM) and H2O2 (25 µM) at 4 C for 30 minutes. Solvents of galbanic acid without H2O2 were used as negative controls. The findings of this study demonstrated that H2O2 exposure leads to a significant concentration-dependent increase in DNA damage. Galbanic acid did not cause DNA damage compared with the control cells. Data showed that galbanic acid does not have a protective effect against H2O2-induced oxidative DNA damage in human lymphocytes. According to the results, it is concluded that the capability of F. szowitsiana in reducing reactive oxygen species and the anti-inflammatory property of its methanolic extract may be due to its other ingredients.

Protective Effects of Quercetin Derivatives against Hydrogen Peroxide-Induced Oxidative Damage in PC-12 Cells

In order to search for new structural modification strategies on quercetin, we have designed and synthesized a series of quercetin derivatives. Several novel quercetin derivatives displayed potent protect effect on H2O2-induced injury in PC12 cells. In the recent study, we investigated the effect of 3,3',4',5,7-pentahydroxyflavone 2-(3,4-dihydroxyphenyl)-3,5,7-trihydroxy-4H-1-benzopyran-4-one (HPS5) on the apoptosis of PC12 cells in vitro. We used neuronal PC12 cell line to study the regulation role of HPS5 in H2O2 induced cell apoptosis. MTT assay was used for detection the proliferation of PC12 cells upon H2O2 treatment. PC12 cell nuclear morphological change was detected with Hoechst 33258 staining. The antioxidative capacity was judged by SOD determinations. The protein levels of Bax and Bcl-2 were deteanined by Western blotting. Our results demonstrated that Quercetin derivatives HPS5 can prevent and protect against H2O2-induced injury in PC12 cells. Together, our studies provided new insights activities of quercetin, and may contribute to pharmacological study of quercetin in future research.

Geniposide and its iridoid analogs exhibit antinociception by acting at the spinal GLP-1 receptors

We recently discovered that the activation of the spinal glucagon-like peptide-1 receptors (GLP-1Rs) by the peptidic agonist exenatide produced antinociception in chronic pain. We suggested that the spinal GLP-1Rs are a potential target molecule for the management of chronic pain. This study evaluated the antinociceptive activities of geniposide, a presumed small molecule GLP-1R agonist. Geniposide produced concentration-dependent, complete protection against hydrogen peroxide-induced oxidative damage in PC12 and HEK293 cells expressing rat and human GLP-1Rs, but not in HEK293T cells that do not express GLP-1Rs. The orthosteric GLP-1R antagonist exendin(9-39) right-shifted the concentration–response curve of geniposide without changing the maximal protection, with identical pA2 values in both cell lines. Subcutaneous and oral geniposide dose-dependently blocked the formalin-induced tonic response but not the acute flinching response. Subcutaneous and oral geniposide had maximum inhibition of 72% and 68%, and ED50s of 13.1 and 52.7 mg/kg, respectively. Seven days of multidaily subcutaneous geniposide and exenatide injections did not induce antinociceptive tolerance. Intrathecal geniposide induced dose-dependent antinociception, which was completely prevented by spinal exendin(9-39), siRNA/GLP-1R and cyclic AMP/PKA pathway inhibitors. The geniposide iridoid analogs geniposidic acid, genipin methyl ether, 1,10-anhydrogenipin, loganin and catalpol effectively inhibited hydrogen peroxide-induced oxidative damage and formalin pain in an exendin(9-39)-reversible manner. Our results suggest that geniposide and its iridoid analogs produce antinociception during persistent pain by activating the spinal GLP-1Rs and that the iridoids represented by geniposide are orthosteric agonists of GLP-1Rs that function similarly in humans and rats and presumably act at the same binding site as exendin(9-39).

Antioxidative effects of fermented sesame sauce against hydrogen peroxide-induced oxidative damage in LLC-PK1 porcine renal tubule cells

Antioxidative effects of fermented sesame sauce against hydrogen peroxide-induced oxidative damage in LLC-PK1 porcine renal tubule cells

Antioxidative effects of fermented sesame sauce against hydrogen peroxide-induced oxidative damage in LLC-PK1 porcine renal tubule cells.

