A high-quality genome of Actinidia eriantha provides new insight into ascorbic acid regulation

Actinidia eriantha is one of the species of kiwifruit with a particularly high ascorbic acid (AsA) content.However, the molecular mechanism driving AsA richness in fruit remains unclear.In order to reveal the molecular mechanism of AsA richness in A. eriantha, this study constructed a regulatory network related to AsA metabolism by combining genomics,metabolomics and transcriptomics.We assembled a high-quality genome of A. eriantha ‘Ganlv 1’ with only five remaining gaps.The assembly is comprised of 29 pseudochromosomes with a total size of 615.95 Mb, and contig N50 of 20.35 Mb.Among them,24 of the pseudochromosomes were obtained directly from telomere-to-telomere.The LTR assembly index score and consensus quality value were 21.34 and 39.90%, respectively.Subsequently, 61 metabolites and 2 092genes were found to be differentially accumulated/expressed during fruit development by metabolome and transcriptome assays, respectively.AsA metabolism and the cyclic regeneration pathway were found to have high expression levels throughout fruit growth and development,suggesting its crucial role in the regulation of AsA.Furthermore,the AsA contents are highly associated with ascorbate peroxidase genes.The genome obtained in this study provides genomic resources for the genetic and breeding research ofA. eriantha, and the constructed regulatory network can provide a public data platform for future research on kiwifruit.

Appraisal of Improvement in Physiological and Metabolic Processes by Exogenously Applied Natural and Synthetic Ascorbic Acid in Okra(Abelmoschus esculentus L.)Fruit Subjected to Water Deficit Stress

To counteract the effects of drought stress,scientists have adopted several approaches including the use of different chemicals both inorganic and organic,which is contemplated as a highly efficient and cost-effective shot-gun approach.Ascorbic acid(AsA)is a potential organic substance,which widely occurs in plants,and is considered to be an effective antioxidant to counteract reactive oxygen species(ROS).Thus,a pot experiment was performed to assess the relative mitigating impacts of synthetic AsA and naturally occurring AsA in the form of lemon juice(LJ)and orange juice(OJ)on two cultivars of okra(Abelmoschus esculentus L.)namely Sabz Pari and Bhindi Sanwali under varying water deficit conditions.After 30 days of seed germination,okra seedlings were subjected to different irrigation regimes,i.e.,water deficit stress[(65%and 50%F.C.)and control conditions(100%F.C.)].Different levels of AsA[control(no spray),14 mg L^(−1)LJ,24 mg L^(−1)OJ and 150 mg L^(−1)AsA]obtained from different sources were applied as a foliar spray to control and water-stressed plants.Drought stress prominently reduced plant growth and yield attributes of the okra cultivars.Water-deficit conditions(65%and 50%F.C.)substantially decreased the fruit chlorophyll(a,b)pigments and the activity of superoxide dismutase(SOD)enzyme,while an increase was observed in the contents of fruit’s hydrogen peroxide(H_(2)O_(2)),malondialdehyde(MDA),total phenolics,total soluble sugars,AsA,and total soluble proteins.Drought stress also increased the activities of antioxidant enzymes like peroxidase(POD)and catalase(CAT).However,plant growth and yield attributes,fruit chlorophyll pigments,total phenolics,total soluble sugars,total free amino acids,total soluble proteins,AsA,GB,H_(2)O_(2),and the activities of antioxidant enzymes(POD and CAT)were increased by the AsA exogenous treatment in both okra cultivars under water deficit and control conditions.Overall,LJ and OJ were more effective than the synthetic AsA in upregulating the physiological and metabolic processes of okra plants.So,cost-effective as well as multi-nutrient natural sources of AsA could be suggested for alleviating the harmful effects of water deficit stress on plants.

