Phenolic compounds protect HepG2 cells from oxidative damage: relevance of glutathione levels

Marine-derived Fungi Extracts Enhance the Cytotoxic Activity of Doxorubicin in Nonsmall Cell Lung Cancer Cells A459

Background:

Drug resistance is a major concern in the current chemotherapeutic approaches and the combination with natural compounds may enhance the cytotoxic effects of the anticancer drugs. Therefore, this study evaluated the cytotoxicity of crude ethyl extracts of six marine-derived fungi – Neosartorya tsunodae KUFC 9213 (E1), Neosartorya laciniosa KUFC 7896 (E2), Neosartorya fischeri KUFC 6344 (E3), Aspergillus similanensis KUFA 0013 (E4), Neosartorya paulistensis KUFC 7894 (E5), and Talaromyces trachyspermum KUFC 0021 (E6) – when combined with doxorubicin (Dox), in seven human cancer cell lines.

Materials and Methods:

The antiproliferative activity was primarily assessed by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay.

Results:

Two extracts, E1 and E2, demonstrated a significant enhancement of Dox’s cytotoxicity in nonsmall cell lung cancer A549 cells. Accumulation of Dox in the nuclei increased when A549 cells were treated in combination with extracts E1 and E2, with induction of cell death observed by the nuclear condensation assay. The combination of E2 with Dox increased the DNA damage as detected by the comet assay. Ultrastructural observations by transmission electron microscopy suggest an autophagic cell death due to an increase of autophagic vesicles, namely with the combination of Dox with E1 and E2.

Conclusion:

These findings led to the conclusion that the fungal extracts E1 and E2 potentiate the anticancer action of Dox, through nuclear accumulation of Dox with induction of cell death mainly by cytotoxic autophagy.

SUMMARY

Fungal extracts increase the cytotoxic activity of doxorubicin (Dox) in lung cancer cells

Nuclear accumulation of Dox, DNA damage, and cell death as a mechanism of action

Fungal extracts may potentiate the anticancer activity of conventional drugs.

Abbreviations Used: A375: Human malignant melanoma cell line, A549: Human non small lung cancer cell line, DAPI: 4,6-Diamidino-2-phenylindole, DMEM: Dulbecco’s Modified Eagle Medium, DMSO: Dimethylsulfoxide, Dox: Doxorubicin, DSBs: DNA double-strand breaks, E1: Neosartorya tsunodae KUFC 9213, E2: Neosartorya laciniosa KUFC 7896, E3: Neosartorya fischeri KUFC 6344, E4: Aspergillus similanensis KUFA 0013, E5: Neosartorya paulistensis KUFC 7894, E6: Talaromyces trachyspermum KUFC 0021, FBS: Fetal bovine serum, HCT116: Human colorectal carcinoma cell line, HEPES: (N-[2-hydroxyethyl] piperazine-N’- [2-ethane-sulfonic acid]), HepG2: Human hepatocellular carcinoma cell line, HT29: Human Caucasian colon adenocarcinoma Grade II cell line, IC₅₀: Concentration of the extract or Dox that inhibits cell viability by 50%, LRP: Lung resistance-related protein, MCF7: Human breast adenocarcinoma cell line, MEM: Minimum Essential Medium Eagle, MRPs: Multidrug resistance-associated proteins, MTT: 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, PBS: Phosphate-buffered saline, NSCLC: Nonsmall cell lung cancer, P-gp: P-glycoprotein, ROS: Reactive oxygen species, RPMI: Roswell Park Memorial Institute Medium, TEM: Transmission electron microscopy, U251: Human glioblastoma astrocytoma cell line.

Antioxidant and in vivo genoprotective effects of phenolic compounds identified from an endophytic Cladosporium velox and their relationship with its host plant Tinospora cordifolia

ETHNOPHARMACOLOGICAL RELEVANCE

Tinospora cordifolia (Willd. Hook. f. & Thomson; family: Menispermaceae), has a long history of use in various traditional medicinal systems including "Ayurveda". It is reported to possess anticancer, antidiabetic, antimicrobial, antispasmodic, and antiinflammatory activities. T. cordifolia has also been well documented for production of various bioactive metabolites and their antioxidant activity, but the microorganisms associated with it have been least explored for the same properties.

AIM OF THE STUDY

Aim of the present study was to evaluate antioxidant and in vivo genoprotective potential of phenolic compounds produced by an endophytic fungus Cladosporium velox TN-9S isolated from T. cordifolia.

MATERIALS AND METHODS

The isolate of C. velox TN-9S was cultivated in malt extract medium and extracted with ethyl acetate. Total phenol content was determined by Folin Ciocalteu reagent. The antioxidant activity was measured in terms of DPPH and FRAP assay. The in vivo genoprotective activity was assessed using fish Channa punctatus as model. Identification of phenolic compounds was carried out using RP-HPLC. The fungal extract was evaluated for biosafety using Salmonella typhimurium His^- strain and CHO cell lines for mutagenicity and cytotoxicity, respectively.

RESULTS

The total phenolic content in the ethyl acetate extract of the fungus was determined to be 730μg gallic acid equivalent/mL. The extract evinced significant antioxidant activity with IC₅₀ value of 22.5µg/mL in DPPH scavenging assay. The phenolic extract showed good in vivo genoprotective activity against the genetic damage induced in fish C. punctatus after treatment with a non-ionic surfactant 4-nonylphenol. RP-HPLC analysis revealed the presence of peaks corresponding to various phenolic compounds in the extract. Mutagenicity and cytotoxicity results revealed the extract to be nonmutagenic and non cytotoxic in nature.