BACKGROUND/OBJECTIVESThis study was performed to investigate the in vitro antioxidant and cytoprotective effects of fermented sesame sauce (FSeS) against hydrogen peroxide (H2O2)-induced oxidative damage in renal proximal tubule LLC-PK1 cells.MATERIALS/METHODS1,1-diphenyl-2-picrylhydrazyl (DPPH), hydroxyl radical (•OH), and H2O2 scavenging assay was used to evaluate the in vitro antioxidant activity of FSeS. To investigate the cytoprotective effect of FSeS against H2O2-induced oxidative damage in LLC-PK1 cells, the cellular levels of reactive oxygen species (ROS), lipid peroxidation, and endogenous antioxidant enzymes including catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GSH-px) were measured.RESULTSThe ability of FSeS to scavenge DPPH, •OH and H2O2 was greater than that of FSS and AHSS. FSeS also significantly inhibited H2O2-induced (500 µM) oxidative damage in the LLC-PK1 cells compared to FSS and AHSS (P < 0.05). Following treatment with 100 µg/mL of FSeS and FSS to prevent H2O2-induced oxidation, cell viability increased from 56.7% (control) to 83.7% and 75.6%, respectively. However, AHSS was not able to reduce H2O2-induced cell damage (viability of the AHSS-treated cells was 54.6%). FSeS more effectively suppressed H2O2-induced ROS generation and lipid peroxidation compared to FSS and AHSS (P < 0.05). Compared to the other sauces, FSeS also significantly increased cellular CAT, SOD, and GSH-px activities and mRNA expression (P < 0.05).CONCULUSIONSThese results from the present study suggest that FSeS is an effective radical scavenger and protects against H2O2-induced oxidative damage in LLC-PK1 cells by reducing ROS levels, inhibiting lipid peroxidation, and stimulating antioxidant enzyme activity.

Antioxidant Effect of Lippia alba (Miller) N. E. Brown.

Lippia alba is a shrub found in all regions of Brazil and other countries in South and Central America. L. alba exhibits variability among its different accessions, showing differences in morphology and in the composition of its essential oil. This study evaluated the phenolic profiles and the antioxidant activities of seven different accessions of L. alba. The seven accessions of L. alba studied exhibited an important phenolic content, and all accessions demonstrated antioxidant activity with different efficacies. The main flavonoids in all accessions were apigenin, luteolin, naringin and rutin. The Santa Vitória do Palmar accession exhibited higher naringin and total phenolic content. This extract was able to reduce hydrogen peroxide-induced oxidative damage in tissue homogenates of cerebellum, cerebral cortex, hippocampus and liver of Wistar rats.

Zingerone Protects Against Stannous Chloride-Induced and Hydrogen Peroxide-Induced Oxidative DNA Damage In Vitro

In this paper, we report the dose-dependent antioxidant activity and DNA protective effects of zingerone. At 500μg/mL, the DPPH radical scavenging activity of zingerone and ascorbic acid as a standard was found to be 86.7 and 94.2% respectively. At the same concentration, zingerone also showed significant reducing power (absorbance 0.471) compared to that of ascorbic acid (absorbance 0.394). The in vitro toxicity of stannous chloride (SnCl2) was evaluated using genomic and plasmid DNA. SnCl2-induced degradation of genomic DNA was found to occur at a concentration of 0.8mM onwards with complete degradation at 1.02mM and above. In the case of plasmid DNA, conversion of supercoiled DNA into the open circular form indicative of DNA nicking activity was observed at a concentration of 0.2mM onwards; complete conversion was observed at a concentration of 1.02mM and above. Zingerone was found to confer protection against SnCl2-induced oxidative damage to genomic and plasmid DNA at concentrations of 500 and 750μg/mL onwards, respectively. This protective effect was further confirmed in the presence of UV/H2O2-a known reactive oxygen species (ROS) generating system-wherein protection by zingerone against ROS-mediated DNA damage was observed at a concentration of 250μg/mL onwards in a dose-dependent manner. This study clearly indicated the in vitro DNA protective property of zingerone against SnCl2-induced, ROS-mediated DNA damage.