Preparation of Cu nanoparticles with ascorbic acid by aqueous solution reduction method

Cu nanoparticles were prepared by reducing Cu2＋ ions with ascorbic acid through aqueous solution reduction method. The effects of solution pH and average size of Cu2O particles on the preparation of Cu nanoparticles were investigated. Cu particles were prepared at pH 3, 5 or 7, with the smallest Cu particles obtained at pH 7. However, Cu particles could not be prepared at pH 9 or 11. The average size of Cu2O particles can affect that of Cu particles. Larger Cu2O particles result in larger Cu particles. In addition, experiments were conducted to explore the reaction process by measuring the X-ray diffraction （XRD） patterns of specimens collected at different time points during the reaction. It was found that Cu（OH）2 was initially formed as a precursor, followed by the formation of Cu2O, which was finally reduced to Cu particles.

VOLTAMMETRIC BEHAVIOR OF ASCORBIC ACID AT α-CYCLODEXTRIN INCORPORATED CARBON NANOTUBES-COATED ELECTRODE

制备了α -环糊精掺杂纳米碳管涂层电极并应用于抗坏血酸的电催化氧化 ,结果表明 ,氧化电位降低了 2 80mV ,电流响应明显增加。我们首次结合两种物质的特性 :纳米碳管的导电性及催化性能、α -环糊精的分子认知能力 ,对电极表面进行修饰。实验了抗坏血酸与α -环糊精超分子络合物的特性。差示脉冲技术用于定量分析抗坏血酸 ,线性范围为 2 .5× 10 -6～ 1.0× 10

Ascorbic Acid Promotes Arsenic-induced Cytotoxicity in Human Hepatocarcinoma Cells and Their Underlying Mechanisms

Objective: To study synergistic effect with Ascorbic acid(AA) on arsenic trioxide inducing human Hepatocarcinoma cell apoptosis, and provide theoretical basis for promoting human Hepatocarcinoma cell apoptosis induced by arsenic trioxide(AT). Methods: Human Hepatocarcinoma cell line BEL-7402 being cultured in vitro, the effect of AT and (or) AA on its growth inhibition and its two intracellular signal molecules was evaluated separately using MTT and Western blot. Results: AT at a few μmol/L concentration could suppress abnormal proliferation of human hepatocarcinoma cells, and initiate their apoptosis by activation of caspase-3, and activate extracellular-signal regulated kinases (ERKs), which were dependent on the dosage of AT conspicuously. The effect of AA on BEL-7402 was not significant; However, AA could effectively enhance AT-induced hepatocarcinoma cell apoptosis and lesion severity through activation of caspase-3 but not ERKs. Conclusion: Caspase-3 and ERKs proteins could involve in arsenic-induced hepatocarcinoma cell apoptosis and differentiation respectively as intracellular signaling molecules; The effect between AT and AA on hepatocarcinoma is synergistic, which further inhibits cell growth and induces apoptosis in human hepatocarcinoma cells through activation of caspase-3 but not ERKs.

Effect of Ascorbic Acid and Silicium on Photosynthesis, Antioxidant Enzyme Activity, and Fatty Acid Contents in Canola Exposure to Salt Stress

The effects of exogenous ascorbic acid and silicium on leaf fresh weigh, seed yield, photosynthesis, changes of the activities of major antioxidant enzymes, nitrate reductase activity, proline accumulation, chlorophyll content, and fatty acid composition were investigated in salt-stressed canola. A hydroponic pot experiment was conducted based on randomized complete block design, factorial arrangement was used with 16 combinations of salinity stress （0, 100, 200, and 300 mmol L-1 NaC1）, ascorbic acid （0 and 30 mmol L-1）, and silicium （2 and 4 mmol L-1 from potassium silicate） with three replicates. The results showed that salinity significantly decreased leaf area and leaf fresh weight, seed yield, photosynthesis, nitrate reductase activity, chlorophyll content, and seed protein percentage. Conversely, respiration, antioxidant enzymes activity, proline accumulation, and linolenic acid percentage increased due to salt stress. Ascorbic acid application improved photosynthesis and seed yield and mitigated antioxidant enzyme activity. In addition, nitrate reductase activity and chlorophyll a and b were positively affected by ascorbic acid. Regarding silicium application, that was found that leaf area, leaf fresh weight, seed yield and photosynthesis, ascorbate peroxidase activity, nitrate reductase activity, and chlorophyll content increased, while respiration decreased. Furthermore, silicium had not significant effect on antioxidant enzyme activity. In general, ascorbic acid and silicium were involved in the defensive mechanisms against salinity stress and it can be suggested that, ascorbic acid and silicium application had positive effect on canola growth under conditions of salt stress.