CONCLUSION

The results indicate the potential of an endophytic C. velox isolated from T. cordifolia as a producer of phenolic compounds with antioxidant and genoprotective activities which could be exploited in pharmaceutical industry. The ability of endophytes to produce similar compounds as the host, is also revealed in the present study.

Intraperitoneal administration of apigenin in liver ischemia/reperfusion injury protective effects

BACKGROUND/AIMS

Hepatic injury caused by ischemia/reperfusion (I/R) is a clinical problem associated with major liver surgery. Among other flavonoids, apigenin has shown a promising effect on I/R cases. In this study, we have investigated the effects of apigenin after liver I/R injury in rats.

MATERIALS AND METHODS

Forty eight rats were randomized into the following eight groups: (1) Control-sham group: rats subjected to the surgical procedure, except for liver I/R; (2) DMSO group: rats subjected to surgery, except for liver I/R given the apigenin solvent dimethyl-sulfoxide intraperitoneally; (3) C60 group; (4) C120 group; (5) C240 group: rats underwent liver ischemia for 45 min followed by reperfusion for 60 min, 120 min, and 240 min; (6) AP60 group; (7) AP120 group; (8) AP240 group: rats underwent liver ischemia for 45 min, and then given apigenin (5 mg) intraperitoneally followed by reperfusion for 60 min, 120 min, and 240 min. Reverse transcription polymerase chain reaction was performed on liver tissues to measure BCL-2/BAX expression, enzyme-linked immunosorbent assay to measure M30/M65 and ICAM-1. Immunohistochemistry was used to identify M30 biomarker in liver tissues.

STATISTICAL ANALYSIS

Quantitative variables were tested by Kolmogorov-Smirnov test, repeated measures analysis of variance/Friedman test. Gene levels were assessed by Student's t-test/Mann-Whitney U-test.

RESULTS

BCL-2 levels were significantly higher in I/R apigenin groups than in I/R control groups. BAX levels were lower in the AP240 group than in C240 group. Prolongation of reperfusion resulted in increased activation of M30. ICAM-1 levels were lower in the AP240 group than in C240 group.

CONCLUSIONS

Apigenin seems to inhibit the process of apoptosis and ameliorate the hepatic I/R injury.

Does rosmarinic acid treatment have protective role against sepsis-induced oxidative damage in Wistar Albino rats?

Reactive oxygen species are believed to be involved in the development of sepsis. Plant-derived phenolic compounds are thought to be possible therapeutic agents against sepsis because of their antioxidant properties. Rosmarinic acid (RA) is a phenolic compound commonly found in various plants, which has many biological activities including antioxidant activity. The aim of this study was to investigate the effects of RA on sepsis-induced DNA damage in the lymphocytes and liver and kidney cells of Wistar albino rats by alkaline comet assay with and without formamidopyrimidine DNA glycosylase protein. The oxidative stress parameters such as superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) activities and total glutathione (GSH) and malondialdehyde (MDA) levels in the liver and kidney tissues and an inflammatory cytokine, tumor necrosis factor α (TNF-α) level in plasma were also evaluated. It is found that DNA damage in the lymphocytes, livers, and kidneys of the RA-treated rats was significantly lower than that in the sepsis-induced rats. RA treatment also decreased the MDA levels and increased the GSH levels and SOD and GSH-Px activities in the livers and kidneys of the sepsis-induced rats. Plasma TNF-α level was found to be decreased in the RA-treated rats. It seems that RA might have a role in the attenuation of sepsis-induced oxidative damage not only by decreasing the DNA damage but also by increasing the antioxidant status and DNA repair capacity of the animals.

Antioxidant Effects of Sheep Whey Protein on Endothelial Cells

Excessive production of reactive oxygen species (ROS) may cause endothelial dysfunction and consequently vascular disease. In the present study, the possible protective effects of sheep whey protein (SWP) from tert-butyl hydroperoxide- (tBHP-) induced oxidative stress in endothelial cells (EA.hy926) were assessed using oxidative stress biomarkers. These oxidative stress biomarkers were glutathione (GSH) and ROS levels determined by flow cytometry. Moreover, thiobarbituric acid-reactive substances (TBARS), protein carbonyls (CARB), and oxidized glutathione (GSSG) were determined spectrophotometrically. The results showed that SWP at 0.78, 1.56, 3.12, and 6.24 mg of protein mL⁻¹ increased GSH up to 141%, while it decreased GSSG to 46.7%, ROS to 58.5%, TBARS to 52.5%, and CARB to 49.0%. In conclusion, the present study demonstrated for the first time that SWP protected endothelial cells from oxidative stress. Thus, SWP may be used for developing food supplements or biofunctional foods to attenuate vascular disturbances associated with oxidative stress.

