Oxidative decomposition of vitamin C in drinking water

We have previously shown that vitamin C (ascorbic acid) can initiate hydroxyl radical formation in copper contaminated household drinking water. In the present study, we have examined the stability of vitamin C in copper and bicarbonate containing household drinking water. In drinking water samples, contaminated with copper from the pipes and buffered with bicarbonate, 35% of the added vitamin C was oxidized to dehydroascorbic acid within 15 min. After 3 h incubation at room temperature, 93% of the added (2 mM) ascorbic acid had been oxidized. The dehydroascorbic acid formed was further decomposed to oxalic acid and threonic acid by the hydrogen peroxide generated from the copper (I) autooxidation in the presence of oxygen. A very modest oxidation of vitamin C occurred in Milli-Q water and in household water samples not contaminated by copper ions. Moreover, addition of vitamin C to commercially sold domestic bottled water samples did not result in vitamin C oxidation. Our results demonstrate that ascorbic acid is rapidly oxidized to dehydroascorbic acid and further decomposed to oxalic- and threonic acid in copper contaminated household tap water that is buffered with bicarbonate. The impact of consuming ascorbic acid together with copper and bicarbonate containing drinking water on human health is discussed.     

Vitamin C (ascorbic acid) induced hydroxyl radical formation in copper contaminated household drinking water: role of bicarbonate concentration

We have previously shown that Vitamin C (ascorbic acid) can trigger hydroxyl radical formation in copper contaminated household drinking water. We report here that the capacity of ascorbic acid to catalyze hydroxyl radical generation in the drinking water samples is strongly dependent on the bicarbonate concentration (buffer capacity and pH) of the samples. We found that at least 50 mg/l bicarbonate was required in the water samples to maintain the pH over 5.0 after ascorbic acid addition. At this pH, that is higher than the pKa

1

4.25 of ascorbic acid, a hydroxyl radical generating redox cycling reaction involving the mono-anion of vitamin C and copper could take place. The ascorbic acid induced hydroxyl radical generating reaction could easily be mimicked in Milli-Q water by supplementing the water with copper and bicarbonate. Our results demonstrate that ascorbic acid can induce a pH dependent hydroxyl radical generating reaction in copper contaminated household tap water that is buffered with bicarbonate. The impact of consuming ascorbic acid together with copper and bicarbonate containing drinking water on human health is discussed.     

对维生素C的新认识

维生素Ｃ（Ｖｃ）是一种广泛使用的药物。它具有氧化还原性质。它既可损伤肿瘤细胞ＤＮＡ起到抑癌作用,又可损伤正常细胞ＤＮＡ而致癌。Ｖｃ可激活Ｔ细胞,增加干扰素产量,限制肿瘤发展。Ｖｃ还具有在肿瘤坏死因子存在下损伤甚至杀死ＨＩＶ－１的作用。研究表明Ｖｃ是一种极其复杂的多功能物质。     

Evaluation of Oxidative Stress, Antioxidant Status and Serum Vitamin C Levels in Cancer Patients

Taking into account the importance role of lipid peroxidation and antioxidants in the prevention and incidence of cancer, the present study was carried out to determine oxidative stress, serum total antioxidant (TAS), and vitamin C levels in cancer patients. Malondialdehyde(MDA), total antioxidant status, and vitamin C levels of 57cancer patients aged 19–80 years and 22 healthy subjects (control group) aged 22–76 years were evaluated. Serum concentrations of MDA as thiobarbitaric acid complexes were measured by fluorometry method, the serum TAS by using commercial test kits from Randox Laboratories, and vitamin C by using spectrocolorimetric method. The mean serum MDA concentrations of all cancer groups except lung cancer were significantly higher than control group (P < 0.004). The mean total antioxidant status was insignificantly higher than control group. The mean serum vitamin C level was significantly lower in patients as compared to the healthy subjects (PV < 0.0001). In conclusion, an alteration in the lipid peroxidation with concomitant changes in antioxidant defense system in cancer patients may be due to excessive oxidative stress. Serum low levels of vitamin C in the different type of cancer patients in spite of adequate daily intake may be due to increased utilization to scavenge lipid peroxides as well as their sequestration by tumor cells.     