Protective effect of polypeptides from larva of housefly (Musca domestica) on hydrogen peroxide-induced oxidative damage in HepG2 cells

Housefly (Musca domestica) is an important medical insect and its larva is an ideal high protein food source. We isolated from housefly larvae the polypeptides hydrolyzed by neutral protease (PHNP), and investigated the protective effect of PHNP on hydrogen peroxide (H₂O₂)-induced oxidative damage in HepG2 cells. Cells exposed to H₂O₂ showed a marked decrease in proliferation and intracellular superoxide dismutase (SOD) activity, and a significant increase in reactive oxygen species (ROS) level and malondialdehyde (MDA) content. H₂O₂ also caused apoptosis and mitochondrial dysfunction including mitochondrial fragmentation and the loss of mitochondrial membrane potential. Pretreatment with PHNP at concentrations of 2.5, 5, 10 μg/mL blocked these H₂O₂-induced cellular events in a dose-dependent manner. The effect of PHNP at 10 μg/mL is equal to that of ascorbic acid at 10 μM. In summary, PHNP has a protective effect against H₂O₂-induced oxidative injury in cells due to its ability to decrease intracellular ROS and elevate antioxidant enzyme activities.

치콘 추출물의 항산화 활성

본 연구는 치콘 추출물의 항산화 효능을 확인하고자 물과 에탄올로 추출하였다. 치콘에 포함된 총 폴리페놀 함량을 측정한 결과, 에탄올 추출물(37.3±5.2 ㎎/GAE/g extract)과 열수 추출물(36.3±1.0 ㎎/GAE/g extract)이 유사한 총 폴리페놀 함량을 포함하고 있었으며, 총 플라보노이드 함량은 물 추출물이 47.0±3.8 ㎎ CE/g extract 그리고 에탄올 추출물이 53.9±5.1 ㎎ CE/g extract를 나타내었다. ABTS를 이용한 라디칼 소거활성, FRAP를 이용한 환원력을 통한 항산화 활성을 측정한 결과에서도 치콘 추출물이 항산화 효과를 나타내었다. 한편, 세포 독성을 살펴보기 위하여 신경세포를 이용하여 MTT assay를 수행한 결과, 세포의 생존율은 1.0 ㎎/㎖의 농도 이상에서는 생존에 영향을 미치지 않았고 신경세포 보호효능 실험에서는 2.5 mM의 H<SUB>2</SUB>O<SUB>2</SUB>로 유발시킨 산화적 손상에 대해 농도 의존적인 신경세포 보호 효과가 있었으며, 항산화 효소 활성을 SOD와 CAT로 분석한 결과 SOD는 0.5 mg/mL 농도에서 95% 이상의 활성과 CAT는 손상그룹에 비해 2배 이상의 활성을 각각 확인하였다. 또한 치콘 추출물이 세포사와 관련이 있는 단백질인 Bax와 Bcl-2의 발현을 조절하는 것을 확인하였다. 이와 같은 결과는 치콘 추출물이 산화적 손상의 억제를 통해 세포를 보호하는 효과가 있는 것으로 사료된다.

Apricot Melanoidins Prevent Oxidative Endothelial Cell Death by Counteracting Mitochondrial Oxidation and Membrane Depolarization

The cardiovascular benefits associated with diets rich in fruit and vegetables are thought to be due to phytochemicals contained in fresh plant material. However, whether processed plant foods provide the same benefits as unprocessed ones is an open question. Melanoidins from heat-processed apricots were isolated and their presence confirmed by colorimetric analysis and browning index. Oxidative injury of endothelial cells (ECs) is the key step for the onset and progression of cardiovascular diseases (CVD), therefore the potential protective effect of apricot melanoidins on hydrogen peroxide-induced oxidative mitochondrial damage and cell death was explored in human ECs. The redox state of cytoplasmic and mitochondrial compartments was detected by using the redox-sensitive, fluorescent protein (roGFP), while the mitochondrial membrane potential (MMP) was assessed with the fluorescent dye, JC-1. ECs exposure to hydrogen peroxide, dose-dependently induced mitochondrial and cytoplasmic oxidation. Additionally detected hydrogen peroxide-induced phenomena were MMP dissipation and ECs death. Pretreatment of ECs with apricot melanoidins, significantly counteracted and ultimately abolished hydrogen peroxide-induced intracellular oxidation, mitochondrial depolarization and cell death. In this regard, our current results clearly indicate that melanoidins derived from heat-processed apricots, protect human ECs against oxidative stress.

