L-抗坏血酸联合超声处理对鲜切芋艿贮藏品质的影响

为探究L-抗坏血酸(L-ascorbic acid,AA)联合超声(ultrasound,US)(AS)处理对鲜切芋艿片贮藏品质的影响,本实验以永定六月红芋为材料,采用质量分数为2%的AA溶液浸泡15 min后,进行US(53 kHz、400 W、10 min)处理,测定贮藏期间鲜切芋艿感官品质及褐变相关酶等指标。结果表明:与对照组相比,AS处理可以降低鲜切芋艿的失水率,维持较高的硬度,延缓褐变指数升高,降低细胞膜通透性,抑制丙二醛含量累积,抑制表面微生物繁殖,从而维持鲜切芋艿较高的感官品质;与对照组相比,贮藏期间AS处理组还能维持较高的过氧化氢酶、超氧化物歧化酶活性,降低过氧化物酶、多酚氧化酶和苯丙氨酸解氨酶活性,抑制酚类物质消耗速率,并减缓淀粉、可溶性蛋白、可溶性固形物等营养物质的流失速率,抑制可溶性醌的积累,延缓风味劣变。上述结果表明,AS处理能够保持鲜切芋艿较好的贮藏品质。

Alteration of chemical behavior of L-ascorbic acid in combination with nickel sulfate at different pH solutions in vitro

Objective:To evaluate the alteration of chemical behavior of L-ascorbic acid(vitamin C) with metal ion(nickel) at different pH solutions in vitro.Methods:Spectra of pure aqueous solution of L-ascorbic acid(E mark) compound and NiSO_4(H_2O)(sigma USA) were evaluated by UV visible spectrophotometer.Spectral analysis of L-ascorbic acid and nickel at various pH(2.0, 7.0,7.4 and 8.6) at room temperature of 29℃ was recorded.In this special analysis,combined solution of L-ascorbic acid and nickel sulfate at different pH was also recorded.Results:The result revealed that λ_(max)(peak wavelength of spectra) of L-ascorbic acid at pH 2.0 was 289.0 run whereas at neutral pH 7.0,λ_(max) was 29S.4 run.In alkaline pH 8.6,λ_(max) was 295.4 nm and at pH 7.4 the λ_(max) of L-ascorbic acid remained the same as 295.4 nm.Nickel solution at acidic pH 2.0 was 394.5 nm,whereas at neutral pH 7.0 and pH 7.4 were the same as 394.5 nm.But at alkaline pH 8.6,λ_(max) value of nickel sulfate became 392.0 nm.The combined solution of L-ascorbic acid and nickel sulfate(6 mg/mL each) at pH 2.0 showed 292.5 nm and 392.5 nm,respectively whereas at pH 7.0,L-ascorbic acid showed 296.5 nm and nickel sulfate showed 391.5 nm.At pH 7.4,L-ascorbic acid showed 297.0 nm and nickel sulfate showed 394.0 nm in the combined solution whereas at pH 8.6(alkaline) L-ascorbic acid and nickel sulfate were showing 297.0 and 393.5 nm,respectively. Conclusions:Results clearly indicate an altered chemical behavior of L-ascorbic acid either alone or in combination with nickel sulfate in vitro at different pH.Perhaps oxidation of L-ascorbic acid to L-dehydro ascorbic acid via the free radical(HSc*) generation from the reaction of H,ASc + Ni(Ⅱ) is the cause of such alteration of λ_(max),value of L-ascorbic acid in the presence of metal nickel.