Vitamin C Prevents Oxidative Damage

Ascorbate - deficiency leads to extensive oxidative damage of proteins and protein loss in the guinea pig tissue microsomes as evidenced by sodium dodecyl sulfate polyacrylamide gel electrophoresis, accumulation of carbonyl, bityrosine as well as by tryptophan loss. Oxidative damage is reversed by ascorbate therapy. Oxidative damage in ascorbate deficiency also leads to lipid peroxidation in guinea pig tissue microsomes as evidenced by accumulation of conjugated dienes, malondialdehyde and fluorescent pigment. Lipid peroxides disappear after ascorbate therapy but not by vitamin E. The observations substantiate the previous in vitro findings that ascorbate specifically prevents oxidative degradation of microsomal membranes. The results indicate that vitamin C may exert a powerful protection against degenerative diseases associated with oxidative damage and play a critical role in wellness and health maintenance.     

Vitamin C Prevents Oxidative Damage

Ascorbate - deficiency leads to extensive oxidative damage of proteins and protein loss in the guinea pig tissue microsomes as evidenced by sodium dodecyl sulfate polyacrylamide gel electrophoresis, accumulation of carbonyl, bityrosine as well as by tryptophan loss. Oxidative damage is reversed by ascorbate therapy. Oxidative damage in ascorbate deficiency also leads to lipid peroxidation in guinea pig tissue microsomes as evidenced by accumulation of conjugated dienes, malondialdehyde and fluorescent pigment. Lipid peroxides disappear after ascorbate therapy but not by vitamin E. The observations substantiate the previous in vitro findings that ascorbate specifically prevents oxidative degradation of microsomal membranes. The results indicate that vitamin C may exert a powerful protection against degenerative diseases associated with oxidative damage and play a critical role in wellness and health maintenance.     

激光联合氨甲环酸、谷胱甘肽及维生素C 治疗黄褐斑的临床观察

目的：探讨黄褐斑应用激光联合氨甲环酸、谷胱甘肽及维生素C 治疗的临床效果。方法：选择2012 年6 月~2014 年6 月期 间我院皮肤科门诊收治的黄褐斑女性患者117 例,根据随机数字表将其平均分为三组,即激光组、药物组、联合治疗组各39 例。 激光组单纯应用激光治疗,药物组应用氨甲环酸、谷胱甘肽及维生素C治疗,联合治疗组应用激光联合氨甲环酸、谷胱甘肽及维 生素C 治疗。对比三组治疗前后黄褐斑面积及黄褐斑颜色评分、临床疗效及治疗后不良反应。结果：联合组治疗后黄褐斑面积及 黄褐斑颜色评分显著低于激光组、药物组及治疗前（P<0.05）。联合组治疗的总有效率显著高于激光组及药物组（P<0.05）。药物组 不良反应发生率为2.56%,其他两组未见明显不良反应。结论：激光联合氨甲环酸、谷胱甘肽及维生素C 治疗黄褐斑的疗效确切, 可以有效改善黄褐斑面积及颜色,安全性佳,适于临床应用。     

不同浓度维生素C对亚油酸微团的促过氧化和抗过氧化作用

不同浓度维生素Ｃ对亚油酸微团的促过氧化和抗过氧化作用于颖彦（河北医学院附属第二医院病理科石家庄０５００００）冈田茂（日本冈山大学医学部病理学教室７００）关键词亚油酸,脂质过氧化,铁离子,维生素Ｃ维生素Ｏ（简称Ｖｃ）在人体内除了参与激素、神经传导介质和...     