Preventive effect of Nile tilapia hydrolysate against oxidative damage of HepG2 cells and DNA mediated by H2O2 and AAPH

Antioxidant activities of protein hydrolysate prepared from Nile tilapia protein isolate using Alcalase (HA), Alcalase followed by papain (HAPa) and their Sephadex G-25 fractions (FHA and FHAPa) were investigated in both chemical and cellular based models. Amongst all samples, FHAPa showed the highest chemical antioxidant activities, however it had no metal chelation activity. Cellular antioxidant ability of HA, HAPa and their fractions against H2O2 and AAPH induced oxidative damage of HepG2 cell and DNA were tested. When cells were pretreated with all hydrolysates or fractions at different concentrations (0.5-2 mg/mL) in the absence and presence of 50 μM Trolox, cell viability was in the range of 91.10-111.40 %. However, no difference in cell viability was observed among samples having various concentrations (P > 0.05). Cell reactive oxygen species (ROS) generation as mediated by H2O2 and AAPH decreased with treatment of hydrolysates or their fractions, especially in combination with 50 μM Trolox. FHAPa effectively inhibited H2O2 and peroxyl radical induced DNA scission in a dose dependent manner. Therefore, Nile tilapia protein hydrolysates could serve as a functional food ingredient.

Structure-antioxidant activity relationships of o-hydroxyl, o-methoxy, and alkyl ester derivatives of p-hydroxybenzoic acid

Anti-DPPH radical effect as well as anti-peroxide activity of o-hydroxyl, o-methoxy, and alkyl ester derivatives of p-hydroxybenzoic acid in a bulk fish oil system and its O/W emulsion were investigated. Electronic phenomena, intra- and/or intermolecular hydrogen bonds, interfacial properties, and chemical reaction of the solvent molecules with phenolic compounds were considered to be mainly involved in the antiradical activities observed. Antioxidant activity of the phenolic acids derivatives as a function of these factors was variously affected by the environmental conditions which may occur in practice.

Rosmarinic acid up-regulates the noise-activated Nrf2/HO-1 pathway and protects against noise-induced injury in rat cochlea

Noise-induced hearing loss depends on progressive increase of reactive oxygen species and lipoperoxidative damage in conjunction with the imbalance of antioxidant defenses. The redox-sensitive transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2) plays a critical role in the regulation of cellular defenses against oxidative stress, including heme oxygenase-1 (HO-1) activation. In this work we describe a link between cochlear oxidative stress damage, induced by noise exposure, and the activation of the Nrf2/HO-1 pathway. In our model, noise induces superoxide production and overexpression of the lipid peroxidation marker 4-hydroxy-nonenals (4-HNE). To face the oxidative stress, the endogenous defense system is activated as well, as shown by the slight activation of superoxide dismutases (SODs). In addition, we observed the activation of the Nrf2/HO-1 pathway after noise exposure. Nrf2 appears to promote the maintenance of cellular homeostasis under stress conditions. However, in this model the endogenous antioxidant system fails to counteract noise-induced cell damage and its activation is not effective enough in preventing cochlear damage. The herb-derived phenol rosmarinic acid (RA) attenuates noise-induced hearing loss, reducing threshold shift, and promotes hair cell survival. In fact, RA enhances the endogenous antioxidant defenses, as shown by decreased superoxide production, reduced expression of 4-HNE, and up-regulation of SODs. Interestingly, RA potentiates the Nrf2/HO-1 signaling pathway, as shown by immunohistochemical and Western blot analyses. Thus, protective effects of RA are associated with the induction/activation of the Nrf2-ARE signaling pathway in addition to RA direct scavenging capability.

Redox-dependent induction of antioxidant defenses by phenolic diterpenes confers stress tolerance in normal human skin fibroblasts: Insights on replicative senescence

Mild stress-induced hormesis represents a promising strategy for targeting the age-related accumulation of molecular damage and, therefore, for preventing diseases and achieving healthy aging. Fruits, vegetables, and spices contain a wide variety of hormetic phytochemicals, which may explain the beneficial health effects associated with the consumption of these dietary components. In the present study, the induction of cellular antioxidant defenses by the phenolic diterpenes carnosic acid (CA) and carnosol (CS) were studied in normal human skin fibroblasts, and insights into the aging process at the cellular level investigated. We observed that CA and CS induced several cytoprotective enzymes and antioxidant defenses in human fibroblasts, whose induction was dependent on the cellular redox state for CS and associated with Nrf2 signaling for both compounds. The stress response elicited by preincubation with CS conferred a cytoprotective action against a following oxidant challenge with tert-butyl hydroperoxide, confirming its hormetic effect. Preincubation of normal fibroblasts with CS also protected against hydrogen peroxide-induced premature senescence. Furthermore, cultivation of middle passage normal human skin fibroblasts in the presence of CS ameliorated the physiological state of cells during replicative senescence. Our results support the view that mild stress-induced antioxidant defenses by CS can confer stress tolerance in normal cells and may have important implications in the promotion of healthy aging.