The Protective Effect of Ascorbic Acid and Thiamine Supplementation against Damage Caused by Lead in the Testes of Mice

Lead is a ubiquitous environmental and industrial pollutant that may have toxic effects on the male. Vitamins may protect against toxic effects of lead in the liver and reproductive system, which is confirmed by our initial research. The aim of this study was to further investigate the protective effects of vitamins （ascorbic acid combined with thiamine） on lead acetate （Pb）-induced reproductive toxicities in mice and study the possible mechanisms underlying these effects. Forty-five male mice were randomly divided into 3 groups, 15 mice in each and received daily intragastric administration with control, Pb （20 mg/kg）, and Pb＋vitamins （ascorbic acid of 420 mg/kg＋thiamine of 30 mg/kg） for 6 weeks, respectively. The Pb-treated animals showed significant decreases in the epididymal sperm count and motility compared to the control group, while the Pb＋vitamins group had significant increases for these variables. Moreover, an increasing apoptosis of germinal cells induced by Pb was reduced by vitamin treatment. Pb induced the activation of Caspase-3, Fas/Fas-L and Bcl-2 with elevated levels, and the adaptor protein primarily regulated signaling through Fas and required for Fas-induced apoptosis. In conclusion, ascorbic acid combined with thiamine exhibited protective effect on reproductive system by inhibiting Pb-induced excessive cell apoptosis.

Mechanism of Ascorbic Acid-induced Reversion Against Malignant Phenotype in Human Gastric Cancer Cells

Objective To find out the mechanisms of redifferentiation and reversion of malignant human gastric cancer cells induced by ascorbic acid. Methods Human gastric cancer cells grown in the laboratory were used. The Trypan blue dye exclusion method was used to determine the cell doubling time. The electrophoresis rate and colonogenic potential were the indices used to measure the rate of redifferentiation. The content of malondialdehyde （MDA） was measured using the thiobarbituric acid （TBA） method. The activities of superoxide dismutase （SOD）, catalase （CAT） and the content of H2O2 were evaluated by spectrophotography. Results Six mmol/L ascorbic acid was used as a positive control. Human gastric cancer cells were treated with 75 μm hydrogen peroxide, which alleviated many of the malignant characteristics. For example, the cell surface charge obviously decreased and the electrophoresis rate dropped from 2.21 to 1.10 pm·s^-1·cm^-1 The colonogenic potential, a measure of cell differentiation, decreased 90.2%. After treatment with ascorbic acid, there was a concentration- and time-dependent increase in hydrogen peroxide （H2O2） and the activity of superoxide dismutase （SOD）. However, the activity of catalase （CAT） resulted in a concentration- and time-dependent decrease. SOD and 3-amino- 1,2,4-triazole （AT） exhibited some effects, but there were statistically significant differences between the SOD and AT group and the H2O2 group, Conclusions Ascurbic acid induces growth inhibition and redifferentiation of human gastric cancer cells through the production of hydrogen peroxide.

A Multiwall Carbon Nanotube-chitosan Modified Electrode for Selective Detection of Dopamine in the Presence of Ascorbic Acid

A novel multiwall carbon nanotube-chitosan modified electrode has been prepared.The modified electrode resolves the overlapping voltammetric response of dopamine and ascorbicacid into two well-defined peak by 212 mV. The mechanism of discrimination of dopamine fromascorbic acid is discussed. Dopamine can be determined selectively with the carbonnanotube-chitosan modified electrode. The electrode shows good sensitivity, selectivity andstability.