2-O-α-D-葡萄糖基-L-抗坏血酸的酶法合成及其应用研究进展

2-O-α-D-葡萄糖基-L-抗坏血酸(2-O-D-glucopyranosyl-L-ascorbic acid,AA-2G)不仅稳定性强且保留了L-抗坏血酸(L-ascorbic acid,L-AA)的大部分生理活性,是L-AA最好的替代品。体外酶法合成AA-2G具有经济、快速、绿色和安全等显著优势,是规模化生产AA-2G的可行方法。该文综述体外酶法合成AA-2G的研究进展,重点梳理环糊精糖基转移酶和蔗糖磷酸化酶合成AA-2G的研究现状,并对AA-2G的功能及应用前景进行讨论和展望。

Organic Media Enhanced Spectrofluorimetric Determination of L-Ascorbic Acid

A novel spectrofluorimetric method for the determination of L ascorbic acid is proposed. It is based on the inhibition of L ascorbic acid on the formation of 2,3 diaminophenazine, which is an oxidation product of o phenylenediamine catalyzed by laccase .The fluorescence (at λ ex /λ em =464 nm /530 nnm) was enhanced strongly in the presence of organic media . The mechanism of o phenylenediamine oxidation reaction catalyzed by laccase in the presence of L ascorbic acid is discussed .L ascorbic acid is determined in the ethanol, 1,4 dioxane and acetone over the linear range of 4.0×10 -7 ～1.2×10 -4 mol/L, 4.0×10 -7 ～ 8.0×10 -5 mol/L and 4.0×10 -7 ～1.0×10 -4 mol/L with a detection limit of 1.20×10 -8 mol/L,1.19×10 -8 mol/L and 1.24×10 -8 mol/L, respectively. The method has been successfully applied to the simple and rapid determination of L ascorbic acid in pharmaceuticals and milk powder.

L-抗坏血酸联合超声处理鲜切芋艿的最佳条件

【目的】确定L-抗坏血酸(L-ascorbic acid,AA)联合超声(ultrasound,US)处理鲜切‘六月红芋’的最佳条件,并探究其保鲜效果。【方法】以永定‘六月红芋’为试材,通过对比自来水、纯水、去离子水、9%蔗糖溶液、1%碳酸钠溶液、1%氯化钠溶液、1%AA溶液以及不同有效氯质量浓度(20、40、60、80 mg/L)的微酸性电解水等11种保鲜护色液,筛选出对鲜切‘六月红芋’保鲜效果最佳的护色液。随后,进行AA与乙醇复配液处理,实验结果显示,AA单独使用的保鲜效果更佳。通过测定褐变度、硬度、pH值、相对电导率及感官评价得分等指标,进一步深入研究AA与US联合(AS)处理对鲜切‘六月红芋’贮藏品质的影响,以明确AS处理对鲜切‘六月红芋’的保鲜效果。【结果】在AA浓度为2%、浸泡时间为15 min、US处理时间为10 min、US频率为53 kHz、US功率为400 W的条件下,鲜切‘六月红芋’的感官品质最好。AS处理有效抑制褐变度的增加,维持酸度稳定性,减缓硬度的下降,保持细胞膜的完整性和较高的感官评分,这些参数为AS处理鲜切‘六月红芋’的最佳条件。【结论】在不同浸泡液中筛选得到AA为最佳护色液,并确定AS处理鲜切芋艿的最佳条件。AS处理能够显著提高鲜切‘六月红芋’的保鲜效果。

Synthesis, Crystal Structure and Antioxidant Activity of 5,6-O-(4-bromophenyl)-L-ascorbic Acid

The title compound 5,6-O-（4-bromophenyl）-L-ascorbic acid （C13H11BrO6, Mr = 343.13） has been synthesized and its structure was characterized by IR, 1H NMR and single-crystal X-ray diffraction. The product is a mixture of two diastereomer compounds （a （7S） and b （7R））. The crystal of a （7S） belongs to orthorhombic system, space group P212121 with a = 6.5362（10）, b = 7.8226（11）, c = 25.294（4） ？, V = 1293.3（3） ？3, Z = 4, Dc = 1.762 g/cm3, μ（MoKα） = 3.202 mm-1, F（000） = 688, R = 0.0235 and wR （I 〉 2σ（I）） = 0.0566. The hydrogen bonding interactions link the molecules to form a three-dimensional system. In addition, 5,6-O-（4-bromophenyl）-L-ascorbic acid （BPAA） exhibits strong free-radical scavenging activities in vitro against 2,2-diphenyl-1-picrylhy- drazyl and superoxide anion. BPAA should be investigated further as a worthy antioxidant.