Effects on Liver Lipid Metabolism of the Naturally Occurring Dietary Flavone Luteolin-7-glucoside

Disruptions in whole-body lipid metabolism can lead to the onset of several pathologies such as nonalcoholic fatty liver disease (NAFLD) and cardiovascular diseases (CVDs). The present study aimed at elucidating the molecular mechanisms behind the lipid-lowering effects of the flavone luteolin-7-glucoside (L7G) which we previously showed to improve plasma lipid profile in rats. L7G is abundant in plant foods of Mediterranean diet such as aromatic plants used as herbs. Results show that dietary supplementation with L7G for one week induced the expression of peroxisome proliferator-activated receptor-alpha (PPAR-α) and of its target gene carnitine palmitoyl transferase 1 (CPT-1) in rat liver. L7G showed a tendency to decrease the hepatic expression of sterol regulatory element-binding protein-1 (SREBP-1), without affecting fatty acid synthase (FAS) protein levels. Although SREBP-2 and LDLr mRNA levels did not change, the expression of HMG CoA reductase (HMGCR) was significantly repressed by L7G. L7G also inhibited this enzyme's in vitro activity in a dose dependent manner, but only at high and not physiologically relevant concentrations. These results add new evidence that the flavone luteolin-7-glucoside may help in preventing metabolic diseases and clarify the mechanisms underlying the beneficial health effects of diets rich in fruits and vegetables.

Protective effect of Lepidium sativum seed extract against hydrogen peroxide-induced cytotoxicity and oxidative stress in human liver cells (HepG2)

CONTEXT

Garden cress [Lepidium sativum (Brassicaceae)] has been widely used to treat a number of ailments in traditional medicine. The pharmacological and preventive potential of Lepidium sativum, such as anti-inflammatory, antipyretic, antihypertensive, anti-ashthamatic, anticancer, and anti-oxidant, are well known.

OBJECTIVE

The present investigation was designed to study the protective effects of chloroform extract of Lepidium sativum seed (LSE) against oxidative stress and cytotoxicity induced by hydrogen peroxide (H2O2) in human liver cells (HepG2).

MATERIALS AND METHODS

Cytotoxicity of LSE and H2O2 was identified by (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT), neutral red uptake (NRU) assays, and morphological changes in HepG2. The cells were pre-exposed to biologically safe concentrations (5-25 μg/ml) of LSE for 24 h, and then cytotoxic (0.25 mM) concentration of H2O2 was added. After 24 h of the exposures, cell viability by MTT, NRU assays, and morphological changes in HepG2 were evaluated. Further, protective effects of LSE on reactive oxygen species (ROS) generation, mitochondrial membrane potential (MMP), lipid peroxidation (LPO), and reduced glutathione (GSH) levels induced by H2O2 were studied.

RESULTS

Pre-exposure of LSE significantly attenuated the loss of cell viability up to 48% at 25 µg/ml concentration against H2O2 (LD50 value = 2.5 mM). Results also showed that LSE at 25 µg/ml concentration significantly inhibited the induction of ROS generation (45%) and LPO (56%), and increases the MMP (55%) and GSH levels (46%).

DISCUSSION AND CONCLUSION

The study suggests the cytoprotective effects of LSE against H2O2-induced toxicity in HepG2. The results also demonstrate the anti-oxidative nature of LSE.

Comparison antioxidant activity of Tarom Mahali rice bran extracted from different extraction methods and its effect on canola oil stabilization

In this study, Tarom Mahali rice bran extracts by ultrasound assisted and traditional solvent (ethanol and ethanol: water (50:50)) extraction method were compared. The total phenolic and tocopherol content and antioxidant activity of the extracts was determined and compared with TBHQ by DPPH assay and β-carotene bleaching method. The results show that the extract from ethanol: water (50:50) ultrasonic treatment with high amount of phenols (919.66 mg gallic acid/g extract, tocopherols (438.4 μg α-tocopherol/ mL extract) indicated the highest antioxidant activity (80.36 % radical scavenging and 62.69 % β-carotene-linoleic bleaching) and thermal stability (4.95 h) at 120 °C in canola oil. Being high in antioxidant and antiradical potential and high content of phenolic and tocopherol compounds of ethanol: water (50:50) ultrasonic extract caused to evaluate its thermal stability at 180 °C in canola oil during frying process. So, different concentrations of Tarom Mahali rice bran extract (100, 800, and 1200 ppm) were added to canola oil. TBHQ at 100 ppm served as standard besides the control. Free fatty acids (FFAs), Peroxide value (PV), carbonyl value (CV), total polar compounds (TPC) and oxidative stability index (OSI) were taken as parameters for evaluation of effectiveness of Tarom Mahali rice bran extract in stabilization of canola oil. Results from different parameters were in agreement with each other, suggesting that 800 ppm of the extract could act better than 100 ppm TBHQ in inhibition of lipid oxidation in canola oil during frying process and can be used as predominant alternative of synthetic antioxidants.

Pennyroyal and gastrointestinal cells: multi-target protection of phenolic compounds against t-BHP-induced toxicity

Pennyroyal infusion maintains gastrointestinal cells antioxidant balance.

Campomanesia adamantium (Myrtaceae) fruits protect HEPG2 cells against carbon tetrachloride-induced toxicity

Campomanesia adamantium (Myrtaceae) is an antioxidant compounds-rich Brazilian fruit popularly known as gabiroba. In view of this, it was evaluated the hepatoprotective effects of pulp (GPE) or peel/seed (GPSE) hydroalcoholic extracts of gabiroba on injured liver-derived HepG2 cells by CCl₄ (4 mM). The results showed the presence of total phenolic in GPSE was (60%) higher when compared to GPE, associated with interesting antioxidant activity using DPPH• assay. Additionally, HPLC chromatograms and thin layer chromatography of GPE and GPSE showed the presence of flavonoids. Pretreatment of HepG2 cells with GPE or GPSE (both at 800–1000 μg/mL) significantly (p < 0.0001) protected against cytotoxicity induced by CCl_4. Additionally, the cells treated with both extracts (both at 1000 μg/mL) showed normal morphology (general and nuclear) contrasting with apoptotic characteristics in the cells only exposed to CCl₄. In these experiments, GPSE also was more effective than GPE. In addition, CCl₄ induced a marked increase in AST (p < 0.05) and ALT (p < 0.0001) levels, while GPE or GPSE significantly (p < 0.0001) reduced these levels, reaching values found in the control group. In conclusion, the results suggest that gabiroba fruits exert hepatoprotective effects on HepG2 cells against the CCl₄-induced toxicity, probably, at least in part, associated with the presence of antioxidant compounds, especially flavonoids.