Electroanalysis and simultaneous determination of dopamine and epinephrine at poly(isonicotinic acid)-modified carbon paste electrode in the presence of ascorbic acid

A carbon paste electrode modified with electropolymerized fills of isonicotinic acid was developed. The modified electrode shows excellent electrocatalytic activity toward the oxidation of both dopamine （DA） and epinephrine （EP）. Separation of the reduction peak potentials for dopamine and epinephrine was about 357 mV in pH 5.3 phosphate buffer solution （PBS） and the character was used for the detection DA and EP simultaneously. The peak currents increase linearly with DA and EP concentration over the range of 8.0×10^-5 to 7.0×10^-4 mol/L and 5.0×10^-6 to 1.0×10^-4 mol/L with detection limits of 2×10^-5 and 1×10^-6 mol/L, respectively. The interference studies showed that the modified electrode exhibits excellent selectivity in the presence of large excess of ascorbic acid （AA）.

Role of dissolved oxygen reduction in improvement inhibition performance of ascorbic acid during copper corrosion in 0.50 mol/L sulphuric acid

The kinetics of dissolved O_2 reduction and hydrogen evolution reactions on copper surface was studied in naturally aerated and air and O_2-saturated 0.50 mol/L H_2SO_4 solutions using polarization measurements combined with the rotating disc electrode (RDE).The Koutecky-Levich plot indicated that the dissolved O_2 reduction at the copper electrode was an apparent four-electron process.A correlation between the presence of dissolved O_2 and the formation of Cu_2O,confirmed from XRD,was discussed. Ascorbic a...

Ascorbic acid synthesis and transportation capacity in old laying hens and the effects of dietary supplementation with ascorbic acid

Background: Laying hens over 75 weeks of age commonly show great declines in immunity and production performance.It is unclear whether these declines can be relieved by supplementing with ascorbic acid(AA) in feed.Two trials were conducted to investigate the synthesis and metabolism of AA in layers of different ages and the effects of dietary supplemental AA on the performance and the immune and antioxidant statuses of 78 weeks old hens.Methods: In Exp.1,equal numbers(24 hens) of 35 weeks old(Young) and 75 weeks old(Old) layers were fed the same diet without AA supplementation for 4 weeks.In Exp.2,360 healthy 78 weeks old laying hens were randomly assigned to 4 treatments(basal diet supplemented with 0,0.25,0.5,or 1 g AA/kg diet) in an 8-week feeding trial.Results: The old hens tended to have decreased L-gulonolactone oxidase(GLO) synthase activity in the kidney and liver than that of the young hens(P = 0.07 and P = 0.05,respectively).Compared with the young hens,the old hens had lower hepatic antioxidant capacity allowing for the lower thioredoxin(TXN),thioredoxin reductase(TXNR) and cytochrome b5 reductase(CYB5 R) gene expression(P < 0.05),whereas increased sodium-dependent vitamin C transporter(SVCT) 1 expression levels in the ileum and kidney and enhanced splenic and hepatic AA concentrations(P < 0.05).Dietary supplementation with AA significantly decreased GLO enzyme activity but increased splenic AA concentration and anti-bovine serum albumin IgG levels(P < 0.05) and tended to increase CD4+T lymphocyte numbers(P = 0.06) in serum.Supplementation of 0.25 g AA/kg diet significantly increased hepatic total antioxidant capacity(T-AOC,P < 0.05) relative to the control group.Conclusions: Laying hens could synthesize AA in both the kidney and the liver,though the GLO enzyme activities were 100 times greater in kidneys than in livers.The old laying hens had greater absorption and reabsorption capacity and higher AA retention in some tissues that did the young hens.Dietary supplementation of AA can improve the health of old layers by enhancing immunity and antioxidant capacity.