Study of Diffusion through the Skin of Coated L-Ascorbic Acid by Fluid Bed Technology

Coating protects substances such as L-ascorbic acid from natural processes like oxidation. In this study, L-ascorbic acid was coated by fluid bed technology. A pH-dependent polymer was used as a coating material in order to release L-ascorbic acid (dissolution above pH 5.5) under conditions closest to the skin’s natural condition. Different techniques were used to determine the coating (SEM and size distribution) and to evaluate the percentage of coated L-ascorbic acid and its diffusion through the skin.

Microencapsulation of L-Ascorbic Acid by Spray Drying Using Sodium Alginate as Wall Material

L-ascorbic acid is a water soluble vitamin (vitamin C) widely used as an additive in foods and cosmetics. It has high instability against certain environmental factors;the main cause of its deterioration is oxidation. Microencapsulation is an effective protection technique of L-ascorbic acid from its degradation reactions. This work is focused on the encapsulation of L-ascorbic acid by spray drying technique using sodium alginate as wall material. The microcapsules morphology was observed by scanning electron microscopy (SEM) and the encapsulation efficiency was determined by spectrophotometric analysis. Results showed that encapsulation efficiency was of 93.48% and after 30 days was of 92.55%;differences were not significant, so that the stability of L-ascorbic acid was not affected. Encapsulation yields obtained were low, at around 30%, but the microcapsules morphology obtained is spherical.

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.

Molecular cloning and functional characterization of a soybean GmG MP1 gene reveals its involvement in ascorbic acid biosynthesis and multiple abiotic stress tolerance in transgenic plants

L-Ascorbic acid （AsA） plays an important role in plants and animals. In plants, GDP-D-mannose pyrophosphorylase （GMP） is essential in the AsA biosynthetic pathway. However, little is known about the genes encoding GMP in soybean and here we report genetic and functional analysis of the GmGMP1 （Glycine max GDP-D-mannose pyrophosphorylase 1） gene in this species. GmGMP1 encoded a GDP-mannose pyrophosphorylase and exhibited higher transcript levels in the leaf than in the root, stem, flower, and seed. Transcript of this gene was ubiquitous in the vegetative and reproductive organs, and was induced by abiotic stress and light. Increasing expression of GmGMP1 in Arabidopsis and soybean through an overexpressing approach caused pronounced enhancement of AsA content, and was implicated in lowering the superoxide anion radical content and lipid peroxidation levels in Arabidopsis, and conferring tolerance to osmotic and high salt stresses during seed germination. The present study represents the first systematic determination of soybean genes encoding GDP-mannose pyrophosphorylase and provides useful evidence for the functional involvement of GmGMP1 in control of AsA content and conferring tolerance to osmotic and salt stress.

Effects ofβ-1,3-glucan and ascorbic acid on the nutritional-immune response and antioxidant signaling pathways of live tiger grouper during simulated transport