猕猴桃(Actinidia Lindl.)叶片与果实维生素C含量的相关性研究

以猕猴桃属中华猕猴桃（Actinidia chinensis）32个品种和1个种间杂交后代群体为研究对象,对猕猴桃属植物叶片与果实维生素C含量的相关性进行了研究。结果表明,在中华猕猴桃种内水平上,幼果与成熟果实的果肉维生素C含量间存在极显著的正相关关系;在种间杂交后代群体中成熟叶片和成熟果实的维生素C含量存在极显著正相关关系,为利用早期相关性状开展猕猴桃育种的可行性提供了理论依据。此外,对15个常见中华猕猴桃品种的果实维生素C含量进行了多重比较,为人工杂交时的亲本选择提供了依据。     

Continuous stress-induced dopamine dysregulation augments PAP-I and PAP-II expression in melanotrophs of the pituitary gland

We studied the acquisition of dehydroascorbic acid by rat hepatocytes, H4IIE rat hepatoma cells and Xenopus laevis oocytes. Transport kinetics and competition and inhibition studies revealed that rat hepatocytes transport oxidized dehydroascorbic acid through a single functional component possessing the functional and kinetic properties expected for the glucose transporter GLUT2. On the other hand, rat hepatoma cells showed expression of at least two dehydroascorbic acid transporters with the expected functional and kinetic properties expected for GLUT1 and GLUT2. Expression studies of GLUT2 in X. laevis oocytes followed by transport kinetics and competition and inhibition studies revealed that GLUT2 is a low affinity dehydroascorbic transporter whose kinetic and functional properties match those observed for the endogenous GLUT2 transporter in rat hepatocytes and rat hepatoma cells. Therefore, GLUT2, a transporter known as a low affinity transporter of glucose and fructose and a high affinity transporter of glucosamine is also a low affinity dehydroascorbic acid transporter.     

Vc二步发酵一株新产酸菌的分子生物学特性

对最近分离到的一株能合成维生素C前体 - 2 -酮基 -L -古龙酸 (2 -KGA)的新产酸菌V6生物学和分子生物学特性进行了初步研究。该菌株为革兰氏阴性菌 ,细胞为短杆状 ,菌体大小为 0 .8- 1.0× 0 .4 - 0 .6 μm ,菌落为淡黄色 ,好氧 ,最适生长温度为 2 8～ 30℃ ,最适pH为 7.0～ 7.8,GCmol%含量为 5 3.1% ,不含质粒 ,能氧化葡萄糖、山梨醇和山梨糖合成 2 -KGA。 16SrDNA同源性分析发现 ,该产酸菌与以前报道的能合成 2 -KGA的三个属Ketogulonigenium属、Gluconobacter属和Acetobacter属的同源性分别是 98.9～ 99.3%、82～ 83%和 81～ 82 %。基于以上特性分析 ,该产酸菌在分类发育学上宜归为Ketogulonigenium属。     

Vitamin C deficiency: more than just a nutritional disorder

Although vitamin C deficiency and scurvy are generally considered as pure nutritional disorders, only a minority of the vitamin C concentration is determined by food intake. In the presence of transition metals (iron and copper), the antiscorbutic factor shifts from an antioxidant to a pro-oxidant function. Haptoglobin (Hp) is a plasma α-2 glycoprotein characterized by 3 common phenotypes (Hp 1-1, Hp 2-1 and Hp 2-2). Its free hemoglobin (Hb)-binding capacity prevents Hb-driven oxidative damage. When the antioxidant capacity of Hp is insufficient, its role is taken over by hemopexin (heme-binding protein) and by vitamin C (free radical scavenger). The Hp 2-2 phenotype has a lower capacity to inhibit oxidation and vitamin C depletion. In this article, two consequences of this major finding are tackled. The Hp polymorphism is an important non-nutritional modifying factor in the pathogenesis of vitamin C deficiency and scurvy, which may explain the success of long-range human migration by the natural selection of some populations characterized by high Hp 1 allele frequencies. Moreover, we propose tailoring the recommended dietary allowance (RDA) values of vitamin C, taking into consideration the Hp phenotype dependency.     