Antioxidant and hepatoprotective effect of (-)-epigallocatechin 3-O-(3-O-methyl) gallate (EGCG3″Me) from Chinese oolong tea

(-)-Epigallocatechin 3-O-(3-O-methyl) gallate (EGCG3″Me) has exhibited various biological activities in oolong tea. However, little information about its hepatoprotective activity is available. The objectives of the present study, therefore, were to determine the hepatoprotective activity of EGCG3″Me. First, high-purity EGCG3″Me was prepared from Chinese oolong tea by column chromatography. In antioxidant assay in vitro, EGCG3″Me exhibited potential antioxidant activity. For hepatoprotective activity in vitro, it was observed that EGCG3″Me effectively alleviated the changes induced by alcohol in a concentration-dependent manner. For hepatoprotective activity in vivo, the administration of EGCG3″Me at a dose of 100 mg/kg BW per day significantly decreased the serum levels of aspartate aminotransferase (AST) and alanine aminotransferase (ALT) from 64.6 ± 3.17 and 97.6 ± 3.78 to 39.6 ± 2.72 and 59.6 ± 3.02 U/L, decreased the liver level of malondialdehyde (MDA) from 1.14 ± 0.08 to 0.77 ± 0.03 nmol/mg protein, and remarkably restored the liver activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) from 247 ± 20.1 U/mg and 6.12 ± 0.17 nmol/mg protein to 261 ± 9.98 U/mg and 8.10 ± 0.03 nmol/mg protein, respectively, in alcohol-induced liver injury mice. This suggested that the protective effect of EGCG3″Me against alcohol-induced liver injury is possibly via its antioxidant activity to protect biological systems against oxidative stress.

Antioxidant activity of raspberry (Rubus fruticosus) leaves extract and its effect on oxidative stability of sunflower oil

Efficacy of R. fruticosus leaves extract in stabilizing sunflower oil during accelerated storage has been studied. Extracts of R. fruticosus were prepared in different solvents which methanolic extract yield with 15.43 % was higher than water and acetone ones (11.87 and 6.62 %, respectively). Methanolic extract was chosen to evaluate its thermal stability at 70 °C in sunflower oil, due to the highest yield, antioxidant and antiradical potential and also high content of phenolic compounds campared to other solvents. So, different concentrations of methanolic extract (200, 400, 600, 800 and 1,000 ppm) were added to sunflower oil. BHA and BHT at 200 ppm served as standards besides the control. Peroxide value (PV) and thiobarbituric acid (TBA) were taken as parameters for evaluation of effectiveness of R. fruticosus leaves extract in stabilization of sunflower oil. Moreover, antioxidant activity index (AAI) of the extract at 120 °C at rancimat were conducted. Results from different parameters were in agreement with each other, suggesting the highest efficiency of 1,000 ppm of the extract followed by BHT, BHA and other concentrations of the extract. Results reveal the R. fruticosus leaves extract to be a potent antioxidant for stabilization of sunflower oil.

APE1/Ref-1 as an emerging therapeutic target for various human diseases: phytochemical modulation of its functions

Apurinic/apyrimidinic endonuclease 1 (APE1) is a multifunctional enzyme involved in the base excision repair (BER) pathway, which repairs oxidative base damage caused by endogenous and exogenous agents. APE1 acts as a reductive activator of many transcription factors (TFs) and has also been named redox effector factor 1, Ref-1. For example, APE1 activates activator protein-1, nuclear factor kappa B, hypoxia-inducible factor 1α, paired box gene 8, signal transducer activator of transcription 3 and p53, which are involved in apoptosis, inflammation, angiogenesis and survival pathways. APE1/Ref-1 maintains cellular homeostasis (redox) via the activation of TFs that regulate various physiological processes and that crosstalk with redox balancing agents (for example, thioredoxin, catalase and superoxide dismutase) by controlling levels of reactive oxygen and nitrogen species. The efficiency of APE1/Ref-1's function(s) depends on pairwise interaction with participant protein(s), the functions regulated by APE1/Ref-1 include the BER pathway, TFs, energy metabolism, cytoskeletal elements and stress-dependent responses. Thus, APE1/Ref-1 acts as a ‘hub-protein' that controls pathways that are important for cell survival. In this review, we will discuss APE1/Ref-1's versatile nature in various human etiologies, including neurodegeneration, cancer, cardiovascular and other diseases that have been linked with alterations in the expression, subcellular localization and activities of APE/Ref-1. APE1/Ref-1 can be targeted for therapeutic intervention using natural plant products that modulate the expression and functions of APE1/Ref-1. In addition, studies focusing on translational applications based on APE1/Ref-1-mediated therapeutic interventions are discussed.