Low-volume plus ascorbic acid vs high-volume plus simethicone bowel preparation before colonoscopy

AIM： To investigate the effectiveness of low-volume plus ascorbic acid [polyethylene glycol plus ascorbic acid （PEG ＋ Asc）] and high-volume plus simethicone [polyethylene glycol plus simethicone （PEG ＋ Sim）] bowel preparations. METHODS： A total of one hundred and forty-four outpatients （76 males）, aged from 20 to 84 years （median age 59.5 years）, who attended our Department, were divided into two groups, age and sex matched, and underwent colonoscopy. Two questionnaires, one for patients reporting acceptability and the other for endoscopists evaluating bowel cleansing effectiveness according to validated scales, were completed. Indications, timing of examination and endoscopical findings were recorded. Biopsy forceps were used as a measuring tool in order to determine polyp endoscopic sizeestimation. Difficulty in completing the preparation was rated in a 5-point Likert scale （1 = easy to 5 = unable）. Adverse experiences （fullness, cramps, nausea, vomiting, abdominal pain, headache and insomnia）, number of evacuations and types of activities performed during preparation （walking or resting in bed） were also investigated. RESULTS： Seventy-two patients were selected for each group. The two groups were age and sex matched as well as being comparable in terms of medical history and drug therapies taken. Fourteen patients dropped out from the trial because they did not complete the preparation procedure. Ratings of global bowel cleansing examinations were considered to be adequate in 91% of PEG ＋ Asc and 88% of PEG ＋ Sim patients. Residual Stool Score indicated similar levels of amount and consistency of residual stool; there was a significant difference in the percentage of bowel wall visualization in favour of PEG ＋ Sim patients. In the PEG ＋ Sire group, 12 adenomas≤ 10 mm diameter （5/left colon ＋ 7/right colon） vs 9 （8/left colon ＋ 1/right colon） in the PEG ＋ Asc group were diagnosed. Visualization of small lesions seems to be one of the primary advantages of the PEG ＋ Sim preparation. CONCLUSION： PEG ＋ Asc is a good alternative solution as a bowel preparation but more improvements are necessary in order to achieve the target of a perfect preparation.

Efficacy of 1.2L polyethylene glycol plus ascorbic acid for bowel preparations

BACKGROUND A low-volume polyethylene glycol(PEG) solution that combines ascorbic acid with PEG-based electrolyte solution(PEG-ASC) is gaining mainstream acceptance for bowel preparation due to reduced volume and improved taste.Although several reports showed that bowel preparation with PEG-ASC volume lower than 2.0 L with laxative agents could be an alternative to traditional preparation regimen, the cleansing protocols have not been fully investigated.AIM To evaluate the cleansing efficacy of 1.2 L PEG-ASC solution comparing with 2.0 L PEG electrolyte(PEG-ELS) for bowel preparations.METHODS A randomized, single-blinded, open-label, single-center, non-inferiority study was conducted. In total, 312 Japanese adult patients(aged > 18 years) who underwent colonoscopy were enrolled. Patients were randomly allocated to bowel lavage with either 1.2 L of PEG-ASC solution with at least 0.6 L of an additional clear fluid(1.2 L PEG-ASC group) or 2.0 L of PEG-ELS(PEG-ELS group). Then, 48 mg of sennoside was administered at bedtime on the day before colonoscopy, and the designated drug solution was administered at the hospital on the day of colonoscopy. Bowel cleansing was evaluated using the Boston Bowel Preparation Scale(BBPS). The volume of fluid intake and required time for bowel preparation were evaluated. Furthermore, compliance, patient tolerance,and overall acceptability were evaluated using a patient questionnaire, which was assessed using a visual analog scale.RESULTS In total, 291 patients(1.2 L PEG-ASC group, 148; PEG-ELS group, 143) completed the study. There was no significant difference in successful cleansing, defined as a BBPS score ≥ 2 in each segment, between the two groups(1.2 L PEG-ASC group, 91.9%; PEG-ELS group, 90.2%; 95%CI:-0.03-0.09). The required time for bowel preparation was significantly shorter(164.95 min ± 68.95 min vs 202.16 min± 68.69 min, P < 0.001) and the total fluid intake volume was significantly lower(2.23 L ± 0.55 L vs 2.47 L ± 0.56 L, P < 0.001) in the 1.2 L PEG-ASC group than in the PEG-ELS group. Palatability, acceptability of the volume of solution, and overall acceptability evaluated using a patient questionnaire, which was assessed by the visual analog scale, were significantly better in the 1.2 L PEG-ASC group than in the PEG-ELS group(7.70 cm ± 2.57 cm vs 5.80 cm ± 3.24 cm, P < 0.001). No severe adverse event was observed in each group.CONCLUSION The 1.2 L PEG-ASC solution was non-inferior to the 2.0 L PEG-ELS solution in terms of cleansing efficacy and had better acceptability among Japanese patients.