Effect of Dietary Vitamin C and Catalase Inhibition on Antioxidants and Molecular Markers of Oxidative Damage in Guinea Pigs

Guinea pigs were fed for five weeks with two diets with different levels of vitamin C, low (33 mg of Vit C/Kg diet) and high (13,200 mg of Vit C/Kg of diet). Catalase was inhibited with 3-amino-1,2,4-triazole (AT) in half of the animals from each dietary group. AT caused an almost complete depletion of liver catalase activity (90%) in both dietary groups. Vitamin C supplementation increased total glutathione peroxidase activity and tissue vitamin C level and decreased levels of protein carbonyls and malondialdehyde (MDA) in both treated and non-treated animals. This vitamin C supplementation did not change any of the other antioxidant defences studied. Our results show that dietary vitamin C supplementation increases global antioxidant capacity and decreases endogenous oxidative damage in the guinea pig liver under normal non-stressful conditions. This supports the protective value of dietary antioxidant supplementation.     

Ameliorative effect of ellagic acid and Vitamin C against malathion-induced toxicity in testis of adult Wistar rats

The pesticide malathion (MT), an organophosphate, is highly neurotoxic and causes cholinergic disorders as well as cytotoxicity, genotoxicity, mutagenicity, carcinogenicity and reproductive toxicity. Our purpose was to study the effect of ellagic acid (EA) and Vitamin C on the testis against MT-induced toxicity in the rats. Thirty-six adult Wistar rats were employed, separated into six groups and were given treatment for 14 days. The toxicity of MT on the testis was evaluated using a variety of physical parameters, such as mortality rate and body weight, as well as biochemical parameters, such as total protein, total cholesterol, serum glutamic-oxaloacetic transaminase and serum glutamic-pyruvic transaminase, and haematological parameters, such as counts of red blood cells, haemoglobin (Hb) and white blood cells, as well as mean corpuscular volume, mean corpuscular Hb, and mean corpuscular Hb concentration. At the end of the experiment, rats were killed and a histological examination of the testis was performed. A sperm count technique and an analysis of sperm motility were used to determine the sperm quality. Biochemical indicators, sperm count, motility, viability and morphology were significantly decreased with MT. When compared with MT and the control group, EA and Vitamin C administration significantly increased sperm motility and count (p < 0.05). After receiving EA and Vitamin C, biochemical indicators and histological characteristics are also intensified. The results of the current investigation show that EA and Vitamin C can both reduce increased levels of biochemical markers and improve pathological alterations in the testis brought on by MT treatment.     

提高植物维生素含量的基因工程

维生素是维持生物正常生长发育必需的一大类微量营养物。对利用基因工程的方法提高植物中维生素A、E和C含量的研究进展作了综述 ,指出了该类研究的一般方法并对未来做了展望。     

猕猴桃(Actinidia Lindl.)叶片与果实维生素C含量的相关性研究

以猕猴桃属中华猕猴桃(Actinidia chinensis)32个品种和1个种间杂交后代群体为研究对象,对猕猴桃属植物叶片与果实维生素C含量的相关性进行了研究。结果表明,在中华猕猴桃种内水平上,幼果与成熟果实的果肉维生素C含量间存在极显著的正相关关系;在种间杂交后代群体中成熟叶片和成熟果实的维生素C含量存在极显著正相关关系,为利用早期相关性状开展猕猴桃育种的可行性提供了理论依据。此外,对15个常见中华猕猴桃品种的果实维生素C含量进行了多重比较,为人工杂交时的亲本选择提供了依据。     

维生素C发酵研究进展

生物发酵法是生产维生素C的主要途径。目前具有工业应用前景的维生素C发酵途径主要有葡萄糖发酵工艺和山梨醇发酵工艺。我们分别从这2条产生维生素C重要前体2-酮基-L-古龙酸反应路线的代谢机制、反应酶系及工程菌构建等方面出发,综述了维生素C生物发酵的研究现状和最新进展,并对维生素C生物发酵应用前景做了展望。