Prevention of cataracts by nutritional and metabolic antioxidants

Among aging disabilities, the one associated with the progressive decline of vision is functionally most disadvantageous. Cataracts are one of the more common causes of such visual disability. Several predisposing factors have been identified in the genesis of this disease. While it is perhaps a multifactorial process, significant developments have taken place in recent years suggesting that oxygen radicals are involved in the development of this aging manifestation. Antioxidant enzymes, such as catalase and superoxide dismutase, have been demonstrated to protect the lens cell membrane from oxidative stress as reflected by the prevention of the Na⁺‐K⁺‐ATPase‐dependent pump deterioration due to oxyradical‐dependent oxidation of its proteins and lipids. From the nutritional point of view, antioxidants such as ascorbate and vitamin E also offer significant protection to the lens against damage due to oxidative stress. Evidence regarding the protective effect of these nutrients has been based on lens organ culture studies in the presence of active oxygen, generated photochemically as well as enzymatically. The experiment involving photochemical environs simulate the status of the eye during the photopic vision. In vivo, the effectiveness of ascorbate against cataracts has been tested in rat pups developing cataracts under the oxidative influence of sodium selenite. Certain antioxidants produced metabolically also may be useful in protecting against cataracts. Pyruvate produced in glucose metabolism seems to be an important antioxidant The efficacy of this compound has been tested within in vitro organ culture as well as in vivo, the latter experiments being done with selenite‐treated rats. There is a hope that these and other nutritional and metabolic antioxidants may one day be useful in delaying or even preventing cataract formation in human beings.     

Purification and characterisation of basic ascorbate oxidase from satsuma mandarin (Citrus unshiu Marc)

Basic ascorbate oxidase of the multiple enzyme forms existing in young fruit of satsuma mandarin (Citrus unshiu Marc) has been separated and subsequently purified to electrophoretic homogeneity through (NH₄)₂SO₄ fractionation and chromatographies on DEAE-Toyopearl 650M, CM-Sephadex C-50 and Sephadex G-100. The native molecular weight was estimated to be 141 kDa by gel filtration and composed of two non-identical subunits with an apparent mass of 74 kDa and 62 kDa. The optimum pH was found to be 5.5 with reasonable stability between pH 5 and 8. The enzyme had an optimum temperature at 45°C and was stable up to 50°C upon heat treatment for 5 min. The presence of sodium diethyldithiocarbamate, metabisulphite and potassium cyanide completely inhibited the enzyme activity. Fluoride also inhibited the activity substantially at higher concentrations. Other tnonovalent and divalent metal ions did not have inhibitory effects.     

抗坏血酸对玫瑰香干白葡萄酒的抗氧化作用

玫瑰香干白葡萄酒在贮存过程中因氧化作用而发生色泽加深、香气变质等现象,其褐变主要是由于酒中酚类化合物发生氧化所致,香气的消失也是由于香味物质的氧化所致.单一使用SO2不能很好地防止葡萄酒的氧化,采用抗坏血酸钠与SO2结合防止玫瑰香干白葡萄酒的氧化的效果很好.D-异抗坏血酸钠的适宜添加量为150 mg/L,在装瓶前加入D-异抗坏血酸钠,可提高玫瑰香干白葡萄酒的瓶贮品质,其货架寿命可延长至2年以上.如果使用PVPP除去大部分的酚类物质,再结合SO2,D-异抗坏血酸钠使用效果会更好.(孙悟)     

Relationship of apple vitamin C and antioxidant contents to harvest date and postharvest pathogen infection

A surprisingly strong correlation between the date of commercial harvest and the mean vitamin C (L ‐ascorbate, L‐AA) contents of fruits from Belgian‐grown Malus × domestica cultivars was reported recently (Davey MW and Keulemans J, J Agric Food Chem 52:8031–8038 (2004)). The study has been extended to show that this correlation remains consistent over different production years and that harvest date is also significantly correlated with fruit L‐AA and total antioxidant activities but not with glutathione (GSH) levels or other physiological parameters of fruits. L‐AA concentrations were also found to be negatively correlated with mean preharvest daytime temperature; however, since preharvest temperature and harvest date themselves are closely linked, it was not possible to definitively separate the relative contributions of genetic and environmental factors to these traits. It is also shown that the susceptibility of fruits of different apple genotypes to postharvest infection with Botrytris cinerea decreases with increasing harvest date and that this susceptibility is correlated with fruit vitamin C but not GSH levels. There is no such relationship underlying the susceptibility of fruits to postharvest infection with Gloeosporium fructigenum. These results are discussed in the context of low‐input breeding for improved fruit quality and disease resistance via selection of fruits with improved antioxidant defence capabilities. Copyright © 2007 Society of Chemical Industry     

Electrochemical and surface analytical studies of synergistic effect of phosphonate,Zn2+ and ascorbate in corrosion control of carbon steel