Evaluation of antioxidant and cytoprotective activities of Arnica montana L. and Artemisia absinthium L. ethanolic extracts.

BackgroundArnica montana L. and Artemisia absinthium L. (Asteraceae) are medicinal plants native to temperate regions of Europe, including Romania, traditionally used for treatment of skin wounds, bruises and contusions. In the present study, A. montana and A. absinthium ethanolic extracts were evaluated for their chemical composition, antioxidant activity and protective effect against H2O2-induced oxidative stress in a mouse fibroblast-like NCTC cell line.ResultsA. absinthium extract showed a higher antioxidant capacity than A. montana extract as Trolox equivalent antioxidant capacity, Oxygen radical absorbance capacity and 2,2-diphenyl-1-picrylhydrazyl free radical-scavenging activity, in correlation with its flavonoids and phenolic acids content. Both plant extracts had significant effects on the growth of NCTC cells in the range of 10–100 mg/L A. montana and 10–500 mg/L A. absinthium. They also protected fibroblast cells against hydrogen peroxide-induced oxidative damage, at the same doses. The best protection was observed in cell pre-treatment with 10 mg/L A. montana and 10–300 mg/L A. absinthium, respectively, as determined by Neutral red and lactate dehydrogenase assays. In addition, cell pre-treatment with plant extracts, at these concentrations, prevented morphological changes induced by hydrogen peroxide. Flow-cytometry analysis showed that pre-treatment with A. montana and A. absinthium extracts restored the proportion of cells in each phase of the cell cycle.ConclusionsA. montana and A. absinthium extracts, rich in flavonoids and phenolic acids, showed a good antioxidant activity and cytoprotective effect against oxidative damage in fibroblast-like cells. These results provide scientific support for the traditional use of A. montana and A. absinthium in treatment of skin disorders.

Protection of lung fibroblast MRC-5 cells against hydrogen peroxide-induced oxidative damage by 0.1–2.8 kDa antioxidative peptides isolated from whey protein hydrolysate

Antioxidative peptides (0.1–2.8kDa) obtained from gel filtration of Alcalase-hydrolysed whey protein were subjected to individual peptide isolation by RP-HPLC. The sub-fraction P4 and a prominent pentapeptide identified by mass spectrometry (Val-His-Leu-Lys-Pro) (P4c) were found to be highly antioxidative, therefore, used to assess the efficacy against hydrogen peroxide (H2O2)-induced human lung fibroblast MRC-5 cell oxidative injury. MRC-5 cells were damaged by incubation with H2O2, but cell death was significantly reduced when exposed to P4 and P4c (P<0.05). Compared to the H2O2-damaged model control, P4 and P4c enhanced the activity of cell superoxide dismutase, glutathione peroxidase, and catalase, and decreased the levels of malonaldehyde (P<0.05). These results, with a more pronounced action of P4c than P4, demonstrated that antioxidative peptides had a significant protection of MRC-5 cells against the toxicity caused by H2O2.

Antioxidant phenolic profile from ethyl acetate fraction of Fructus Ligustri Lucidi with protection against hydrogen peroxide-induced oxidative damage in SH-SY5Y cells

In this study, we demonstrated the antioxidant and protective properties of crude extract and fractions from Fructus Ligustri Lucidi (FLL) against hydrogen peroxide (H2O2)-induced oxidative damage in SH-SY5Y cells. The contents of their phytochemical profiles were determined by spectrophotometric methods and high performance liquid chromatography using a photodiode array detector. FLL crude extract possessed appreciable scavenging capacity against 1,1-diphenyl-2-picrylhydrazyl and H2O2. The ethyl acetate (EtOAc) fraction was the most active fraction in scavenging free radicals and H2O2. Following exposure of cells to H2O2, there was a marked decrease in cell survival and intracellular antioxidant enzymes, and then intracellular oxidative stress, the level of lipid peroxidation, and caspase-3 activity were increased. Simultaneous treatment with the EtOAc fraction blocked these H2O2-induced cellular events. Hydroxytyrosol and salidroside are major components of the EtOAc fraction. These results show that the phenolic-enriched EtOAc fraction of FLL contains tyrosol-related derivatives and exerts the protective effects against H2O2 toxicity via its free radical scavenging activity and ability to elevate the levels of antioxidant enzymes.