Chemical constituents from aerial parts of Caryopteris incana and cytoprotective effects in human HepG2 cells

An ethyl acetate fraction of the aerial parts of Caryopteris incana (Verbenaceae) showed potent cytoprotective effects against damage to HepG2 cells induced by tert-butylhydroperoxide (t-BHP). To search for hepatoprotective components of C. incana, various chromatographic separations of the ethyl acetate soluble fraction of C. incana led to isolation of three phenylpropanoid glycosides, 6‴-O-feruloylincanoside D, 6‴-O-sinapoylincanoside D and caryopteroside, and two iridoid glycosides, incanides A and B, together with 17 known compounds. Structures of these compounds were determined by spectroscopic analyses. The absolute stereochemistry of the caryopteroside was established with the help of circular dichroism data and in comparison with literature data. All isolated substances were determined for their cytoprotective effects against t-BHP-induced toxicity in HepG2 cells. Among the tested compounds, 6'-O-caffeoylacteoside exhibited the most potent cytoprotective activity with an IC50 value of 0.8±0.1 μM against t-BHP-induced toxicity. Structure-activity relationships of the assay results indicated an important role of the catechol moiety in phenylpropanoid, iridoid and flavonoid derivatives in eliciting cytoprotective effects.

Antioxidant activity of gallic acid and methyl gallate in triacylglycerols of Kilka fish oil and its oil-in-water emulsion

The anti-DPPH radical effect as well as anti-peroxide activity of gallic acid, methyl gallate, and α-tocopherol in a bulk Kilka fish oil and its oil-in-water emulsion stabilized by soy protein isolate at 55°C were investigated. Gallic acid with the lowest hydrophobicity (log P=-0.28) was found to be the most active antiradical agent (IC50=29.5 μM), followed by methyl gallate (IC50=38.0 μM, log P=-0.23) and α-tocopherol (IC50=105.3 μM, log P=0.70). The anti-peroxide activity in the bulk oil system decreased in the order of methyl gallate>gallic acid>α-tocopherol. In the emulsion system, methyl gallate still behaved better than gallic acid, but the highest activity belonged to α-tocopherol. Based on the calculation of a number of kinetic parameters, the antioxidants, in general, showed better performances in the bulk oil system than in the emulsion system.

Inhibition of oxidative stress and lipid peroxidation by anthocyanins from defatted Canarium odontophyllum pericarp and peel using in vitro bioassays

Canarium odontophyllum, also known as CO, is a highly nutritious fruit. Defatted parts of CO fruit are potent sources of nutraceutical. This study aimed to determine oxidative stress and lipid peroxidation effects of defatted CO pericarp and peel extracts using in vitro bioassays. Cell cytotoxic effect of the CO pericarp and peel extracts were also evaluated using HUVEC and Chang liver cell lines. The crude extracts of defatted CO peel and pericarp showed cytoprotective effects in t-BHP and 40% methanol-induced cell death. The crude extracts also showed no toxic effect to Chang liver cell line. Using CD36 ELISA, NAD(+) and LDL inhibition assays, inhibition of oxidative stress were found higher in the crude extract of defatted CO peel compared to the pericarp extract. Hemoglobin and LDL oxidation assays revealed both crude extracts had significantly reduced lipid peroxidation as compared to control. TBARS values among defatted CO pericarp, peel, and cyanidin-3-glucoside showed no significant differences for hemoglobin and LDL oxidation assays. The protective effects of defatted CO parts, especially its peel is related to the presence of high anthocyanin that potentially offers as a pharmaceutical ingredient for cardioprotection.

Simultaneous determination of 14 phenolic compounds in grape canes by HPLC-DAD-UV using wavelength switching detection

The paper described a novel chromatographic method for the simultaneous determination of phenolic compounds such as gallic, protocatechuic, vanillic, caffeic, syringic, p-coumaric and salicylic acid, (+)-catechin, (‒)-epicatechin, rutin, morin, quercetin, coumarin and trans-resveratrol at their maximum absorbance wavelengths (MAW) employing reverse-phase high performance liquid chromatography combined with DAD and UV detection via detection wavelength switching. The method was based on MAW acquisition by DAD and quantification by UV. The separation process was performed on a Shim-Pack VP-ODS C₁₈ column (250 mm × 4.6 mm, 5 μm) held at 30 °C, utilizing 3.0% acetic acid and acetonitrile as mobile phase at a flow rate of 0.8 mL/min in the gradient elution mode. The method was fully validated in terms of linearity (r² > 0.9990, 10‒350 mg/L), precision (both intra-day and inter-day RSD < 4.22%), accuracy (97.31%‒104.66%), specificity, robustness (0.59% < RSD < 2.86%), limit of detection and quantification. The switching method significantly improved the sensitivities of most phenolics studied in comparison with the standard constant wavelength detection (280 nm). The proposed method has been successfully applied to the determination of 14 phenolic compounds in 89 varieties of one-year-old Chinese grape one-year-canes. Grape canes contain many phenolics, especially trans-resveratrol, (‒)-epicatechin, and (+)-catechin.