Synergistic inhibition of corrosion of carbon steel in low chloride environment using ascorbate as a synergist along with 2‐phosphonobutane‐1,2,4‐tricarboxylic acid (PBTC) and Zn²⁺ is presented. The synergistic effect of ascorbate has been established from the present studies. In the presence of ascorbate, lower concentrations of PBTC and Zn²⁺ are sufficient in order to obtain good inhibition, thus making this formulation more environmentally friendly. Potentiodynamic polarisation studies inferred that this mixture functions as a mixed inhibitor, predominantly cathodic. Impedance studies revealed that an immersion period of 24 h is necessary for the formation of the protective film, with a very high charge transfer resistance. The film is stable even at 60 °C in the presence of the inhibitor in the corrosive environment. The surface analysis by X‐ray photoelectron spectroscopy (XPS) showed the presence of iron, oxygen, phosphorus, carbon and zinc in the protective film. The XPS spectra inferred the presence of oxides/hydroxides of iron(III), Zn(OH)₂ and [Zn(II)–PBTC–ascorbate] complex in the surface film. This inference was further supported by the reflection absorption Fourier transform infrared spectrum of the surface film. A plausible mechanism of corrosion inhibition has been proposed.     

Effect of protein additives, sodium ascorbate, and microbial transglutaminase on the texture and colour of red tilapia surimi gel

Beef plasma protein (BPP) and egg white, at levels of 10, 20 and 30 g kg⁻¹, and sodium ascorbate (SA) and microbial transglutaminase (MTGase), at levels of 1, 2 and 3 g kg⁻¹, were individually added into red tilapia surimi. This gel was set at 40 °C for 90 min followed by heating at 90 °C for 30 min. Gel qualities were analysed and compared with those of non-supplemented red tilapia control gel. Compared with the control, each additive significantly affected gel strength due to an increase in breaking force. Although BPP could improve texture characteristics, higher addition levels of BPP significantly affected gel whiteness. The addition of SA and MTGase were found to increase surimi gel strength and improve whiteness. Amongst all treatments, the addition of 2 g kg⁻¹ MTGase was found to provide the best gel qualities.     

组合生物技术处理D-抗坏血酸钠工业废水

对高浓度制药废水首先进行浓缩蒸发预处理,彻底除硫除盐以后,再通过一系列的厌氧、兼氧、缺氧-好氧组合处理,充分发挥在不同环境条件下各类微生物代谢降解有机污染物的功能,使废水中COD由2.8×104 mg/L降到300 mg/L以下,经过5个月的稳定运行后,于2005年1月12日顺利通过郑州市环保局组织的达标验收.     

Antioxidant activity determines on‐tree maturation in ‘Golden Smoothee’ apples

BACKGROUND: Harvest date clearly determines the postharvest storage behaviour and sensitivity of fruit to physiological disorders. Generally fruit are picked following their maturity indexes but often these indexes poorly represent the physiological state of the fruit. With this in mind, this work aimed to determine a biochemical marker capable of predicting on‐tree maturation in ‘Golden Smoothee’ apples. Changes in the non‐enzymatic and in enzymatic antioxidant potential of fruit were assessed for different harvest dates. RESULTS: Significant differences in antioxidant levels, especially ascorbate and catalase, were found. These changes were related to climatic variations, especially relating to temperature, that appeared to determine the capability of the fruit to produce ethylene. Fruit exposed to higher temperature produced less ethylene and exhibited a significant delay in the induction of their climacteric. In both seasons, changes in quality parameters during on‐tree ripening were not related to the capability of the fruit to produce ethylene, but rather to endogenous levels of antioxidants, especially catalase and ascorbate, at the earliest picking date. CONCLUSION: We hypothesize that ascorbate and antioxidant activity play a role in changes in maturity patterns exhibited by apples in orchards. Both parameters appear to be interesting markers to follow these changes. Copyright © 2009 Society of Chemical Industry     

Ascorbate Oxidase Mimetic Activity of Copper(II) Oxide Nanoparticles

Although oxidase mimetic nanozymes have been widely investigated, specific biological molecules have rarely been explored as substrates, particularly in the case of ascorbate oxidase (AAO) mimetic nanozymes. Herein, we demonstrate for the first time that copper(II) oxide nanoparticles (CuO NPs) catalyze the oxidation of ascorbic acid (AA) by dissolved O₂ (as a green oxidant) to form dehydroascorbic acid (DHAA), thus functioning as a new kind of AAO mimic. Under neutral conditions, the Michaelis–Menten constant of CuO NPs (0.1302 mm ) is similar to that of AAO (0.0840 mm ). Furthermore, the robustness of CuO NPs is greater than that of AAO, thus making them suitable for applications under various conditions. As a demonstration, a fluorescence AA sensor based on the AAO mimetic activity of CuO NPs was developed. To obtain a fluorescent product, o-phenylenediamine (OPDA) was used to react with the DHAA produced by the oxidation of AA catalyzed by CuO NPs. The developed sensor was cost-effective and easy to fabricate and exhibited high selectivity/sensitivity with a wide linear range (1.25×10⁻⁶ to 1.125×10⁻⁴ m ) and a low detection limit (3.2×10⁻⁸ m ). The results are expected to aid in expanding the applicability of oxidase mimetic nanozymes in a variety of fields such as biology, medicine, and detection science.