Constructing liposomal nanovesicles of ginseng extract against hydrogen peroxide-induced oxidative damage to L929 cells

In this study, a liposomal nanovesicle was applied as a nanocarrier of ginseng extract (GE) to enhance the intracellular antioxidant activity of GE. The optimal condition of preparing GE liposomal nanovesicle (GELN) was prepared by tagging with 3.0mol% of polyethenyl glycol (PEG3.0) followed by homogenisation at 15,000psi for 5min to reduce its diameter to ∼150nm. PEG3.0-GELN encapsulated the most ginsenosides (234.1±13.9mg/g) with a higher reducing power than GELNs tagged with lower amounts of PEG (0–1.5mol%). After treatment with PEG3.0-GELN (20μg ginsenoside/ml), the % increase in mitochondrial membrane potential (ΔΨ) of H2O2-damaged cells rose 20.9% and the % decrease in apoptosis increased 12.4%, compared with those treated with GE. Therefore, this investigation proved that utilising liposomal nanovesicles to encapsulate GE can effectively suppress the depolarisation of ΔΨ and thus enhance the survival rate of H2O2-damaged cells.

Radical Scavenging Activity of Poncirus trifoliata Extracts and Their Inhibitory Effect Against Hydrogen Peroxide Induced Cell Damage

Poncirus trifoliate was evaluated for antioxidant potential by several radical-scavenging assays, including 1,1-diphenyl-2-picrylhydrazyl, superoxide, hydroxyl, and alkyl radicals, using electron spin resonance technique. P. Trifoliate extracts were prepared by using water and methanol, partitioning with different organic solvents. Among the tested samples, water extract and dichloromethane fraction evidenced relatively higher scavenging activities than those of other samples on reactive radicals and have high amount of antioxidant component such as flavonoids (8.5±0.3 and 8.3±0.2 mg rutin equivalents/g dry weight basis) and proanthocyanidin (2.6±0.3 and 2.8±0.5 mg catechin equivalents/g dry weight basis), respectively. Moreover, the water extract showed significantly high enhancement of cell viability against hydrogen peroxide-induced oxidative damage as well as reduction in the hydrogen peroxide-induced intracellular reactive oxygen species on CCL 13 cell line. These results indicate that P. trifoliate exerts various antioxidant effects against several reactive radicals and hydrogen peroxide-mediated cell damage. Thus, P. trifoliate could be a potential therapeutic modality for the treatment or prevention of several diseases associated with oxidative stress.

Cytoprotective activity against peroxide-induced oxidative damage and cytotoxicity of flavonoids in C6 rat glioma cells

The aim of this study was to investigate the relationship between cytoprotective and cytotoxic activities of selected plant flavonoids in C6 glioma cells. Apigenin, kaempferol, luteolin, and quercetin were cytotoxic at low μM concentrations (LOECs: 5–20μM), whereas myricetin was less toxic (LOEC>20μM). Cytotoxicity was not due to H2O2 generation from flavonoids in culture medium. Quercetin, luteolin, and kaempferol protected the cells from peroxide-induced cytotoxicity. Concentration-effect curves for cytoprotection had a biphasic shape. In contrast, apigenin and myricetin did not exhibit any cytoprotective activity. The first three compounds also inhibited cellular lipid peroxidation induced by CHP, while the latter were ineffective. Importantly, concentrations of luteolin and kaempferol protecting cells under oxidative stress were identical to those causing cell damage under normal conditions. Only in case of quercetin there was a narrow range of concentrations protecting cells without being cytotoxic to non-stressed cells. Thus, even for flavonoids with a high antioxidant capacity in cell-free systems the cytoprotective selectivity (LOECcytotox/LOECcytoprot) was very low or even absent. These results should be taken into account when the prophylactic or therapeutic application of flavonoids as antioxidants is discussed.