Transport in water is the most common method for transporting live fish in China,however,transport is a strong stressor.Transport stress could lead to a reduced immune and antioxidant system function of tiger grouper,resulting in sickness and death.Besides,tiger grouper were continuously stressed during transport,which resulted in quality deterioration.It is necessary that find a way to relieve the stress of transportation of tiger grouper.Ascorbic acid is not only a good anti-stress agent,but it is also an effective immunostimulant.β-1,3-glucan is a feed additive that can enhance the immune response of fish.Therefore,this study evaluated the effects ofβ-1,3-glucan and ascorbic acid on the nutritional-immune response and antioxidant signaling pathways of live tiger grouper during simulated transport.Results indicated that addingβ-1,3-glucan and ascorbic acid in transport-water muted the increase of alanine aminotransferase(ALT)and aspartate aminotransferase(AST)activity.In addition,β-1,3-glucan and ascorbic acid activated Nrf2 and mediated TOR expression and then up-regulate related mRNA expression of antioxidant and immune enzymes.We concluded that the application ofβ-1,3-glucan and ascorbic acid inhibit the increase of metabolism enzymes and inflammatory factors and activate immune and antioxidant signaling pathways to relieve oxidant stress,immune response,and apoptosis.Reducing the loss of amino acids provided nutrients to relieve oxidative stress and immune response,which demonstrated immune-nutritional response in live tiger grouper during simulated transport.These results may provide a new solution for alleviating the decline of immune and antioxidant function of tiger grouper caused by transportation stress.

新型环保阻垢剂L-CCQDs的制备及性能研究

以无水柠檬酸、L-抗坏血酸为主要原料,通过熔融缩聚法合成了一种CQDs衍生物L-CCQDs,并通过红外光谱分析仪等手段对其进行表征,得到了与理论相符合的结果。将L-CCQDs在0~80℃条件下进行阻垢静态测试,结果表明,在极少量L-CCQDs的加入条件下,阻硫酸钙和阻碳酸钙垢的阻垢率均可达到100%,与单一的无水柠檬酸相比得到明显的改善。通过SEM等方法对L-CCQDs的阻垢机制进行研究,发现随着L-CCQDs加入量的增大,碳酸钙垢的晶型逐渐由方解石向尺寸更小的霰石结构发展,证明L-CCQDs对钙垢生长有显著的抑制作用。

L-抗坏血酸对α-FeOOH类Fenton降解罗丹明B的增效作用

以L-抗坏血酸(AA)作还原物质,采用沉淀法制备了针铁矿(α-FeOOH),用以作为类芬顿的催化剂降解染料罗丹明B(RhB),考察不同体系和不同因素对RhB降解效果的影响,并探究α-FeOOH重复利用的效果。结果表明,α-FeOOH/H_(2)O_(2)/AA体系在α-FeOOH投加量1.2 g/L、H_(2)O_(2)浓度为10 mmol/L、AA浓度4 mmol/L、RhB浓度20 mg/L、溶液pH值为5.5的条件下反应60 min后,RhB的降解率达95.55%,重复利用5次后,对RhB仍有76.62%的降解率。其降解过程符合准一级反应动力学模型,最大反应速率常数为0.0459 min^(-1)。·O_(2)^(-),·OH和1O_(2)是反应体系产生的活性氧物种,其中·O_(2)^(-)在RhB的降解中起着主要作用。

Effects of exogenous salicylic acid on growth and H_2O_2-metabolizing enzymes in rice seedlings under lead stress

Salicylic acid （SA） was an essential component of the plant resistance to pathogens and also plays an important role in mediating plant response to some abiotic stress. The possible effects of SA on the growth and H2O2-metabolizing enzymes in rice seedlings under lead stress were studied. When rice seedlings grown in nutrient solution containing Pb^2＋ （0, 0.05, 0.15, 0.25 mmol/L） for 18 d, the plant biomass as well as the chlorophyll content of leaves decreased with increasing Pb concentration. The pre-treatment with SA （treated with 0.1 mmol/L SA for 48 h before Pb stress） partially protected seedlings from Pb toxicity. The chlorophyll contents were significant higher in leaves of Pb-exposed with SA pre-treatment seedlings than in Pb-exposed plants at the same Pb intensity. SA pre-treated alone could significantly increase the length of shoot and root of seedlings but the vigour difference was not marked under long-term exposure to Pb toxicity. SA pre-treated influence the H2O2 level in leaves of seedlings by up-regulating the activity of superoxide dismutase （SOD）, repressing the activity of catalase （CAT） and ascorbate peroxidase （APX） depending on the concentrations of Pb^2＋ in the growth medium. The results supported the conclusion that SA played a positive role in rice seedlings against Pb toxicity.