Cytoprotective effects of amifostine,ascorbic acid and N-acetylcysteine against methotrexate-induced hepatotoxicity in rats

AIM: To investigate the potential role of oxidative stress and the possible therapeutic effects of N-acetyl cysteine (NAC), amifostine (AMF) and ascorbic acid (ASC) in methotrexate (MTX)-induced hepatotoxicity.

Perioperative topical ascorbic acid for the prevention of phacoemulsification-related corneal endothelial damage:Two case reports and review of literature

BACKGROUND The current case report describes successful phacoemulsification with the aid of perioperative topical ascorbic acid(AA) in two patients with corneal endothelial disorders to prevent postoperative corneal endothelial decompensation.CASE SUMMARY Two eyes of two patients underwent phacoemulsification with pre-existing corneal endothelial disorders including Fuchs corneal endothelial dystrophy(Patient 1) and endotheliitis(Patient 2). Topical AA was applied to both patients at least one month before and after with a frequency of four times per day. After the surgery, both eyes improved best-corrected visual acuity(BCVA) and there was limited human corneal endothelial cell loss without signs of corneal endothelial decompensation, such as deteriorated BCVA or persistent corneal edema during the follow-up of at least two years.CONCLUSION Perioperative administration of topical AA may be an alternative therapy to the triple procedure in patients expecting to undergo cataract surgery.

Protective effect of ascorbic acid on cyclophosphamide induced testicular gametogenic and androgenic disorders in male rats

Aim:To study the detrimental effects of cyclophosphamide on the testicular androgenic and gametogenic activities through endocrine inhibition and/or induction of oxidative stress in male albino rats and to evaluate the protective effect of ascorbic acid.Methods:The testicular△^(5),3β-hydroxysteroid dehydrogenase(HSD),17β-HSD,peroxidase and catalase activities along with the levels of malondialdehyde(MDA)and conjugated dienes in testicular tissue were measured for the evaluation of testicular oxidative stress.The plasma testosterone(T)level was measured by immunoassay.Various germ cells at stageⅦof spermatogenic cycle were quantified from testicular stained sections.Results:Cyclophosphamide treatment results in a significant inhibition in the testicular△^(5),3β-HSD and 17β-HSD activities,a decrease in plasma T level and a diminution in the counts of various germ cells.Moreover,this treatment was also associated with a significant inhibition of the peroxidase and catalase activities along with high levels of MDA and conjugated dienes in the testis.All these changes were reversed by ascorbic acid co-administration.Conclusion:Cyclophosphamide treatment at the dosage used caused testicular gametogenic and androgenic disorders as well as induced testicular oxidative stress that can be reversed by ascorbic acid co-administration.