Spanish honeys protect against food mutagen-induced DNA damage

BACKGROUND

Honey contains a variety of polyphenols and represents a good source of antioxidants, while the human diet often contains compounds that can cause DNA damage. The present study investigated the protective effect of three commercial honey samples of different floral origin (rosemary, heather and heterofloral) from Madrid Autonomic Community (Spain) as well as an artificial honey on DNA damage induced by dietary mutagens, using a human hepatoma cell line (HepG2) as in vitro model system and evaluation by the alkaline single-cell gel electrophoresis or comet assay.

RESULTS

Rosemary, heather and heterofloral honeys protected against DNA strand breaks induced by N-nitrosopyrrolidine (NPYR), benzo(a)pyrene (BaP) and 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), but none of the honey samples tested prevented DNA strand breaks induced by N-nitrosodimethylamine (NDMA). Heterofloral and heather (unifloral) honeys with higher phenolic content were most effective in protecting HepG2 cells against DNA damage induced by food mutagens. Heterofloral honey was more protective against NPYR and BaP, while heather honey was more protective against PhIP. Artificial honey did not show a protective effect against DNA damage induced by any of the food mutagens tested, indicating that the protective effects of honeys could not be due to their sugar components.

CONCLUSION

The results suggest that the protective effect of three kinds of Spanish honey of different floral origin could be attributed in part to the phenolics present in the samples. Honeys with higher phenolic content, i.e. heather and heterofloral honeys, were most effective in protecting against food mutagen-induced DNA damage in HepG2 cells. In addition, a possible synergistic effect between other minor honey components could also be involved.

Synthesis and biological properties of caffeic acid-PNA dimers containing guanine

Caffeic acid (CA; 3,4-dihydroxycinnamic acid) is endowed with high antioxidant activity. CA derivatives (such as amides) have gained a lot of attention due to their antioxidative, antitumor and antimicrobial properties as well as stable characteristics. Caffeoyl-peptide derivatives showed different antioxidant activity depending on the type and the sequence of amino acid used. For these reasons, we decided to combine CA with Peptide Nucleic Acid (PNA) to test whether the new PNA-CA amide derivatives would result in an improvement or gain of CA's biological (i.e., antioxidant, cytotoxic, cytoprotective) properties. We performed the synthesis and characterization of seven dimer conjugates with various combinations of nucleic acid bases and focused NMR studies on the model compound ga-CA dimer. We demonstrate that PNA dimers containing guanine conjugated to CA exhibited different biological activities depending on composition and sequence of the nucleobases. The dimer ag-CA protected HepG2, SK-B-NE(2), and C6 cells from a cytotoxic dose of hydrogen peroxide (H₂O₂).

Cocoa phenolic extract protects pancreatic beta cells against oxidative stress

Diabetes mellitus is associated with reductions in glutathione, supporting the critical role of oxidative stress in its pathogenesis. Antioxidant food components such as flavonoids have a protective role against oxidative stress-induced degenerative and age-related diseases. Flavonoids constitute an important part of the human diet; they can be found in most plant foods, including green tea, grapes or cocoa and possess multiple biological activities. This study investigates the chemo-protective effect of a cocoa phenolic extract (CPE) containing mainly flavonoids against oxidative stress induced by tert-butylhydroperoxide (t-BOOH) on Ins-1E pancreatic beta cells. Cell viability and oxidative status were evaluated. Ins-1E cells treatment with 5–20 μg/mL CPE for 20 h evoked no cell damage and did not alter ROS production. Addition of 50 μM t-BOOH for 2 h increased ROS and carbonyl groups content and decreased reduced glutathione level. Pre-treatment of cells with CPE significantly prevented the t-BOOH-induced ROS and carbonyl groups and returned antioxidant defences to adequate levels. Thus, Ins-1E cells treated with CPE showed a remarkable recovery of cell viability damaged by t-BOOH, indicating that integrity of surviving machineries in the CPE-treated cells was notably protected against the oxidative insult.

Evaluation of anti-oxidant and anti-cancer properties of Dendropanax morbifera Léveille

Dendropanax morbifera Léveille, an endemic species in Korea, is best known as a tree that produces a resinous sap. Although D. morbifera is used in folk medicine, its biological activities are poorly understood. In this study, the methanolic extracts of D. morbifera branches, debarked stems, bark, and two different stages of leaves were evaluated for anti-oxidant activity and anti-cancer potential. The debarked stem extract exhibited strong 1,1-diphenyl-2-picrylhydrazyl (DPPH) scavenging activity and reducing power compared with other samples. In addition, the cytotoxic activities of these extracts were investigated in human tumour cell lines. The results suggested that the extracts of debarked stems, green leaves, and yellow leaves were the potent source of anti-cancer compounds, particularly in Huh-7 cells. Furthermore, treatment with the extracts of debarked stems, green leaves, and yellow leaves caused an increase of apoptotic or senescent cells in Huh-7 cells. Twenty-four hour treatment with debarked stems extract resulted in the strong induction of p53 and p16, whereas both leaf extracts inhibited the activation of ERK. The debarked stems and green leaf extracts reduced Akt levels in Huh-7 cells, indicating that D. morbifera extracts caused the activation of p16 and p53 pathways. This, together with the inhibition of Akt or ERK signalling, resulted in suppression of Huh-7 cell proliferation. These results suggest that methanolic leaf and debarked stems extracts are a source of anti-oxidant and anti-cancer compounds, and could be developed as a botanical drug.