L-抗坏血酸促进人胚胎干细胞向心肌细胞分化的研究

目的用不同浓度的L-抗坏血酸(VitC)作为分化基础培养液中的诱导剂,观察其对人胚胎干细胞(hESC)分化为心肌细胞的影响,探寻一种成分明确、成本低廉且高效的诱导方法。方法复苏hESC,使用干细胞培养液培养至细胞融合度90%后,分别用含不同浓度(0、10、20、30、40、50、60、70μmol/L)VitC的分化培养液对其进行诱导分化,在光学显微镜下观察分化过程。用实时定量聚合酶链式反应(real-time PCR)分别检测干细胞特异性标志物Nanog和性别决定因子同源盒2(Sox2),心肌细胞特异性标志物心肌肌钙蛋白T(cTnT)、心脏特异性同源盒转录因子(Nkx2.5)的表达。用免疫荧光检测Nanog、cTnT、Nkx2.5的蛋白表达变化。结果在分化基础培养液中,低浓度VitC(10~30μmol/L)不能诱导h ESC向心肌分化,随着VitC浓度的增高,干细胞逐渐往心肌方向分化,心肌分化效率逐渐提高,Nanog和Sox2的表达量逐渐下降;VitC浓度为40μmol/L或50μmol/L组在第8天开始出现自发跳动细胞,且有cTnT和Nkx2.5阳性表达。realtime PCR结果显示随分化时间延长,cTnT和Nkx2.5的mRNA表达逐渐增加,心肌表面标志物Nkx2.5、cTnT的mRNA表达量在VitC浓度40μmol/L和50μmol/L要比60μmol/L和70μmol/L的诱导效果更高。提示浓度大于60μmol/L就开始出现抑制分化的作用。结论实验研究证实VitC在hESC向心肌分化中是不可或缺的因子,研究还明确了VitC诱导h ESC分化为心肌细胞的适宜浓度范围。

基于NaIO_(3)转化NaIO_(4)回用合成S-甘油醛缩丙酮及其寡聚研究

S-甘油醛缩丙酮是合成手性药物的重要中间体。以L-抗坏血酸为原料,经缩酮化,硼氢化钠还原,高碘酸钠氧化制得S-甘油醛缩丙酮,收率为46.8%;探讨了含碘酸钠母液转化成高碘酸钠以循环套用,回收率为83.90%;初步考察了S-甘油醛缩丙酮的聚合度与时间的关系,并推测其寡聚化合物的结构和反应机理;用^(1)H NMR、IR和LC-MS等对化合物结构进行表征。

Enhanced Iontophoretic Delivery of Magnesium Ascorbyl 2-Phosphate and Sodium Fluorescein to Hairless and Hairy Mouse Skin

We recently reported that L-ascorbic acid 2-phosphate (AP) stimulates the growth of human dermal papilla (DP) cells, induces secretion of IGF-1 from the DP cells to promote hair shafts elongation in cultured human hair follicles, and triggers early progression from the telogen to anagen phase in mice. Since the magnesium salt of AP (APMg) is a highly hydrophilic ionic molecule, it is not easy to deliver this reagent to the skin or hair follicles by topical application alone. In order to enhance skin penetration of APMg without changing any molecular properties, a non-invasive iontophoretic delivery method was introduced. Iontophoresis of the negatively charged APMg under the electrode bearing same charge (cathode) significantly enhanced the in vitro penetration of APMg into a Franz cell equipped with mouse dorsal skin. In contrast, iontophoretic movement with the anode inhibited APMg penetration achieved with passive diffusion alone. The effect of iontophoresis on enhancing the penetration of APMg was also found to be much higher in the skin of hairy mice (3 - 8 times) compared to hairless mice (1.5 - 2.5 times). These findings indicated that iontophoretic movement induced the transfollicular pathway more strongly and effectively than the transdermal pathway. This phenomena was also demonstrated by the in vivo iontophoretic delivery of sodium fluorescein using hairy and hairless mice. The degree of iontophoretic enhancement during APMg penetration was also dependent on various conditions such as current density and application duration.