Comparative Study of Ascorbic Acid and Tocopherol Concentrations in Hydroponic- and Soil-Grown Lettuces

Hydroponically-grown produce may be a way of helping to feed the world a variety of fruits and vegetables, regardless of soil quality, space availability or climate. The objective of this study was to determine whether hydroponicallygrown lettuce contains as much ascorbic acid and tocopherol as soil-grown lettuce. We analyzed four varieties of lettuce, including: Waldmann’s Dark Green, Red Lollo Antago, Red Romaine Annapolis, and Butterleaf. The tocopherol content of hydroponically-grown Waldmann’s Dark Green, Red Lollo Antago, and Red Romaine Annapolis was 229%, 497% and 492% higher, respectively, compared to their soil-grown counterpart. The ascorbic acid content of hydroponically-grown Waldmann’s Dark Green, Red Lollo Antago, and Red Romaine Annapolis was 93%, 171% and 216% higher, respectively, compared to their soil-grown counterparts. Hydroponically grown lettuce varieties are significantly higher in both ascorbic acid and tocopherol content than their soil-grown counterparts, and hydroponic gardening is a viable option for producing nutritious fruits and vegetables.

Redifferentiation of Human Gastric Cancer Cells Induced by Ascorbic Acid and Sodium Selenite

Objective To explore the effects and mechanisms of ascorbic acid (AA) and sodium selenite (SS) on growth inhibition and redifferentiation in human gastric cancer cells. Methods In the present study, trypan blue dye exclusion method was used to determine the cell growth curve and mitotic index, cell electrophoresis and colonogenic potential were used as the indexes of redifferentiation. In order to find out the mechanisms of redifferentiation, the activities of superoxide dismutase (SOD), glutathione peroxidase (GPX) and catalase (CAT) were assayed, the content of malondialdehyde (MDA), reduced glutathione (GSH) and H2O2 were evaluated. Results After treatment with AA 3 mol/L + SS 2μmol/L, the growth rate and mitotic index of human gastric cancer cells (MGc-803) decreased remarkably. The indexes related with cell malignancy were alleviated. For example, cell surface charge was obviously decreased, the electrophoresis rate was dropped from 2.21 to 1.15μm·s-1·V-1·cm-1. The indexes related with cell redifferentiation were promoted. For example, the colonogenic potential was decreased to 93.5%. These results indicated that redifferentiation of human gastric cancer cells was successfully induced by AA + SS. The activities of SOD and GPX were significantly higher, while the activity of CAT was slower in treated group than that in the control. The content of MDA was slightly decreased, GSH was sharply decreased, and H2O2 content was dramatically increased. Conclusion These results indicated that combination of ascorbic acid and sodium selenite may induce the redifferentiation of human gastric cancer cells and inhibit cell growth by virtue of enhancing the activities of antioxidative enzymes and inducing the formation of H2O2, and altering the cell redox status. Combination of ascorbic acid and sodium selenite may be a potent anticancer agent for human gastric cancer.

Electro-oxidation of Ascorbic Acid on PVP-stabilized Graphene Electrode

Polyvinylpyrrolidone-stabilized graphene（PVP-graphene） was synthesized and investigated as a modifier for the determination of ascorbic acid（AA）. With PVP acting as stabilizer and dispersant, the resulting PVP-graphene material could disperse well into water. And the PVP-graphene modified glassy carbon electrode（PVP-graphene-GCE） showed an obvious electrocatalytical activity toward the oxidation of AA in a phosphate buffer solution（PBS, pH=7.0） with an oxidation potential of AA at 0.052 V vs. AglAgCl（sat. KCl）. The calibration curve for APt was linear in a concentration range from 1.0×10^-5 to 5.0×10^-4 mol/L with a correlation coefficient of 0.9998. And the detection limit was found to be 1 μtmol/L. During the oxidation of AA, the π-π interaction of graphene plane with conjugated hexenoic aeid-lactone in AA molecules might play a key role. As a result, an obvious decrease of overpotential was achieved at such a PVP-graphene electrode through a possible adsorption/enrichment process, which will probably trigger potential applications for the electroanalysis of some aromatic and heterocyclic compounds.