The effect of rosmarinic acid on 1,2-dimethylhydrazine induced colon carcinogenesis

This study was carried out to investigate the chemopreventive potential of rosmarinic acid (RA) against 1,2-dimethylhydrazine (DMH) induced rat colon carcinogenesis by evaluating the effect of RA on tumour formation, antioxidant enzymes, cytochrome P450 content, p-nitrophenol hydroxylase and GST activities. Rats were divided into six groups and fed modified pellet diet for the entire experimental period. Group 1 served as control, group 2 received RA (10 mg/kgb.w.). Groups 3-6 were induced colon cancer by injecting DMH (20 mg/kgb.w.) subcutaneously once a week for the first four weeks (groups 3-6). In addition, RA was administered at the doses of 2.5, 5 and 10 mg/kgb.w. to groups 4-6 respectively. DMH treated rats showed large number of colonic tumours; decreased lipid peroxidation; decreased antioxidant status; elevated CYP450 content and PNPH activities; and decreased GST activity in the liver and colon. Supplementation with RA (5 mgkg/b.w.) to DMH treated rats significantly decreased the number of polyps (50%); reversed the markers of oxidative stress (21.0%); antioxidant status (38.55%); CYP450 content (29.41%); and PNPH activities (21.9%). RA at the dose of 5 mg/kgb.w. showed a most pronounced effect and could be used as a possible chemopreventive agent against colon cancer.

The hepatoprotection of caffeic acid and rosmarinic acid, major compounds of Perilla frutescens, against t-BHP-induced oxidative liver damage

Perilla frutescens leaves are often used in East Asian gourmet food. In this study, we investigated the hepatoprotective effects of caffeic acid (CA), rosmarinic acid (RA), and their combination. P. frutescens contains 1.32μg CA/mg dry material (DM) and 26.84μg RA/mg DM analyzed by HPLC-DAD and HPLC-MS. CA remarkably reduced the oxidative damage than rosmarinic acid in an in vitro study. Oral intubation with CA or RA alone for five days was conducted prior to treatment with a single dose of tert-butyl hydroperoxide (0.5mmol/kg b.w., i.p.), which led to a significant reduction of indicators of hepatic toxicity, such as aspartate aminotransferase, alanine aminotransferase, oxidized glutathione, lipid peroxidation and enzyme activities related to antioxidant such as catalase, glutathione peroxidase and superoxide dismutase. Interestingly, compared to treatment with CA or RA alone, a combination of both compounds more increased the endogenous antioxidant enzymes and glutathione (GSH) and decreased lipid peroxidation in livers. These results suggest that CA from perilla leaves plays a role in the increased hepatic GSH concentration, and shows an additive hepatic protection with RA against oxidative hepatic damage.

Hepatoprotective potential of Lavandula coronopifolia extracts against ethanol induced oxidative stress-mediated cytotoxicity in HepG2 cells

The present investigations were carried out to study the protective potential of four extracts (namely petroleum ether extract (LCR), chloroform extract (LCM), ethyl acetate extract (LCE), and alcoholic extract (LCL)) of Lavandula coronopifolia on oxidative stress-mediated cell death induced by ethanol, a known hepatotoxin in human hapatocellular carcinoma (HepG2) cells. Cells were pretreated with LCR, LCM, LCE, and LCL extracts (10-50 μg/ml) of L. coronopifolia for 24 h and then ethanol was added and incubated further for 24 h. After the exposure, cell viability using (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) and neutral red uptake assays and morphological changes in HepG2 cells were studied. Pretreatment with various extracts of L. coronpifolia was found to be significantly effective in countering the cytotoxic responses of ethanol. Antioxidant properties of these L. coronopifolia extracts against reactive oxygen species (ROS) generation, lipid peroxidation (LPO), and glutathione (GSH) levels induced by ethanol were investigated. Results show that pretreatment with these extracts for 24 h significantly inhibited ROS generation and LPO induced and increased the GSH levels reduced by ethanol. The data from the study suggests that LCR, LCM, LCE, and LCL extracts of L. coronopifolia showed hepatoprotective activity against ethanol-induced damage in HepG2 cells. However, a comparative study revealed that the LCE extract was found to be the most effective and LCL the least effective. The hepatoprotective effects observed in the study could be associated with the antioxidant properties of these extracts of L. coronopifolia.

Synthesis and bioactivity profile of 5-s-lipoylhydroxytyrosol-based multidefense antioxidants with a sizeable (poly)sulfide chain

Novel polyfunctionalized antioxidants, 5-S-lipoylhydroxytyrosol (1) and its disulfide 2, trisulfide 3, and tetrasulfide 4, were prepared from tyrosol and dihydrolipoic acid in the presence, when appropriate, of sulfur. Compound 1 exhibited significant activity in the ferric reducing/antioxidant power (FRAP) assay (1.60 Trolox equiv), whereas polysulfides 2-4 were more efficient in the DPPH reduction assay (88-93% reduction vs 68% by Trolox). At 10 μM concentration, all compounds 1-4 proved to be efficient hydroxyl radical scavengers (56-69% inhibition) in a Fenton reaction assay. When administered to human HepG2 cells, 1-4 proved to be nontoxic and exhibited marked protective effects against reactive oxygen species (ROS) generation (60-84% inhibition at 1 μM concentration) and cell damage induced by 400 μM tert-butylhydroperoxide. All compounds 1-4 exhibited overall greater antioxidant activity than hydroxytyrosol.