高效液相色谱法同时测定水果蔬菜中L-抗坏血酸、D-异抗坏血酸、脱氢抗坏血酸及总维生素C的含量

建立了同时测定水果或蔬菜中L-抗坏血酸、D-异抗坏血酸、脱氢抗坏血酸及总维生素C含量的高效液相色谱分析方法。用偏磷酸提取水果或蔬菜样品中L-抗坏血酸、D-异抗坏血酸和脱氢抗坏血酸,提取液中的L-抗坏血酸、D-异抗坏血酸可直接进行检测,脱氢抗坏血酸在磷酸钠溶液中（pH 7.0-7.2）用L-半胱氨酸还原成L-抗坏血酸,之后测定以L-抗坏血酸表达总维生素C含量,脱氢抗坏血酸含量由总维生素C含量减去L-抗坏血酸含量获得。采用C18色谱柱分离,以甲醇-磷酸盐缓冲溶液（pH 3.5）为流动相,在245 nm下检测,外标法定量。结果表明,在0.5-50 mg/L的浓度范围内L-抗坏血酸和D-异抗坏血酸的线性关系良好,相关系数大于0.999,检出限分别为42.0,19.4μg/kg,脱氢抗坏血酸的检出限为262μg/kg。低、中、高3个浓度的加标水平下,3种物质的加标回收率为82.8%-111.3%,相对标准偏差（RSD）小于15%。该方法操作简单,灵敏度高,准确性好,适用于水果和蔬菜中维生素C的测定。

聚L-谷氨酸/石墨充蜡修饰电极测定多巴胺

用充蜡石墨电极 (WGE)在L 谷氨酸 (GA)无水乙醇溶液中恒电位于 1.6V(vs.SCE)氧化制备了一种聚GA修饰电极 (GA/WGE) ,该电极可用于肾上腺素 (EP)和抗坏血酸 (AA)共存下对多巴胺 (DA)的测定。该电极的灵敏度和选择性主要取决于阳极极化电位与极化时间、富集电位和溶液的pH。DA在该电极上呈现一对循环伏安峰 ,Em=0 .14 5V ,为 1电子 / 1质子的准可逆氧化还原过程。AA和EP也能够在电极上富集和催化氧化 ,伏安峰分别在 0 .30V和 0 .17V。当AA浓度小于 0 .1mmol/L时 ,电极对AA基本不响应 ,可以用DA的氧化峰电流做定量分析。线性范围为 2 .0× 10 -4～ 5 .0× 10 -7mol/L ;检出限为 2 .5× 10 -7mol/L。当AA的浓度较大或在AA、EP共存下 ,可利用DA氧化的再还原峰电流做定量分析。线性范围为 1.0× 10 -4～ 2 .5× 10 -6mol/L ;检出限为 7.5× 10 -7mol/L。该电极制作简便 ,重现性良好 。

L-抗坏血酸-6-对羟基苯甲酸酯的合成及抗氧化活性研究

采用直接酯化法,合成了L-抗坏血酸-6-对羟基苯甲酸酯(APHB),并从清除羟自由基、超氧阴离子自由基、DPPH自由基能力及还原能力测试4个方面研究了它的体外抗氧化活性。结果表明,L-抗坏血酸-6-对羟基苯甲酸酯对上述3种自由基均有较好的清除效果,还原能力也较强,其抗氧化性能总体上与VC相当,优于市面上常用的抗氧化剂TBHQ,是一种有潜力的VC衍生物。